Bioethanol produced from waste lignocellulosic biomass is a promising renewable fuel in environmental and sustainable views. The thermochemical process that can readily decompose lignocellulosic biomass to carbohydrate-rich bio-oil is more appealing compared to biochemical process due to its low costs and less time. However, levoglucosan, the dominant carbohydrate present in the bio-oil, is problematic to be efficiently converted to bioethanol by native and recombinant microorganisms. Here, a synthetic metabolic pathway based on the heterologous genes encoding levoglucosan kinase, pyruvate decarboxylase, and alcohol dehydrogenase, was constructed and introduced into Escherichia coli to generate new platforms for ethanol production from levoglucosan. The engineered E. coli strains overexpressing levoglucosan kinase could, for the first time, completely consume 1–2% (wt/vol) levoglucosan present in the minimal media to produce ethanol with relatively high yield; while E. coli LGE2 exhibited the maximal ethanol yield of 0.43 g/g levoglucosan, rising by ~23% compared to the only existing recombinant strain E. coli KO11 + lgk. Although levoglucosan utilization was inferior to the utilization of other substrates like fructose and complex media, our results suggest that desired high-yield bioethanol production from levoglucosan-based minimal media could be efficiently achieved by the newly engineered strains, which could provide a solution for complete bioethanol fermentation from the thermochemically decomposed biomass feedstock.

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新改造的大肠杆菌提高了左旋葡聚糖生物乙醇的转化效率

从废弃的木质纤维素生物质中生产的生物乙醇在环境和可持续方面是一种很有前途的可再生燃料。与生化过程相比，热化学过程可以很容易地将木质纤维素生物质分解为富含碳水化合物的生物油，因为其成本低、时间短。然而，生物油中存在的主要碳水化合物左旋葡聚糖难以通过天然和重组微生物有效转化为生物乙醇。在这里，基于编码左旋葡聚糖激酶、丙酮酸脱羧酶和乙醇脱氢酶的异源基因的合成代谢途径被构建并引入大肠杆菌中，以产生用于从左旋葡聚糖生产乙醇的新平台。工程大肠杆菌过表达左旋葡聚糖激酶的菌株首次可以完全消耗基本培养基中存在的 1-2% (wt/vol) 左旋葡聚糖，从而以相对较高的产量生产乙醇；而大肠杆菌LGE2 的最大乙醇产量为 0.43 g/g 左旋葡聚糖，与唯一存在的重组菌株大肠杆菌KO11 +  lgk相比提高了约 23% 。虽然左旋葡聚糖的利用不如果糖和复杂培养基等其他底物的利用，但我们的结果表明，新改造的菌株可以有效地从基于左旋葡聚糖的基本培养基中生产所需的高产生物乙醇，这可以为完整的解决方案提供解决方案。来自热化学分解的生物质原料的生物乙醇发酵。