Showing papers in "World Journal of Microbiology & Biotechnology in 2019"
TL;DR: Yeasts represent a largely unexplored field of research and plentiful opportunities for the development of commercial, yeast-based applications for plant protection exist, but the scarcity of fundamental studies on yeast biocontrol mechanisms and of registered yeast- based biocOntrol products is highlighted.
Abstract: Yeasts occur in all environments and have been described as potent antagonists of various plant pathogens. Due to their antagonistic ability, undemanding cultivation requirements, and limited biosafety concerns, many of these unicellular fungi have been considered for biocontrol applications. Here, we review the fundamental research on the mechanisms (e.g., competition, enzyme secretion, toxin production, volatiles, mycoparasitism, induction of resistance) by which biocontrol yeasts exert their activity as plant protection agents. In a second part, we focus on five yeast species (Candida oleophila, Aureobasidium pullulans, Metschnikowia fructicola, Cryptococcus albidus, Saccharomyces cerevisiae) that are or have been registered for the application as biocontrol products. These examples demonstrate the potential of yeasts for commercial biocontrol usage, but this review also highlights the scarcity of fundamental studies on yeast biocontrol mechanisms and of registered yeast-based biocontrol products. Yeast biocontrol mechanisms thus represent a largely unexplored field of research and plentiful opportunities for the development of commercial, yeast-based applications for plant protection exist.
187 citations
TL;DR: This review presents a state-of-the-art technology for potential use of algae as a low-cost biosorbent for the removal of HMs from wastewater.
Abstract: Urbanization, industrialization, and natural earth processes have potentially increased the contamination of heavy metals (HMs) in water bodies. These HMs can accumulate in human beings through the consumption of contaminated water and food chains. Various clean-up technologies have been applied to sequester HMs, especially conventional methods including electrolytic technologies, ion exchange, precipitation, chemical extraction, hydrolysis, polymer micro-encapsulation, and leaching. However, most of these approaches are expensive for large-scale projects and require tedious control and constant monitoring, along with low efficiency for effective HMs removal. Algae offer an alternative, sustainable, and environmentally friendly HMs remediation approach. This review presents a state-of-the-art technology for potential use of algae as a low-cost biosorbent for the removal of HMs from wastewater. The mechanisms of HMs removal, including biosorption and bioaccumulation along with physical and chemical characterization of the algae are highlighted. The influence of abiotic factors on HMs removal and changes in algal biocomponents (including, carbohydrate, lipid, and protein) are discussed. Recent progresses made in the development of HMs-tolerant algal strains and the direction of future research toward the development of sustainable technology for advanced wastewater treatment and biomass production are covered.
116 citations
TL;DR: This work demonstrates that G. officinalis extract is a feasible medium for the synthesis of silver nanoparticles and that the control of the reaction parameters can determine the nanoparticle characteristics and therefore their antimicrobial effectiveness.
Abstract: In this work, the biosynthesis of silver nanoparticles by Galega officinalis extract using AgNO3 as a precursor was reported. The reaction parameters for the biosynthesis and efficiency in their antimicrobial control against Escherichia coli, Staphylococcus aureus and Pseudomonas syringae were determined. For biosynthesis, a central composite design combined with response surface methodology was used to optimize the process parameters (pH, AgNO3 and extract concentration), and the design was assessed through the size distribution, zeta potential and polydispersity index of the nanoparticles. The results demonstrated that at pH 11, 1.6 mM of AgNO3 and 15% vv−1 of G. officinalis extract were the optimal reaction parameters. Transmission electron microscope (TEM) images and X-ray diffraction (XRD) confirmed the formation of small spherical silver nanoparticles. Antimicrobial assays showed a high inhibitory effect against E. coli, S. aureus and P. syringae, and that effect was larger with silver nanoparticles of a smaller size (23 nm). This work demonstrates that G. officinalis extract is a feasible medium for the synthesis of silver nanoparticles and that the control of the reaction parameters can determine the nanoparticle characteristics and therefore their antimicrobial effectiveness.
84 citations
TL;DR: All four strains were able to ameliorate the adverse effects of osmotic-stress (induced by 25% PEG in MS-Agar medium) in the plants, as evidenced by their enhanced fresh weight, dry weight and plant water content, as opposed to osmosis-stressed, non-inoculated plants.
