Highly efficient production of FAMEs and β-farnesene from a two-stage biotransformation of waste cooking oils

Abstract

This is the first report on an ecofriendly process for producing FAMEs and β-farnesene via a two-stage biotransformation of waste cooking oils (WCOs), in which the FAMEs are referred to as biodiesel products and β-farnesene is used as a jet biofuel. First, the yield of FAMEs from untreated WCOs by Novozym 435 was 33% under the initial transesterification conditions with crude glycerol containing 46% (w/w) methanol. However, crude glycerol with highly concentrated methanol seriously inhibited fermentation for the production of β-farnesene by an engineered E. coli strain with a relatively balanced mevalonate (MVA) pathway that was constructed with the recombinant plasmids pMevT, pMBIS and pFiI. The pretreatment of WCOs and optimization of the transesterification process were successfully performed to completely eliminate fermentation repression, and the methanol content in the crude glycerol was reduced to zero. The production of β-farnesene (5.29 g/L) using this crude glycerol as a substrate was approximately 50% higher than that (3.56 g/L) produced under the initial conditions, which was more than 100% higher than that (2.62 g/L) produced using crude glycerol via chemical transesterification methods. Furthermore, the optimal transesterification process resulted in a sharply increased yield of FAMEs (96%) compared that (33%) obtained under the initial conditions. Therefore, this biotechnology achieved a high FAMEs yield and β-farnesene production and might be suitable for industrial-scale implementation.