Abstract:

Polygalacturonases has great application value in food and feed industry, so finding new polygalacturonase can not only supply related enzyme information, but also provide more choices for industrial applications. In the study, a thermophilic fungus Neosartorya fischeri P1 was isolated from an acid mine in Yunnan Province. A novel exo-polygalacturonase gene, Nf-pg, was cloned from its genome. The gene Nf-pg was transformed into Pichia pastoris GS115 for heterologous expression. The recombinant enzyme Nf-PG was purified and characterized. The results indicated that the purified Nf-PG was most active at pH 4.5 and 55℃, and showed high stability at pH 2.0~9.0 and good thermal stability. There was still 80% residual enzyme activity after 60 min heat treatment at 50℃. The optimal temperature of deglycosylated recombinant enzyme Nf-PG-D was 50℃. Compared to Nf-PG, enzyme Nf-PG-D showed a decreased thermal stability, but the properties of optimal pH and pH stability were similar to Nf-PG. Product analysis proved that Nf-PG was a strict exo-type polygalacturonase. The excellent properties made Nf-PG an ideal candidate for applying in food processing.

Key words: exo-polygalacturonase, Neosartorya fischeri P1, pectin, Pichia pastoris

摘要：

聚半乳糖醛酸酶在食品和饲料行业具有很大的应用价值，发现新的聚半乳糖醛酸酶不仅能够补充该酶的相关信息，还能为工业应用提供更多选择。从一株嗜热费希新萨托菌（Neosartorya fischeri P1）的基因组中克隆得到一个外切聚半乳糖醛酸酶基因（Nf-pg），将Nf-pg在毕赤酵母GS115中进行异源表达，重组酶Nf-PG纯化后进行性质测定。Nf-PG在pH 4.5和55℃时活性最高，在pH 2.0~9.0具有较好的稳定性，50℃热处理60 min仍能保持80%的剩余酶活；去除N-糖基化的酶蛋白Nf-PG-D最适温度为50℃，热稳定性降低，最适pH和酸碱稳定性无明显改变。产物分析证明Nf-PG是严格的外切聚半乳糖醛酸酶，优异的性质使其成为食品加工行业的良好选择。

关键词: 外切聚半乳糖醛酸酶, Neosartorya fischeri P1, 果胶, 毕赤酵母