Affordable CO₂-derived alkyl carbamate ionic liquids boosting enzymatic production of renewable hydrocarbon fuels via Chlorella variabilis NC64A fatty acid photodecarboxylase (C_VFAP)

The development of sustainable aviation fuel (SAF) presents a promising alternative to conventional jet fuel, with biofuels offering net-zero CO₂ emissions. However, the conventional SAF production process typically involves expensive metal catalysts and extreme operating conditions. In contrast, the enzymatic approach offers a milder alternative; however, it is hindered by several limitations, including prolonged reaction times, reliance on cosolvents and low productivity. This study investigates the impact of CO₂-based alkyl carbamate ionic liquids (ILs) on the enzymatic photodecarboxylation reaction catalyzed by Chlorella variabilis algal fatty acid photodecarboxylase (CvFAP). Notably, the study examines four ILs: N,N-dimethylammonium N′,N′-dimethylcarbamate (DIMCARB), N,N-dipropylammonium N′,N′-dipropylcarbamate (DPCARB), N,N-diallylammonium N′,N′-diallylcarbamate (DACARB), and bis(2-ethylhexyl)-ammonium bis(2-ethylhexyl)carbamate (DBCARB). The results demonstrated that DACARB was the most optimal IL as it enhanced hydrocarbon conversion by 40 % and was able to reduce DMSO usage up to 86.7 % as compared to the absence of DACARB. This enhancement is attributed to DACARB's optimal balance of hydrophobic and hydrophilic properties, which increased enzyme activity while serving as a viable DMSO replacement, as well as acting as an allosteric modulator, as shown by Michaelis-Menten model fitting. Overall, this study highlights the potential of DACARB to facilitate process intensification in enzymatic SAF production, contributing to sustainable aviation practices.