产低温蛋白酶动性球菌的筛选及其在低盐鱼露发酵中的应用

探究4?株从传统虾酱中筛选出的动性球菌对低盐鱼露品质的影响。采用水解透明圈的方法，从传统发酵虾酱中筛选并分离出4?株在低温条件（15?℃）下具有蛋白酶活性的菌株。通过酶活力的测定（40?℃）进行复筛，其中编号为XJ11的菌株酶活力最高，为（10.07±0.11）U/mL。通过形态学观察和16S?rRNA序列比对，鉴定4?株菌均属于动性球菌（Planococcus），分别命名为P. maritimus XJ2、P. plakortidis XJ10、P. dechangensis XJ11和P. rifietoensis XJ12。4?株动性球菌在低温、低盐、碱性的环境中生长良好。动性球菌所产的蛋白酶在40?℃、pH?9.0时有最高酶活力，并具有一定的耐盐性。将4?株动性球菌作为起始发酵剂（1∶1∶1∶1，3%）应用到低盐鱼露的发酵中，结果表明：添加发酵剂的低盐鱼露氨基酸态氮质量浓度（（1.33±0.08）g/100?mL）极显著高于未添加发酵剂的鱼露（（0.89±0.02）g/100?mL，P＜0.01），并且主要的挥发性风味物质含量也高于对照组，例如醇类、酮类、酸类、酯类和吡嗪。因此，该发酵剂能够提高低盐鱼露的氨基酸态氮含量并有效改善风味。

Screening of Low-temperature Protease-producing Planococcus and Its Application in Low-salt Fish Sauce Fermentation

We investigated the effects of four strains of Planococcus with protease activity at low temperature (15 ℃) isolated from traditional fermented shrimp paste on the quality of low-salt fish sauce. The strains were screened for their enzymatic activity at 40 ℃. Among these, strain XJ11 showed the highest protease activity of (10.07 ± 0.11) U/mL. Based on morphological observation and 16S rRNA sequence alignment, all four strains were identified as Planococcus and named P. maritimus XJ2, P. plakortidis XJ10, P. dechangensis XJ11 and P. rifietoensis XJ12, respectively. The strains grew well in a low-temperature, low-salt, and alkaline environment. The protease produced by Planococcus exhibited the highest enzymatic activity at 40 ℃ at pH 9.0 and showed good salt tolerance. A 1:1:1:1 mixture of the four strains was inoculated at 3% as a starter culture in low-salt fish sauce fermentation. The results showed that the amino acid nitrogen content of low-salt fish sauce inoculated with the starter culture was (1.33 ± 0.08) g/100 mL, which was significantly higher than that of the control prepared without the starter culture ((0.89 ± 0.02) g/100 mL) (P < 0.01). The amounts of the key desirable volatiles such as alcohols, ketones, acids, esters and pyrazine were higher than in the control. In summary, the starter culture increased the amino acid nitrogen content of low-salt fish sauce and improved the flavor effectively.