CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Siences, Qingdao, 266101, China.
Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao, 266101, China.
Microb Cell Fact. 2018 Mar 28;17(1):51. doi: 10.1186/s12934-018-0900-4.
Glycolate is a valuable chemical with extensive applications in many different fields. The traditional methods to synthesize glycolate are quite expensive and toxic. So, the biotechnological production of glycolate from sustainable feedstocks is of interest for its potential economic and environmental advantages. D-Xylose is the second most abundant sugar in nature and accounts for 18-30% of sugar in lignocellulose. New routes for the conversion of xylose to glycolate were explored.
Overexpression of aceA and ghrA and deletion of aceB in Escherichia coli were examined for glycolate production from xylose, but the conversion was initially ineffective. Then, a new route for glycolate production was established in E. coli by introducing NAD-dependent xylose dehydrogenase (xdh) and xylonolactonase (xylC) from Caulobacter crescentus. The constructed engineered strain Q2562 produced 28.82 ± 0.56 g/L glycolate from xylose with 0.60 ± 0.01 g/L/h productivity and 0.38 ± 0.07 g/g xylose yield. However, 27.18 ± 2.13 g/L acetate was accumulated after fermentation. Deletions of iclR and ackA were used to overcome the acetate excretion. An ackA knockout resulted in about 66% decrease in acetate formation. The final engineered strain Q2742 produced 43.60 ± 1.22 g/L glycolate, with 0.91 ± 0.02 g/L/h productivity and 0.46 ± 0.03 g/g xylose yield.
A new route for glycolate production from xylose was established, and an engineered strain Q2742 was constructed from this new explored pathway. The engineering strain showed the highest reported productivity of glycolate to date. This research opened up a new prospect for bio-refinery of xylose and an alternative choice for industrial production of glycolate.
乙醇酸是一种具有广泛应用价值的化学物质，在许多不同领域都有应用。传统的乙醇酸合成方法成本高且有毒，因此，从可持续原料生物合成乙醇酸具有潜在的经济和环境优势。D-木糖是自然界中第二丰富的糖，占木质纤维素中糖的 18-30%。探索了将木糖转化为乙醇酸的新途径。
在大肠杆菌中过表达 aceA 和 ghrA 并缺失 aceB 以生产乙醇酸，但最初转化率无效。然后，通过引入新月柄杆菌中的 NAD 依赖型木糖脱氢酶（xdh）和木酮糖内酯酶（xylC），在大肠杆菌中建立了生产乙醇酸的新途径。构建的工程菌 Q2562 以 0.60±0.01 g/L/h 的产率从木糖生产 28.82±0.56 g/L 的乙醇酸，木糖得率为 0.38±0.07 g/g。然而，发酵后积累了 27.18±2.13 g/L 的乙酸盐。缺失 iclR 和 ackA 用于克服乙酸盐排泄。ackA 敲除导致乙酸盐形成减少约 66%。最终的工程菌 Q2742 生产 43.60±1.22 g/L 的乙醇酸，产率为 0.91±0.02 g/L/h，木糖得率为 0.46±0.03 g/g。
建立了从木糖生产乙醇酸的新途径，并从这条新探索的途径构建了工程菌 Q2742。该工程菌表现出迄今为止报道的最高乙醇酸生产率。这项研究为木糖的生物炼制开辟了新的前景，为工业生产乙醇酸提供了另一种选择。
