Abstract:

Optimal preparation conditions such as strain, fermentation medium and fermentation processing parameters were explored. The growth of strain and second stage of seed were achieved by the growth curve of ATCC31555 in medium. The optimal fermentation medium for preparing Welan gum were explored by single factor and orthogonal experiments to be 40 g/L sucrose, 3 g/L yeast extract, 5 g/L K2HPO4·7H2O, 2 g/L MgSO4·7H2O, 1 mg/L FeSO4·7H2O and 0.5 g/L CaCl2. The yield of Welan gum was increased from 7.31 to 17.23 g/L by using the improved medium. The optimal fermentation conditions were the seed age of 18 hours, inoculation amount of 0.5% (V/V), medium volume of 40 mL in 250 mL flask, pH 7.0, shaking speed of 220 r/min, fermentation temperature of 30 ℃ and fermentation time of 72 h. Under the optimal fermentation conditions, the yield of Welan gum was up to 20.64 g/L.

Key words: microbial polysaccharide, Welan gum, fermentation