Exploiting the bacterial exopolysaccharide bioconversion using residual cheese whey as culture medium.

Abstract

Cheese whey (CW) represents a potential substrate in biotechnological processes due to the presence of valuable nutrients in its composition. Therefore, CW is used as a low-cost substrate in fermentation for microbial growth and the synthesis of value-added compounds, while mitigating the environmental impact that this by-product can cause. The current study aimed to obtain exopolysaccharides (EPS) by fermenting lactic acid bacteria in CW followed by optimizing production using Response Surface Methodology (RSM) and evaluating the biological properties. Out of 64 isolates, Enterococcus sp. 133 V exhibited a high concentration with 5.58 mg/mL of EPS. With optimization using RSM, 21.74 mg/mL of EPS was obtained with temperature and fermentation time fixed at 42 °C and 22 h, respectively. The characterization of the new EPS revealed a hetero-polysaccharide consisting of galactose, glucose, mannose, arabinose, rhamnose and fucose, including proteins and uric acid in the structure. With a concentration of 2 mg/mL, the purified EPS showed good scavenging effects against DPPH (27%), ABTS (72%) and superoxide (43%), except for the hydroxyl radical (1.29%) which needs a high EPS concentration. These findings underscore the interest in using cheap residue as culture medium to produce biopolymers with potential for applications, particularly in the food and biotechnology sectors.