Development and Utilization of a Pair of Sol-Gel Entrapped Lipases for Biodiesel Production from High Free Fatty Acid Oils

Esterification and transesterification of high free fatty acid (FFA) oils to fatty acid alkyl ester (FAAE) by sol-gel entrapped lipase B from Candida antarctica (CalB) and lipase from Burkholderia cepacia were investigated. The optimal conditions for the esterification catalyzed by the immobilized CalB were determined to be 50 °C, 1.7:1 molar ratio of methanol to fatty acid, and 0.36 g of water per 8 g oil. The immobilized lipases were used together to yield 92 wt.% conversion of a model 50 wt.% FFA oil substrate and 91% conversion of yellow grease to FAAE in 6 h and over 97 wt.% conversion of the model 50% FFA oil substrate and 94% conversion of yellow grease to FAAE in 24 h. The pair of immobilized lipases was further examined for its stability and showed to retain over 95 % of its activity over 10 cycles of 6 h reuses.