Biosynthesis of exopolysaccharide by a Bacillus licheniformis strain isolated from ropy cider

A strain of Bacillus licheniformis displaying a ropy phenotype was isolated from a French ropy cider. The influence of culture conditions on the production of exopolysaccharide (EPS) was investigated. When B. licheniformis was grown in Man, Rogosa and Sharpe (MRS) medium, the highest amount of EPS was observed at mid exponential growth phase whatever the carbon source, glucose, fructose or sucrose. Interestingly at mid exponential growth phase, EPS amounts did not increase with increasing sugar concentrations. Incubation of B. licheniformis cells in media supplemented with ethanol (1-7%, v/v) revealed that EPS production was enhanced by the presence of ethanol, in exponential as well as in stationary phase. High Performance Liquid Chromatography (HPLC) and Nuclear Magnetic Resonance (NMR) analysis of EPS composition indicated that it was a heteropolymer in which mannose was the predominant monosaccharide as it constituted more than 80% of total polysaccharide.