Evaluation of Biocompatible Ionic Liquids for Their Application in Phytosterols Bioconversion by Mycobacterium sp Resting Cells

The application of ionic liquids (ILs) as novel solvents in whole-cell bioconversion has a practical significance in innovation of green process engineering for sustainable environment. Therefore, a systematical evaluation of Its based on their cationic and anionic composition is urgently demanded in the whole-cell system. In this work, production of androst-4-ene-3,17-dione (AD) via side-chain cleavage of phytosterols catalyzed by Mycobacterium sp. resting cells was employed to investigate the relationships of ILs structures with their biocompatibility and bioconversion performances. For 13 of biocompatible ILs, the viscosity, hydrophobicity, polarity and hydrogen-bond basicity, as well as IL/water composition at phase equilibrium were measured. Based upon cell membrane integrity and metabolic activity retention, some ILs with anions of [PF6] or [NTf2] showed proper Mycobacterium sp. biocompatibility. Among bioconversion systems containing water-immiscible or water-miscible ILs, [PrMIM] [PF6] generated the highest AD production of 2.35 g L-1 after 12 h conversion by Mycobacterium sp. resting cells, indicating the superior of IL/aqueous biphasic system. Furthermore, IL recovery after bioconversion was conducted to alleviate industrial expense and environmental concerns. This work presented a general procedure of Its application in a given whole-cell bioconversion process, which can guide the design of novel Its favorable for bioconversion process.