Lipase-catalyzed process for biodiesel production: Enzyme immobilization, process simulation and optimization

Transesterification of oil feedstocks using immobilized lipase (IL) is a promising process for biodiesel production. However, the running cost of this process is still higher than that of conversional chemical-catalyzed approaches. To address this challenge, both upstream and downstream processes have to be optimized. This review provides an overview of recent progresses in improving IL-catalyzed biodiesel production, focusing on mid- and down-stream processing such as immobilization of lipase, bioreactors development, process optimization, simulation and techno-economic evaluation. The immobilization of lipase is a costly process. Most of the commercial ILs are prepared by adsorption of free lipase on polymeric materials. However, to further reduce cost, works should be focused on developing cheap carriers and strengthening the interaction between enzyme and carrier but without significant loss of lipase activity. Running cost of lipase also can be reduced by improving its lifetime during transesterification. To achieve this goal, solvents can be used to prevent lipase leaching and eliminate the inhibitive effects of alcohol (usually methanol) and glycerol. Downstream processing includes important units to purify biodiesel products. In this part, works should be focused on minimizing energy consumption and waste effluents. A global process integration and optimization with economic evaluation also should be figured out to improve the economic feasibility of Il-catalyzed production of biodiesel.