Showing papers in "Applied Microbiology and Biotechnology in 2003"
TL;DR: An overview of the most frequently used and interesting recombinant hybrids containing a polypeptide fusion partner, termed affinity tag, to facilitate the purification of the targetpolypeptides are given.
Abstract: In response to the rapidly growing field of proteomics, the use of recombinant proteins has increased greatly in recent years. Recombinant hybrids containing a polypeptide fusion partner, termed affinity tag, to facilitate the purification of the target polypeptides are widely used. Many different proteins, domains, or peptides can be fused with the target protein. The advantages of using fusion proteins to facilitate purification and detection of recombinant proteins are well-recognized. Nevertheless, it is difficult to choose the right purification system for a specific protein of interest. This review gives an overview of the most frequently used and interesting systems: Arg-tag, calmodulin-binding peptide, cellulose-binding domain, DsbA, c-myc-tag, glutathione S-transferase, FLAG-tag, HAT-tag, His-tag, maltose-binding protein, NusA, S-tag, SBP-tag, Strep-tag, and thioredoxin.
1,521 citations
TL;DR: In this paper, the authors show that the dominance of At. ferrooxidans or Leptospirillum in mesophilic leaching habitats is highly likely to result from differences in their biochemical iron(II) oxidation pathways, especially the involvement of rusticyanin.
Abstract: Bioleaching of metal sulfides is caused by astonishingly diverse groups of bacteria. Today, at least 11 putative prokaryotic divisions can be related to this phenomenon. In contrast, the dissolution (bio)chemistry of metal sulfides follows only two pathways, which are determined by the acid-solubility of the sulfides: the thiosulfate and the polysulfide pathway. The bacterial cell can effect this sulfide dissolution by “contact” and “non-contact” mechanisms. The non-contact mechanism assumes that the bacteria oxidize only dissolved iron(II) ions to iron(III) ions. The latter can then attack metal sulfides and be reduced to iron(II) ions. The contact mechanism requires attachment of bacteria to the sulfide surface. The primary mechanism for attachment to pyrite is electrostatic in nature. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions in the contact mechanism is mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in the non-contact mechanism. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a complex redox chain located below the outer membrane, the periplasmic space, and the cytoplasmic membrane of leaching bacteria. The dominance of either At. ferrooxidans or Leptospirillum ferrooxidans in mesophilic leaching habitats is highly likely to result from differences in their biochemical iron(II) oxidation pathways, especially the involvement of rusticyanin.
1,033 citations
TL;DR: The lack of industrially suitable microorganisms for converting biomass into fuel ethanol has traditionally been cited as a major technical roadblock to developing a bioethanol industry, but in the last two decades, numerous microorganisms have been engineered to selectively produce ethanol.
Abstract: The lack of industrially suitable microorganisms for converting biomass into fuel ethanol has traditionally been cited as a major technical roadblock to developing a bioethanol industry. In the last two decades, numerous microorganisms have been engineered to selectively produce ethanol. Lignocellulosic biomass contains complex carbohydrates that necessitate utilizing microorganisms capable of fermenting sugars not fermentable by brewers' yeast. The most significant of these is xylose. The greatest successes have been in the engineering of Gram-negative bacteria: Escherichia coli, Klebsiella oxytoca, and Zymomonas mobilis. E. coli and K. oxytoca are naturally able to use a wide spectrum of sugars, and work has concentrated on engineering these strains to selectively produce ethanol. Z. mobilis produces ethanol at high yields, but ferments only glucose and fructose. Work on this organism has concentrated on introducing pathways for the fermentation of arabinose and xylose. The history of constructing these strains and current progress in refining them are detailed in this review.
788 citations
TL;DR: This review describes the variety of sterol structures found in microalgae, yeasts, fungi, protozoans and microheterotrophs, and possible application areas for sterols derived from mass culture of micro algae and other microorganisms are highlighted.
Abstract: Sterols are vital components of all eukaryotic cells. This review describes the variety of sterol structures found in microalgae, yeasts, fungi, protozoans and microheterotrophs. Reports of the occurrence of sterols in prokaryotic cells are critically assessed. Methylotrophic bacteria contain unusual 4-methylsterols, but reports of 4-desmethyl sterols in cyanobacteria and other bacteria are limited and many of these seem dubious. Possible application areas for sterols derived from mass culture of microalgae and other microorganisms are highlighted.