Abstract: The ability of plant growth promoting rhizobacteria (PGPR) for imparting abiotic stress tolerance to plants has been widely explored in recent years; however, the diversity and potential of these microbes have not been maximally exploited. In this study, we characterized four bacterial strains, namely, Pseudomonas aeruginosa PM389, Pseudomonas aeruginosa ZNP1, Bacillus endophyticus J13 and Bacillus tequilensis J12, for potential plant growth promoting (PGP) traits under osmotic-stress, induced by 25% polyethylene glycol (PEG) in the growth medium. Growth curve analysis was performed in LB medium with or without PEG, in order to understand the growth patterns of these bacteria under osmotic-stress. All strains were able to grow and proliferate under osmotic-stress, although their growth rate was slower than that under non-stressed conditions (LB without PEG). Bacterial secretions were analyzed for the presence of exopolysaccharides and phytohormones and it was observed that all four strains released these compounds into the media, both, under stressed and non-stressed conditions. In the Pseudomonas strains, osmotic stress caused a decrease in the levels of auxin (IAA) and cytokinin (tZ), but an increase in the levels of gibberellic acid. The Bacillus strains on the other hand showed a stress-induced increase in the levels of all three phytohormones. P. aeruginosa ZNP1 and B. endophyticus J13 exhibited increased EPS production under osmotic-stress. While osmotic stress caused a decrease in the levels of EPS in P. aeruginosa PM389, B. tequilensis J12 showed no change in EPS quantities released into the media under osmotic stress when compared to non-stressed conditions. Upon inoculating Arabidopsis thaliana seedlings with these strains individually, it was observed that all four strains were able to ameliorate the adverse effects of osmotic-stress (induced by 25% PEG in MS-Agar medium) in the plants, as evidenced by their enhanced fresh weight, dry weight and plant water content, as opposed to osmotic-stressed, non-inoculated plants.
76 citations
TL;DR: An approach of enzyme selection (and mode of application thereof) during xylan degradation is proposed, as this can improve the economic viability of the degradation of xylan for producing precursors of value added products.
Abstract: This review examines the recent models describing the mode of action of various xylanolytic enzymes and how these enzymes can be applied (sequentially or simultaneously) with their distinctive roles in mind to achieve efficient xylan degradation. With respect to homeosynergy, synergism appears to be as a result of β-xylanase and/or oligosaccharide reducing-end β-xylanase liberating xylo-oligomers (XOS) that are preferred substrates of the processive β-xylosidase. With regards to hetero-synergism, two cross relationships appear to exist and seem to be the reason for synergism between the enzymes during xylan degradation. These cross relations are the debranching enzymes such as α-glucuronidase or side-chain cleaving enzymes such as carbohydrate esterases (CE) removing decorations that would have hindered back-bone-cleaving enzymes, while backbone-cleaving-enzymes liberate XOS that are preferred substrates of the debranching and side-chain-cleaving enzymes. This interaction is demonstrated by high yields in co-production of xylan substituents such as arabinose, glucuronic acid and ferulic acid, and XOS. Finally, lytic polysaccharide monooxygenases (LPMO) have also been implicated in boosting whole lignocellulosic biomass or insoluble xylan degradation by glycoside hydrolases (GH) by possibly disrupting entangled xylan residues. Since it has been observed that the same enzyme (same Enzyme Commission, EC, classification) from different GH or CE and/or AA families can display different synergistic interactions with other enzymes due to different substrate specificities and properties, in this review, we propose an approach of enzyme selection (and mode of application thereof) during xylan degradation, as this can improve the economic viability of the degradation of xylan for producing precursors of value added products.
73 citations
TL;DR: Several positive effects in health have been associated with the substitution of meat for mycoprotein, including improvements in blood cholesterol concentration and glycemic response, and questions regarding the consumer’s experience on the sensory and health aspects are still being investigated.
Abstract: The term mycoprotein refers to the protein-rich food made of filamentous fungal biomass that can be consumed as an alternative to meat. In this paper, the impact caused by the substitution of anima ...
70 citations
TL;DR: It is strongly suggested that endophytic diazotroph LSE-2 can be used as potent bio-inoculant along with LSBR-3 as bio-enhancer for improving soybean productivity in a sustainable system.
Abstract: The present study was aimed to assess the scope of native potential endophyte Pseudomonas aeruginosa (LSE-2) strain (KX925973) with recommended Bradyrhizobium sp. (LSBR-3) (KF906140) for synergistic effect to develop as consortium biofertilizer of soybean. A total of 28 non-rhizobial endophytic bacteria were isolated from cultivated and wild sp. of soybean. All isolates were screened for multifarious PGP traits viz. Indole-3-acetic acid (IAA), phosphate (P) and zinc (Zn) solubilization, siderophore, cell wall degrading enzymes and pathogenicity. Compatible of LSBR-3 and LSE-2 enhanced IAA, P-solubilization, 1-aminocyclopropane-carboxylate deaminase and biofilm formation over the single inoculant treatment. Further, consortium was evaluated in vivo for growth, symbiotic traits, nutrient acquisition, soil quality parameters and yield attributes of soybean. Improvement in growth parameters were recorded with dual inoculant LSBR-3 + LSE-2 as compared to LSBR-3 alone and un-inoculated control treatments. Significantly (p ≥ 0.05) high symbiotic and soil quality parameters (phosphatase and soil dehydrogenase activity) was recorded with LSBR-3 + LSE-2 at vegetative and flowering stage as compared to LSBR-3 alone and un-inoculated control treatments. Single inoculation of LSBR-3 improved grain yield by 4.25% over the un-inoculated control treatment, further, enhancement in yield was recorded with consortium inoculant (LSBR-3 and LSE-2) by 3.47% over the LSBR-3 alone. Application of consortium inoculant (LSBR-3 + LSE-2) gave an additional income of Rs. 5089/ha over the un-inoculated control treatment. The results, thus strongly suggest that endophytic diazotroph LSE-2 can be used as potent bio-inoculant along with LSBR-3 as bio-enhancer for improving soybean productivity in a sustainable system.
