Production of exopolysaccharides from Lactobacillus species and optimization of physiochemical parameters by response...

Exopolysaccharides (EPS) are high molecular weight carbohydrate polymers secreted by microorganisms. The aim of the study was to isolate Lactobacillus strains that produce EPS from dairy sources and to enhance EPS production. The dairy source milk, yogurt, and cheese were collected from the local market for isolation of EPS producing strain. The maximum EPS-producing strain was further identified based on biochemical, morphological, and 16S RNA sequencing. Whey was used as a substrate due to its low cost and nutrient- rich composition. Different organic and inorganic nitrogen sources were screened. Central Composite Design (CCD) of Response Surface Methodology (RSM) was used for the optimization of physiochemical parameters. Five various physio-chemical parameters i.e. pH, temperature, nitrogen source, substrate concentration, and incubation period, were optimised. The process was subsequently upscaled in a 1.5 L lab scale bioreactor. Among these, the isolate obtained from cheese exhibited the highest EPS yield. The isolated strain was identified as Limosilactobacillus fermentum-CP158463.1. The yeast extract was found to be the best source of nitrogen 1.7 ± 0.15 mg/ml of EPS yield. The optimal conditions for maximum EPS (2.729 mg/mL) were observed at pH 8, 40 °C, 1% nitrogen concentration, 20% substrate concentration, and a 48-h incubation time. The maximum yield (8.396 ± 1.73 mg/ml) was obtained at 200 rpm with 96 h incubation period. The study shows that Lactobacillus originating from dairy has the capacity to produce EPS, and the RSM model can be used for effective low-cost production.