Improvement of biodiesel production using waste cooking oil and applying single and mixed immobilised lipases on polyhydroxyalkanoate

This study describes the production of biodiesel via the enzymatic transesterification reaction, using waste cooking oil as a substrate. Lipases from Candida rugosa and Rhizomucor miehei were immobilised on polyhydroxybutyrate to serve as environment-friendly catalysts. This enzyme mixture yielded the highest biodiesel production. The optimum conditions for biodiesel production included a reaction temperature of 45 degrees C, 5% water content, 1% of mixed lipase (50% of each lipase), a methanol:oil ratio of 6:1, a 24-h reaction period, and a 250 rpm stirring speed, which resulted in the highest biodiesel yields (96.5%). This catalyst can be reused for more than six cycles, after which the lipase activity begins to decrease. The chemical and fuel properties such as the density at 15 degrees C, viscosity at 40 degrees C and cloud point of the resulting biodiesel were similar to those of other diesels/biodiesels and complied with international specifications (EN 14214 and ASTM D 6751). (C) 2020 Elsevier Ltd. All rights reserved.