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 K1(T)-9 was isolated from the marine bacterium Neorhizobium urealyticum K1(T) sp. nov. that showed pH stable emulsification activity. This EPS K1(T)-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 K1(T)-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 K1(T)-9 obtained from Neorhizobium urealyticum sp. nov. holds plausible applications in food and related industries.

Automated summary

The study isolated a marine exopolysaccharide EPS K1(T)-9 from Neorhizobium urealyticum sp. nov. and investigated its potential as a replacement for synthetic emulsifiers. EPS K1(T)-9 exhibited pH stable emulsification activity and functional properties such as non-Newtonian pseudoplastic behavior, high water and oil holding capacity, and swelling capacity. The findings suggest that EPS K1(T)-9 has promising applications in the food and related industries.