Design of experiments for enhanced production of bioactive exopolysaccharides from indigenous probiotic lactic acid bacteria

Exopolysaccharides (EPS) produced by several bacteria including the probiotic lactic acid bacteria (LAB) not only help them to execute certain vital life functions, but offers huge potential for applications in sectors like medical/pharmaceutical, food, agriculture, and environmental health. However, low yield of EPS from probiotic LAB has always been a challenge. Previously we have reported that EPS from two LAB probiotic strains i.e. Enterococcus faecium K1 (isolate from kalarei), and Lactobacillus paracasei M7 (isolate from human breast milk) possessed several bioactive functional attributes like hypocholesterolemic activity, antioxidant potential, antibiofilm activity, antimicrobial activity, emulsification ability, and desirable physiochemical properties. However, the EPS yield was low. Current study reports optimization of process variables by Design of Experiments (DoE) to enhance EPS yield from these bacteria. The most effective process variables for EPS production were earmarked for E. faecium K1 (lactose, ammonium citrate, incubation time and pH), and for L. paracasei M7 (glucose, incubation time and pH), by Plackett-Burman design, and the same were optimized using central composite design (CCD) of response surface methodology (RSM). The EPS yield from E. faecium K1 was enhanced by 101.40% at optimal level of variables (lactose 10.07 g/L, ammonium citrate 2.49 g/L, incubation time 94.05 h and pH 5.4). Similarly, EPS yield was enhanced by 79.6% from L. paracasei M7 using optimal level of variables (glucose 10 g/L, incubation time 48 h and pH 7.6). Thus, DoE represents a powerful approach for optimization of process variables.