Response surface optimization of lipase production by Pseudomonas sp. on a low-cost shea-nut cake using solid state fermentation

Abstract

Shea nut cake (SNC) is the solid residue produced after the shea butter extraction process. The SNC could provide a low-cost substrate for  bacterial lipase production. Greater yield are among the benefits Solid State Fermentation (SSF). However, there have been less  instances of lipase production by bacteria than fungi in SSF. The current study aimed at improving bacterial lipase production on SNC in  SSF using Response Surface Methodology. Lipase-producing bacteria (LPB) were isolated from the shea butter mill effluent pond and screened for lipase production on a tributyrin agar plate. The influence of four independent parameters (temperature, pH, moisture  content and biosurfactant) on lipase production was studied using Box Behnken Design (BBD) of RSM. Results showed that isolate AO  (Pseudomonas sp.) displayed the highest zone of hydrolysis 2 (53 mm). A quadratic regression with R = 0.931 showed that the model is  best fitting, and predicted the optimum conditions of significant (P>0.05) growth parameters, including temperature at 40°C, moisture content at 50%, and biosurfactant at 2 mL, which produced 408.25 U/g of experimental lipase. The findings indicate that the model was useful for predicting optimal growth conditions for incresing lipase production in SSF and the low-cost agro- industrial SNC could be a promising substrate for industrial applications.