This article summarizes the current progress in understanding the characteristics of mixed culture fermentation and interaction mechanism of Lactobacillus bulgaricus and Streptococcus thermophilus as well as the influences of mixed culture fermentation on the synthesis of exopolysaccharides and flavor substances. The aim of this review is to provide useful information for researchers to apply them and screen starter cultures.

In this study, the recombinant Lactobacillus casei LC2W were constructed for overexpressing four bsh genes from L. plantarum ST-III and the Bile salt hydrolase (BSH) enzyme activities were determined. It was shown that the four recombinant strains all showed a lower enzyme activity than the host, indicating that the bsh gene overexpression could not achieve the goal of enhancing the hydrolysis of the bile salts.

Lactic acid is a valuable organic acid widely used in the food, pharmaceutical, cosmetic, and chemical industries, which is also the major end product of carbohydrate fermentation by homofermentative lactic acid bacteria. This paper summarizes the current status of studies on the species distribution of the microbial genus, and the biosynthesis pathway and metabolic regulation of lactic acid. Future prospects in this area are also discussed.

Bile salt hydrolase (BSH) is considered to be especially relevant for microbes that reside in the mammalian gastrointestinal tract, which also helps to reduce the blood cholesterol level of the host. This review focuses on the occurrence of bile salt hydrolase among different microorganisms and its physiological characterization, enzyme activity, substrate specificity and genetics involved with recent updates. The current perspective reveals a huge market potential of probiotics with bile salt hydrolase.