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

Abstract

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 <em>i.e</em>. <em>Enterococcus faecium</em> K1 (isolate from <em>kalarei</em>)<em>, </em>and <em>Lactobacillus paracasei</em> 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 <em>E. faecium</em> K1 (lactose, ammonium citrate, incubation time and pH), and for <em>L. paracasei</em> M7 (glucose, incubation time and pH), by Plackett&ndash;Burman design, and the same were optimized using central composite design (CCD) of response surface methodology (RSM). The EPS yield from<em> E. faecium</em> 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 <em>L. paracasei</em> 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.