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Microbial biosurfactants are considered environmentally friendly alternatives to synthetic surfactants in numerous applications. One of the main bottlenecks to their widespread use is the lack of effective processes for their production on an industrial scale. Biosurfactant production using conventional aerated bioreactors results in excessive foaming due to the combination of air injection and their tensioactive properties. A not widely explored approach to overcome this problem is the development of foam-free production processes, which require the identification and characterization of appropriate microorganisms. Bacillus licheniformis EL3 was evaluated for biosurfactant production under oxygen-limiting conditions in a bioreactor, using a mineral medium containing glucose as a carbon source and NaNO3 and NH4Cl as nitrogen sources. After optimizing the operational conditions, glucose concentration, and inoculum strategy, B. licheniformis EL3 produced 75 ± 3 mg biosurfactant/L in 43 h. The purified biosurfactant exhibited exceptional surface active properties, with minimum surface tension values (29 mN/m) and a critical micelle concentration (27 mg/L) similar to those achieved with commercial surfactin. Furthermore, biosurfactant yield per substrate (YP/S = 0.007 g biosurfactant/g glucose) was similar to the figures reported for Bacillus subtilis strains grown in similar conditions, whereas biosurfactant yield per biomass (YP/X = 0.755 g biosurfactant/g biomass) and specific biosurfactant productivity (qBS = 0.018 g biosurfactant/(g biomass × h)) were almost three times higher when compared to previous reports. The results obtained indicate that B. licheniformis EL3 is a promising candidate for the development of foam-free biosurfactant production processes at an industrial scale. [ABSTRACT FROM AUTHOR]

Microbial exopolysaccharides (EPS) are promising alternatives to synthetic polymers in a variety of applications. Their high production costs, however, limit their use despite their outstanding properties. The use of low-cost substrates such as agro-industrial wastes in their production, can help to boost their market competitiveness. In this work, an alternative low-cost culture medium (CSLM) was developed for EPS production by Rhizobium viscosum CECT908, containing sugarcane molasses (60 g/L) and corn steep liquor (10 mL/L) as sole ingredients. This medium allowed the production of 6.1 ± 0.2 g EPS/L, twice the amount produced in the standard medium (Syn), whose main ingredients were glucose and yeast extract. This is the first report of EPS production by R. viscosum using agro-industrial residues as sole substrates. EPSCSLM and EPSSyn exhibited a similar carbohydrate composition, mainly 4-linked galactose, glucose and mannuronic acid. Although both EPS showed a good fit to the Herschel–Bulkley model, EPSCSLM displayed a higher yield stress and flow consistency index when compared with EPSSyn, due to its higher apparent viscosity. EPSCSLM demonstrated its potential use in Microbial Enhanced Oil Recovery by enabling the recovery of nearly 50% of the trapped oil in sand-pack column experiments using a heavy crude oil. [ABSTRACT FROM AUTHOR]

Marine microorganisms possess unique metabolic and physiological features and are an important source of new biomolecules, such as biosurfactants. Some of these surface-active compounds synthesized by marine microorganisms exhibit antimicrobial, anti-adhesive and anti-biofilm activity against a broad spectrum of human pathogens (including multi-drug resistant pathogens), and could be used instead of existing drugs to treat infections caused by them. In other cases, these biosurfactants show anti-cancer activity, which could be envisaged as an alternative to conventional therapies. However, marine biosurfactants have not been widely explored, mainly due to the difficulties associated with the isolation and growth of their producing microorganisms. Culture-independent techniques (metagenomics) constitute a promising approach to study the genetic resources of otherwise inaccessible marine microorganisms without the requirement of culturing them, and can contribute to the discovery of novel biosurfactants with significant biological activities. This paper reviews the most relevant biosurfactants produced by marine microorganisms with potential therapeutic applications and discusses future perspectives and opportunities to discover novel molecules from marine environments. [ABSTRACT FROM AUTHOR]

Most biosurfactants are obtained using costly culture media and purification processes, which limits their wider industrial use. Sustainability of their production processes can be achieved, in part, by using cheap substrates found among agricultural and food wastes or byproducts. In the present study, crude glycerol, a raw material obtained from several industrial processes, was evaluated as a potential low-cost carbon source to reduce the costs of surfactin production by Bacillus subtilis #309. The culture medium containing soap-derived waste glycerol led to the best surfactin production, reaching about 2.8 g/L. To the best of our knowledge, this is the first report describing surfactin production by B. subtilis using stearin and soap wastes as carbon sources. A complete chemical characterization of surfactin analogs produced from the different waste glycerol samples was performed by liquid chromatography–mass spectrometry (LC-MS) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the surfactin produced in the study exhibited good stability in a wide range of pH, salinity and temperatures, suggesting its potential for several applications in biotechnology. [ABSTRACT FROM AUTHOR]

Studies on the specific and nonspecific interactions of biosurfactants with proteins are broadly relevant given the potential applications of biosurfactant/protein systems in pharmaceutics and cosmetics. The aim of this study was to evaluate the interactions of divalent counterions with the biomolecular anionic biosurfactant surfactin-C15 through molecular modeling, surface tension and dynamic light scattering (DLS), with a specific focus on its effects on biotherapeutic formulations. The conformational analysis based on a semi-empirical approach revealed that Cu2+ ions can be coordinated by three amide nitrogens belonging to the surfactin-C15 cycle and one oxygen atom of the aspartic acid from the side chain of the lipopeptide. Backbone oxygen atoms mainly involve Zn2+, Ca2+ and Mg2+. Subsequently, the interactions between metal-coordinated lipopeptide complexes and bovine serum albumin (BSA) were extensively investigated by fluorescence spectroscopy and molecular docking analysis. Fluorescence results showed that metal-lipopeptide complexes interact with BSA through a static quenching mechanism. Molecular docking results indicate that the metal-lipopeptide complexes are stabilized by hydrogen bonding and van der Waals forces. The biosurfactant-protein interaction properties herein described are of significance for metal-based drug discovery hypothesizing that the association of divalent metal ions with surfactin allows its interaction with bacteria, fungi and cancer cell membranes with effects that are similar to those of the cationic peptide antibiotics. [ABSTRACT FROM AUTHOR]