发酵过程中产生的过量乙酸会严重影响色氨酸发酵的效率，通常采用严格控制发酵液中葡萄糖浓度来减少发酵过程中乙酸的积累。通过敲除乙酸代谢途径中具有乙酸激酶活性的丙酸激酶编码基因（tdcD）控制乙酸溢流，并分别研究在“微糖”及“高糖”控制条件下乙酸含量的变化及其对发酵的影响。结果显示，在“高糖”控制条件下tdcD 缺失菌株在对数生长后期保持较高的生长速率和产酸效率，色氨酸产量最高为48.85 g/L，比对照菌提高了54.88%；而产生的乙酸为2.79 g/L，比对照菌降低了64.72%。tdcD 缺失菌可以适应更灵活的残糖控制范围。

Excessive acetic acid is harmful to tryptophan fermentation, and thus the level of acetic acid is normally restricted through the regulation of glucose content in the broth. In this study, the tdcD gene in Escherichia coli was knocked out in order to reduce the accumulation of acetic acid during tryptophan fermentation. The acetic acid content variation was investigated under various glucose levels. It showed that under high glucose content, the tdcD deletion strain YPTRP01 had a higher growth rate and exhibited increased tryptophan production in late exponential phase. The tryptophan yield was increased by 54.88% to 48.85g/L and the acetic acid level was reduced by 62.8% to 2.79g/L. In conclusion, the tdcD mutant showed more flexibility in the control of glucose contents during the tryptophan fermentation.