Achieving high biomass of probiotic Enterococcus faecium by affordable culture media using response surface methodology

Abstract

By increased consumption of probiotics as health-improving supplements by humans and livestock, there is a necessity for cost-effective large-scale production of these beneficial microorganisms. A cost-efficient and optimal culture medium was designed for large-scale production of probiotic E. faecium and operating conditions were optimized using response surface methodology. A three-stage sequential optimization process was designed to optimize media composition and operating conditions.

The results showed that an economic combination of CSL and yeast extract at a ratio of 70:30 as nitrogen source and sucrose as carbon source could achieve a biomass yield of 1.5 × 10⁹ CFU/mL. Further optimizations revealed the negligible effect of agitation and temperature, while the initial pH and phosphate buffer concentration significantly influenced the biomass yield. A confirmation experiment with culture medium composed of sucrose 20 g/L, CSL 8.4 g/L, yeast extract 3.6 g/L, phosphate buffer 0.06 M under the initial pH of 8.0, and temperature of 32.5 °C obtained a final biomass concentration of 1.9 × 10⁹ CFU/mL. The scaled up processes in 10-L and 75-L fermenters under the optimized conditions successfully produced biomass yields of 2 × 10⁹ and 3 × 10⁹ CFU/mL, respectively. These findings showed the feasibility of formulating an innovative and cost-effective culture medium with readily available ingredients to achieve high biomass concentrations of probiotics.