Streptococcus thermophilus separated from tibetan kefirs as well as separation method and applications thereof

Abstract

The invention discloses streptococcus thermophilus separated from tibetan kefirs as well as a separation method and applications thereof, belonging to the field of microbial technology. The separation method is characterized in that an operation of streaking separation is performed on a M17 culture medium plate, an operation of culturing is performed 48 hours at a temperature of 42 DEG C, a bacterial colony is circular and raised, neat in edge and milk white in color, bacterial colonies which are non-transparent, contain spherical bacteria, can be subjected to wiredrawing, provided with wet and smooth surface, and mostly arranged in chains with different lengths are selected, and no spore is produced; the streptococcus thermophilus is negative in a catalase test, positive in gram stain, negative in a nitrate reduction test, and has no motility and aerobic and facultative anaerobic growth, gelatin is not liquefied, hydrogen sulfide is not produced, and the streptococcus thermophilus is negative in an indole test; the streptococcus thermophilus does not grow at a temperature of 15 DEG C; the growth temperature is 37-45 DEG C; the highest and lowest initial growth pH values are respectively 9.0 and 4.0, and the growth initial pH value is 6.5-7.0. The streptococcus thermophilus aas well as separation method and applications thereof disclosed by the invention have the beneficial effects that the maximum quantity of exopolysaccharides produced when the streptococcus thermophilus is fermented 30 hours by using a M17 culture solution under the condition of 42 DEG C is 111 mg / L; and when a fermented yoghurt is prepared by using strains provided by the invention, the amounts of a thickener and a stabilizer can be reduced.

Description

technical field [0001] The invention belongs to the technical field of microorganisms. Background technique [0002] Streptococcus thermophilus is a Gram-positive bacterium, usually used together with Lactobacillus bulgaricus as a yogurt starter, and is an important strain of yogurt starter, which can produce lactic acid, exopolysaccharide and characteristics by fermenting milk Flavor substances that give yogurt products their unique texture and flavor. The difference in the fermentation characteristics of Streptococcus thermophilus directly affects the quality of yogurt products, and there are significant differences in the fermentation characteristics of different strains, so the screening of Streptococcus thermophilus with excellent characteristics is the basis for the successful preparation of yogurt starter. [0003] Western countries with developed dairy industry have developed commercial production of Streptococcus thermophilus concentrated lactic acid bacteria start...

AI Technical Summary

Problems solved by technology

However, domestic problems such as imperfect preparation of Streptococcus thermophilus starter, poor strain viability, and poor texture of fermented milk lead to a low level of industrial application