Study On The Fermentation Mechanism And Kinetics Of D-alanine Production By Microbial Asymmetric Degradation

Based on the principle of asymmetric microbial degradation,the bacteria Ala-D45 was cultivated in particular culture conditions,which can produce L-alanine oxidase with strong oxidation ability,L-alanine in DL-alanine was degraded by the L-alanine oxidase,so D-alanine was achieved.The degradation mechanism of L-alanine was studied in this paper,the results showed that bacteria Ala-D45 only degraded L-alanine,the process of degradation was that,L-alanine generated pyruvate after deamination,part of which was oxidized thoroughly in the Krebs cycle,another part was used for the growth of bacteria.The effects of substrate concentration on the production of D-alanine in batch and fed-batch fermentation were studied.The experimental results showed that:the optimal concentration of substrate was 14%in the batch fermentation.And in the fed-batch fermentation,the optimal concentration of substrate should be maintained at about 8%.Adding the mixture of 10%DL-alanine and hydrochloric acid in the fed-batch culture,when the fermentation completed,the concentration of D-alanine in fermentation liquid was up to 12%,so the concentration of added substrate reached 24%.By measuring,continuous flow with low concentration of substrate can make substrate concentration increased by 85.71%,and it can make the accessories costs fell by 71.41%.Fermentation kinetics of bacteria Ala-D45 for producing D-alanine were studied.Based on the logistic equation,dynamic models of bacteria growth and substrate consumption were put forward.Using Origin8.0 software to deal with test data,the dynamics of microbial fermentation production D-alanine model parameters.Results showed that the model can be well fitted with the test data and accumulate a certain theoretical basis for industrialized production of D-alanine.