69 citations
TL;DR: Results proved that algal extracts have high potential to be applied in modern horticulture and agriculture and could help to ensure production of sufficient human food to meet the needs of rising population and protection of the environment.
Abstract: In the present paper, products obtained from a blue-green microalga Spirulina platensis filtrate (applied for seed soaking and for foliar spray) and homogenate (used for seed coating) were tested in the cultivation of radish. Their effect on length, wet mass, multielemental composition and the greenness index of the radish leaves was examined. Multi-elemental analyses of the algal products, and radish were also performed using inductively coupled plasma-optical emission spectrometry (ICP-OES). The best soaking time, concentrations of filtrate and doses of homogenate were established. The longest and heaviest plants were observed for homogenate applied at a dose of 300 µL per 1.5 g of seeds and 15% of filtrate applied as foliar spray. The highest chlorophyll content was found in the group treated with 100 µL of homogenate and 5% of filtrate. In the case of soaking time, the longest plants were in the group where seeds were soaked for 6 h, but the heaviest and greenest were after soaking for 48 h. The applied algal products increased the content of elements in seedlings. Obtained results proved that algal extracts have high potential to be applied in modern horticulture and agriculture. The use of Spirulina-based products is consistent with the idea of sustainable agriculture that could help to ensure production of sufficient human food to meet the needs of rising population and protection of the environment.
64 citations
TL;DR: A robust potential for Bifidobacterium to modulate humoral and cellular immune responses and induce balanced Th1/Th2 immune responses against influenza infection is indicated.
Abstract: The limited efficacy of available influenza vaccines against rapidly emerging new viral strains stresses the need for the development of new antigen-independent prophylactic treatment for enhancing immunity against influenza infection. Recent studies suggest that probiotics possess immunomodulatory properties and can reduce the severity of respiratory infections. Here, we investigated the potential of prophylactic Bifidobacterium bifidum in improving anti-influenza immune responses in an experimental lethal mouse-adapted influenza A (H1N1) infection in a BALB/c mouse model. One week after viral challenge, splenocyte proliferation assay (MTT), IFN-gamma, IL-12, and IL-4 in spleen and IL-6 in the lung homogenates were conducted using ELISA assays. Sera samples were collected to measure IgG1 and IgG2a levels. Furthermore, the mice challenged with lethal influenza virus were assessed for survival rate. The findings demonstrated a strong induction of both humoral and cellular immunities, as well as decreased level of IL-6 production in the lung and an increase in survival rate in the mice receiving Bifidobacterium than those of the control group were observed. Taken together, the results indicate a robust potential for Bifidobacterium to modulate humoral and cellular immune responses and induce balanced Th1/Th2 immune responses against influenza infection.
63 citations
TL;DR: The critical factors necessary to adequately characterise novel L-asparaginase therapeutic products, including enzyme kinetic parameters, glutaminase activity, and toxicity are discussed, and recent research in the area is reviewed.
Abstract: L-asparaginase is a critical part of the treatment of acute lymphoblastic leukaemia in children and adolescents, and has contributed to the improvement in patient outcomes over the last 40 years. The main products used in clinical treatment are L-asparaginase enzymes derived from Escherichia coli and Erwinia chrysanthemi. However, a very active area of research is the identification and characterisation of potential new L-asparaginase therapeutics, from existing or novel prokaryotic and eukaryotic sources, including mutations to improve function. In this review, we discuss the critical factors necessary to adequately characterise novel L-asparaginase therapeutic products, including enzyme kinetic parameters, glutaminase activity, and toxicity. One critical consideration is to ensure that the substrate affinity of novel enzymes, as measured by the Michaelis constant KM, is sufficiently low to enable efficient reaction rates in human clinical use. The activity of L-asparaginases towards glutamine as a substrate is discussed and reviewed in detail, as there is much debate in the scientific literature about the importance of this feature for therapeutic enzymes. The recent research in the area is reviewed, including identification of new sources of the enzyme, modulating glutaminase activity, and improving the thermal stability and immunogenic response. New research in the area may benefit from these considerations, to enable the next generation of therapeutic product design. Critical to future work in this area is a complete characterisation of novel enzymes with respect to performance for both L-asparagine and L-glutamine as substrates.
61 citations
TL;DR: The present review describes microalgae polysaccharides, their biological activities and their possible application in agriculture as a potential sustainable alternative for enhanced crop performance, nutrient uptake and resilience to environmental stress.
