Exopolysaccharide production by Pediococcus damnosus 2.6 in a semidefined medium under different growth conditions

Abstract

Ropy Pediococcus damnosus (strain 2.6) was used for production of exopolysaccharide (EPS) in a semidefined medium. From a kinetic point of view, an experiment conducted in SMD medium containing 30 g l(-1) glucose and 5 g l(-1) Bacto casamino acids (Difco Laboratories, Detroit, MI), without pH control, showed that EPS production took place mainly during the growth phase. The viscosity of the cultures developed in parallel to the EPS synthesis until 94 h of incubation; after 200 h of fermentation, viscosity decreased. The effect of glucose, Bacto casamino acid concentrations and temperature on growth and EPS production was determined by using a full factorial design. Within the domain of experimental conditions considered, the concentration of glucose and Bacto casamino acids has a significant effect on the production of exopolysaccharide. The incubation at 12 degrees C produced a prolonged lag phase and due to the lower growth yield, higher specific EPS production was found at this temperature. At 25 degrees C the EPS production was mainly enhanced by the increase in glucose concentration. The increase in nitrogen concentration from 5 to 15 g l(-1) did not yield greater EPS production. However, at 12 degrees C optimal EPS production was obtained when both higher glucose and nitrogen concentrations were used.