Cell Catalytic Activity Research Articles

Highly enantioselective resolution of racemic 1-phenyl-1,2-ethanediol to (S)-1-phenyl-1,2-ethanediol by Kurthia gibsonii SC0312 in a biphasic system

The asymmetric resolution of racemic 1-phenyl-1,2-ethanediol (PED) to (S)-PED by Kurthia gibsonii SC0312 (K. gibsonii SC0312) was conducted in a biphasic system comprised of an organic solvent and aqueous phosphate buffer. The impacts of organic solvents on the whole cell catalytic activity, metabolic activity, membrane integrity, and material distribution were first evaluated. The results showed that all organic solvents, except for dibutyl phthalate, showed a detrimental effect on the metabolic activity of the cells, especially for those with low log P values. All organic solvents were capable of changing the membrane permeability and membrane integrity of the cells. Moreover, some organic solvents showed a good extraction of the oxidation product. Finally, a high yield of 47.7 % of (S)-PED was obtained by the asymmetric resolution of racemic PED using K. gibsonii SC0312 in a biphasic system under the optimal conditions: racemic PED 120 mM, temperature 35 °C, reaction time 6 h, 180 rpm, and a volume ratio of dibutyl phthalate to aqueous phosphate buffer of 1:1. The optical purity of (S)-PED increased from 51.3 % to >99 %. This work described an efficient approach to improve reaction efficiency, and constructed a highly effective biphasic reaction system for the fabrication of (S)-PED via K. gibsonii SC0312.

Exploring the effects of oil inducer on whole cell-mediated methanolysis for biodiesel production

Whole cell-mediated methanolysis of renewable oils for biodiesel production has drawn much attention in recent years since it can avoid the complex preparation procedures of traditional immobilized lipase. During the cultivation of Rhizopus oryzae whole cell catalyst, plant oils are usually added into the medium as inducer for lipase synthesis. It was found that oil inducer not only influenced lipase production, but also led to varied whole cell's catalytic performance. In this paper, the related mechanisms were explored and it was found that the higher unsaturated fatty acid (UFA) was contained in oil inducer, the higher intracellular lipase could be obtained. Different oil inducers also resulted in varied compositions of cell membrane, which was further found to be responsible for the operational stability of the catalyst. Cells with membrane enriched with saturated fatty acid (SFA) exhibited better stability than those enriched with UFA. And further study showed that after glutaraldehyde cross-linking treatment, the operational stability of both UFA enriched cells and SFA enriched cells were enhanced greatly and no loss in cell's catalytic activity was detected after being repeatedly used for 15 batches.