Background Fed-batch fermentation has been conventionally implemented for the production of lactic acid with a high titer and high productivity. However, its operation needs a complicated control which increases the production cost. Results This issue was addressed by simplifying the production scheme. Escherichia coli was manipulated for its glycerol dissimilation and d-lactate synthesis pathways and then subjected to adaptive evolution under high crude glycerol. Batch fermentation in the two-stage mode was performed by controlling the dissolved oxygen (DO), and the evolved strain deprived of poxB enabled production of 100 g/L d-lactate with productivity of 1.85 g/L/h. To increase productivity, the producer strain was further evolved to improve its growth rate on crude glycerol. The fermentation was performed to undergo the aerobic growth with low substrate, followed by the anaerobic production with high substrate. Moreover, the intracellular redox of the strain was balanced by fulfillment of the anaerobic respiratory chain with nitrate reduction. Without controlling the DO, the microbial fermentation resulted in the homofermentative production of d-lactate (ca. 0.97 g/g) with a titer of 115 g/L and productivity of 3.29 g/L/h. Conclusions The proposed fermentation strategy achieves the highest yield based on crude glycerol and a comparable titer and productivity as compared to the approach by fed-batch fermentation. It holds a promise to sustain the continued development of the crude glycerol-based biorefinery.

中文翻译：

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一种在利用粗甘油的大肠杆菌中有效生产 d-乳酸的简单策略。

背景技术 补料分批发酵通常用于生产具有高滴度和高产率的乳酸。然而，其操作需要复杂的控制，增加了生产成本。结果 此问题已通过简化生产方案得到解决。大肠杆菌被操纵其甘油异化和d-乳酸合成途径，然后在高粗甘油下进行适应性进化。通过控制溶解氧（DO）进行两阶段模式的分批发酵，去除poxB的进化菌株能够生产100 g/L d-乳酸，生产率为1.85 g/L/h。为了提高生产力，生产者菌株进一步进化以提高其在粗甘油上的生长速率。发酵先进行低底物好氧生长，再进行高底物厌氧生产。此外，菌株的细胞内氧化还原通过完成厌氧呼吸链和硝酸盐还原来平衡。在不控制 DO 的情况下，微生物发酵导致 d-乳酸（约 0.97 g/g）的同型发酵生产，滴度为 115 g/L，生产率为 3.29 g/L/h。结论与通过补料分批发酵的方法相比，所提出的发酵策略基于粗甘油实现了最高产率以及相当的滴度和生产率。它有望维持以粗甘油为基础的生物精炼厂的持续发展。通过完成厌氧呼吸链和硝酸盐还原来平衡菌株的细胞内氧化还原。在不控制 DO 的情况下，微生物发酵导致 d-乳酸（约 0.97 g/g）的同型发酵生产，滴度为 115 g/L，生产率为 3.29 g/L/h。结论与通过补料分批发酵的方法相比，所提出的发酵策略基于粗甘油实现了最高产率以及相当的滴度和生产率。它有望维持以粗甘油为基础的生物精炼厂的持续发展。通过完成厌氧呼吸链和硝酸盐还原来平衡菌株的细胞内氧化还原。在不控制 DO 的情况下，微生物发酵导致 d-乳酸（约 0.97 g/g）的同型发酵生产，滴度为 115 g/L，生产率为 3.29 g/L/h。结论与通过补料分批发酵的方法相比，所提出的发酵策略基于粗甘油实现了最高产率以及相当的滴度和生产率。它有望维持以粗甘油为基础的生物精炼厂的持续发展。97 g/g），滴度为 115 g/L，产率为 3.29 g/L/h。结论与通过补料分批发酵的方法相比，所提出的发酵策略基于粗甘油实现了最高产率以及相当的滴度和生产率。它有望维持以粗甘油为基础的生物精炼厂的持续发展。97 g/g），滴度为 115 g/L，产率为 3.29 g/L/h。结论与通过补料分批发酵的方法相比，所提出的发酵策略基于粗甘油实现了最高产率以及相当的滴度和生产率。它有望维持以粗甘油为基础的生物精炼厂的持续发展。