Combined effects of temperature and medium compositionon exopolysaccharide pyroduction by lactobacillus rhamnosus RW-9595M in a whey permeate based medium

摘要

The effect of temperature(22-42degC),whey permeate concentration(WP,1.6-8.4%),and supplementation level with yeast nitrogen bases(YNB,0-2.0%)on exopolysaccharide(EPS)production was studied during 20pH-controlled(pH=6.0)batch cultures with Lactobacillus rhamnosus RW-9595M,using a central composite design(CCD).The EPS production of EPS and a new ultrafiltraction(UF)method.EPS production was not growth-associated for high temperatures(32-42degC)and WP concentrations (7.0-8.4%).In contrast,at suboptimal temperature(22-26degC),EPS production was growth-associated.Maximal EPS production measured with the UF method was approximately 2-fold higher than those measured with the conventional method and varied from 125 to 477mg/L.This parameter was significantly influenced by WP and YNBWP interaction,whereas ANOVA for maximal EPS production measured by the conventional method did not show significant factor effects.EPS volumetric productivities varied from 3.0 to 16.4mg EPS/L·h.YNB supplementation did not promote cell growth but did increase EPS proudction at high WP concentrationb.Our data indicate the potential of L.rhamnosus RW-9595M for producing EPS in a supplemented WP medium and suggest that this production could be further increased by the addition of a growth-limiting nutrient inthe medium.