调控黑曲霉葡萄糖转运系统增强柠檬酸的合成

Regulation of Glucose Transporter Systems for Enhancing Citrate Production in Aspergillus niger

柠檬酸是目前世界上需求量最大的有机酸,年产量达到170万吨,主要由黑曲霉进行深层有氧发酵来生产。强化葡萄糖的吸收是增强柠檬酸合成的重要策略。对黑曲霉基因组中预测到的葡萄糖转运蛋白进行进化树分析和多序列比对,鉴定到与KlHGT1亲缘关系较近的高亲和力葡萄糖转运蛋白基因,其编码的蛋白质序列含11个跨膜区,命名为AnHGT1。在葡萄糖限制性培养基上进行生长测定,发现HGT1转化子的菌落直径比H915-1增加了50%~150%。通过在发酵后期添加30 g/L葡萄糖,发现HGT1的葡萄糖消耗速率比H915-1快12 h。最终HGT1转化子的柠檬酸产量比野生型菌株H915-1增加14.7%,发酵时间减少6 h,最大比产酸速率增加了29.5%。

Citrate is one of the high-volume organic acids with the global production of 1.7 million tons annually mainly produced by microbial process using Aspergillus niger as natural producer.Glucose absorption was the first step of citrate fermentation and needed to be enhanced.The sugar transporters were analyzed based on transcriptome data,phylogenetic tree analysis and sequences alignment.The evm.model.unitig_0.1770 gene,whose relationship was the closest with KlHGT1,was predicted containing 11 transmembrane segments and named as HGT1.The growth test on glucose limited medium showed the diameter of HGT1 transformants were 50%to 150%larger than the diameter of H915-1.After addition of 30 g/L glucose into fermentation medium,the glucose consuming time of HGT1 transformants reduced for 12 h than that of H915-1.Finally,the citrate titer of HGT1 tranformant was increased for 14.7%comparing to H915-1,the fermentation time reduced for 6 h and the maximum specific citrate production rate increased for 29.5%.