Abstract: Food processing by-products are rich in pectin substances and can be degraded into pectin oligosaccharides by pectinase. It is not only can effectively control the degree of polymerization and structure of pectin oligosaccharides, but also can achieve the reuse of waste resources of food processing by-products and create new economic benefits. In present research, a pectin methylesterase gene belonging to carbohydrate esterase (CE) family 8, Pme8A, was cloned from acidophilic fungus Bispora sp. MEY-1, and the efficient heterologous expression in Pichia pastoris GS115 were realized after ligated to the expression vector of pPIC9. Enzymatic characterization determination of PME8A showed that the temperature with maximum activity was 60 ℃, and more than 80% of the activity was retained at 55～80 ℃. Its optimal pH was 3.5, and more than 50% of the activity was retained at pH 2.5～5.0. It was an acidophilic rare pectin methylesterase from fungus resource. The demethylation of pectin crude extracts from apple pomace and orange peel treated with PME8A showed an obvious effection, and the activities of endo-polygalacturonase PG8fn from Achaetomium sp. Xz8 increased by 8.5 and 1 times, respectively, showing a good synergistic effect. It was demonstrated that pectin methylesterase PME8A could be used in the production of pectin oligosaccharides by food processing by-products, providing a new method for the extraction of pectin oligosaccharides.

Key words: Bispora sp. MEY-1, acidophilic pectin methylesterase, synergistic effect, food processing by-products

摘要： 食品加工副产物富含果胶类物质，果胶酶可以将其降解为果胶低聚糖，不仅可以有效控制果胶低聚糖的聚合度及结构，还能实现食品加工副产物废弃资源的再利用，创造新的经济效益。从嗜酸真菌Bispora sp. MEY-1克隆获得一个碳水化合物第8家族的果胶甲酯酶基因Pem8A，将其连接到表达载体pPIC9上，在毕赤酵母 GS115 中实现高效异源表达。对纯化后的重组蛋白PME8A的酶学性质进行测定，发现其最适温度为60 ℃，在55～80 ℃可保持80%以上的酶活；最适pH为3.5，在pH 2.5～5.0范围内维持50%以上的酶活，是真菌来源中少数的嗜酸果胶甲酯酶。用PME8A处理苹果渣、橘皮果胶粗提物后，去甲基化效果明显，使得Achaetomium sp. Xz8来源的内切多聚半乳糖醛酸酶PG8fn酶活分别提高了8.5倍和1倍，表现出很好的协同效应。研究证明果胶甲酯酶PME8A可以应用于从食品加工副产物生产果胶寡糖，为果胶低聚糖的获取提供了新的方法。

关键词: Bispora sp. MEY-1, 嗜酸果胶甲酯酶, 协同降解, 食品加工副产物