Current Progress in Enzymatic Biodiesel Research, Development, and Commercialization

Dear Colleagues,

Biodiesel is viewed as a renewable, biodegradable, nontoxic, and clean-burning alternative to fossil fuels, which can be used in existing engines and infrastructure with practically no changes. The greenhouse gas emissions from biodiesel are several times lower than gasoline and petrodiesel. The chemical-catalyzed transesterification of vegetable oils to biodiesel has been industrially adopted due to its high conversion rates and low production time. However, this process suffers from several inherent drawbacks related to energy-intensive and environmentally unfriendly processing steps, such as catalyst and product recovery, and wastewater treatment. This has prompted the development of enzymatic catalysis for biodiesel production, characterized by several environmental and economic advantages over the conventional chemical method. These include room-temperature reaction conditions, elimination of treatment costs associated with recovery of chemical catalysts, enzyme reuse, high substrate specificity, the ability to convert both free fatty acids and triglycerides to biodiesel in one step, lower alcohol-to-oil ratio, avoidance of side reactions and minimized impurities, easier product separation and recovery, biodegradability, and environmental acceptance. The main constraints for biodiesel production are the feedstock and enzyme costs. Up to 80% of the total biodiesel production cost arise from the use of expensive, high-quality, non-refined, and edible virgin oils, and a first-generation biodiesel feedstock that has also raised ‘food or fuel’ concerns. Non-edible oils (e.g., waste cooking oils, animal fats, jatropha oil, etc.) as the second-generation feedstock for biodiesel production are a viable alternative to edible vegetable oils due to their lower price and wide adaptability with minimal production requirements. Microbial oils, regarded as the third-generation biodiesel feedstock, are produced through the cultivation of microorganisms, such as oleaginous yeast and microalgae, that can accumulate up to 80% lipids from their total single-cell biomass. Enzyme costs can be reduced by the discovery of new, more efficient lipase producers; strain improvement and use of highly productive recombinant strains for production of lipase with improved activity and methanol tolerance; optimization of fermentation media and parameters for lipase production; biocatalyst reuse through lipase and whole cell immobilization; enzyme pretreatment for activity regeneration and extended lipase life, etc. Robust enzymes with high activity, thermostability, and resistance to the harsh conditions of biodiesel production are needed.

This Special Issue aims to contribute to the current state of enzymatic biodiesel research, development, and commercialization. High-quality papers are sought on topics including but not limited to feedstocks, production and properties of enzymatic biodiesel, biocatalyst production and characterization, parameters for enzymatic catalysis, enzyme reuse, enzyme inhibition, solvent and solvent-free systems, biodiesel yield, glycerol, mass transfer limitations, bioreactor design, technoeconomic evaluation, environmental impact, and pilot and large-scale developments in enzymatic biodiesel.

Dr. Lew P. Christopher
Guest Editor

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• biodiesel
• enzyme
• lipase
• transesterification
• catalysis
• solvent
• immobilization
• whole cell
• feedstock
• triglycerides
• lipids
• commercialization