Effects of Cultural Conditions on Exopolysaccharide Production by Bacillus sp. ZBP4

Microbial exopolysaccharides (EPSs) are of great interest for the application in various industries due to their gelling, stabilizing, emulsifying, and antioxidant properties. In the present study, EPS production of 12 Bacillus strains were investigated and the best producer, namely Bacillus sp. ZBP4, was selected for further studies in order to determine the effects of fermentation conditions on the biosynthesis of EPSs. Beet molasses was used as substrate in the experiments. The highest amount of EPS was obtained at 60 g L-1 molasses concentration within 24 h. Optimum temperature and pH were determined as 45 oC and 5.0, respectively. Various carbon sources (glucose, starch, lactose, whey, mannitol, sucrose, beet molasses) have been tested for EPS production and beet molasses was found as the best. Using inorganic nitrogen source (ammonium sulfate) caused a decrease in the production of EPS. Tryptone gave the highest EPS yields amongst the organic nitrogen sources (yeast extract, peptone, tryptone) tested. Considerable increase in EPS production (1071 mg L-1) has been observed when the experiment was conducted under the optimized conditions (using tryptone and 60 g L-1 molasses at pH 5.0 and 45 °C in 24 h) which was 143 mg L-1 before the optimization studies.