Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Proc Natl Acad Sci U S A. 2013 Apr 30;110(18):7182-7. doi: 10.1073/pnas.1302420110. Epub 2013 Apr 15.
The global demand for food could double in another 40 y owing to growth in the population and food consumption per capita. To meet the world's future food and sustainability needs for biofuels and renewable materials, the production of starch-rich cereals and cellulose-rich bioenergy plants must grow substantially while minimizing agriculture's environmental footprint and conserving biodiversity. Here we demonstrate one-pot enzymatic conversion of pretreated biomass to starch through a nonnatural synthetic enzymatic pathway composed of endoglucanase, cellobiohydrolyase, cellobiose phosphorylase, and alpha-glucan phosphorylase originating from bacterial, fungal, and plant sources. A special polypeptide cap in potato alpha-glucan phosphorylase was essential to push a partially hydrolyzed intermediate of cellulose forward to the synthesis of amylose. Up to 30% of the anhydroglucose units in cellulose were converted to starch; the remaining cellulose was hydrolyzed to glucose suitable for ethanol production by yeast in the same bioreactor. Next-generation biorefineries based on simultaneous enzymatic biotransformation and microbial fermentation could address the food, biofuels, and environment trilemma.
由于人口增长和人均食物消费，全球对食物的需求可能在未来 40 年内增加一倍。为了满足世界未来对食物和生物燃料及可再生材料的可持续性需求，必须大幅增加富含淀粉的谷物和富含纤维素的生物能源植物的产量，同时将农业的环境足迹和生物多样性保护最小化。在这里，我们展示了一种一锅法的酶促转化方法，通过由来自细菌、真菌和植物来源的内切葡聚糖酶、纤维二糖水解酶、纤维二糖磷酸化酶和α-葡聚糖磷酸化酶组成的非天然合成酶途径，将预处理生物质转化为淀粉。来自马铃薯α-葡聚糖磷酸化酶的特殊多肽帽对于将部分水解的纤维素中间产物向前推进到直链淀粉的合成是必不可少的。纤维素中多达 30%的脱水葡萄糖单元被转化为淀粉；剩余的纤维素被水解成葡萄糖，适合酵母在同一个生物反应器中用于生产乙醇。基于同时进行酶生物转化和微生物发酵的下一代生物精炼厂可以解决食物、生物燃料和环境的三重困境。
