Effects of Yeast Extract on Pullulan Molecular Weight by Aureobasidium pullulans

Abstract:

The effect of different concentration of yeast extract on pullulan yield，structure，and molecular weight ware studied by using Aureobasidium pullulans CGMCC 11062. The results showed that the pullulan yield and molecular weight were significantly influenced but the structure had not been effected by different concentration of yeast extract. The contents of biomass，pullulan and residual sugar were respectively 5.29 g/L，34.74 g/L，44.18 g/L，when yeast extract were absent in the medium. The highest yield could reach 61.32 g/L，when the concentration of yeast extract was 1.5 g/L. Nevertheless，excessive yeast powder supply caused carbon source flowing to the organism，pullulan yield reduction. The maximal molecular weight of pullulan were produced with no yeast extract medium，which is 529 528 Da. With the increase of the concentration of yeast powder，the pullulan molecular weight gradually decreased from 529 528 reduced to 183 278. The results showed that the yeast extract may induce pullulan degrading enzymes，and lead to the decrease of the yield and molecular weight. These studies could provide technical guidance for the different pullulan production.