Abstract: Plant biostimulants are defined as materials containing microorganisms or substances whose function when applied to plants or the rhizosphere is to stimulate natural mechanisms to enhance plant growth, nutrient use efficiency, tolerance to abiotic stressors and crop quality, independent of their nutrient content. In agriculture, seaweeds (Macroalgae) have been used in the production of plant biostimulants while microalgae still remain unexploited. Microalgae are single cell microscopic organisms (prokaryotic or eukaryotic) that grow in a range of aquatic habitats, including, wastewaters, pounds, lakes, rivers, oceans, and even humid soils. These photosynthetic microorganisms are widely described as renewable sources of biofuels, bioingredients and biologically active compounds, such as polyunsaturated fatty acids (PUFAs), carotenoids, phycobiliproteins, sterols, vitamins and polysaccharides, which attract considerable interest in both scientific and industrial communities. Microalgae polysaccharides have so far proved to have several important biological activities, making them biomaterials and bioactive products of increasing importance for a wide range of applications. The present review describes microalgae polysaccharides, their biological activities and their possible application in agriculture as a potential sustainable alternative for enhanced crop performance, nutrient uptake and resilience to environmental stress. This review does not only present a comprehensive and systematic study of Microalgae polysaccharides as plant biostimulants but considers the fundamental and innovative principles underlying this technology.
TL;DR: The architecture and function of both prokaryotic and eukaryotic promoters are introduced, and the recent achievements and advances by promoter engineering for the optimization of metabolite biosynthetic pathways in multiple widely-used model microorganism are discussed.
Abstract: Cell metabolism in living organisms is largely regulated at the transcriptional level, and the promoters are regarded as basic regulatory elements responsible for transcription initiation. Promoter engineering is an important technique to regulate gene expression and optimize metabolite biosynthesis in metabolic engineering and synthetic biology. The rational and precise control of gene expression in the multi-gene pathways can significantly affect the metabolic flux distribution and maximize the production of specific metabolites. Thus, many efforts have been made to identify natural promoters, construct inducible or hybrid promoters, and design artificial promoters for fine-tuning specific gene expression at the transcriptional level and improving production levels of the metabolites of interest. In this review, we will briefly introduce the architecture and function of both prokaryotic and eukaryotic promoters, and provide an overview of several major approaches for promoter engineering. The recent achievements and advances by promoter engineering for the optimization of metabolite biosynthetic pathways in multiple widely-used model microorganism, including Escherichia coli, Corynebacterium glutamicum and Saccharomyces cerevisiae, will also be extensively discussed.
TL;DR: Recent achievements in the use of metabolomics methods in bacterial identification, differentiation, the interconnection between genome and metabolome, the influence of external factors on the bacterial metabolome and identification of new metabolites produced by P. aeruginosa are discussed.
Abstract: Pseudomonas aeruginosa is a common, Gram-negative environmental organism. It can be a significant pathogenic factor of severe infections in humans, especially in cystic fibrosis patients. Due to its natural resistance to antibiotics and the ability to form biofilms, infection with this pathogen can cause severe therapeutic problems. In recent years, metabolomic studies of P. aeruginosa have been performed. Therefore, in this review, we discussed recent achievements in the use of metabolomics methods in bacterial identification, differentiation, the interconnection between genome and metabolome, the influence of external factors on the bacterial metabolome and identification of new metabolites produced by P. aeruginosa. All of these studies may provide valuable information about metabolic pathways leading to an understanding of the adaptations of bacterial strains to a host environment, which can lead to new drug development and/or elaboration of new treatment and diagnostics strategies for Pseudomonas.
TL;DR: This review will compare the chemical and biological routes for the synthesis of UAAs and provide an overview of their applications.
Abstract: Unnatural amino acids (UAAs) are valuable building blocks in the manufacture of a wide range of pharmaceuticals. UAAs exhibit biological activity as free acids and they can be incorporated into linear or cyclic peptides with biological activity. However, the scope of biotechnological application of UAAs goes beyond this, as they can be used to investigate the structure and dynamics of proteins, to study protein interactions, or to modulate the activity of proteins in living cells. The means to expand nature's repertoire of amino acids include chemical and biological routes. An UAA can be made through chemical modifications of natural amino acids, or related compounds. These modifications typically rely on utilisation of ligands and palladium catalysts. Employing biocatalysts in the synthesis of UAAs can also afford novel molecules with different physical and chemical properties. A number of transaminases for example have been identified and employed in the production of UAAs. This review will compare the chemical and biological routes for the synthesis of UAAs and provide an overview of their applications.
TL;DR: This review focuses on the most frequently studied issues related to the microbial silage quality and the recent trends in increasing the quality by LAB inoculants, with respect to recent directions for selecting types of modern LAB for inoculation.
Abstract: Ensiling is one of the best known method to preserve fodder. The forage before ensiling intended for silages usually contains a low number of lactic acid bacteria (LAB), so it is necessary to apply starter cultures of selected strains. Traditionally, LAB starter cultures were applied to lower the pH by producing lactic acid and to inhibit the growth of undesirable epiphytic microorganisms by competing for nutrients. Nowadays, LAB inoculants have become an effective tool for creating microbial quality of silages by selecting species with extraordinary features. Epiphytic microflora characteristic of plant material used for the production of silages and the sources of undesirable microflora in the ensiling process are discussed. This review focuses on the most frequently studied issues related to the microbial silage quality and the recent trends in increasing the quality by LAB inoculants, with respect to recent directions for selecting types of modern LAB for inoculation. Among them, the main trends described were prevention of the growth of filamentous fungi and detoxification of mycotoxins by LAB inoculants, inhibition of yeast growth by LAB present in preparations and limiting the development of pathogenic bacterial microflora through controlled fermentation with the participation of LAB and the presence of their metabolites.
