Yang Jiangang, Zhu Yueming, Men Yan, Sun Shangshang, Zeng Yan, Zhang Ying, Sun Yuanxia, Ma Yanhe
National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China.
J Agric Food Chem. 2016 Dec 21;64(50):9497-9505. doi: 10.1021/acs.jafc.6b03423. Epub 2016 Dec 8.
Rare sugars are valuable natural products widely used in pharmaceutical and food industries. In this study, we expected to synthesize rare ketoses from abundant glycerol using dihydroxyacetone phosphate (DHAP)-dependent aldolases. First, a new glycerol assimilation pathway was constructed to synthesize DHAP. The enzymes which convert glycerol to 3-hydroxypropionaldehyde and l-glyceraldehyde were selected, and their corresponding aldehyde synthesis pathways were constructed in vivo. Four aldol pathways based on different aldolases and phosphorylase were gathered. Next, three pathways were assembled and the resulting strains synthesized 5-deoxypsicose, 5-deoxysorbose, and 5-deoxyfructose from glucose and glycerol and produce l-fructose, l-tagatose, l-sorbose, and l-psicose with glycerol as the only carbon source. To achieve higher product titer and yield, the recombinant strains were further engineered and fermentation conditions were optimized. Fed-batch culture of engineered strains obtained 38.1 g/L 5-deoxypsicose with a yield of 0.91 ± 0.04 mol product per mol of glycerol and synthesized 20.8 g/L l-fructose, 10.3 g/L l-tagatose, 1.2 g/L l-sorbose, and 0.95 g/L l-psicose.
稀有糖是有价值的天然产物，广泛应用于制药和食品工业。在本研究中，我们期望利用依赖磷酸二羟丙酮（DHAP）的醛缩酶从丰富的甘油合成稀有酮糖。首先，构建了一条新的甘油同化途径来合成DHAP。筛选了将甘油转化为3-羟基丙醛和L-甘油醛的酶，并在体内构建了它们相应的醛合成途径。收集了基于不同醛缩酶和磷酸化酶的四条醛缩途径。接下来，组装了三条途径，所得菌株从葡萄糖和甘油合成了5-脱氧阿洛酮糖、5-脱氧山梨糖和5-脱氧果糖，并以甘油作为唯一碳源生产了L-果糖、L-塔格糖、L-山梨糖和L-阿洛酮糖。为了获得更高的产物滴度和产量，对重组菌株进行了进一步改造，并优化了发酵条件。工程菌株的补料分批培养获得了38.1 g/L的5-脱氧阿洛酮糖，每摩尔甘油的产物产量为0.91±0.04摩尔，合成了20.8 g/L的L-果糖、10.3 g/L的L-塔格糖、1.2 g/L的L-山梨糖和0.95 g/L的L-阿洛酮糖。
