Statistical optimisation of the exopolysaccharide production by Lactobacillus fermentum Lf2 and analysis of its chemical composition

Lactobacillus fermentum Lf2 produces high amounts of exopolysaccharides (EPS) (~1 g/L) with demonstrated functional and technological roles when applied as a food ingredient in dairy matrices, properties that made these EPS interesting in comparison with other similar molecules from lactic acid bacteria (LAB). Those characteristics encouraged us to optimise the production. The EPS extract is composed of a high molecular mass beta-glucan and a medium molecular mass heteroglycan. In the present work, the optimal conditions that doubled the EPS yield using a semidefined medium (SDM, 0.63% yeast nitrogen base, 0.53% bacto casitone, 0.53% ammonium citrate, 6.25% sucrose, pH 6.5) were found by means of response surface methodology (RSM). The chemical characterisation indicated that under optimised conditions the synthesis of the heteroglycan was favoured compared with that of the beta-glucan.