Isolation of an exopolysaccharide from a novel marine bacterium Neorhizobium urealyticum sp. nov. and its utilization in nanoemulsion formation for encapsulation and stabilization of astaxanthin

The increasing health awareness among population has resulted in demand for foods with minimum side effects. In recent times, natural biomolecules are more preferred as compared to their synthetic counterparts. Microbial polysaccharides have shown potential to replace synthetic food additives. The present study aims to explore marine exopolysaccharide (EPS) as a replacement for synthetic emulsifiers such as sorbates and polysorbates. In the process, an EPS designated as K1T-9 was isolated from the marine bacterium Neorhizobium urealyticum K1T sp. nov. that showed pH stable emulsification activity. This EPS K1T-9 was utilized as an emulsifier for nanoemulsion formation through ultrasonication to encapsulate and enhance the bioavailability of astaxanthin. Partial characterization of the EPS suggested that it is a heteropolysaccharide consisted of glucose and galacturonic acid with a molecular weight of 207 kDa. Interestingly, the functional properties of K1T-9 have revealed that the molecule exhibited non-Newtonian pseudoplastic and shear-thinning flow behavior along with high water (356 ± 0.8%), oil holding (697 ± 1% for coconut oil, and 317 ± 1.3% for olive oil), and swelling capacity (200 ± 1.1%). Thus, the EPS K1T-9 obtained from Neorhizobium urealyticum sp. nov. holds plausible applications in food and related industries.