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BACKGROUND Ionic liquids are generally considered to be green solvents, and can be potential substitutes for traditional flammable and volatile solvents due to such suitable properties as low volatility, high thermal stability, non‐flammability, and good recyclability. This study aimed to optimize 1‐ethyl‐3‐methylimidazolium acetate ([EMIM][OAc]) pretreatment processing conditions by evaluating the effect of three pretreatment processing parameters (temperature, residence time and solids loading) on the enzymatic hydrolysis of [EMIM][OAc]‐treated energy cane bagasse via response surface methodology (RSM). RESULTS The model fitted by RSM indicated that a higher glucose yield of [EMIM][OAc]‐treated biomass could be obtained at higher pretreatment temperatures with shorter residence times within the design space. The optimal processing conditions were pretreatment of energy cane bagasse at 131.9°C for 28.1 min at 8.4% solids loading, resulting in a final glucose yield of 35.96 g glucose per 100 g of native biomass compared with the predicted value of 35.89. CONCLUSION The results suggest that this model can predict accurately the glucose yield within the specified design space. The model can also provide valuable insight to further industry application. © 2013 Society of Chemical Industry

Biochemical conversion of lignocellulosic biomass to ethanol involves size reduction, preprocessing, pretreatment, enzyme hydrolysis, and fermentation. In recent years, microbial preprocessing has been gaining attention as a means to produce labile biomass for lessening the requirement of pretreatment severity. However, loss of sugars due to microbial consumption is a major consequence, suggesting its minimization through optimization of nutrients, temperature, and preprocessing time. In this work, we emphasized estimation of fungal preprocessing time, at which higher sugar yields can be achieved after preprocessing and enzyme hydrolysis. The estimation is based on the enzymatic activity profile obtained by treating switchgrass with Phanerochaete chrysosporium for 28 days. Enzyme assays were conducted once in every 7 days for 28 days, for activities of phenol oxidase, peroxidase, beta-glucosidase, beta-xylosidase, and cellobiohydrolase. We found no activity for phenol oxidase and peroxidase, but the greatest activities for cellulases on the seventh day. We then treated switchgrass for 7 days with P. chrysosporium and observed that the preprocessed switchgrass had higher glucan (39%), xylan (17.5%), and total sugar yields (25.5%) than the unpreprocessed switchgrass (34%, 37.5%, and 20.5%, respectively, p < 0.05). This verifies the utility of using enzyme assays for initial estimation of preprocessing time to enhance sugar yields.

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