743 citations
TL;DR: This review will concentrate on examples of work with entomopathogenic fungi, which illustrate the principles or strategies which can be used to reduce losses by insect pests.
Abstract: The Order Insecta contains nearly one million described species (May 2000) which comprise approximately 67% of the world’s described fauna and flora. Insects are central to the performance of many ecosystem processes. However, it is in their role as herbivores that conflicts arise with agricultural production due to direct consumption of cultivated crops and indirect damage by plant virus transmission or spoilage of potential yield. Natural enemies such as predators, parasitic wasps and flies, as well as pathogens have long been studied for exploitation in biological control and integrated pest management (IPM) strategies. For the purposes of this review, we will concentrate on examples of work with entomopathogenic fungi, which illustrate the principles or strategies which can be used to reduce losses by insect pests.
591 citations
TL;DR: A novel methodology that merges genomics with classical strain improvement has been developed and applied for the reconstruction of classically derived production strains and the path from genomics to biotechnological processes is presented.
Abstract: Corynebacterium glutamicum has played a principal role in the progress of the amino acid fermentation industry. The complete genome sequence of the representative wild-type strain of C. glutamicum, ATCC 13032, has been determined and analyzed to improve our understanding of the molecular biology and physiology of this organism, and to advance the development of more efficient production strains. Genome annotation has helped in elucidation of the gene repertoire defining a desired pathway, which is accelerating pathway engineering. Post genome technologies such as DNA arrays and proteomics are currently undergoing rapid development in C. glutamicum. Such progress has already exposed new regulatory networks and functions that had so far been unidentified in this microbe. The next goal of these studies is to integrate the fruits of genomics into strain development technology. A novel methodology that merges genomics with classical strain improvement has been developed and applied for the reconstruction of classically derived production strains. How can traditional fermentation benefit from the C. glutamicum genomic data? The path from genomics to biotechnological processes is presented.
548 citations
TL;DR: A review of the industrially most relevant exudate gums: gum arabic, gum karya, and gum tragacanth, which covers the chemical structure, occurrence and production of the different gums.
Abstract: This paper presents a review of the industrially most relevant exudate gums: gum arabic, gum karya, and gum tragacanth. Exudate gums are obtained as the natural exudates of different tree species and exhibit unique properties in a wide variety of applications. This review covers the chemical structure, occurrence and production of the different gums. It also deals with the size and relative importance of the various players on the world market. Furthermore, it gives an overview of the main application fields of the different gums, both food and non-food.
518 citations
TL;DR: Non-viral vectors, although less efficient at introducing and maintaining foreign gene expression, have the profound advantage of being non-pathogenic and non-immunogenic; they are the subject of this review and could be further modified with cell- targeting ligands to enhance their utility for in vivo applications.
Abstract: Gene therapy, i.e., the expression in cells of genetic material with therapeutic activity, holds great promise for the treatment of human diseases. A delivery vehicle (vector), of either viral or non-viral origin, must be used to carry the foreign gene into a cell. Viral vectors take advantage of the facile integration of the gene of interest into the host and high probability of its long-term expression but are plagued by safety concerns. Non-viral vectors, although less efficient at introducing and maintaining foreign gene expression, have the profound advantage of being non-pathogenic and non-immunogenic; they are the subject of this review. Polycation-DNA complexes are particularly attractive for non-viral gene therapy. To perform, they have to attach to the target cell surface, be internalized, escape from endosomes, find a way to the nucleus, and, finally, be available for transcription. The clinical usefulness of polycationic vectors depends on elucidating the role each of these steps plays in gene transfer. Recent progress in consequent rational vector improvement is highlighted by our finding of polyethylenimine derivatives more potent and yet less cytotoxic than the 25-kDa polyethylenimine (one of the most effective non-viral vectors). Such vectors could be further modified with cell-targeting ligands to enhance their utility for in vivo applications.
497 citations
TL;DR: The industrial production of beta-lactam antibiotics by fermentation over the past 50 years is one of the outstanding examples of biotechnology as mentioned in this paper, and major improvements in the productivity of the producer organisms, Penicillium chrysogenum (syn. Cephalosporium acremonium) and improved fermentation technology have culminated in enhanced productivity and substantial cost reduction.
