制备富含γ-氨基丁酸酸奶的乳酸菌筛选及相关特性分析

为获得能够在乳基底物中生产富含γ-氨基丁酸(gamma-aminobutyric acid,GABA)酸奶所需的食品安全级乳酸菌,从国内市售发酵食品中分离出171株乳酸菌作为实验菌株。采用16S rDNA序列分析对实验菌株进行种属鉴定,采用改进后的高效液相色谱法(HPLC)测定发酵后GABA产量。经肉汤培养基初筛和乳基底物培养基复筛,得到一株在乳基底物中具备高产GABA潜力的乳酸乳球菌乳酸亚种(Lactococcus lactis subsp.lactis),编号4043。将该菌以3%(V/V)接种于含L-谷氨酸钠(L-Glu-Na)2 g/L的10%(m/V)乳基底物培养基中,在30℃下单菌种发酵48 h,GABA产量约0.39 g/L,在目前属于较高水平。该菌能够代谢葡萄糖、半乳糖等18种糖分。将其于30℃下接种于M17培养基中,对数生长期为2~8 h。该菌持续产酸能力较弱,在pH值3~5.5的环境中具备良好的酸耐受性,菌株自凝聚力良好,但对胆盐的耐受性极差;且属于表面弱疏水性菌株,粘附特性较差,难以在人体肠道内有效粘附与定植,不适宜作为胃肠道内益生菌。该菌可作为多菌种混合发酵生产富含GABA的酸奶的发酵剂。

Screening and Characteristics of Lactic Acid Bacteria for Preparingγ-Aminobutyric Acid-rich Yogurt

In order to obtain lactic acid bacteria within food safety level,which is needed for preparing gamma-aminobutyric acid(GABA)-rich yogurt from dairy-based substrates,171 lactic acid bacterial strains were isolated from fermented food in domestic market as tested strains.Species identification of these strains was conducted by 16S rDNA sequence analysis,and GABA yield after-fermentation was determined by improved HPLC.After primary screening in broth medium and rescreening in dairy-based medium,one strain of Lactococcus Lactis subsp.lactis(No.4043)was obtained,which had high-yield potential of GABA in dairy-based medium.Inoculated into 10%(W/V)skimmed reconstituted milk with sodium L-glutamate of 2 g/L,the yield of GABA was about 0.39 g/L after fermenting by single strain at 30℃for 48 h,which ranked relatively high level at present.18 kinds of sugars such as glucose,galactose,etc.,couldbe metabolizedby strain No.4043.Inoculated intoM17 medium at 30℃,the logarithmic growth period was 2~8 h.The strain No.4043 was weak in continuous acid-producing capacity,showed good acid tolerance in the environment with pH 3~5.5,good in auto-aggregation but poor in bile salt tolerance.Surface hydrophobicity and adhesion of the strain No.4043 were weak,leading to difficulties in adhering and colonizing in human intestinal effectively,which was not suitable to be probiotics in gastrointestinal tract.The strain No.4043 could be used as a starter for producing yoghurt rich in GABA by mixed fermentation of multiple strains.