Conversion of waste cooking oil by rhodococcal lipase immobilized in gellan gum

Recently, the application of lipase enzyme as biocatalyst in the conversion of waste cooking oil (WCO) to free fatty acids and glycerol has been trending well. Therefore, the present study attempts to use WCO which is found in abundance in Malaysia as the substrate for halal microbial lipase conversion to glycerol which can be exploited in the food industry. The workability of free lipase for WCO conversion, however suffers severely due to potential denaturation of the enzyme and extended reaction time. Thus, this study embraced the immobilization method to encapsulate crude lipase extracted from Rhodococcus pyridinivorans strain UCC 0009 in gellan gum and calcium alginate, respectively and compared their ability for WCO conversion to free crude lipase. The gellan gum and calcium alginate-immobilized crude lipase evidently exhibited greater WCO conversion, demonstrating 2.18-fold and 1.61-fold enhanced lipase activity, respectively in comparison to free crude lipase. The repeated reuse of the gellan gum-immobilized crude lipase maintained reasonable lipase activity for 9 cycles, retaining an average 85 % WCO conversion for the first seven cycles and 67 % conversion in the subsequent batches. Thus, the immobilized halal lipase can be foreseen as a green substitute to chemical catalyst for WCO conversion which meets the worldwide demand for clean technologies.