Abstract: The industrial production of beta-lactam antibiotics by fermentation over the past 50 years is one of the outstanding examples of biotechnology. Today, the beta-lactam antibiotics, particularly penicillins and cephalosporins, represent the world's major biotechnology products with worldwide dosage form sales of approximately 15 billion US dollars or approximately 65% of the total world market for antibiotics. Over the past five decades, major improvements in the productivity of the producer organisms, Penicillium chrysogenum and Acremonium chrysogenum (syn. Cephalosporium acremonium) and improved fermentation technology have culminated in enhanced productivity and substantial cost reduction. Major fermentation producers are now estimated to record harvest titers of 40-50 g/l for penicillin and 20-25 g/l for cephalosporin C. Recovery yields for penicillin G or penicillin V are now >90%. Chemical and enzymatic hydrolysis process technology for 6-aminopenicillanic acid or 7-aminocephalosporanic acid is also highly efficient (approximately 80-90%) with new enzyme technology leading to major cost reductions over the past decade. Europe remains the dominant manufacturing area for both penicillins and cephalosporins. However, due to ever increasing labor, energy and raw material costs, more bulk manufacturing is moving to the Far East, with China, Korea and India becoming major production countries with dosage form filling becoming more dominant in Puerto Rico and in Ireland.
490 citations
TL;DR: A review of the historical development and current state of metals leaching and sulfide mineral biooxidation by the minerals industries can be found in this paper, where the authors describe the main steps in this area.
Abstract: This review describes the historical development and current state of metals leaching and sulfide mineral biooxidation by the minerals industries. During the past 20 years commercial processes employing microorganisms for mineral recovery have progressed from rather uncontrolled copper dump leaching to mineral oxidation and leaching in designed bioheaps for oxidation of refractory gold ores and for copper recovery. Also during this period of time, stirred tank bioleaching has been commercialized for cobalt recovery and for biooxidation of refractory gold ores. Chalcopyrite bioleaching in stirred tanks is on the verge of commercialization. Commercial applications of biohydrometallurgy have advanced due to favorable process economics and, in some cases, reduced environmental problems compared to conventional metal recovery processes such as smelting. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.
448 citations
TL;DR: This review describes certain factors for the phytoremediation of metal ion decontamination and various aspects of plant metabolism during metallic decontamination.
Abstract: In recent years, phytoremediation has emerged as a promising ecoremediation technology, particularly for soil and water cleanup of large volumes of contaminated sites. The exploitation of plants to remediate soils contaminated with trace elements could provide a cheap and sustainable technology for bioremediation. Many modern tools and analytical devices have provided insight into the selection and optimization of the remediation process by plant species. This review describes certain factors for the phytoremediation of metal ion decontamination and various aspects of plant metabolism during metallic decontamination. Metal-hyperaccumulating plants, desirable for heavily polluted environments, can be developed by the introduction of novel traits into high biomass plants in a transgenic approach, which is a promising strategy for the development of effective phytoremediation technology. The genetic manipulation of a phytoremediator plant needs a number of optimization processes, including mobilization of trace elements/metal ions, their uptake into the root, stem and other viable parts of the plant and their detoxification and allocation within the plant. This upcoming science is expanding as technology continues to offer new, low-cost remediation options.
TL;DR: The last few years have seen a resurgence in interest in pullulan, particularly for higher-value health and pharmaceutical applications, and few of these potential uses have been widely adopted.
Abstract: Pullulan is a unique biopolymer with many useful traits and hundreds of patented applications. However, despite the fact that pullulan has been in commercial production for more than 25 years, few of these potential uses have been widely adopted. In large part this may be due to the relatively high price of pullulan. Nevertheless, the last few years have seen a resurgence in interest in pullulan, particularly for higher-value health and pharmaceutical applications.
TL;DR: In so-called lower termites, a dual decomposing system, consisting of the termite's own cellulases and those of its gut protists, was elucidated at the molecular level, and the nature of symbioses in the gut shows a highly structured spatial organization.