TL;DR: In the present review-article, aspects concerning SCOs (economics, biochemistry, substrates, technology, scale-up), with emphasis on the potential of Mortierella isabellina were presented.
Abstract: The last years a constantly rising number of publications have appeared in the literature in relation to the production of oils and fats deriving from microbial sources (the “single cell oils”—SCOs). SCOs can be used as precursors for the synthesis of lipid-based biofuels or employed as substitutes of expensive oils rarely found in the plant or animal kingdom. In the present review-article, aspects concerning SCOs (economics, biochemistry, substrates, technology, scale-up), with emphasis on the potential of Mortierella isabellina were presented. Fats and hydrophilic substrates have been used as carbon sources for cultivating Zygomycetes. Among them, wild-type M. isabellina strains have been reported as excellent SCO-producers, with conversion yields on sugar consumed and lipid in DCW values reported comparable to the maximum ones achieved for genetically engineered SCO-producing strains. Lipids produced on glucose contain γ-linolenic acid (GLA), a polyunsaturated fatty acid (PUFA) of high dietary and pharmaceutical importance, though in low concentrations. Nevertheless, due to their abundance in oleic acid, these lipids are perfect precursors for the synthesis of 2nd generation biodiesel, while GLA can be recovered and directed to other usages. Genetic engineering focusing on over-expression of Δ6 and Δ12 desaturases and of C16 elongase may improve the fatty acid composition (viz. increasing the concentration of GLA or other nutritionally important PUFAs) of these lipids.
TL;DR: The results showed that the EF–KV bacterial consortium can be used for efficient removal of RR198 dye from textile effluent, and it was found that the best conditions included a bacterial concentration of 3.5 mL × 105 cells/mL and incubation time of 72 h.
Abstract: The present study investigated biodegradation and removal of Reactive Red 198 (RR198) dye from aqueous environments using a new bacterial consortium isolated from textile wastewater sludge on laboratory scale via batch study. Two bacterial species, Enterococcus faecalis (EF) and Klebsiella variicola (KV), were identified after isolation, through biochemical assays, Polymerase chain reaction (PCR), and 16S rRNA gene sequencing. To determine their ability to biodegrade RR198 dye, physicochemical parameters, including bacterial concentration, time, pH, and temperature, were tested; the results showed that the best conditions included a bacterial concentration of 3.5 mL × 105 cells/mL and incubation time of 72 h. Under such conditions, the removal efficiency of RR198 dye at an initial concentration of 10–25 mg/L was more than 98%; however, for concentrations of 50, 75, and 100 mg/L, removal efficiency was reduced to 55.62%, 25.82%, and 15.42%, respectively (p = 0.005). The highest removal efficiency occurred at pH 8.0, reaching 99.26% after 72 h of incubation. With increasing the incubation temperature from 25 °C to 37 °C, removal efficiency increased from 71.71 to 99.26% after 72 h of incubation, and increasing the temperature from 37 to 45 °C, the removal efficiency was reduced (p ≤ 0.001). Therefore, the EF–KV bacterial consortium can be used for efficient removal of RR198 dye from textile effluent.
TL;DR: Improving the understanding of how this interaction between biofilm and metallic surface occurs will enable better evaluation of strategies to avoid or decelerate the degradation of metallic structures in marine environments.
Abstract: Metal corrosion is a major global concern in many economic sectors. The degradation of metal surfaces is responsible for losses in values that account for about 3% of gross domestic product (GDP) only in the US. Parts of all corrosion processes described in different environments are present mainly in marine environments. The marine environment is characterized as favoring the corrosion processes of several metallic alloys, damaging structures used in the construction of ships, ports, oil pipelines, and others. Despite chemical corrosion being the most frequently described in these environments, studies show the participation of microorganisms in direct corrosion processes or in the acceleration/influence of the corrosive action, through the formation of complex biofilms. These structures create favorable conditions for microorganisms to degrade metal surfaces, causing damage known as pitting and crevices. Currently, diverse technicians are employed in biocorrosion research, e.g. electronic microscopy, and DNA sequencing. These techniques have clarified the dynamic process of the formation of biofilm structures, allowing understanding of the succession of different species during the evolution of the structure. Improving the understanding of how this interaction between biofilm and metallic surface occurs will enable better evaluation of strategies to avoid or decelerate the degradation of metallic structures in marine environments.
TL;DR: The aim of this study was to present well-known yeast species Y. lipolytica as a rare opportunistic fungal pathogen and possible pathogenicity and epidemiology of this yeast species were discussed.
Abstract: Yarrowia lipolytica is one of the most studied "non-conventional" yeast species capable of synthesizing a wide group of valuable metabolites, in particular lipases and other hydrolytic enzymes, microbial oil, citric acid, erythritol and γ-decalactone. Processes based on the yeast have GRAS status ("generally recognized as safe") given by Food and Drug Administration. The majority of research communications regarding to Y. lipolytica claim that the yeast species is non-pathogenic. In spite of that, Y. lipolytica, like other fungal species, can cause infections in immunocompromised and critically ill patients. The yeast possess features that facilitate invasion of the host cell (particularly production of hydrolytic enzymes), as well as the protection of the own cells, such as biofilm formation. The aim of this study was to present well-known yeast species Y. lipolytica as a rare opportunistic fungal pathogen. Possible pathogenicity and epidemiology of this yeast species were discussed. Antifungal drugs susceptibility and increasing resistance to azoles in Y. lipolytica yeasts were also presented.
