Response Surface Optimization Of Ammonium Sulfite Pretreatment For Fermentable Sugar Production From Wheat Straw

With the increasing consumption of fossil fuels,the development of environment-friendly and renewable energy has received special attention.Lignocellulose is the most abundant renewable material,converting lignocellulosic biomass into liquid fuel,valuable chemical and materials has been the research hotspot in recent years.And it can make up for the shortage of grain as liquid fuel source.Cellulose and hemicellulose contained in lignocellulose biomass can be enzymatic hydrolyzed to produce fermentable sugars,which can be converted into biofuels.However,a high lignin content of lignocellulosic biomass could restrict the enzymatic hydrolysis.Thus,the development of a more economical and eco-friendly pretreatment process for efficient delignification of lignocellulose is of crucial importance for the production of fermentable sugars via enzymatic saccharification,particularly for industrial applicationIn this study,the single factor experiment of ammonium sulfite(AS)pretreatment of wheat straw was carried out firstly.The effects of AS dosage,reaction time and reaction temperature on the pretreatment were analyzed,and the effectiveness of AS pretreatment was evaluated by the standard enzymatic hydrolysis procedure.Considering the interaction of variables in the system on the total sugar yield,AS pretreatment of wheat straw was optimized based on response surface methodology with a three-level,three-factor Box-Behnken design.The investigated factors were AS dosage,pretreatment time,and pretreatment temperature.A second-order polynomial fit was performed to fit the experimental data,and the model analysis showed that the effect of AS dosage on final total sugar yields was much higher than that of the othertwo factors.Under the optimum pretreatment conditions(27% of AS dosage(based on the dry wheat straw)at 160? for 63 min),the final total sugar yield reached to 74.4%after saccharification,which was in agreement with the predicted value(76.5%).Furthermore,it was found that pre-impregnation with acetic acid before AS pretreatment and the post-mechanical refining after AS pretreatment could further improve the fermentable sugar yields to about 78%.In addition,the spent liquor containing N could be used for the production of lignin-based fertilizer,thus making the whole process clean and sustainable.