Abstract: Termites thrive in great abundance in terrestrial ecosystems and play important roles in biorecycling of lignocellulose. Together with their microbial symbionts, they efficiently decompose lignocellulose. In so-called lower termites, a dual decomposing system, consisting of the termite's own cellulases and those of its gut protists, was elucidated at the molecular level. Higher termites degrade cellulose apparently using only their own enzymes, because of the absence of symbiotic protists. Termite gut prokaryotes efficiently support lignocellulose degradation. However, culture-independent molecular studies have revealed that the majority of these gut symbionts have not yet been cultivated, and that the gut symbiotic community shows a highly structured spatial organization. In situ localization of individual populations and their functional interactions are important to understand the nature of symbioses in the gut. In contrast to cellulose, lignin degradation does not appear to be important in the gut of wood-feeding termites. Soil-feeding termites decompose humic substances in soil at least partly, but little is known about the decomposition. Fungus-growing termites are successful in the almost complete decomposition of lignocellulose in a sophisticated cooperation with basidiomycete fungi cultivated in their nest. A detailed understanding of efficient biorecycling systems, such as that for lignocellulose, and the symbioses that provide this efficiency will benefit applied microbiology and biotechnology.
TL;DR: The mechanism of the inhibitory effect of ε-PL on microbial growth is the electrostatic adsorption to the cell surface of microorganisms on the basis of its poly-cationic property.
Abstract: e-Poly-l-lysine (e-PL) is a homo-poly-amino acid characterized by the peptide bond between the carboxyl and e-amino groups of l-lysine. e-PL shows a wide range of antimicrobial activity and is stable at high temperatures and under both acidic and alkaline conditions. The mechanism of the inhibitory effect of e-PL on microbial growth is the electrostatic adsorption to the cell surface of microorganisms on the basis of its poly-cationic property. Due to this antimicrobial activity, e-PL is now industrially produced in Japan as a food additive by a fermentation process using Streptomyces albulus. In spite of the practical application of e-PL, the biosynthetic mechanisms of e-PL have not been clarified at all. e-PL producers commonly possess membrane-bound e-PL-degrading aminopeptidase, which might play a role in self-protection.
TL;DR: Media and growth conditions were optimized for the microaerobic cultivation of Magnetospirillum gryphiswaldense in flasks and in a fermentor, resulting in significantly increased cell and magnetosome yields, compared with earlier studies, and provide the basis for large-scale cultivation of magnetospirilla under defined conditions.
Abstract: Media and growth conditions were optimized for the microaerobic cultivation of Magnetospirillum gryphiswaldense in flasks and in a fermentor, resulting in significantly increased cell and magnetosome yields, compared with earlier studies A reliable method was established for the automatic control of low dissolved oxygen tensions (pO2) in the fermentor (oxystat) Growth and magnetosome formation by M gryphiswaldense, M magnetotacticum and Magnetospirillum sp AMB-1 were studied at various oxygen concentrations Despite differences in their growth responses with respect to oxygen, we found a clear correlation between pO2 and magnetosome formation in all three Magnetospirillum strains Magnetite biomineralization was induced only below a threshold value of 20 mbar O2 and optimum conditions for magnetosome formation were found at a pO2 of 025 mbar (1 bar = 105 Pa) A maximum yield of 63 mg magnetite l-1 day-1 was obtained with M gryphiswaldense grown under oxystat conditions, which is the highest magnetosome productivity reported so far for a magnetotactic bacterium In conclusion, the presented results provide the basis for large-scale cultivation of magnetospirilla under defined conditions
TL;DR: In this review, the various parameters that influence flocculation in real-scale brewing are critically discussed and many of the conclusions will also be useful in various other industrial processes where control over yeast flocculations is desirable.
