Optimization, kinetics and radioprotective potential of a heteropolysaccharide from L. rhamnosus RVPI

The probiotic potential of Lactobacillus rhamnosus RVP1 isolated from Sardinella longiceps was investigated in vitro. The bacterium exhibited highest tolerance at low pH, high bile salt concentration and demonstrated good antioxidant activity, hydrophobicity and inhibited both gram-negative and gram-positive indicator bacteria. To aid in process design and to unravel the fermentation kinetics, response surface methodology was devised to optimize the EPS production from L. rhamnosus and mechanistic models were developed to describe the fermentation kinetics. The optimum pH, dextrose and peptone concentrations for EPS production were 7.07, 19.995 g/L and 23.4 g/L, respectively, with a predicted yield of 724 mg/L. The actual yield under these conditions was 708±29 mg/L which was within the 95% confidence interval. The simulated mechanistic model fit the experimental values with a high degree of correlation with R2 = 0.99, 0.96 and 0.97 for the logistic growth, substrate consumption and EPS production and degradation curves respectively. The kinetic constants μ_max = 0.29 hr^-1 , Xmax = 3.44 g/L, kf = 348 mg of EPS/ g of dry biomass and kd = 0.53 hr^-1 were derived from the model. The EPS administration improved the survival of irradiated mice by 50% proving it radioprotective potential and showed positive effects on structural integrity of intestinal tissue. This article is protected by copyright. All rights reserved.