Effects Of A Two Step Acetic Acid And Peroxide-acetic Acid Pretreatment On Enzymatic Hydrolysis Of Poplar

Poplar tree species are considered as promising biomass feedstock for biofuels and biochemicals production due to their fast growing,short vegetative cycle,and widely distribution.China has the largest area of poplar cultivation in the world.With the popularization of poplar planting,the area of poplar plantation in China has exceeded 6600,000 hectare.In the process of poplar utilization,a lot of waste poplar was produced.Direct burning poplar not only caused the waste of poplar resources,but also made some environmental pollution problems.Use the poplar as the feedstock of biomass energy and biomass chemicals can greatly improve the utilization of poplar resources and solve some energy and environmental problems.In this work,poplar was pretreated with acetic acid(AC)to produce xylooligosaccharides(XOS),and hydrogen peroxide–acetic acid(HPAC)was used to remove residual lignin in AC-pretreated poplar for enzymatic hydrolysis.The aim of this work is to produce XOS and monosaccharides from poplar by a two-step pretreatment method.The chemical composition,structural characteristics and enzymatic hydrolysis of poplar during in two-step pretreatment were analyzed.The results were showed as follows:1.After AC pretreatment,the crystallinity and hydrophobicity of AC treated poplar were increased,and the oxygen carbon ratio was decreased.With the pretreatment time increased,the content of acetyl group,crystallinity,and ratio of oxygen to carbon increased,and the hydrophobicity decreased.2.The optimal AC pretreatment conditions of poplar were 5% AC,170 ° C and 30 min.Under thisl condition,71.3% xylan and 5.5% cellulose were removed.The highest XOS yield in AC pretreatment supernatant was 55.8%.The glucose yield of enzymatic hydrolysis from poplar was lower than 30%.3.The acetyl group,oxygen carbon ratio,crystallinity and of HPAC treated poplar were increased,the hydrophobicity of the HPAC treated poplar was decreased.Lignin droplets on the surface of the poplar were disappeared.With the HPAC concentration and pretreatment temperature increased,the content of acetyl group,ratio of oxygen and crystallinity increased,and the hydrophobicity was decreased.4.The optimal HPAC pretreatment conditions of AC treated poplar were 80% AC,60 °C and 2 h.Under the optimal conditions,92.7% lignin and 5.6% cellulose were removed.67.2% Glucose yield was obtained from HPAC treated poplar by enzymatic hydrolysis.The glucose yields of enzymatic hydrolysis were improved to 93.1% and 93.8% with β-glucosidase and Tween 80,respectively.The AC and HPAC two-step pretreatments can produce the XOS and fermentable sugars with a low cellulase loading.This process is a potential biomass refining method.