Optimization and extraction of edible microbial polysaccharide from fresh coconut inflorescence sap: An alternative substrate

Abstract

The objective of the study is to evaluate the potential usage of fresh coconut inflorescence sap (FCIS) as a fermentation medium for levan production using Bacillus subtilis. The fermentation conditions such as temperature, pH and agitation speed were optimized using Response Surface Methodology (RSM). The levan yield was enhanced by optimizing the downstream process by altering the pH (5–12) with different solvents (Ethanol, Methanol and Isopropanol) at different ratios. The yield was enhanced further by fed batch fermentation process by feeding with sucrose alone or sucrose and yeast extract. The maximum levan yield was observed as 51.84 g/L at the optimized conditions (Temperature - 35 °C, pH 6.5, and Agitation speed - 150 rpm) using Response Surface Methodology. Whereas, in fed-batch fermentation process the levan yield was increased to 62.1 g/L. The maximum levan was obtained at pH 10 with ethanol at 1:5 ratio. The obtained levan was characterised and confirmed by TLC, FTIR, NMR and GPC analysis. To best of our knowledge, this is the first study conducted to produce levan from FCIS and results showed that FCIS can be a natural low-cost substrate for levan production.