Influence of pH, sucrose concentration and agitation speed on exopolysaccharide production by Lactobacillus confusus TISTR 1498 using coconut water as a raw material substitute.

Coconut water (CW) was used as a complex nitrogen source for exopolysaccharide (EPS) production by Lactobacillus confusus TISTR 1498 to reduce the cost of fermentation medium. EPS production was carried out in a bioreactor using (0.5×) modified MRS-sucrose-CW medium, in which three relatively expensive complex nitrogen sources (peptone, yeast extract and beef extract) were halved relative to those present in (1×) modified MRS-sucrose medium. Fermentation parameters (pH, sucrose concentration and agitation speed) were varied in the process of optimisation. Under an optimised condition (pH 5.5, sucrose concentration of 100 g/L and agitation rate of 50 rpm), the maximum EPS level of 38.2 g/L was produced at 35C after 30 h of cultivation. This EPS concentration (38.2 g/L) from the (0.5×) medium was higher than those produced in the (1×) modified MRS-sucrose and (1×) modified MRS-sucrose-CW media (21.3 and 31.5 g/L respectively), both having the original concentration of all three complex nitrogen sources. Thus, in a bioreactor where the pH level was properly controlled, the EPS production was greatly enhanced. Sugar concentration also played an important role in the production of EPS.