一株乳酸乳球菌产γ-氨基丁酸能力及其安全性评价

探讨了乳酸乳球菌乳亚种HUCM 201产γ-氨基丁酸的能力，并初步评价了其安全性。以γ-氨基丁酸含量为评价指标，通过正交试验优化了乳酸乳球菌乳亚种HUCM 201菌株产γ-氨基丁酸的发酵条件，即接种量为4%、初始pH值6.5，发酵温度31 ℃，发酵时间60 h，其发酵液中γ-氨基丁酸的质量浓度可达218.7 μg/mL。通过硝基还原酶活性检测、生物胺产生能力分析、吲哚试验和溶血性试验，初步评价了菌株HUCM 201的安全性，发现其硝基还原酶阴性，吲哚试验阴性，无溶血，不能产生酪胺、组胺、尸胺和腐胺生物胺类物质，可初步认为是一株安全的益生菌。

γ-aminobutyric acid-producing ability and safety evaluation of Lactococcus lactis

The γ-aminobutyric acid-producing ability of Lactococcus lactis subsp. lactis HUCM 201 was discussed and the strain safety was preliminarily evaluated. Using γ-aminobutyric acid concentration as evaluation index, the optimal fermentation condition of strain HUCM 201 was evaluated by orthogonal experiments. The optimal fermentation condition was inoculum 4%, initial pH 6.5, fermentation temperature 31 ℃ and time 60 h. The γ-aminobutyric acid concentration was determined as 218.7 μg/ml based on the optimal fermentation condition. Moreover, the safety of L. lactis subsp. lactis HUCM 201 was evaluated via nitroreductase activity determination, biogenic amines production analysis, indole experiments and haemolysis experiments. The results suggested that the strain HUCM 201 was a nitroreductase-negative, indole-negative, haemolysis-negative bacterium, and could not produce biogenic amines, such as tyramine, histamine, cadaverine, and putrescine. Thus, L. lactis subsp. lactis HUCM 201 was preliminarily considered as safe probiotic bacterium.