Letizia Fracchia

Bio: Letizia Fracchia is an academic researcher from University of Eastern Piedmont. The author has contributed to research in topics: Biofilm & Candida albicans. The author has an hindex of 16, co-authored 34 publications receiving 2018 citations.

Microbial biosurfactants production, applications and future potential

Abstract: Microorganisms synthesise a wide range of surface-active compounds (SAC), generally called biosurfactants. These compounds are mainly classified according to their molecular weight, physico-chemical properties and mode of action. The low-molecular-weight SACs or biosurfactants reduce the surface tension at the air/water interfaces and the interfacial tension at oil/water interfaces, whereas the high-molecular-weight SACs, also called bioemulsifiers, are more effective in stabilising oil-in-water emulsions. Biosurfactants are attracting much interest due to their potential advantages over their synthetic counterparts in many fields spanning environmental, food, biomedical, and other industrial applications. Their large-scale application and production, however, are currently limited by the high cost of production and by limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and the latest advances in biosurfactant applications and the biotechnological strategies being developed for improving production processes and future potential.

Bacterial diversity in a finished compost and vermicompost: differences revealed by cultivation-independent analyses of PCR-amplified 16S rRNA genes.

Abstract: Bacterial communities are important catalysts in the production of composts. Here, it was analysed whether the diversity of bacteria in finished composts is stable and specific for the production process. Single-strand conformation polymorphism (SSCP) based on polymerase chain reaction amplified partial 16S rRNA genes was used to profile and analyse bacterial communities found in total DNA extracted from finished composts. Different batches of compost samples stored over a period of 12 years and a 1-year-old vermicompost were compared to each other. According to digital image analysis, clear differences could be detected between the profiles from compost and vermicompost. Differences between three different periods of compost storage and between replicate vermicompost windrows were only minor. A total of 41 different 16S rRNA genes were identified from the SSCP profiles by DNA sequencing, with the vast majority related to yet-uncultivated bacteria. Sequences retrieved from compost mainly belonged to the phyla Actinobacteria and Firmicutes. In contrast, vermicompost was dominated by bacteria related to uncultured Chloroflexi, Acidobacteria, Bacteroidetes and Gemmatimonadetes. The differences were underscored with specific gene probes and Southern blot hybridizations. The results confirmed that different substrates and composting processes selected for specific bacterial communities in the finished products. The specificity and consistency of the bacterial communities inhabiting the compost materials suggest that cultivation-independent bacterial community analysis is a potentially useful indicator to characterize the quality of finished composts in regard to production processes and effects of storage conditions.

Biosurfactants and Bioemulsifiers Biomedical and Related Applications – Present Status and Future Potentials

Abstract: Many microorganisms are able to produce a wide range of amphipathic compounds, with both hydrophilic and hydrophobic moieties present within the same molecule which allow them to exhibit surface activities at interfaces and are generally called biosurfactants or bioemulsifiers. These surface-active compounds (SAC) are mainly classified according to their mode of action, molecular weight and general physico-chemical properties. In literature, the terms ‘biosurfactants’ and ‘bioemulsifiers’ are often used interchangeably, however in general those that reduce surface and interfacial tension at gas-liquid-solid interfaces are called biosurfactants and those that mainly reduce the interfacial tension between immiscible liquids or at the solid-liquid interfaces leading to the formation of more stable emulsions are called bioemulsifiers or bioemulsans. The former group includes lowmolecular-weight compounds, such as lipopeptides, glycolipids, proteins, while the latter includes high-molecular-weight polymers of polysaccharides, lipopolysaccharides proteins or lipoproteins (Smyth et al., 2010a, 2010c). In heterogeneous systems, biosurfactants tend to aggregate at the phase boundaries or interfaces. They form a molecular interfacial film that affects the properties (surface energy and wettability) of the original surface. This molecular layer, in addition to lowering the surface tension in liquids, also lowers the interfacial tension between different liquid phases on the interfacial boundary existing between immiscible phases and therefore can have an impact on the interfacial rheological behaviour and mass transfer. When at interfaces (solidliquid, liquid-liquid or vapour-liquid), the hydrophobic moiety of the surface active molecules aggregates at the surface facing the hydrophobic phase (usually the oil phase) while the hydrophilic moiety is oriented towards the solution or hydrophilic phase (mainly water). Their diverse functional properties namely, emulsification, wetting,

Inhibition of Candida albicans adhesion on medical‐grade silicone by a Lactobacillus‐derived biosurfactant

