以L-缬氨酸(L-Val)生产菌黄色短杆菌XV0505为供试菌株,以(NH4)2SO4为唯一添加N源,考察不同NH4+浓度对发酵过程中菌体干质量、L-Val产量和葡萄糖消耗速率以及菌体内代谢流量的影响.研究表明:NH4+浓度过高或不足都会影响发酵水平,降低L-Val的产量.合适的初始NH4+浓度为225 mmol/L,产酸期NH4+维持浓度为35mmol/L时,有利菌体产酸.在此NH4+浓度下,在30L发酵罐发酵60h,发酵液中菌体生物量和L-Val质量浓度分别可达22.35和59.12g/L.%The ammonium sulfate was selected as the only feeding nitrogen source in the L-valine fermentation process by Brevibacterium flavum XV0505. Effects of different N H4+ concentrations on biomass,yield of L-valine,glucose consumption rate and the metabolic flux were studied in a 30 L fermentor. Results showed that excessive or insufficient concentrations of NH4+ would adversely affect the yield of L-valine and bacterial growth. Therefore,the appropriate additive dosage of NH4+ (225 mmol/l) was determined,and L-valine production was increased by keeping low NH4+ concentration(35 mmol/L) in the synthesis period of L-valine. With the optimum additional dosage of NH4+ , the yields of L-valine and DCW were up to 59. 12 and 22. 35 g/L (60 h) in the 30 L fermentor.
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