产β-半乳糖苷酶乳酸菌的筛选及酶法合成低聚半乳糖的GC-MS分析

Screening of β-Galactosidase-producing Lactic Acid Bacteria and Analysis of the Enzymatic Synthesis of Galactooligosaccharides by GC-MS

从分离自13种中国传统发酵食品的148株乳酸菌中筛选产高转糖基活性β-半乳糖苷酶的菌株。实验采用X-Gal平板初筛、薄层层析(TLC)复筛、气相色谱(GC)定量的方法,得到一株产β-半乳糖苷酶转糖基活性最高的菌株,并以乳糖为单底物,利用该高转糖基活性β-半乳糖苷酶酶法合成低聚半乳糖(GOS),并采用GC-MS的方法对其各个组分进行鉴定。研究结果表明,菌株70810所产β-半乳糖苷酶转糖基活性最高,其合成GOS产率达到39.23%(m/m);该菌株为实验室已鉴定乳酸菌,为植物乳杆菌(HQ259238)(Lactobacillus plantarum);酶法合成的GOS产物鉴定为9种低聚二糖和3种低聚三糖,主要结构多为β(1→6)和β(1→3)糖苷键。菌株70810来源于泡菜,安全性好,所产β-半乳糖苷酶转糖基活性最高,且可不经纯化直接利用,在食品与乳品加工等方面将具有很好的应用前景。

Lactic acid bacteria (LAB) strains producing β-galactosidases with high transgalactosylation activity were screened from 148 LAB strains found in 13 kinds of traditional Chinese fermented foods. The strain 70810 produced β-galactosidases with the highest transgalactosylation activity and was isolated using a 5-bromo-4-chloro-3-indolyl β-D-galactopyranoside (X-Gal) plate for the primary screening, thin layer chromatography (TLC) for the secondary screening, and gas chromatography (GC) for quantitation. Lactose was used as a single substrate, the synthesis of galactooligosaccharides (GOS) was catalyzed by β-galactosidases with high transgalactosylation activity, and gas chromatography-mass spectrometry (GC-MS) was used to identify each component. The results showed that the β-galactosidases produced by strain 70810 had the highest transgalactosylation activity, and the yield of GOS was 39.23 % (m/m). This LAB strain was identified as Lactobacillus plantarum (HQ259238). Among the GOS products derived from enzymatic synthesis, there were nine disaccharides and three trisaccharides and the main structures contained β-1,6 and β-1,3 glycosidic bonds. Because strain 70810 was isolated from Chinese Paocai, it is safe. The resulting β-galactosidases have the highest transgalactosylation activity and can be directly used without separation and purification. Therefore, this strain has potential applications in food and dairy industries. © 2015, South China University of Technology. All right reserved.