By analyzing the L-valine fermentation process by Brevibacterium flavum XV0505,one of important factors influenced on the bacterial productivity and L-valine yield is nitrogen source and its additional strategies.The effect of nitrogen sources on the fermentation of L-valine was studied by adding different nitrogen sources with different concentrations.Therefore,soybean hydrolysates and ammonium sulfate were selected as the appropriate nitrogen source,and the best L-valine yield was obtained with the medium supplemented low initial concentration of 225 mmol/L.In the case of the same initial nitrogen concentration,the effects of three nitrogen feeding strategies(intermittent nitrogen feeding,constant concentration feeding and power function feeding) on biomass,yield of L-valine,concentration of byproduct and conversion rate were studied in the 30L fermentor.The result showed that the concentration and the feed rate of nitrogen source were effectively and timely manipulated by power function feeding,while lacking of online monitoring and feedback controlled system.The yield of L-valine was further improved up to 63.17 g/L by power function feeding strategy with the conversion rate of 24.69%.