为探究蛋白酶及脂肪酶活性存在差异的牛肉源假单胞菌对冷鲜牛肉的致腐能力，该研究首先通过酶活性的测定共筛出7株产酶能力差异较大的假单胞菌株，其中荧光假单胞菌（PP3413、PP754、PL1415）3株、恶臭假单胞菌（P011）1株、草假单胞菌（PL347）1株、Pseudomonas salomonii（PP1438）1株、Pseudomonas libanensis（PL1459）1株。在无菌冷鲜牛肉中回归污染以上菌株，发现贮藏末期（8 d）接种荧光假单胞菌（PP3413、PP754和PL1415）的样品中假单胞菌数和挥发性盐基氮（total volatile base-nitrogen，TVB-N）值均较高（分别为8.97~9.65 log CFU/g、20.35~25.02 mg/100 g）。而接种PL347（脂肪酶活性最强）的样品其假单胞菌数（6.25 log CFU/g）和TVB-N值（13.95 mg/100 g）均显著低于其他处理组（p<0.05）。此外，产蛋白酶能力较强的PP754（25.02 mg/100 g）、PP3413（22.06 mg/100 g）的TVB-N值高于产脂肪酶能力较强的PL1459（21.80 mg/100 g）、PL1415（20.35 mg/100 g）。综上所述，荧光假单胞菌的产酶能力和腐败能力较强，且产蛋白酶能力较强的假单胞菌其腐败能力可能优于产脂肪酶能力较强的菌株，但假单胞菌对冷鲜牛肉的致腐能力与其产酶能力的具体关系有待进一步确证。

In order to explore the decay-causing abilities of beef-derived Pseudomonas strains with varying protease activities and lipase activities towards chilled beef, seven Pseudomonas strains with greatly different enzyme-producing abilities were screened based on enzymatic activities. The isolated strains included three strains of Pseudomonas fluorescens (PP3413、PP754、PL1415), one strain of P. putida (P011), one strain of P. poae (PL347), one strain of P. salomonii (PP1438), and one strain of Pseudomonas libanensis (PL1459). Then, the stains were used to re-contaminate the surface of sterile chilled fresh beef. At the end of storage (8 d), the number of Pseudomonas and TVB-N values for the samples inoculated with Pseudomonas fluorescens (PP3413, PP754 and PL1415) were relatively high (8.97~9.65 log CFU/g, and 20.35~25.02 mg/100 g, respectively). However, the number of Pseudomonas and TVB-N values of the beef samples inoculated with PL347 (which had the highest lipase activity) were 6.25 log CFU/g and 13.95 mg/100 g, respectively, which were significantly lower than those of other treatment groups (p<0.05). In addition, the TVB-N values of the samples contaminated by the strains with stronger protease-producing abilities, PP754 (25.02 mg/100 g) and PP3413 (22.06 mg/100 g) were higher than those of the strains with stronger lipase-producing abilities, PL1459 (21.80 mg/100 g) and PL1415 (20.35 mg/100 g). In summary, P. fluorescens had relatively high enzymes-producing ability and decay-causing ability, with the strains with stronger protease-producing abilities likely having higher decay-causing abilities towards beef than those with stronger lipase-producing abilities. However, the specific relationship between the decay-causing ability of Pseudomonas towards chilled fresh beef and its enzyme-producing ability needs to be further confirmed.

国家现代农业产业技术体系建设专项（CARS-37）；山东省现代农业产业技术体系牛产业创新团队项目（SDAIT-09-09）