College of food engineering, Harbin Commercial University
乳酸菌在食品及食品发酵行业具有广阔的应用。其中以乳酸菌酸浆为凝固剂的酸浆豆腐已逐渐成为人们关注的热点。豆腐酸浆发酵过程中以乳酸菌为优势菌，在酸浆豆腐点浆时，需在75 ℃以上高温下进行。普通乳酸菌无法耐受此温度且大量失活，影响产品的后熟。本研究为了开发耐高温乳酸菌，以课题组从云南建水豆腐酸浆中分离的菌株为出发菌，通过紫外诱变的方式，筛选获得四株耐高温产酸性能好的菌。诱变获得四个菌株可在75 ℃30 min的条件下耐高温30 min并保持较好的活性和产酸效果。对其进行形态学观察、生理生化特征及16S rDNA序列鉴定,结果表明:4株乳酸菌HCUL 1.1801-1912Z、HCUL 1.1802-1912Z、HCUL 1.1706-1912Z、HCUL 1.1707-1912Z分别为鼠李唐乳杆菌、德式乳杆菌、弯曲乳杆菌及棒状乳杆菌。本研究所得突变菌株相比原始菌株均具有更好的耐热性和产酸性。其中鼠李唐乳杆菌（HCUL 1.1801-1912Z）活性最强、产酸能力最好，为四株菌中最优菌株该菌株用于发酵生产酸浆豆腐，将显著提高乳酸菌在豆腐中的活性和豆腐的品质。
Lactic acid bacteria are widely used in food and food fermentation industry. Among them, yogurt tofu with lactic acid bacteria as coagulant has gradually become a hot spot. Lactic acid bacteria was the dominant bacteria in the fermentation process of tofu sourdough. The high temperature above 75 ℃should be used when the sour milk tofu was used as the starter. Ordinary lactic acid bacteria can not tolerate this temperature and a large number of inactivation, affecting the ripening of the product. In order to develop high temperature resistant lactic acid bacteria, four strains of high temperature resistant and acid producing bacteria were screened by UV mutagenesis with the strains isolated from Jianshui tofu acid pulp in Yunnan Province. The results showed that the four strains could resist high temperature for 30 min at 75 ℃for 30 min, and maintain good activity and acid production. Morphological observation, physiological and biochemical characteristics and 16S rDNA sequence identification showed that the four lactic acid bacteria hcul 1.1801-1912z, hcul 1.1802-1912z, hcul 1.1706-1912z and hcul 1.1707-1912z were Lactobacillus rhamnoides, Lactobacillus germanica, Lactobacillus campylosus and Lactobacillus Corynebacterium respectively. Compared with the original strain, the mutant strains obtained in this study have better heat resistance and acid production. Among them, Lactobacillus rhamnoides (hcul 1.1801-1912z) has the strongest activity and the best acid production capacity, which is the best among the four strains. The strain used in the fermentation of sour milk tofu will significantly improve the activity of lactic acid bacteria in tofu and the quality of tofu.