Sunday, April 29, 2007

Effect of nonionic surfactants and noncatalytic protein on the enzymatic hydrolysis of saline creeping wild rye grass

Yi Zheng1, Zhongli Pan1, Ruihong Zhang1, Donghai Wang2, John Labavitch3, and Bryan Jenkins1. (1) Biological and Agricultural Engineering, University of California, Davis, 3022 Bainer Hall, One Shields Ave., Davis, CA 95616, (2) Biological and Agricultural Engineering, Kansas State University, Seaton Hall, Manhattan, KS 66506, (3) Plant Science, University of California, Davis, 2055 Wickson Hall, Davis, CA 95616

Our previous research has shown that saline Creeping Wild Rye Grass, Leymus triticoides, has a great potential to be used for bioethanol production due to its high fermentable sugar yield. However, the sugar production depends on a number of factors such as loading rate of enzymes (cellulase and β-glucosidase). The high cost of enzymes is one of the obstacles making large-scale bioethanol production from biomass economically difficult. It is desirable to use reduced enzyme loading to produce sugar with high yield. For reducing the enzyme loading rate, the effect of addition of nonionic surfactants and noncatalytic proteins on enzymatic hydrolysis of Creeping Wild Rye Grass was investigated in this study. Tween 20, Tween 80 and bovine serum albumin (BSA) were used as additives to improve the enzymatic hydrolysis of dilute sulfuric acid pretreated Creeping Wild Rye Grass. Under the loading of 0.1 g additives/g substrate, Tween 20 was the most effective additive followed by Tween 80 and BSA. With the addition of Tween 20 mixed with cellulase loading of 15 FPU/g cellulose, the enzymatic digestibility of cellulose in pretreated Creeping Wild Rye Grass was increased by 14% (from 75% to 89%). This result was the same as that under cellulase loading of 30 FPU/ g cellulose without the addition of additives. The addition of additives could be a promising method to improve the enzymatic hydrolysis and make bioethanol cheaper with the reduction in enzyme usage, especially β-glucosidase.