Abstract

Although the use of oily waste as a cost-effective substrate for lipase production has recently gained importance, 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 study describes the optimization of nutritional parameters for improving lipase production by a thermophilic lipase producing bacteria isolated from hot compost using Response Surface Methodology (RSM). The bacteria were isolated on tributyrin agar plate and used for lipase production on olive oil, SNC and their combination. Using Plackett-Burman Design (PBD) for screening and Central Composite Design (CCD) of RSM for optimization studies, factors influencing lipase production on SNC substrate were identified. One of the four most potent isolates, Bacillus velezensis EAC9, was identified using 16S rRNA and observed to show the maximum lipase activity on a mixture of olive oil and SNC (103.66 U/mL), which was higher than that of olive oil (65.22 U/mL) and SNC (41.72 U/mL) alone. The validity of the optimization model was confirmed, and an optimum medium containing olive oil and Tween 80 at 1.0% (v/v), sucrose at 1.0% (w/v), and (NH4)2SO4 at 0.1% (w/v) resulted in maximum lipase production at 200 U/mL, a 4.79-fold increase over the unoptimized medium. The findings suggest that SNC could be considered a cheap substrate for enhancing lipase production by the thermophilic B. velezensis EAC9 and suggest a model of nutritional parameters for optimal lipase production which could be scale up for industrial applications.