TL;DR: This review shows advances in biosurfactant production carried out using different waste materials or by-products from agro-industrial activities, aiming to reduce the accumulation of compounds that cause environmental damage.
Abstract: Biosurfactants are amphiphilic molecules produced by a variety of microorganisms, including bacteria, yeast and filamentous fungi. Unlike chemically synthesized surfactants, biosurfactants present advantages, such as biodegradability, low toxicity, high selectivity and activity under extreme temperature, pH and salinity conditions, as well as a low critical micelle concentration. Moreover, they can be produced from agro-industrial waste and renewable sources. Their structural diversity and functional properties mean that they have potential applications in various industrial processes as wetting agents, dispersants, emulsifiers, foaming agents, food additives and detergents, as well as in the field of environmental biotechnology. However, opportunities for their commercialization have been limited due to the low yields obtained in the fermentation processes involved in their production as well as the use of refined raw materials, which means higher cost in production. In an attempt to solve these limitations on the commercialization of biosurfactants, various research groups have focused on testing the use of inexpensive alternative sources, such as agro-industrial waste, as substrates for the production of different biosurfactants. In addition to enabling the economical production of biosurfactants, the use of such waste aims to reduce the accumulation of compounds that cause environmental damage. This review shows advances in biosurfactant production carried out using different waste materials or by-products from agro-industrial activities.
TL;DR: Experimental evidence on anti-biofilm activity of quercetin can open up new horizons in a wide range of biomedical areas, from food industry to medicine.
Abstract: Bacterial biofilms are multicellular aggregates enclosed in a self-created biopolymer matrix. Biofilm-producing bacteria have become a great public health problem worldwide because biofilms enable these microorganisms to evade several clearance mechanisms produced by host and synthetic sources. Over the past years, different flavonoids including quercetin have engrossed considerable interest among researchers owing to their potential anti-biofilm properties. To our knowledge, there is no review regarding effects of quercetin towards bacterial biofilms, prompting us to summarize experimental evidence on its anti-biofilm properties. Quercetin inhibits biofilm development by a diverse array of bacterial pathogens such as Enterococcus faecalis, Staphylococcus aureus, Streptococcus mutans, Escherichia coli, and Pseudomonas aeruginosa. Prevention of bacterial adhesion, suppression of quorum-sensing pathways, disruption or alteration of plasma membrane, inhibition of efflux pumps, and blocking nucleic acid synthesis have been documented as major anti-biofilm mechanisms of quercetin. Overall, anti-biofilm activity of quercetin can open up new horizons in a wide range of biomedical areas, from food industry to medicine.
TL;DR: The transcriptional profile supported the repair time frame observed in the phenotypic profile, but the complete repair may take a longer duration as the transcriptional levels of several important repair- related DEGs did not show a decrease and the DNA repair-related pathways were the major enriched pathway in Kyoto Encyclopaedia of Genes and Genomes pathway analysis throughout the whole course of the study.
Abstract: In this study, we examined the dynamics of phenotypic and transcriptional profiles in Saccharomyces cerevisiae following semi-lethal X-ray irradiation. Post-irradiation, reproductive death was revealed as the predominant form of death in S. cerevisiae and almost all the irradiated cells were physically present and intact. In addition, cell cycle arrest reached its peak and cell division was at its valley at 2 h. Cell cycle arrest, cell division potential, DNA damage, and mitochondrial transmembrane potential (MTP) showed significant recovery at 4 h (P > 0.05 vs. control). The improvements of DNA damage and MTP decrease were evaluated as at least 77% and 84% for the original irradiated cells at 4 h, respectively. In the transcriptional profile, the amount of differentially expressed genes (DEGs) and the fold change in the repair-related DEGs were highest at 1 h post-irradiation and then decreased. The DEGs at 1 h (but not 2 h or 3 h) were significantly enriched in gene ontology (GO) categories of detoxification (up) and antioxidant activity (up). Although the transcriptional profile supported the repair time frame observed in the phenotypic profile, the complete repair may take a longer duration as the transcriptional levels of several important repair-related DEGs did not show a decrease and the DNA repair-related pathways (up) were the major enriched pathway in Kyoto Encyclopaedia of Genes and Genomes pathway analysis throughout the whole course of the study. These results provide an important reference for the selection of key time points in further studies.
TL;DR: The yeast were able to grow and biosynthesize lipids and carotenoids in the presence of the applied stress factors and in oxidative stress conditions, yeast synthesized torulene more efficiently than under other conditions, whereas white light irradiation increased the production of torularhodin.