Abstract: Aims The study aimed at investigating the ability of biosurfactant (BS) produced by a Lactobacillus brevis isolate (CV8LAC) to inhibit adhesion and biofilm formation of Candida albicans on medical-grade silicone elastomeric disks (SEDs). Methods and Results Biosurfactant activity was evaluated at physiological conditions, by means of co-incubation and precoating assays. Additionally, BS extract was tested for antifungal susceptibility against C. albicans in both planktonic and sessile form. Biofilm covered surface and hyphae and blastospores occurrence were quantified by scanning electron microscopy (SEM) and image analysis. BS did not inhibit growth of C. albicans in both planktonic and sessile form. Nevertheless, co-incubation with 2000 μg ml−1 BS significantly reduced biofilm formation on SEDs surface by 89, 90 and 90% after 24, 48 and 72 h of incubation. Fungal adhesion and biofilm formation to precoated SEDs was reduced by 62, 53, 50 and 44% after 1·5, 24, 48 and 72 h. SEM showed a significant reduction of biofilm covered surface in precoated disks but no differences in the production of hyphae or blastospores, except at 1·5 h of incubation. Conclusions This study demonstrated that CV8LAC BS has the ability to counteract significantly the initial deposition of C. albicans to silicone surfaces and to effectively slow biofilm growth. Significance and Impact of the Study The anti-adhesive properties of the CV8LAC BS suggest a potential role of the coating for preventing fungal infection associated to silicone medical devices.

Environmental applications of biosurfactants: Recent advances

Abstract: Increasing public awareness of environmental pollution influences the search and development of technologies that help in clean up of organic and inorganic contaminants such as hydrocarbons and metals. An alternative and eco-friendly method of remediation technology of environments contaminated with these pollutants is the use of biosurfactants and biosurfactant-producing microorganisms. The diversity of biosurfactants makes them an attractive group of compounds for potential use in a wide variety of industrial and biotechnological applications. The purpose of this review is to provide a comprehensive overview of advances in the applications of biosurfactants and biosurfactant-producing microorganisms in hydrocarbon and metal remediation technologies.

Three Genomes from the Phylum Acidobacteria Provide Insight into the Lifestyles of These Microorganisms in Soils

Abstract: The complete genomes of three strains from the phylum Acidobacteria were compared. Phylogenetic analysis placed them as a unique phylum. They share genomic traits with members of the Proteobacteria, the Cyanobacteria, and the Fungi. The three strains appear to be versatile heterotrophs. Genomic and culture traits indicate the use of carbon sources that span simple sugars to more complex substrates such as hemicellulose, cellulose, and chitin. The genomes encode low-specificity major facilitator superfamily transporters and high-affinity ABC transporters for sugars, suggesting that they are best suited to low-nutrient conditions. They appear capable of nitrate and nitrite reduction but not N2 fixation or denitrification. The genomes contained numerous genes that encode siderophore receptors, but no evidence of siderophore production was found, suggesting that they may obtain iron via interaction with other microorganisms. The presence of cellulose synthesis genes and a large class of novel high-molecular-weight excreted proteins suggests potential traits for desiccation resistance, biofilm formation, and/or contribution to soil structure. Polyketide synthase and macrolide glycosylation genes suggest the production of novel antimicrobial compounds. Genes that encode a variety of novel proteins were also identified. The abundance of acidobacteria in soils worldwide and the breadth of potential carbon use by the sequenced strains suggest significant and previously unrecognized contributions to the terrestrial carbon cycle. Combining our genomic evidence with available culture traits, we postulate that cells of these isolates are long-lived, divide slowly, exhibit slow metabolic rates under low-nutrient conditions, and are well equipped to tolerate fluctuations in soil hydration.

Biosurfactants: Multifunctional Biomolecules of the 21st Century

Abstract: In the era of global industrialisation, the exploration of natural resources has served as a source of experimentation for science and advanced technologies, giving rise to the manufacturing of products with high aggregate value in the world market, such as biosurfactants. Biosurfactants are amphiphilic microbial molecules with hydrophilic and hydrophobic moieties that partition at liquid/liquid, liquid/gas or liquid/solid interfaces. Such characteristics allow these biomolecules to play a key role in emulsification, foam formation, detergency and dispersal, which are desirable qualities in different industries. Biosurfactant production is considered one of the key technologies for development in the 21st century. Besides exerting a strong positive impact on the main global problems, biosurfactant production has considerable importance to the implantation of sustainable industrial processes, such as the use of renewable resources and “green” products. Biodegradability and low toxicity have led to the intensification of scientific studies on a wide range of industrial applications for biosurfactants in the field of bioremediation as well as the petroleum, food processing, health, chemical, agricultural and cosmetic industries. In this paper, we offer an extensive review regarding knowledge accumulated over the years and advances achieved in the incorporation of biomolecules in different industries.

Critical review on biofilm methods

Abstract: Biofilms are widespread in nature and constitute an important strategy implemented by microorganisms to survive in sometimes harsh environmental conditions. They can be beneficial or have a negative impact particularly when formed in industrial settings or on medical devices. As such, research into the formation and elimination of biofilms is important for many disciplines. Several new methodologies have been recently developed for, or adapted to, biofilm studies that have contributed to deeper knowledge on biofilm physiology, structure and composition. In this review, traditional and cutting-edge methods to study biofilm biomass, viability, structure, composition and physiology are addressed. Moreover, as there is a lack of consensus among the diversity of techniques used to grow and study biofilms. This review intends to remedy this, by giving a critical perspective, highlighting the advantages and limitations of several methods. Accordingly, this review aims at helping scientists in finding the most appropriate and up-to-date methods to study their biofilms.