Research on Producation of a New Type of Biological High Molecular Material Poly(γ-Glutamic Acid)

摘要

Poly-γ-glutamic acid (γ-PGA) is a kind of water-soluble and biodegradable polymer, as a potential targeted biopolymer that can be refined from biomass directly. In this work, the effect of environmental parameters on γ-PGA formation by Bacillus licheniformis is investigated. The influence of culture temperature, pH and culture time on cell growth, γ-PGA production and molecular weight, polymer°C stereochemistry are determined. The γ-PGA yield is higher(30.13g/L) at culture temperature 37°C, pH 7.0. Alteration of the medium pH, temperature, culture time and aeration had little to no significant effects on the product quality as measured by stereochemical composition. But alteration of the medium pH, temperature, culture time and aeration have obvious effects on the γ-PGA yield and molecular weight, increasing the biomass and γ-PGA yields. Under the optimal environmental conditions yields of γ-PGA in excess of 36g/L is obtained in submerged culture. Finally, the large-scale fermentation of γ-PGA production was successfully scaled up to a 100-l fermentor, with the highest γ-PGA productivity for over 57.5 g/l.