title: Cracking Streptococcus thermophilus to stimulate the growth of the probiotic Lactobacillus casei in co-culture.
abstract: Lactobacillus casei, a probiotic, and Streptococcus thermophilus, a fast acidifying lactic acid bacterial strain, are both used in the food industry. The aim of this study was to investigate the interaction between L. casei and S. thermophilus in the presence or absence of S. thermophilus-specific bacteriophage during milk fermentation. The acidification capability of L. casei co-cultured with S. thermophilus was significantly higher than that observed for L. casei or S. thermophilus cultured alone. However, the probiotic content (i.e., L. casei cell viability) was low. The fastest acidification and the highest viable L. casei cell count were observed in co-cultures of L. casei and S. thermophilus with S. thermophilus phage. In these co-cultures, S. thermophilus compensated for the slow acid production of L. casei in the early exponential growth phase. Thereafter, phage-induced lysis of the S. thermophilus cells eliminated the competition for nutrients, allowing L. casei to grow well. Additionally, the ruptured S. thermophilus cells released intracellular factors, which further promoted the growth and function of the probiotic bacteria. Crude cellular extract isolated from S. thermophilus also significantly accelerated the growth and propagation of L. casei, supporting the stimulatory role of the phage on this micro-ecosystem.
authors.affiliation: State Key Laboratory of Dairy Biotechnology, Technology Center of Bright Dairy & Food Co., Ltd., 1518 Jiangchang Road (W), Shanghai 200436, China; Wuhan Bright Dairy Co., Ltd., 1 Zhangbai Road, Wuhan 430040, China.
authors.forename: Chengjie
authors.initials: C
authors.lastname: Ma
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Street, Wuhan 430070, China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Dairy Biotechnology, Technology Center of Bright Dairy & Food Co., Ltd., 1518 Jiangchang Road (W), Shanghai 200436, China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Dairy Biotechnology, Technology Center of Bright Dairy & Food Co., Ltd., 1518 Jiangchang Road (W), Shanghai 200436, China.
authors.forename: Zhenmin
authors.initials: Z
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Dairy Biotechnology, Technology Center of Bright Dairy & Food Co., Ltd., 1518 Jiangchang Road (W), Shanghai 200436, China.
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Dairy Biotechnology, Technology Center of Bright Dairy & Food Co., Ltd., 1518 Jiangchang Road (W), Shanghai 200436, China. Electronic address: guobenheng@gmail.com.
authors.forename: Benheng
authors.initials: B
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Street, Wuhan 430070, China. Electronic address: zhengjun.chen@gmail.com.
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000818:Animals; D018920:Coculture Techniques; D005285:Fermentation; D005516:Food Microbiology / Q000379:methods*; D007780:Lacticaseibacillus casei / Q000254:growth & development*; D056265:Microbial Interactions; D008892:Milk / Q000382:microbiology*; D019936:Probiotics; D048249:Streptococcus thermophilus / Q000737:chemistry* / Q000821:virology*
keywords: Co-culture; Fermented milk; Lactobacillus casei; Streptococcus thermophilus; Streptococcus thermophilus phage