Abstract: For many industrial applications in which the yeast Saccharomyces cerevisiae is used, e.g. beer, wine and alcohol production, appropriate flocculation behaviour is certainly one of the most important characteristics of a good production strain. Yeast flocculation is a very complex process that depends on the expression of specific flocculation genes such as FLO1, FLO5, FLO8 and FLO11. The transcriptional activity of the flocculation genes is influenced by the nutritional status of the yeast cells as well as other stress factors. Flocculation is also controlled by factors that affect cell wall composition or morphology. This implies that, during industrial fermentation processes, flocculation is affected by numerous parameters such as nutrient conditions, dissolved oxygen, pH, fermentation temperature, and yeast handling and storage conditions. Theoretically, rational use of these parameters offers the possibility of gaining control over the flocculation process. However, flocculation is a very strain-specific phenomenon, making it difficult to predict specific responses. In addition, certain genes involved in flocculation are extremely variable, causing frequent changes in the flocculation profile of some strains. Therefore, both a profound knowledge of flocculation theory as well as close monitoring and characterisation of the production strain are essential in order to gain maximal control over flocculation. In this review, the various parameters that influence flocculation in real-scale brewing are critically discussed. However, many of the conclusions will also be useful in various other industrial processes where control over yeast flocculation is desirable.
TL;DR: Insect cells used in conjunction with the baculovirus expression vector system (BEVS) are gaining ground rapidly as a platform for recombinant protein production, and engineering issues related to high-density culture are addressed in view of their relevance to large-scale culture.
Abstract: Insect cells used in conjunction with the baculovirus expression vector system (BEVS) are gaining ground rapidly as a platform for recombinant protein production. Insect cells present several comparative advantages to mammalian cells, such as ease of culture, higher tolerance to osmolality and by-product concentration and higher expression levels when infected with a recombinant baculovirus. Here we review some of the recent developments in protein expression by insect cells and their potential application in large-scale culture. Our current knowledge of insect cell metabolism is summarised and emphasis is placed on elements useful in the rational design of serum-free media. The culture of insect cells in the absence of serum is reaching maturity, and promising serum substitutes (hydrolysates, new growth and production-enhancing factors) are being evaluated. Proteolysis is a problem of the BEVS system due to its lytic nature, and can, therefore, be a critical issue in insect cell bioprocessing. Several cell- or baculovirus proteases are involved in degradation events during protein production by insect cells. Methods for proteolysis control, the optimal inhibitors and culture and storage conditions which affect proteolysis are discussed. Finally, engineering issues related to high-density culture (new bioreactor types, gas exchange, feeding strategies) are addressed in view of their relevance to large-scale culture.
TL;DR: The present review summarizes molecular details of fungal siderophore biosynthesis and uptake, and the regulatory mechanisms involved in control of the corresponding genes.
Abstract: To acquire iron, all species have to overcome the problems of iron insolubility and toxicity. In response to low iron availability in the environment, most fungi excrete ferric iron-specific chelators—siderophores—to mobilize this metal. Siderophore-bound iron is subsequently utilized via the reductive iron assimilatory system or uptake of the siderophore-iron complex. Furthermore, most fungi possess intracellular siderophores as iron storage compounds. Molecular analysis of siderophore biosynthesis was initiated by pioneering studies on the basidiomycete Ustilago maydis, and has progressed recently by characterization of the relevant structural and regulatory genes in the ascomycetes Aspergillus nidulans and Neurospora crassa. In addition, significant advances in the understanding of utilization of siderophore-bound iron have been made recently in the yeasts Saccharomyces cerevisiae and Candida albicans as well as in the filamentous fungus A. nidulans. The present review summarizes molecular details of fungal siderophore biosynthesis and uptake, and the regulatory mechanisms involved in control of the corresponding genes.
TL;DR: This Mini-Review summarizes the current knowledge on the biochemical and physiological events leading to massive citric acid accumulation by Aspergillus niger under industrially comparable conditions, thereby particularly emphasizing the roles of glycolytic flux and its control, excretion ofcitric acid from the mitochondria and the cytosol, and the critical fermentation variables.
Abstract: This Mini-Review summarizes the current knowledge on the biochemical and physiological events leading to massive citric acid accumulation by Aspergillus niger under industrially comparable conditions, thereby particularly emphasizing the roles of glycolytic flux and its control, excretion of citric acid from the mitochondria and the cytosol, and the critical fermentation variables The potential of novel techniques for metabolic analysis and genomic approaches in understanding this fermentation is also discussed
TL;DR: MBFA9 is nontoxic and can be used in food industries for suspended solids recovery and when applied to starch wastewater treatment, MBFA9 greatly accelerated the formation of flocs and the settling of organic particles in the presence of Ca2+ salt.
