酶催化乳酸铵制备乳酸乙酯工艺条件的研究

Study on Enzymatic Reaction Conditions of Ethyl Lactate Production from Ammonium Lactate

研究了在有机溶剂体系下利用脂肪酶催化乳酸铵与乙醇合成乳酸乙酯的反应条件,对脂肪酶和有机溶剂进行了筛选,考察了影响合成乳酸乙酯的因素(底物物质的量配比、反应时间、乳酸铵浓度、温度、酶浓和摇床转速).结果表明,以叔丁醇为反应介质、脂肪酶Novozym435为催化剂时乳酸乙酯产率最高.在底物物质的量比为1∶24,反应时间24 h,乳酸铵浓度0.2 mol/L,反应温度60℃,酶浓40 g/mol,摇床转速150 r/min时乳酸乙酯产率可达32.38%,酶重复使用5次后乳酸乙酯得率仍可达到22.1%,反映出该酶具有良好的稳定性.

The feasibility of using lipase to synthesize ethyl lactate from ammonium lactate was proved.The proper lipase and organic solvent were determined.The results showed that tert-butanol was the best solvent,and the commercial im-mobilized lipase from Candida antarctica（Novozym 435） greatly exceeded all other enzymes using ethanol as an acyl acceptor.The optimal conditions for the esterification has been found to be： molar ratio 1∶24（ammonium lactate/ ethanol）,ammonium lactate concentration 0.2 mol/L,temperature 60 ℃,enzyme concentration 40 g/mol and agitation speed 150 r/min,respectively.Under these conditions,32.38% of ammonium lactate conversion to ethyl lactate was achieved after 24 h of reaction.Yields of ethyl lactate around 22.1% were obtained when the lipase was repeatedly used for 5 cycles under the optimal conditions.This indicated that lipase exhibits good stability under the conditions employed.