Abstract: In this study, we aimed to determine the effect of exogenous stress factors (sodium chloride as osmotic stressor, hydrogen peroxide as an inducer of oxidative stress, white light irradiation, and low temperature) on the biosynthesis of carotenoids and lipids by red yeast (Rhodotorula glutinis, R. mucilaginosa, and R. gracilis) during cultivation in media containing potato wastewater and glycerol. According to our results, the yeast were able to grow and biosynthesize lipids and carotenoids in the presence of the applied stress factors. Low temperature caused an increase in the biosynthesis of intracellular lipids and carotenoids. R. gracilis synthesized lipids (21.1 g/100 gd.w.) and carotenoids (360.4 µg/gd.w.) in greater quantities than that of other strains. Under these conditions, there was also an increase in the content of unsaturated fatty acids, especially linoleic and linolenic acids. The highest percentage of polyunsaturated fatty acid (PUFA) (30.4%) was synthesized by the R. gracilis yeast after cultivation at 20°C. Their quantity was 2.5-fold greater than that of the biomass grown in control conditions. The contribution of individual carotenoid fractions depended both on the yeast strain and the culture conditions. Induction of osmotic stress and low temperature intensified the biosynthesis of β-carotene (up to 73.9% of the total carotenoid content). In oxidative stress conditions, yeast synthesized torulene (up to 82.2%) more efficiently than under other conditions, whereas white light irradiation increased the production of torularhodin (up to 20.0%).
TL;DR: This study summarizes its biosynthesis, regulation, transportation, and subcellular location of enzymes in yeast, and advocates metabolic engineering and fermentation strategies for high-level production of ergosterol.
Abstract: Sterols are crucial functional components for eukaryotic cell membrane. Due to versatile activities, sterols show wide applications in food and pharmaceutical industries. Ergosterol not only reflects cell growth but also serves as the precursor for manufacturing steroid drugs. To date, the ergosterol biosynthetic pathway in yeast has been reported, and the industrial production of ergosterol is achieved by yeast fermentation or extraction from fungal mycelia. Here, we summarize its biosynthesis, regulation, transportation, and subcellular location of enzymes in yeast. In particular, we review the regulation of ergosterol biosynthesis at transcriptional, translational and post-translational levels. Furthermore, we advocate metabolic engineering and fermentation strategies for high-level production of ergosterol. This study may provide evaluable insights into metabolic engineering of yeast for scaled-up fermentation production of ergosterol or beyond.
TL;DR: The present review strives to clarify perspectives and critically discusses the advances and limitations of microbial chitinase in the further production of functional foods.
Abstract: Chitinases are a group of hydrolytic enzymes that catalyze chitin, nd are synthesized by a wide variety of organisms. In nature, microbial chitinases are primarily responsible for chitin decomposition. Several chitinases have been reported and characterized, and they are garnering increasing attention for their uses in a wide range of applications. In the food industry, the direct fermentation of seafood, such as crab and shrimp shells, using chitinolytic microorganisms has contributed to increased nutritional benefits through the enhancement of chitin degradation into chitooligosaccharides. These compounds have been demonstrated to improve human health through their antitumor, antimicrobial, immunomodulatory, antioxidant, and anti-inflammatory properties. Moreover, chitinase and chitinous materials are used in the food industry for other purposes, such as the production of single-cell proteins, chitooligosaccharides, N-acetyl D-glucosamines, biocontrol, functional foods, and various medicines. The functional properties and hydrolyzed products of chitinase, however, depend upon its source and physicochemical characteristics. The present review strives to clarify these perspectives and critically discusses the advances and limitations of microbial chitinase in the further production of functional foods.
TL;DR: Only environmentally safe construction biotechnologies should be used for such environmental and geotechnical engineering works as control of the seepage in dams, channels, landfills or tunnels, sealing of the channels and the ponds, prevention of soil erosion and soil dust emission, mitigation of soil liquefaction, and immobilization of soil pollutants.
Abstract: The topics of Construction Biotechnology are the development of construction biomaterials and construction biotechnologies for soil biocementation, biogrouting, biodesaturation, bioaggregation and biocoating. There are known different biochemical types of these biotechnologies. The most popular construction biotechnology is based on precipitation of calcium carbonate initiated by enzymatic hydrolysis of urea which follows with release of ammonia and ammonium to environment. This review focuses on the hazards and remedies for construction biotechnologies and on the novel environmentally friendly biotechnologies based on precipitation of hydroxyapatite, decay of calcium bicarbonate, and aerobic oxidation of calcium salts of organic acids. The use of enzymes or not living bacteria are the best options to ensure biosafety of construction biotechnologies. Only environmentally safe construction biotechnologies should be used for such environmental and geotechnical engineering works as control of the seepage in dams, channels, landfills or tunnels, sealing of the channels and the ponds, prevention of soil erosion and soil dust emission, mitigation of soil liquefaction, and immobilization of soil pollutants.
TL;DR: The electrons transported through the thermodynamically favourable pathway for the reduction to H2O (downhill pathway) and against the redox potential gradient reduce to NAD(P)(H) (uphill pathway) during the oxidation of Fe(II) were reviewed.
