Effects of cellulase and xylanase enzymes on the deconstruction of solids from pretreatment of poplar by leading technologies

Authors

  • Rajeev Kumar,

    1. Thayer School of Engineering, Dartmouth College, NH 03755
    Search for more papers by this author
  • Charles E. Wyman

    Corresponding author
    1. Dept. of Chemical and Environmental Engineering and Center for Environmental Research and Technology, University of California, Riverside, CA 92507
    • Dept. of Chemical and Environmental Engineering and Center for Environmental Research and Technology, University of California, Riverside, CA 92507
    Search for more papers by this author

Abstract

Comparative data is presented on glucose and xylose release for enzymatic hydrolysis of solids produced by pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid, flowthrough (FT), lime, and sulfur dioxide (SO2) technologies. Sugar solubilization was measured for times of up to 72 h using cellulase supplemented with β-glucosidase at an activity ratio of 1:2, respectively, at combined protein mass loadings of 5.8–116 mg/g of glucan in poplar wood prior to pretreatment. In addition, the enzyme cocktail was augmented with up to 11.0 g of xylanase protein per gram of cellulase protein at combined cellulase and β-glucosidase mass loadings of 14.5 and 29.0 mg protein (about 7.5 and 15 FPU, respectively)/g of original potential glucose to evaluate cellulase–xylanase interactions. All pretreated poplar solids required high protein loadings to realize good sugar yields via enzymatic hydrolysis, and performance tended to be better for low pH pretreatments by dilute sulfuric acid and sulfur dioxide, possibly due to higher xylose removal. Glucose release increased nearly linearly with residual xylose removal by enzymes for all pretreatments, xylanase leverage on glucan removal decreased at high cellulase loadings. Washing the solids improved digestion for all pretreatments and was particularly beneficial for controlled pH pretreatment. Furthermore, incubation of pretreated solids with BSA, Tween 20, or PEG6000 prior to adding enzymes enhanced yields, but the effectiveness of these additives varied with the type of pretreatment. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009

Ancillary