Effect Of Water-soluble Lignin On The Enzymatic Saccharification Of Pretreated Poplar

Lignocellulosic biomass is mainly composed of lignin, cellulose and hemicellulose. Cellulose and hemicellulose in the pretreated substrates can be digested into mono-sugars such as glucose and xylose which can be used to produce ethanol and other chemicals. However, nonproductive cellulose adsorption on lignin in the substrate, which reduced the efficiency enzymatic hydrolysis saccharification. In this study, using additives can enhance the enzymatic hydrolysis of lignocellulosic biomass. In this study, the effects of sulfonated lignin or kraft lignin on the saccharification of enzymatic hydrolysis were investigated using green liquor(GL), acid sodium bisulfite(AS) and sodium sulfite-formaldehyde(SF) pretreated poplar as substrates.The effects of pH and sulfonated lignin on the saccharification of enzymatic hydrolysis were investigated using AS-pretreated poplar as substrates. During the AS pretreatment of poplar, the increasing of sodium bisulfite charge resulted in enhanced delignification, whereas an increased degradation of carbohydrate as well. The sugar conversion of enzymatic hydrolysis went up rapidly with the increasing sodium bisulfite charge in AS pretreatment. The sugar conversion of enzymatic hydrolysis tended to increase, then became gentle with the increase of pH, and reached high levels at pH 4.8. The sugar yield of total sugar is 66.1%. At the same pH condition, the sugar conversion of enzymatic hydrolysis went up and then level off with the increase of Reax 85 A charge. At the same Reax 85 A charge condition, the sugar conversion of enzymatic hydrolysis tended to increase, then became gentle with the increase of pH, and reached high levels at pH 5.1. The sugar conversion of total sugar is 83.5%.The effects of sulfonated lignin and PEG 4000 on the saccharification of enzymatic hydrolysis were investigated using GL-pretreated poplar as substrates. During the GL pretreatment of poplar, the increasing of temperature and maintain time resulted in enhanced delignification, whereas an increased degradation of hemicellulose as well. The sugar conversion of enzymatic hydrolysis went up rapidly with the increasing cellulase loading. At the same pretreatment condition, the sugar conversion of enzymatic hydrolysis went up and then level off with the increase of Reax 85A/PEG 4000 charge. 0.3 g/g-substrates Reax 85A/PEG 4000 increased total sugar conversion to 79.8% and 84.5%.The effect of kraft lignin on the saccharification of enzymatic hydrolysis were investigated using GL-, AS- and SF-pretreated poplar as substrates. The insoluble kraft lignin addition inhibited the saccharification of enzymatic hydrolysis. At GL pretreatment condition, the sugar conversion of enzymatic hydrolysis went up and then level off with the increase of soluble lignin(KL5) charge. 0.1 g/g-substrates KL5 increased total sugar conversion to 83.1%. The addition of KL5 can not only reduce the cellulose loading, but also shorten the enzymatic incubation time. The effects of KL5 on AS- and SF-pretreated poplar were same as GLpretreated poplar.Lignin, the proportion of 30% in lignocellulose biomass and being byproduct of pulping and papermaking, was cheap and abundant. Kraft lignin and sulfonated lignin, getting from precipitation and chemical modification, can enhance the efficiency of enzymatic hydrolysis, which could improve the utilization of lignocellulosic biomass and promote the development of bioethanol industry.