@article{yang_zhang_luo_liu_shiga_li_kim_rubinelli_overton_subramanyam_et al._2019, title={Overcoming cellulose recalcitrance in woody biomass for the lignin-first biorefinery}, volume={12}, ISSN={1754-6834}, url={http://dx.doi.org/10.1186/s13068-019-1503-y}, DOI={10.1186/s13068-019-1503-y}, abstractNote={Low-temperature swelling of cotton linter cellulose and subsequent gelatinization in trifluoroacetic acid (TFA) greatly enhance rates of enzymatic digestion or maleic acid-AlCl3 catalyzed conversion to hydroxymethylfurfural (HMF) and levulinic acid (LA). However, lignin inhibits low-temperature swelling of TFA-treated intact wood particles from hybrid poplar (Populus tremula × P. alba) and results in greatly reduced yields of glucose or catalytic conversion compared to lignin-free cellulose. Previous studies have established that wood particles from transgenic lines of hybrid poplar with high syringyl (S) lignin content give greater glucose yields following enzymatic digestion.Low-temperature (- 20 °C) treatment of S-lignin-rich poplar wood particles in TFA slightly increased yields of glucose from enzymatic digestions and HMF and LA from maleic acid-AlCl3 catalysis. Subsequent gelatinization at 55 °C resulted in over 80% digestion of cellulose in only 3 to 6 h with high-S-lignin wood, compared to 20-60% digestion in the wild-type poplar hybrid and transgenic lines high in guaiacyl lignin or 5-hydroxy-G lignin. Disassembly of lignin in woody particles by Ni/C catalytic systems improved yields of glucose by enzymatic digestion or catalytic conversion to HMF and LA. Although lignin was completely removed by Ni/C-catalyzed delignification (CDL) treatment, recalcitrance to enzymatic digestion of cellulose from the high-S lines was reduced compared to other lignin variants. However, cellulose still exhibited considerable recalcitrance to complete enzymatic digestion or catalytic conversion after complete delignification. Low-temperature swelling of the CDL-treated wood particles in TFA resulted in nearly complete enzymatic hydrolysis, regardless of original lignin composition.Genetic modification of lignin composition can enhance the portfolio of aromatic products obtained from lignocellulosic biomass while promoting disassembly into biofuel and bioproduct substrates. CDL enhances rates of enzymatic digestion and chemical conversion, but cellulose remains intrinsically recalcitrant. Cold TFA is sufficient to overcome this recalcitrance after CDL treatment. Our results inform a 'no carbon left behind' strategy to convert total woody biomass into lignin, cellulose, and hemicellulose value streams for the future biorefinery.}, number={1}, journal={Biotechnology for Biofuels}, publisher={Springer Science and Business Media LLC}, author={Yang, Haibing and Zhang, Ximing and Luo, Hao and Liu, Baoyuan and Shiga, Tânia M. and Li, Xu and Kim, Jeong Im and Rubinelli, Peter and Overton, Jonathan C. and Subramanyam, Varun and et al.}, year={2019}, month={Jun} }
 @article{xu_zhang_cheng_2012, title={Pretreatment of corn stover for sugar production with switchgrass-derived black liquor}, volume={111}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2012.02.006}, abstractNote={To improve the cost-effectiveness of biomass-to-sugar conversion, sodium hydroxide (NaOH) pretreatment of switchgrass was carried out at 21°C using previously determined optimum conditions (2% NaOH (w/v), 6h), and the spent alkaline liquid (black liquor) was collected and used for pretreatment of corn stover, a feedstock exhibiting a higher susceptibility to NaOH attack, for improved enzymatic hydrolysis at a reduced cost. The results showed that, because of the high pH and the appreciable amount of carbohydrates in the black liquor, sugar production during enzymatic hydrolysis of corn stover pretreated with black liquor was comparable to that of biomass pretreated with 1% NaOH. After black liquor pretreatment at the best residence time (24h), the total reducing sugar, glucose, and xylose yields of corn stover reached 478.5, 287.7, and 145.3mg/g raw biomass, respectively, indicating the viability of this novel pretreatment technology.}, journal={BIORESOURCE TECHNOLOGY}, author={Xu, Jiele and Zhang, Ximing and Cheng, Jay J.}, year={2012}, month={May}, pages={255–260} }
 @article{zhang_xu_cheng_2011, title={Pretreatment of Corn Stover for Sugar Production with Combined Alkaline Reagents}, volume={25}, ISSN={["0887-0624"]}, DOI={10.1021/ef201130d}, abstractNote={Corn stover pretreatment using a combination of sodium hydroxide (NaOH) and calcium oxide (CaO) at room temperature was investigated for improved cost-effectiveness of biomass-to-sugar conversion in this study. The effects of NaOH loading, CaO loading, and residence time on enzymatic hydrolysis were studied, and the total reducing sugar yield in the enzymatic hydrolysis was used to evaluate the pretreatment conditions. Compared with NaOH pretreatment, pretreatment with the combination of NaOH and CaO resulted in a similar sugar production rate but at a potentially lower cost. The addition of CaO not only increased the alkalinity, which favored biomass digestibility improvement, but also contributed to better biomass preservation in the pretreatment. On the basis of the sugar production rate and cost-benefit considerations, the two recommended pretreatment conditions were 3 h, 0.05 g NaOH g–1 raw biomass, 0.1 g CaO g–1 raw biomass and 6 h, 0.05 g NaOH g–1 raw biomass, 0.05 g CaO g–1 raw biomass, at which t...}, number={10}, journal={ENERGY & FUELS}, author={Zhang, Ximing and Xu, Jiele and Cheng, Jay J.}, year={2011}, month={Oct}, pages={4796–4802} }