Exploring the properties of Rhizobium sp. HR1101-4 exopolysaccharide: introducing a novel exopolysaccharide in food industry.

Microbial exopolysaccharides (EPSs) exhibit distinct physiological properties, including anti-inflammatory, anti-tumor, and anti-microbial activities that may have a range of industrial, pharmaceutical, and medical uses. This study aimed to separate, purify, and examine the properties of the Rhizobium sp. HR1101-4 EPS. The optimum parameter set (time, temperature, pH, sugar) for the production of EPS was determined. The highest yield was obtained at a temperature of 39 °C, a pH range of 8-10, and using mannose (0.2%) as the carbon source. The results of FT-IR and the NMR analysis revealed that the EPS is a mixture of hexoses with possible pentose sugars. Moreover, this structure showed positive antibiofilm activity against five pathogenic bacteria; Acinetobacter sp., Staphylococcus aureus, Shigella sonnei, Salmonella sp., and Shigella flexneri, as well as antioxidant activity (42%). Furthermore, the high water-holding (355%) and oil-holding capacity (170%) of the EPS may enhance the nutritional value and rheological characteristics of food products. The improved emulsifying activity of mustard oil suggested potential use for stabilizing emulsions. Additionally, the EPS showed promising flocculating activity, indicating its potential application in treatment of industrial wastewater. This also could be employed as a safe rheological agent and a nutritious food-grade additive for industrial use, paving the way for manufacturing innovation in near future.