Lipase and photodecarboxylase coexpression: A potential strategy for alkane-based biodiesel production from natural triglycerides

Alkane-based biodiesel is considered the next generation of biodiesel owing to its potential environmental benefits and the fact that it exhibits much higher specific caloric values than traditional biodiesel.However,the formidable obstacle impeding the commercialization of this cutting-edge fuel alternative lies in the cost associated with its production.In this study,an engineered strain Escherichia coli(E.coli)showcasing harmonized coexpression of a lipase(from Thermomyces lanuginosus lipase,TLL)and a fatty acid photodecarboxylase(from Chlorella variabilis,CvFAP)was first constructed to transform triglycerides into alkanes.The potential of E.coli BL21(DE3)/pRSFDuet-1-TLL-CvFAP for alkane synthesis was evaluated with tripalmitin as a model substrate under various process conditions.Following a comprehensive examination of the reaction parameters,the scope of the biotransformation was expanded to‘real’substrates(vegetable oils).The results showed that bioderived oils can be transformed into alkanes with high yields(0.80-10.20 mmol·L^(-1))under mild conditions(35℃,pH 8.0,and 36 h)and blue light illumination.The selected processes were performed on an increased lab scale(up to 100 ml)with up to 24.77 mmol·L^(-1) tripalmitin,leading to a yield of 18.89 mmol·L^(-1) pentadecane.With the employment of a method for efficiently producing alkanes under mild conditions and a simple procedure to isolate alkanes from the reaction system,the utilization of sustainable biomass as a fundamental feedstock emerges as the primary solution to lower the cost of alkane-based biodiesel.Thus,this study proposes a readily implementable and highly effective approach for alkane-based biodiesel production.

Anaerobic environment as an efficient approach to improve the photostability of fatty acid photodecarboxylase

Fatty acid photodecarboxylase of Chlorella variabilis NC64A(CvFAP) is a novel photoenzyme with great potential in the treatment of waste lipids and production of sustainable aviation fuel. However, the fragile nature of Cv FAP to blue light is an urgent challenge. Herein, we demonstrated anaerobic environment could significantly improve the photostability of Cv FAP for the first time. The decarboxylation of palmitic acid by Cv FAP for 3 h under anaerobic environment increased pentadecane yield by 44.7% as compared to that under aerobic environment. The residual activity of Cv FAP after blue-light preillumination in the absence of palmitic acid for 0.5 h under anaerobic environment was 80.4%, which was 258.7 times higher than that under aerobic environment. Remarkable accumulation of superoxide radical and singlet oxygen in Cv FAP under aerobic environment led to the poor photostability of Cv FAP. Anaerobic environment helped to mitigate the production of superoxide radical and singlet oxygen in Cv FAP, improving the photostability of Cv FAP.