| Sulfamic acid is a common chemical cleaning agent with similar acidity to sulfuric acid.It has many excellent characteristics such as non-hygroscopicity,non-corrosion,and easy for storage and transportation.In this study,sulfamic acid was used as an acid pretreatment reagent in bagasse pretreatment for the first time.The effects of three acids pretreatment including sulfamic acid,sulfuric acid,and hydrochloric acid were compared on the composition and enzymolysis of bagasse after pretreatment.The sulfamic acid could remove hemicellulose,and the alkaline hydrogen peroxide could remove lignin.So the two methods were combined together to degrade bagasse and maximize the conversion of the bagasse cellulose.After pretreatment,the bagasse was subjected to different fermentation methods for ethanol production.The results of different acid pretreatments showed that the removal of hemicellulose and lignin using sulfamic acid was not as good as that of sulfuric acid and hydrochloric acid.However,sulfamic acid had the least effect on cellulose and could maintain the most cellulose compared with the other two acids.Under the same enzymolysis conditions,the cellulose conversion rate of bagasse after pretreatment with sulfamic acid was 6.77%,which was significantly higher than that of sulfuric acid and hydrochloric acid.The sulfamic acid pretreated conditions were optimized by single factor and orthogonal experiments and judged by the removal rate of hemicellulose.The hemicellulose removal rate reached the highest when bagasse was pretreated with 3% sulfamic acid at 121°C for 1.0 h.The sulfamic acid pretreatment was then combined with alkaline hydrogen peroxide pretreatment at pH 13.5 to further remove lignin.And the cellulose conversion rate of bagasse reached the highest of 78% using 36 U cellulases /g substrate in the enzymatic hydrolysis.The sulfamic acid pretreatment combined with alkaline hydrogen peroxide pretreatment demonstrated significantly better results than that of either single pretreatment.After these two-step pretreatment,the concentration of ethanol reached the highest of 6.05 g/L in separate hydrolysis and fermentation(SHF).And the ethanol yield of bagasse was 66.45% of the theoretical value,which was 55.94% higher than that of the unpretreated bagasse.In the simultaneous saccharification and fermentation(SSF),the concentration of ethanol was the highest of 4.90 g/L and the yield of ethanol was 53.82% of the theoretical value,which was 46.32% higher than the unpretreated bagasse.Comparing these two fermentation methods,the ethanol productivity and ethanol yield was better in SHF than in SSF. |
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