Abstract: A bioflocculant, MBFA9, was produced from a strain of bioflocculant-producing bacteria isolated from a soil sample and identified as Bacillus mucilaginosus. MBFA9 had a good flocculating capability and could achieve a flocculating rate of 99.6% for kaolin suspension at a dosage of only 0.1 ml/l. The major component of MBFA9 was found to be polysaccharide composed mainly of uronic acid (19.1%), neutral sugar (47.4%) and amino sugar (2.7%). Infrared spectrum analysis showed the presence of carboxyl and hydroxyl groups in the bioflocculant. MBFA9 is nontoxic and can be used in food industries for suspended solids (SS) recovery. When applied to starch wastewater treatment, MBFA9 greatly accelerated the formation of flocs and the settling of organic particles in the presence of Ca2+ salt. After 5 min of settling, the removal rate of SS and chemical oxygen demand were up to 85.5% and 68.5%, respectively, which is better than traditional chemical flocculants.
TL;DR: It is hypothesized that growth-associated extracellular biosurfactant production and modulation of cell surface hydrophobicity plays an important role in hydrocarbon assimilation/uptake in Pseudomonas sp.
Abstract: Pseudomonas sp. strain PP2 isolated in our laboratory efficiently metabolizes phenanthrene at 0.3% concentration as the sole source of carbon and energy. The metabolic pathways for the degradation of phenanthrene, benzoate and p-hydroxybenzoate were elucidated by identifying metabolites, biotransformation studies, oxygen uptake by whole cells on probable metabolic intermediates, and monitoring enzyme activities in cell-free extracts. The results obtained suggest that phenanthrene degradation is initiated by double hydroxylation resulting in the formation of 3,4-dihydroxyphenanthrene. The diol was finally oxidized to 2-hydroxymuconic semialdehyde. Detection of 1-hydroxy-2-naphthoic acid, α-naphthol, 1,2-dihydroxy naphthalene, and salicylate in the spent medium by thin layer chromatography; the presence of 1,2-dihydroxynaphthalene dioxygenase, salicylaldehyde dehydrogenase and catechol-2,3-dioxygenase activity in the extract; O2 uptake by cells on α-naphthol, 1,2-dihydroxynaphthalene, salicylaldehyde, salicylate and catechol; and no O2 uptake on o-phthalate and 3,4-dihydroxybenzoate supports the novel route of metabolism of phenanthrene via 1-hydroxy-2-naphthoic acid → [α-naphthol] → 1,2-dihydroxy naphthalene → salicylate → catechol. The strain degrades benzoate via catechol and cis,cis-muconic acid, and p-hydroxybenzoate via 3,4-dihydroxybenzoate and 3-carboxy-cis,cis-muconic acid. Interestingly, the culture failed to grow on naphthalene. When grown on either hydrocarbon or dextrose, the culture showed good extracellular biosurfactant production. Growth-dependent changes in the cell surface hydrophobicity, and emulsification activity experiments suggest that: (1) production of biosurfactant was constitutive and growth-associated, (2) production was higher when cells were grown on phenanthrene as compared to dextrose and benzoate, (3) hydrocarbon-grown cells were more hydrophobic and showed higher affinity towards both aromatic and aliphatic hydrocarbons compared to dextrose-grown cells, and (4) mid-log-phase cells were significantly (2-fold) more hydrophobic than stationary phase cells. Based on these results, we hypothesize that growth-associated extracellular biosurfactant production and modulation of cell surface hydrophobicity plays an important role in hydrocarbon assimilation/uptake in Pseudomonas sp. strain PP2.
TL;DR: The present review includes the considerable progress made in the characterization of plant P-450 limonene hydroxylases and the cloning of the encoding genes.
Abstract: The past 5 years have seen significant progress in the field of limonene biotransformation, especially with regard to the regiospecificity of microbial biocatalysts. Whereas earlier only regiospecific biocatalysts for the 1,2 position (limonene-1,2-diol) and the 8-position (α-terpineol) were available, recent reports describe microbial biocatalysts specifically hydroxylating the 3-position (isopiperitenol), 6-position (carveol and carvone), and 7-position (perillyl alcohol, perillylaaldehyde, and perillic acid). The present review also includes the considerable progress made in the characterization of plant P-450 limonene hydroxylases and the cloning of the encoding genes.
