Effect of medium supplementation on exopolysaccharide production by Lactobacillus rhamnosus RW-9595M in whey permeate

摘要

Exopolysaccharide (EPS) production by Lactobacillus rhamnosus RW-9595M was studied in when permeate medium supplemented with different nitrogen sources or with yeast extract and vitamins, salts and amino acids used in the formulation of defined basal minimum medium (BMM). All nitrogen sources tested exhibited very limited or no effect on biomass production using acidification and automated spectrophotometry test. A multilevel-factorial design was used to determine the main effects and interactions of BMM nutrient groups during pH-controlled batch fermentations in order to find the limiting nutrient group for EPS production in a whey permeate medium supplemented with yeast extract. Maximum populations during batch fermentations in whey permeate medium with yeast extract and BMM components varied between 4.4 x 10(9) and 1.1 x 10(10) CFU mL(-1), with the highest population obtained when salts and amino acids or the three groups of supplements were added. Maximum EPS productions were very high, in the range from 440 to 2775 mg L-1. The addition of salts largely increased this production, and a strong interaction was observed between amino acids and salts. In this study, the EPS production (2767 mg L-1) obtained using Lb. rhamnosus RW-9595M in the culture medium containing salts and vitamins is the highest reported for lactobacilli.