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.

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Staphylococcus aureus and Staphylococcus epidermidis are considered two of the most important pathogens, and their biofilms frequently cause device-associated infections. Microbial biosurfactants recently emerged as a new generation of anti-adhesive and anti-biofilm agents for coating implantable devices to preserve biocompatibility. In this study, R89 biosurfactant (R89BS) was evaluated as an anti-biofilm coating on medical-grade silicone. R89BS is composed of homologues of the mono- (75%) and di-rhamnolipid (25%) families, as evidenced by mass spectrometry analysis. The antimicrobial activity against Staphylococcus spp. planktonic and sessile cells was evaluated by microdilution and metabolic activity assays. R89BS inhibited S. aureus and S. epidermidis growth with minimal inhibitory concentrations (MIC99) of 0.06 and 0.12 mg/mL, respectively and dispersed their pre-formed biofilms up to 93%. Silicone elastomeric discs (SEDs) coated by R89BS simple adsorption significantly counteracted Staphylococcus spp. biofilm formation, in terms of both built-up biomass (up to 60% inhibition at 72 h) and cell metabolic activity (up to 68% inhibition at 72 h). SEM analysis revealed significant inhibition of the amount of biofilm-covered surface. No cytotoxic effect on eukaryotic cells was detected at concentrations up to 0.2 mg/mL. R89BS-coated SEDs satisfy biocompatibility requirements for leaching products. Results indicate that rhamnolipid coatings are effective anti-biofilm treatments and represent a promising strategy for the prevention of infection associated with implantable devices.

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.

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The anti-adhesive properties of the CV8LAC BS suggest a potential role of the coating for preventing fungal infection associated to silicone medical devices.

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Aims:  The purpose of this study was to evaluate the degree of bacterial contamination generated by three Italian composting plants (1, 2 and 3) in two different seasons and to assess the health risk for the employees. Methods and Results:  Aerosols samples were collected with an agar impact sampler. Several plant sites and external upwind and downwind controls were examined. Total colony‐forming counts of mesophilic and thermophilic bacteria, actinomycetes and streptomycetes, Gram‐negatives, coliforms and sulfite‐reducers were determined. Selective media were used in order to isolate pathogenic bacteria. The levels of total mesophilic and thermophilic micro‐organisms ranged between 33 and >40 000 CFU m−3 in plant 1, 39 and 18 700 CFU m−3 in plant 2 and 261 and 6278 CFU m−3 in plant 3. Strains of Escherichia coli, Staphylococcus aureus and Clostridium perfringens were also found. Conclusions:  The plants monitored in this study have proved to be sources of aerosolized bacteria. The activities involving mechanical movement of the composting mass and the indoor activities were of greatest potential risk. In all the studied plants, a statistically significant dependence was found between the bacterial contamination and the season for some or almost all the analysed parameters, but a clear seasonal trend could not be observed. Significance and Impact of the Study:  This study provides broad evidence of bacterial aerosol dispersion and site‐related biological hazards that may be useful to the regional government to implement regulations on worker safety in composting plants.