TL;DR: This review reports recent advances in knowledge of the fungal degradation of microbial and synthetic polyesters and discusses the ecological importance and contribution of fungi in the biological recycling of waste polymeric materials in the biosphere.
Abstract: A variety of biodegradable polyesters have been developed in order to obtain useful biomaterials and to reduce the impact of environmental pollution caused by the large-scale accumulation of non-degradable waste plastics. Polyhydroxyalkanoates, poly(e-caprolactone), poly(l-lactide), and both aliphatic and aromatic polyalkylene dicarboxylic acids are examples of biodegradable polyesters. In general, most aliphatic polyesters are readily mineralized by a number of aerobic and anaerobic microorganisms that are widely distributed in nature. However, aromatic polyesters are more resistant to microbial attack than aliphatic polyesters. The fungal biomass in soils generally exceeds the bacterial biomass and thus it is likely that fungi may play a considerable role in degrading polyesters, just as they predominantly perform the decomposition of organic matter in the soil ecosystem. However, in contrast to bacterial polyester degradation, which has been extensively investigated, the microbiological and environmental aspects of fungal degradation of polyesters are unclear. This review reports recent advances in our knowledge of the fungal degradation of microbial and synthetic polyesters and discusses the ecological importance and contribution of fungi in the biological recycling of waste polymeric materials in the biosphere.
TL;DR: This review focuses on the establishment of a novel bioreduction system using an Escherichia coli transformant co-expressing genes for carbonyl reductase and cofactor-regeneration enzyme that could be useful as an all-purpose catalyst for asymmetric reduction reactions.
Abstract: Chiral alcohols are useful intermediates for many pharmaceuticals and chemicals. Enzymatic asymmetric reduction of prochiral carbonyl compounds is a promising method for producing chiral alcohols. There have been many attempts to construct bioreduction systems for the industrial production of chiral alcohols. This review focuses on the establishment of a novel bioreduction system using an Escherichia coli transformant co-expressing genes for carbonyl reductase and cofactor-regeneration enzyme. This bioreduction system could be useful as an all-purpose catalyst for asymmetric reduction reactions.
TL;DR: This mini-review summarises the considerable amount of data accumulated over the past three decades regarding promoters of genes encoding hydrolytic enzymes, inducer molecules, and models for the recognition of the insoluble substrates cellulose and xylan.
Abstract: The genus Trichoderma comprises a group of filamentous ascomycetes that are now widely used in industrial applications because of their ability to produce extracellular hydrolases in large amounts. In addition, strong inducible promoters together with high secretory capacity have made Trichoderma an attractive host for heterologous protein production. Several promoters of genes encoding hydrolytic enzymes have been investigated in detail regarding their cis-acting elements and trans-acting factors. Potent inducer molecules, for both xylanolytic and cellulolytic enzyme systems, have been identified and characterized. Furthermore, models for the recognition of the insoluble substrates cellulose and xylan have been developed based on a large set of experiments. This mini-review summarises the considerable amount of data accumulated over the past three decades.
TL;DR: A summary of biotin biosynthesis and its biological role is presented; and current strategies for the improvement of microbial biotin production using modern biotechnological techniques are discussed.
Abstract: Biotin (vitamin H) is one of the most fascinating cofactors involved in central pathways in pro- and eukaryotic cell metabolism. Since its original discovery in 1901, research has led to the discovery of the complete biotin biosynthesis pathways in many different microbes and much work has been done on the highly intriguing and complex biochemistry of biotin biosynthesis. While humans and animals require several hundred micrograms of biotin per day, most microbes, plants and fungi appear to be able to synthesize the cofactor themselves. Biotin is added to many food, feed and cosmetic products, creating a world market of 10–30 t/year. However, the majority of the biotin sold is synthesized in a chemical process. Since the chemical synthesis is linked with a high environmental burden, much effort has been put into the development of biotin-overproducing microbes. A summary of biotin biosynthesis and its biological role is presented; and current strategies for the improvement of microbial biotin production using modern biotechnological techniques are discussed.
TL;DR: The characterization of genes involved in aflatoxins formation affords the opportunity to examine the mechanism of molecular regulation of the aflatoxin biosynthetic pathway, particularly during the interaction between a flatoxin-producing fungi and plants.
