Effects of water-miscible ionic liquids on cell growth and nitro reduction using Clostridium sporogenes

Abstract

Water miscible ionic liquids had various effects on the physiology of Clostridium sporogenes when tested as additives in culture media or reaction media for reduction of nitrobenzene. 2-Hydroxy ethyl trimethyl-ammonium dimethyl phosphate ([EtOHNMe₃][Me₂PO₄]) and N,N-dimethylethanolammonium acetate (DMEAA) increased the growth rate of C. sporogenes by as much as 28%, suggesting that they were either metabolised or increased the availability of nutrients. By contrast, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMim][BF₄]) and AMMOENG™ 100 inhibited growth. Although 1-ethyl-3-methyl imidazolium ethylsulfate ([EMim][EtSO₄]; 2% w/v) inhibited growth by 58%, it was sufficiently non-toxic to allow efficient reduction of nitrobenzene using harvested cells, providing aniline yields up to 79%. The high product yield with reactions in [EMim][EtSO₄] represented a significant improvement over conventional solvents, since the yield was only 8% in aqueous ethanol (4% v/v) and 45% in a biphasic heptane/aqueous system (phase ratio 0.33). The ionic liquid appeared to suppress unproductive substrate consumption by an unknown mechanism