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.

Lipolytic bacterial strains mediated transesterification of non-edible plant oils for generation of high quality biodiesel.

Biodiesel is one of the best alternative to depleting fossil fuels for transport sector. However, biodiesel production via lipase mediated transesterification has limitation of high costing microbial enzymes. In order to overcome this limitation, a process of sequential treatment of oil industry wastewater using isolated lipolytic bacterial strains and biodiesel production from non-edible plant oils was studied. In this study, efficient lipase producing bacteria were isolated and evaluated for production of biodiesel from mustard, soybean, jatropha and taramira oils utilizing methanol for the transesterification of oils and bioremediation. Selected strains were then identified, using 16s rRNA sequencing. Further, Bacillus subtilis strain Q1 KX712301 was optimized for biodiesel production from non-edible taramira oil via Plackett-Burman and central composite design. Highest volumetric yield of biodiesel obtained was 102% at optimized parameters. Finally, a sequential bioremediation of vegetable oil contaminated wastewater and then microbial production of biodiesel from non-edible taramira oil was carried out using efficient lipase producer B. subtilis strain Q1 at optimized conditions. During sequential process, complete chemical oxigen demand reduction of oil containing wastewater and theoretical volumetric yield of biodiesel was achieved. Gas chromatography/mass spectrometry chromatogram revealed that the total fatty acid methyl ester content of the produced biodiesel was >98% which is in accordance with the biodiesel quality standards specified by both ASTM and EU-14103.