Abstract: Aflatoxins, produced by some Aspergillus species, are toxic and extremely carcinogenic furanocoumarins. Recent investigations of the molecular mechanism of AFB biosynthesis showed that the genes required for biosynthesis are in a 70 kb gene cluster. They encode a DNA-binding protein functioning in aflatoxin pathway gene regulation, and other enzymes such as cytochrome P450-type monooxygenases, dehydrogenases, methyltransferases, and polyketide and fatty acid synthases. Information gained from these studies has led to a better understanding of aflatoxin biosynthesis by these fungi. The characterization of genes involved in aflatoxin formation affords the opportunity to examine the mechanism of molecular regulation of the aflatoxin biosynthetic pathway, particularly during the interaction between aflatoxin-producing fungi and plants.
TL;DR: An overview of biotechnological techniques, mainly based on solubilization processes involving agro-industrial residues, is presented, and potential advantages of composting, solid-state fermentation, and liquid submerged fermentation employing free and immobilized microorganisms that produce organic acids and simultaneouslysolubilize RP are discussed.
Abstract: Rock phosphate (RP) is an important natural material traditionally used for the production of phosphorus (P) fertilizers. Compared with chemical treatment, microbial solubilization of RP is an alternative environmentally mild approach. An overview of biotechnological techniques, mainly based on solubilization processes involving agro-industrial residues, is presented. Potential advantages of composting, solid-state fermentation, and liquid submerged fermentation employing free and immobilized microorganisms that produce organic acids and simultaneously solubilize RP are discussed. Subsequent introduction of the final fermented products into soil-plant systems promotes plant growth and P acquisition.
TL;DR: Regulation of the main metabolic pathways of Escherichia coli K12 was investigated based on 2-dimensional electrophoresis (2DE) and the measurement of enzyme activities, and protein abundance obtained by 2DE correlated well with enzyme activity, with a few exceptions.
Abstract: Regulation of the main metabolic pathways of Escherichia coli K12 was investigated based on 2-dimensional electrophoresis (2DE) and the measurement of enzyme activities. The cells were grown aerobically in different carbon sources, such as glucose, acetate, gluconate or glycerol. Microaerobic cultivation was also conducted with glucose as a carbon source. Fifty-two proteins could be identified based on 2DE, and 26 enzyme activities from the main metabolic pathways—including glycolysis, pentose phosphate pathway, TCA cycle, Entner-Doudoroff pathway and fermentative pathway—were assayed. These enzyme activities, together with global and quantitative protein expression, gave us a clear picture of metabolic regulation. The results show that, compared with the control experiment with glucose as a carbon source under aerobic conditions, glycolytic enzymes were slightly up-regulated ( 10-fold) under microaerobic conditions in glucose medium. When acetate was used as a carbon source, pfkA, pykF, ppc and zwf were down-regulated, while fbp, pckA, ppsA and mez were significantly up-regulated. Glyoxylate enzymes such as aceA and aceB were strongly up-regulated (>10-fold) and TCA-cycle-related enzymes were also up-regulated to some extent. With gluconate as a carbon source, edd, eda, fbp and TCA cycle enzymes were up-regulated. With glycerol as a carbon source, fbp and TCA cycle enzymes were up-regulated, while ackA was significantly down-regulated. Protein abundance obtained by 2DE correlated well with enzyme activity, with a few exceptions (e.g., isocitrate dehydrogenase), during aerobic growth on acetate.
TL;DR: This review describes the most recent developments in the biotechnological applications of penicillin acylases, including advances in detection of new enzyme specificities towards other natural penicillins, enzyme immobilization, and optimization of enzyme-catalyzed hydrolysis and synthesis in the presence of organic solvents.
Abstract: This review describes the most recent developments in the biotechnological applications of penicillin acylases. This group of enzymes is involved mainly in the industrial production of 6-aminopenicillanic acid and the synthesis of semisynthetic β-lactam antibiotics. In addition, penicillin acylases can also be employed in other useful biotransformations, such as peptide synthesis and the resolution of racemic mixtures of chiral compounds. Particular emphasis is placed on advances in detection of new enzyme specificities towards other natural penicillins, enzyme immobilization, and optimization of enzyme-catalyzed hydrolysis and synthesis in the presence of organic solvents.