Overexpression of CO2-responsive CCT protein , a key regulator of starch synthesis strikingly increases the glucose yield from rice straw for bioethanol production.

Production of bioethanol from rice straw has attracted attention from the point of effective use of agricultural residue. Starch content is an important determinant for bioethanol production from rice straw. The overexpression ofCO2-responsive CCT protein(CRCT), which is the positive regulator of starch synthesis in vegetative organs, notably increased the starch content in rice straw. To produce the bioethanol from rice straw, the dilute acid pretreatment is a general pretreatment method. Importantly, the glucose yields in liquid hydrolyzate after dilute acid pretreatment was markedly increased in theCRCToverexpression lines compared with non-transgenic rice. In addition, the overexpression ofCRCTenhanced the biomass production. In contrast,CRCTdid not affect on the glucose yields from cellulose in acid-insoluble residue obtained after dilute acid pretreatment. With respect to byproduct in liquid hydrolyzate which inhibits the fermentation, the formic acid content was increased, whereas the furfural, 5-hydroxymethylfurfural and acetic acid contents were unchanged by the overexpression ofCRCT. These results demonstrate that genetic engineering ofCRCTis an effective method to increase the bioethanol production from rice straw. [ABSTRACT FROM PUBLISHER]