A Solvent-tolerant Alkaline Lipase from Bacillus sp. DM9K3 and Its Potential Applications in Esterification and Polymer Degradation

Abstract

Solvent-tolerant lipase produced by Bacillus sp. DM9K3 has been isolated from the hypersaline area, White Rann of Kachchh, Gujarat, India. The strain initially showed lipase activity of 11.1 U/mL in a basal medium which increased to 52.0 U/mL under optimized culture conditions. Bacillus sp. DM9K3 exhibited stability at 7% salinity, pH 9.0 and 50°C. The extracellular lipase was partially purified by acetone precipitation followed by DEAE-cellulose resulting in 39-fold purification with 40% yield. Metals ions such as Mg²⁺, Ca²⁺ and K⁺ showed enhanced enzyme activity. EDTA did not have a significant effect on activity suggesting that lipase is not metalloenzyme. The lipase under study showed the highest activity when palmitate (C16) was used as a substrate and was also highly stable in organic solvents such as cyclooctane and benzene. The partially purified enzyme was immobilized for increasing the efficiency of the ethyl caprylate (an orange flavored ester) synthesis in the presence of cyclooctane. Additionally, lipase of Bacillus sp. DM9K3 was explored for biodegradation of polycaprolactone microspheres and showed promising results for potential applications in drug delivery system.