Isolation and Identification of Symbiotic Bacteria from <i>Brasenia schreberi</i> and Analysis of their Polysaccharide Producing Characteristics and Antioxidant Activity

Abstract

Brasenia schreberi (water shield), a perennial freshwater aquatic plant of the family Nymphaeaceae , is rich in polysaccharides with positive biological activity and potential application value. As an indicator plant of the environment in wetlands, B. schreberi original and wild water environment faced increasing deterioration and has been listed as a critically endangered species in several countries of East Asia. Seeking an alternative method to produce B. schreberi mucilage polysaccharide is of top priority. The morphological structure of the stem and leaf of B. schreberi was studied. Well-developed glandular cells and aerenchyma tissue were observed in the stem and leaves of water shield, which were related to its aquatic habitat and polysaccharide secretion and then three endophytic bacteria were successfully isolated and purified from its stem and leaf and identified as Micromonospora sp. YG-1, Xylariaceae sp. strain UT-X and Psychrobacter pulmonis strain T-15. Symbiotic bacteria from B. schreberi produced polysaccharides with similar spectral peaks and chemical functional groups to those of B. chinensis . Further, analysis of hydroxyl free radicals showed that symbiotic bacteria in water shield had significant antioxidant activity against hydroxyl free radicals. This study provides a theoretical and practical basis for further study using symbiotic bacteria to produce polysaccharides to overcome the environmental limitations of the growth and development of B. schreberi .