Abstract

The optimum conditions for enzymatic treatment of Miscanthus sacchariflorus var. No. 1, a newly developed genotype in Korea, to produce water soluble carbohydrate were investigated using statistical methods. The individual effects of cellulase, hemicellulase and xylanase on water soluble carbohydrate (WSC) production were investigated. Then, the effects of combined addition of enzyme and M. sacchariflorus were evaluated and optimized using a Box Benhken design (BBD) and response surface model (RSM). Enzyme treatment was performed in a 45°C water bath for 12 h. The effects of alkali pretreatment conditions on enzymatic saccharification of M. sacchariflorus were investigated using the Taguchi design. Hemicellulase was the effective enzyme for WSC yield (mg of produced glucose/g M. sacchariflorus). This enzyme then became the fixed component, with cellulase, xylanase and M. sacchariflorus applied as variables. The optimum blend of enzymes was determined to be hemicellulase 5.0 U/ml, cellulase 8.0 U/ ml and xylanase 6.0 U/ ml. Incubation time, concentration of NaOH and M. sacchariflorus level were used as variables for investigation of alkali pretreatment conditions effects. The pretreatment was performed at 80°C and the optimized enzyme mixture was used. The maximum WSC yield was achieved using a 1 h reaction time, 1% NaOH and 50 g/L of M. sacchariflorus. Through a series of experiments, WSC yield was improved from 10 mg glucose/g M. sacchariflorus before optimization to 220 mg glucose/g M. sacchariflorus after optimization.

Key words: Miscanthus sacchariflorus var., enzymatic saccharification, cellulase, hemicellulase, xylanase.