西藏、川西青藏高原牧区自然发酵牦牛酸奶中优良乳酸菌的筛选及鉴定

Isolation and Identification of Lactic Acid Bacteria from Natural Yak Yogurt in Tibet Plateau Pastoral Areas of Tibet and Western Sichuan

从西藏、川西青藏高原牧区自然发酵的牦牛酸奶样品中分离出56株乳酸菌菌株，通过初筛选出遗传稳定性好、凝乳时间短、感官性能好的乳酸菌10株，再通过对各种发酵性能的测定最终筛选出7株性能优良的乳酸菌。这7株菌的凝乳时间在6～8h之间，凝乳时的酸度在69.99～92.31°T之间，冷藏期间滴定酸度增加了8.46～20.94°T，活菌数为107～1011CFU/mL，产生的乙醛和双乙酰含量分别为14.21～30.76μg/mL和0.51～1.55μg/mL。通过16S rDNA分子鉴定得出：TG1-1为干酪乳杆菌或副干酪乳杆菌，TG1-11为副干酪乳杆菌，TG3-2和DLDQ2-1为干酪乳杆菌，TG2-4、KDLL-2为屎肠球菌，TG3-4为坚忍肠球菌。

Totally 56 strains of lactic acid bacteria were isolated from self-made yoghurt samples collected from Tibet plateau pastoral areas of Tibet and western Sichuan. Ten strains with better fermentation performance LAB were obtained through preliminary screening by genetic stability, coagulation time, titratable acidity and sensory evaluation. Finally, 7 trains of LAB with excellent fermentation performance were selected. Coagulation time and titratable acidity at the coagulation time of these 7 strains were 6-8 h and 69.99-92.31 °T. During cold storage, the titratable acidity was 8.46- 20.94 °T, and the viable bacterial pollution was 107-1011 CFU/mL. The contents of produced acetaldehyde and diacetyl were 14.21-30.76 μg/mL and 0.51-1.55 μg/mL. Based on 16S rDNA sequence analysis, TG1-1 was identified as Lactobacillus casei or Lactobacillus paracasei; TG1-11 as Lactobacillus paracasei, TG3-2 and DLDQ2-1 as Lactobacillus casei, TG2-4 and KDLL-2 as Enterococcus faecium; and TG3-4 as Enterococcus durans.