Effects of environmental factors and nutritional requirements on EPS production and bioactivity.

Marine bacteria release exopolymeric substances (EPS) molecules released in response to the harsh environmental conditions of the environment as a survival strategy. Nitrogen or carbon sources affects the metabolic synthesis of EPS in microorganisms. In this study, 2 different nutritional sources were used to extract EPS from a marine bacterium associated with the sponge Hyrtios erectus collected from the Red Sea. The antibacterial activity and chemical composition of the EPS from Bacillus subtilis M5 grown in Zobell marine broth (ZBE) and nutrient broth (NBE) was studied. The organism demonstrated potential activity against tested pathogenic bacteria. We observed differences in the antibacterial activity and the chemical composition of EPS polymers isolated from the organism. Fourier transform infrared (FTIR) spectrum revealed the peaks for carbonyl, alkyl and hydroxyl functional groups confirming the presence of functional groups characteristic of polysaccharides. Minor differences was observed in the relative intensities and slight peak shifts between the two spectra may be attributed to variations in the specific EPS compositions or extraction conditions. Scanning electron microscopic images revealed crystalline and amorphous characteristics of EPS for ZBE and NBE respectively. Only little differences were observed between the two EPS biopolymers both in antibacterial activity and chemical composition. [ABSTRACT FROM AUTHOR]