Edited* by Arnold L. Demain, Drew University, Madison, NJ, and approved March 27, 2013 (received for review February 5, 2013)
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.
↵1C.Y. and H.C. contributed equally to this work.
Author contributions: C.Y., H.C., and Y.-H.P.Z. designed research; C.Y. and H.C. performed research; S.M., H.M., and X.-Z.Z. contributed new reagents/analytic tools; C.Y., H.C., N.S., J.L., and Y.-H.P.Z. analyzed data; and H.C. and Y.-H.P.Z. wrote the paper.
Conflict of interest statement: The authors have filed a provisional patent disclosure (Zhang Y-HP, Chen H. Conversion of cellulose to starch through an in vitro synthetic enzymatic pathway. Filed on December 17, 2012.).
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1302420110/-/DCSupplemental.
