Optimization on fermentation conditions ofγ-polyglutamic acid and preliminary analysis on its characters

In order to improve the yield ofγ-polyglutamic acid(γ-PGA),Bacillus subtilis was used for fermentation and the production condi- tions were investigated by single factor or orthogonal tests.The results indicated that the optimal medium forγ-PGA production was as follows: glucose 40g/L,yeast extract 5g/L,L-sodium glutamate 30g/L,NI-hCl 3g/L,K_2RPO_4 2/L,MgSO_4 0.25 g/L.And the optimal fermentation conditions were:inoculum level 2%,medium volume 40ml per 250ml flask,temperature 37~C,rotate speed 200 r/min,initial pH 7.0 and culture time 48h.Under above conditions,the yield ofγ-PGA reached 20.15g/L.Besides,paper chromatography spectrums and Fourier transform infrared spectroscopy were used to confirm the product wasγ-PGA.