来自混合菌群的聚乙烯醇降解酶的性能

Properties of PVA-degrading enzymes produced by a mixed microbial culture

以在无锡桃花山垃圾填埋场筛选出的具有较好降解聚乙烯醇(PVA)能力的混合菌群所产的PVA降解酶为研究对象,对其对不同聚合度和醇解度的PVA的降解能力以及降解条件进行了研究,并对其降解PVA的机理进行了初步探索。实验结果表明,PVA降解酶降解PVA的能力受PVA聚合度和醇解度的影响较大,对PVA1799的降解效率远远高于对PVA1788和PVA124的降解效率;混合菌群产生的PVA降解酶降解PVA的最适温度为40℃,最适pH为7.0;Fe^(2+)对PVA降解酶酶活有一定的促进作用,外加Fe^(2+)能使酶活提高26%左右。PVA降解酶在最适条件下作用1 g/L的PVA1799 6 h后,PVA相对分子质量降低14.8%,熔点由221.3℃降低至216.7℃。高效液相色谱(HPLC)结果分析表明降解产物中存在乙酸,碘仿反应表明降解产物中存在甲基酮,PVA的降解途径有可能是长碳链上相邻的两个羟基被氧化成羰基后水解断裂并最终产生乙酸。

The crude PVA-degrading enzymes were extracted from a mixed culture obtained by selective culturing with PVA as the sole carbon source. The degradation capability,enzymatic properties and degradation products of the enzymes were investigated in this study. The results indicated that the degradation of PVA1799 by the PVA-degrading enzymes was much better than those of PVA1788 and PVA124. The optimal temperature for the crude enzymes was 40℃ and the optimal pH was 7.0. Fe^2＋ addition promoted the PVA-degrading enzymes＇ activity. It could increase the enzyme activity by about 26%. The relative molecular mass of PVA1799 decreased by 14.8% after 6 hours under the optimum conditions. At the same time,the melting point of the PVA sample was reduced from 221.3℃ to 216.7℃ after 6h. The results of High Performance Liquid Chromatography（HPLC） analysis indicated degradation products containing acetic acid. The iodoform reaction indicated the presence of methyl ketone in degradation products. A possible degradation pathway of PVA was oxidation to carbonyl group and breaking of the two adjacent hydroxyl groups on the long carbon chain. Acetic acid is the final product.