Unravelling the efficacy of Enterococcus faecalis: A statistical approach to select cost effective medium

The human gut microbiota comprises millions of microbes that confer various health benefits. Maintaining a healthy gut microbiome necessitates the consumption of appropriate dietary supplements. This study endeavours to identify an optimal dietary supplement for fostering the growth of Enterococcus faecalis (isolated from human origin) and Lactobacillus acidophilus (MTCC 10307). E. faecalis displays notable tolerance under simulated gastrointestinal conditions (87%), akin to L. acidophilus (88%). Initially, a screening of diverse dietary materials (including millets and legumes) was conducted using the Plackett-Burman Design (PBD) method. Among the 11 materials assessed, foxtail millet, barnyard millet, finger millet, and cowpea demonstrated significant effects on the growth rate of probiotics. However, further optimization of conditions is necessary to augment the growth of these probiotics. Subsequently, the Box-Behnken Design (BBD) was employed to derive the ANOVA for a quadratic model utilizing Design Expert software. The growth rate was positively influenced by variables such as (A) foxtail millet, (B) barnyard millet, (C) finger millet, and (D) cowpea, either individually or in combinations of two variables (AB, AC, BC, BD, CD). Particularly noteworthy was the enhancement of E. faecalis growth by approximately 92.78% with the supplementation of foxtail and barnyard millets at a concentration of 100 mg/ml. Moreover, growth kinetics indicated that increased microbial growth resulted in a reduction of substrate (foxtail millet) concentration. The specific growth rate of 1.26 Log CFU/ml was observed in E. faecalis monoculture, with foxtail consumption accounting for 95% of this growth. However, co-cultures of E. faecalis and L. acidophilus led to an inhibition of up to 84% in the growth rate of S. typhimurium . Consequently, millet-based media showcased a superior capacity to enhance probiotic growth compared to MRS media. Thus, foxtail millets emerge as a compelling dietary supplement for augmenting the human gut microbiome.