Optimization of organic solvent-tolerant lipase production by Acinetobacter sp. UBT1 using deoiled castor seed cake

Organic solvent-tolerant lipase-producing microorganisms were isolated from petrol spilled soil. From ten morphologically distinct lipase-producing bacterial isolates, highest amount of lipase-producing isolate UBT1 was identified as Acinetobacter sp. using 16S rRNA gene sequencing (NCBI Accession No: MH879815). An increase in lipase production from 42 U/mL to 243 U/mL was obtained when different deoiled seed cakes were supplemented instead of olive oil in the medium. Further optimization of media components by the statistical approach assisted in discerning the main influencing media components and their optimum concentrations. Nine components glucose, castor seedcake, potassium nitrate, gum arabic, calcium chloride, magnesium sulphate, potassium di-hydrogen phosphate, dipotassium hydrogen phosphate, and ferric chloride were selected for Plackett-Burman design. The optimum concentrations of three significant selected components for the lipase production were found to be 0.025 gm% glucose, 0.002 gm% calcium chloride, and 0.2 gm% potassium di-hydrogen phosphate as determined by Response Surface Methodology. Increase in lipase production with 292.29 U/mL was achieved in the media containing optimized components and 2 gm% deoiled castor seed cake. Purification studies with ammonium sulphate precipitation, dialysis, and gel permeation chromatography resulted in 77.54% recovery with 5.77-fold partially purified lipase. The residual activity of lipase in 50 and 75% concentration of n-hexane among other solvents after 24 h was 105.05 and 90.42%, respectively, indicating its solvent tolerance. The present study reports the isolation of organic solvent-tolerant lipase-producing Acinetobacter sp. UBT1, optimization of the culture media for lipase production using the deoiled castor seed cake, and its partial purification.