一株高产琼胶酶菌株MA-B22的分子鉴定与产酶条件优化

琼胶酶在多糖降解应用中的作用日益重要，而从海洋微生物中筛选琼胶酶高产菌株成为一个重要途径。本研究从养殖的杂色鲍体内分离到一株高产琼胶酶的菌株MA-B22。该菌为革兰氏阴性菌，经16S rRNA序列鉴定表明，与Tamlana agarivorans sp. nov.具有99%同源性，因此初步定为Tamlana sp.。在2216E培养基中该菌株在培养时间60 h，温度25 ℃，起始pH为6.0条件下产酶活性最高。基于上述培养条件，通过单因素和正交实验确定了培养基的最佳基本组成：氮源为牛肉膏（其最适浓度为6.0 ‰），碳源为琼脂（其最适浓度为2.5 ‰），配制培养基的人工海水的最适盐度为25。经培养条件优化后，该菌胞外琼胶酶活力可达1021.79 U/mL，较优化前提高8.82倍。实验首次对Tamlana sp.属的琼胶酶活性进行确定并优化其产酶条件，为构建琼胶酶高产工程菌株提供了基础,并可能为今后鲍养殖提供潜在的益生菌。

Isolation and identification of a bacterium MA-B22 producing agarase and the optimal cultivation of enzyme production

Agarase plays a key role in degrading many complex polysaccharides. The screening of agar-degrading bacteria from marine environment and organisms becomes an important means. A gram-negative bacterial strain, MA-B22 with high agarase activity was isolated from small abalone Haliotis diversicolor. By 16S rRNA analysis, this strain has 99% homology to Tamlana agarivorans sp. Nov. , it was named Tamlana sp. In this report. Under 2216E medium, the optimal temperature, pH value and culture time are 25℃, 6.0 and 60h respectively. With one-factor-at-a-time method and orthogonal designed experiment, the optimal compositions of the ferment medium were confirmed. It contained 2.5‰ agar, 6.0‰ beef extract based on the salinity of 25. The highest enzyme activity of agarase was detected by DNS method at 1021.79 U/mL, which is 8.82 times higher than before. MA-B22 demonstrated high-performance characteristics of enzyme production. This is the first report on the agar-degrading Tamlana sp. And optimal cultivation to enhance its enzyme activity. The results provide a basis for constructing engineering bacterium for expression agarase genes and potential probiotics of abalone aquaculture in the future.