Semi-defined media for the exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 and evaluation of the components interfering with the EPS quantification

Abstract

Growth and exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 was evaluated in semi-defined media. Lactose (as carbon source) and CaCl2 proved to be the major stimulating factors for an optimal EPS synthesis while the highest specific EPS yield was obtained when CaCl2 and MnSO4 were the only salts added to the medium. Both EPS and cell growth were slightly affected by the nitrogen source. The analysis of the interference components (EPS-eq) in uninoculated media revealed an overestimation in EPS of ca. 76% due to beef extract and yeast extract, and of 64% due to the presence of peptone. Nevertheless, in fermented cultures, the level of interference may be lower since nitrogen compounds are used by the microorganism during growth and residual lactose showed to be easily removed by dialysis before EPS quantification.