Current advances in the classification, production, properties and applications of microbial biosurfactants - A critical review.

This review discusses the classification, characteristics, and applications of biosurfactants. The biosynthesis pathways for different classes of biosurfactants are reviewed. An in-depth analysis of reported research is carried out emphasizing the synthetic pathways, culture media compositions, and influencing factors on production yield of biosurfactants. The environmental, pharmaceutical, industrial, and other applications of biosurfactants are discussed in detail. A special attention is given to the biosurfactants application in combating the pandemic COVID-19. It is found that biosurfactant production from waste materials can play a significant role in enhancing circular bioeconomy and environmental sustainability. This review also details the life cycle assessment methodologies for the production and applications of biosurfactants. Finally, the current status and limitations of biosurfactant research are discussed and the potential areas are highlighted for future research and development. This review will be helpful in selecting the best available technology for biosynthesis and application of particular biosurfactant under specific conditions.

Crude oil biodegradation potential of biosurfactant-producing Pseudomonas aeruginosa and Meyerozyma sp.

This study investigates the potential of crude oil degrading capabilities of biosurfactant-producing strains of Pseudomonas aeruginosa MF069166 and Meyerozyma sp. MF138126. P. aeruginosa produced mono-/di-rhamnolipids congeners whereas, Meyerozyma sp. produced acidic and lactonic forms of sophorolipids with crude oil. The values of critical micelle concentrations of rhamnolipids and sophorolipids were 40 mg/L and 50 mg/L with reductions in surface tension of water to 29 mN/m and 33 mN/m. Dynamic light scattering revealed that the average diameter of micellar aggregates of rhamnolipids ranged between 300 and 350 nm and the average size of sophorolipids micelles was 309 nm and 380 nm. Biosurfactants from P. aeruginosa and Meyerozyma sp. exhibited emulsification activities of 87% and 84% in crude oil. Cell surface hydrophobicity of both strains was higher in the presence of hydrophobic contaminants. The biosurfactants showed stability under varying pH, NaCl concentrations and temperatures. Gravimetric and GC-MS analyses demonstrated that P. aeruginosa degraded 91% of the petroleum hydrocarbons while Meyerozyma sp. showed 87% biodegradation efficiency. P. aeruginosa and Meyerozyma sp. have also been found to degrade halogen-containing compounds and showed excellent crude oil degradation efficiency. It is concluded that both strains have high potential of applications in the bioremediation of hydrocarbons-contaminated sites.

Catalytic Role of Thermostable Metalloproteases from Bacillus subtilis KT004404 as Dehairing and Destaining Agent.

Proteases with characteristic stabilities are considered attractive candidates for industrial catalysis. In the present study, a potent bacterial strain KT004404, an inhabitant of hydrothermal vents, was isolated and characterized for protease production. Initial screening indicated that this strain produced a hydrolytic zone of 30 mm 16S rRNA-based identification revealed that our isolate was a strain of Bacillus subtilis. Optimum reaction condition for maximum protease production was determined as 55 °C, pH 6, 1 % inoculum size and malt extract as primary growth substrate supplemented with 1 % dextrose. Yield of the enzyme was increased up to 7.53 folds with a specific activity of 55.125 U/mg after gel filtration chromatography. SDS-PAGE analysis confirmed the size of protease as 28.24 kDa. Purified enzyme retained its catalytic activity over a broad range of temperature (5 to 65 °C) and pH [5-8]. Addition of metal ions shown to have a stimulatory effect on catalytic properties while EDTA inhibited the efficiency of the enzyme confirming it as a metalloprotease. Protease exhibited excellent stability and activity in the presence of anionic surfactants, solvents, and detergents. The results of dehairing and destaining experiments suggested that the protease produced by B. subtilis KT004404 could be used in leather and textile industries with ecological benefits.