米根霉全细胞脂肪酶在化学-酶法环氧化反应体系中的稳定性

Stability of Rhizopus oryzae whole-cell lipase in a chemo-enzymatic epoxidation reaction

为了提高米根霉(Rhizopus oryzae CGMCC 3.5040)全细胞脂肪酶在化学-酶法环氧化反应体系中的稳定性,以α-蒎烯为模式底物,考察柠檬酸三钠用量、戊二醛交联细胞、过氧化氢(H_(2)O_(2))用量和回用方式对催化剂稳定性的影响。结果表明:过氧有机酸会影响酶稳定性,添加3.5 mmol柠檬酸三钠会与质量分数为30%H_(2)O_(2)水溶液形成高渗液,防止细胞涨破,同时能中和过量过氧酸,提高反应选择性与细胞的回用稳定性;经过戊二醛交联后,全细胞催化剂的热稳定性、储存稳定性和回用稳定性都显著提高;蒎烯环氧化的最适H_(2)O_(2)用量为5 mmol;可采用直接分离有机相,再加入新鲜有机相的方式进行回用。优化回用方式后,该全细胞催化剂第7次使用时,催化反应仍然有77.3%的转化率。

Effects of trisodium citrate dosage,glutaraldehyde cross-linking of cells,H_(2)O_(2) dosage and recycling methods on catalyst stability were examined usingα-pinene as the model substrate,in order to enhance the stability of Rhizopus oryzae CGMCC 3.5040 whole-cell lipase in a chemo-enzymatic epoxidation reaction system.The results indicate that peroxyacid could affect enzyme stability.Addition of 3.5 mmol trisodium citrate could form a hypertonic solution with a 30%H_(2)O_(2) solution,which prevented cell swelling and neutralized excess peroxyacid,thereby improved reaction selectivity and cell recycling stability.The thermal stability,storage stability,and recycling stability of the whole-cell catalyst were significantly enhanced after glutaraldehyde cross-linking.The optimal H_(2)O_(2) dosage for theα-pinene epoxidation was 5 mmol.Recycling could be achieved by directly separating the organic phase and adding fresh organic phase.After optimizing the recycling method,the catalyst retains a conversion rate of 77.3%even after the 7th usage.