Abstract
We previously engineered E. coli YL104H to efficiently produce succinate from glucose. Furthermore, the present study proved that YL104H could also co-utilize xylose and glucose for succinate production. However, anaerobic succinate accumulation using xylose as the sole carbon source failed, probably because of an insufficient supply of energy. By analyzing the ATP generation under anaerobic conditions in the presence of glucose or xylose, we indicated that succinate production was affected by the intracellular ATP level, which can be simply regulated by the substrate ratio of xylose to glucose. This finding was confirmed by succinate production using an artificial mixture containing different xylose to glucose ratios. Using xylose mother liquor, a waste containing both glucose and xylose derived from xylitol production, a final succinate titer of 61.66 g/L with an overall productivity of 0.95 g/L/h was achieved, indicating that the regulation of the intracellular ATP level may be a useful and efficient strategy for succinate production and can be extended to other anaerobic processes.
Highlights
Succinic acid, a C4-dicarboxylic acid, is a precursor of many important chemicals in the food, chemical, and pharmaceutical industries [1]
By analyzing the ATP generation under anaerobic conditions in the presence of glucose or xylose, we indicated that succinate production was affected by the intracellular ATP level, which can be regulated by the substrate ratio of xylose to glucose
Co-utilization of both sugars by E. coli is inhibited by carbon catabolite repression (CCR) [32]
Summary
A C4-dicarboxylic acid, is a precursor of many important chemicals in the food, chemical, and pharmaceutical industries [1]. The widespread importance of succinate has secured its listing among the top 12 chemical building blocks by the U.S Department of Energy [2]. Industrial succinate producers, such as Escherichia coli, Actinobacillus succinogenes, Anaerobiospirillum succiniciproducens, Mannheimia succiniciproducens and Corynebacterium glutamicum, constitute a small percentage of all succinate-producing organisms [3]. A sufficient supply of reducing equivalents is essential for maximizing the yield of target fermentation products [11]. This need has been demonstrated by providing additional reduced carbohydrates (such as sorbitol) [12] and increasing the in vivo NADH availability [10,11,13]
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