Abstract: Acidithiobacillus ferrooxidans is a gram-negative, autotrophic and rod-shaped bacterium. It can gain energy through the oxidation of Fe(II) and reduced inorganic sulfur compounds for bacterial growth when oxygen is sufficient. It can be used for bio-leaching and bio-oxidation and contributes to the geobiochemical circulation of metal elements and nutrients in acid mine drainage environments. The iron and sulfur oxidation pathways of A. ferrooxidans play key roles in bacterial growth and survival under extreme circumstances. Here, the electrons transported through the thermodynamically favourable pathway for the reduction to H2O (downhill pathway) and against the redox potential gradient reduce to NAD(P)(H) (uphill pathway) during the oxidation of Fe(II) were reviewed, mainly including the electron transport carrier, relevant operon and regulation of its expression. Similar to the electron transfer pathway, the sulfur oxidation pathway of A. ferrooxidans, related genes and operons, sulfur oxidation mechanism and sulfur oxidase system are systematically discussed.
TL;DR: Results showed that the optimized LAMP performed at 60 °C for 60 min, and LFD can specifically and visually detect M. ovipneumoniae with a minimum detectable concentration at 1.0 × 102 CFU/mL, a method that was highly specific, sensitive, and easy to operate, and provides a new method for the prevention and diagnosis of M. ovarian infection.
Abstract: In order to establish a rapid detection method for Mycoplasma ovipneumoniae, this study used the loop-mediated isothermal amplification (LAMP) technique to carry out nucleic acid amplification and chromatographic visualization via a lateral flow dipstick (LFD) assay. The M. ovipneumoniae elongation factor TU gene (EF-TU) was detected using a set of specific primers designed for the EF-TU gene, and the EF-TU FIP was detected by biotin labeling, which was used in the LAMP amplification reaction. The digoxin-labeled probe specifically hybridized with LAMP products, which were visually detected by LFD. Here, we established the M. ovipneumoniae LAMP-LFD rapid detection method and tested the specificity, sensitivity, and clinical application of this method. Results showed that the optimized LAMP performed at 60 °C for 60 min, and LFD can specifically and visually detect M. ovipneumoniae with a minimum detectable concentration at 1.0 × 102 CFU/mL. The sensitivity of LAMP-LFD was 1000 times that of the conventional PCR detection methods, and the clinical lung tissue detection rate was 86% of 50 suspected sheep infected with M. ovipneumoniae. In conclusion, LAMP-LFD was established in this study to detect M. ovipneumoniae, a method that was highly specific, sensitive, and easy to operate, and provides a new method for the prevention and diagnosis of M. ovipneumoniae infection.
TL;DR: The origin and environmental distribution of cyanide waste along with different bioremediation pathways and enzymes involved therein are discussed, which will help to recoup the environment from cyanide effluent.
Abstract: Cyanide is a nitrile which is used extensively in many industries like jewelry, mining, electroplating, plastics, dyes, paints, pharmaceuticals, food processing, and coal coking. Cyanides pose a serious health hazard due to their high affinity towards metals and cause malfunction of cellular respiration by inhibition of cytochrome c oxidase. This inhibition ultimately leads to histotoxic hypoxia, increased acidosis, reduced the functioning of the central nervous system and myocardial activity. Different physicochemical processes including oxidation by hydrogen peroxide, alkaline chlorination, and ozonization have been used to reduce cyanide waste from the environment. Microbial cyanide degradation which is considered as one the most successful techniques is used to take place through different biochemical/metabolic pathways involving reductive, oxidative, hydrolytic or substitution/transfer reactions. Groups of enzymes involved in microbial degradation are cyanidase, cyanide hydratase, formamidase, nitrilase, nitrile hydratase, cyanide dioxygenase, cyanide monooxygenase, cyanase and nitrogenase. In the future, more advancement of omics technologies and protein engineering will help us to recoup the environment from cyanide effluent. In this review, we have discussed the origin and environmental distribution of cyanide waste along with different bioremediation pathways and enzymes involved therein.
TL;DR: The status quo of the applications of Shewanella species in microbial fuel cells for bioelectricity generation, microbial electrosynthesis for biotransformation of valuable chemicals and bioremediation of environment-hazardous pollutants with synoptical discussion on their EET mechanism is summarized.
Abstract: Microbial electrochemical system (MES) has attracted ever-growing interest as a promising platform for renewable energy conversion and bioelectrochemical remediation. Shewanella species, the dissimilatory metal reduction model bacteria with versatile extracellular electron transfer (EET) strategies, are the well-received microorganisms in diverse MES devices for various practical applications as well as microbial EET mechanism investigation. Meanwhile, the available genomic information and the unceasing established gene-editing toolbox offer an unprecedented opportunity to boost the applications of Shewanella species in MES. This review thoroughly summarizes the status quo of the applications of Shewanella species in microbial fuel cells for bioelectricity generation, microbial electrosynthesis for biotransformation of valuable chemicals and bioremediation of environment-hazardous pollutants with synoptical discussion on their EET mechanism. Recent advances in rational design and genetic engineering of Shewanella strains for either promoting the MES performance or broadening their applications are surveyed. Moreover, some emerging applications beyond electricity generation, such as biosensing and biocomputing, are also documented. The challenges and perspectives for Shewanella-based MES are also discussed elaborately for the sake of not only discovering new scientific lights on microbial extracellular respiratory but also propelling practical applications.