Utilization of shea-nut cake for lipase production by thermophilic Bacillus valezensis EAC 9 isolated from hot compost and optimization of nutritional parameters

Abstract

The use of oily waste as a cost-effective substrate for lipase production is gaining more importance. However, shea-nut cake (SNC) remains under-explored in this regard. Lipases of thermophilic origin such as hot compost bacteria, are of significant biotechnological and industrial importance due to favorable robust properties. This paper describes the isolation of potential lipase producing thermophilic bacteria from hot compost and improvement of its lipase through optimization of nutritional parameters. The bacteria were isolated on tributyrin agar plate and applied for the production of lipase on Olive oil, Shea-nut cake (SNC) and the mixture of olive oil and SNC. Using Plackett-Burman Design (PBD) for screening and Central Composite Design (CCD) of Response Surface Methodology (RSM) for optimization studies, factors influencing lipase production on SNC substrate were identified. One (EAC 9) out of the 4 most potent isolates was identified as Bacillus velezensis EAC9 using 16S rRNA, and produced the highest lipase activity on mixture of olive oil and SNC (103.66 U/ml) than olive oil (65.22) and SNC (41.72 U/ml) alone. Optimization model validity was verified and revealed an optimum medium containing olive oil and Tween 80 at 1.0 % v/v, sucrose of 1.0 % w/v and (NH4)2SO4 of 0.1 % w/v led to maximum lipase production at 200 U/ml which was 4.79-fold increase from the unoptimized. The results indicate that SNC is a better prospective substrate for improving lipase production by thermophilic Bacillus valezensis EAC9, and that statistical methods may be used to deduce optimal parameters for effective lipase production.