Isolation and evaluation of a soil bacterial strain for exopolymer Production and Functional Characterization

Abstract

Background and objectiveThe ability of microorganisms to synthesize Exopolysaccharides (EPSs) has garnered considerable interest in the food sector because of their functional properties, particularly their role as natural thickeners and their contribution to improving the rheological behavior of fermented products. This study aimed to assess the ability of soil bacterial isolates to generate EPS under different environmental conditions.Materials and methodsBased on their physical characteristics and 16S rRNA gene sequencing, the selected bacterial isolate was identified to Priestia flexa (Pg). The single-variable-at-a-time approach was adapted to customize cultivation environments to maximize the EPS production for the isolated strain. Functional groups forming the exopolysaccharide were identified using FTIR, while the monosaccharide composition was measured using HPLC. The brine shrimp toxicity was investigated to ensure that the EPS produced had nontoxic effect.Results and conclusionThe EPS maximum yield of 11.16 g/L was achieved by the isolate Priestia flexa and the EPS extract infrared (FT-IR) spectra showed the usual polysaccharide patterns absorption. Furthermore, HPLC analysis showed that EPSs is heteropolysaccharides composed mainly of glucose, galactose, mannose, arabinose, xylose, raminose and fructose. The produced polysaccharide was consists of high ratios of carbon, oxygen, phosphorus, calcium, and chloride, as verified by Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The EPS exhibited both antioxidant properties and antibacterial activity against serious human pathogens, including Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella typhimurium, indicating its potential use in the food sector. Moreover, the bacteria showed a nonhemolytic effect on the blood agar medium. Also, the produced EPS had a nontoxic effect on brine shrimp toxicity (Artemia salina).