@article{wang_xu_pandey_cheng_li_qu_2012, title={Improvement of Sugar Production from Transgenic Switchgrass with Low-Temperature Alkali Pretreatment}, volume={26}, ISSN={["1520-5029"]}, DOI={10.1021/ef3004575}, abstractNote={Genetically modified switchgrass (cv. Alamo) and its conventional plant were both pretreated using two groups of conditions: lime at 50 °C and the combination of lime and NaOH at ambient temperature. The results show that the transgenic plant (with altered lignin content and composition) was more susceptible to alkali pretreatment than the conventional plant. At the recommended conditions (0.1 g/g of raw biomass and 12 h) for lime pretreatment at 50 °C, the glucan and xylan conversions of transgenic switchgrass were 12 and 10%, respectively, higher than those of the conventional plant. These increases were reduced to 7 and 8% for glucan and xylan conversions, respectively, when the best conditions (0.025 g of lime/g of raw biomass, 0.1 g of NaOH/g of raw biomass, and 6 h) for combined alkali pretreatment at ambient temperature were employed. The advantage of transgenics over a conventional plant in sugar production could be maximized if proper pretreatment conditions were used.}, number={5}, journal={ENERGY & FUELS}, author={Wang, Ziyu and Xu, Jiele and Pandey, Pankaj and Cheng, Jay J. and Li, Ruyu and Qu, Rongda}, year={2012}, month={May}, pages={3054–3061} }
 @article{xu_cheng_stomp_2012, title={Nutrient removal from swine wastewater by growing duckweed: A pilot study}, volume={55}, DOI={10.13031/2013.41264}, abstractNote={A pilot-scale duckweed pond was installed and integrated into the existing swine wastewater management system of a swine farm in Zebulon, North Carolina to investigate its effectiveness in removing nutrients from anaerobically treated swine wastewater. The nutrient-rich wastewater was added intermittently into the duckweed pond to maintain an ammonium (NH4-N) concentration of about 20 mg L-1, and the duckweed was harvested regularly to ultimately remove nutrients from the water body. The results show that duckweed (Spirodela polyrrhiza) grew rapidly on swine wastewater under field conditions, with a dry biomass yield of 10.7 g m-2 d-1 in August and September. Over the 16-week experimental period, NH4-N, the major nutrient concern in swine wastewater, was removed at 1.12 g m-2 d-1. The fast duckweed growth and an average duckweed protein content of 26.3% enabled a protein yield of 2.11 g m-2 d-1 throughout the experiment.}, number={1}, journal={Transactions of the ASABE}, author={Xu, J. and Cheng, Jay and Stomp, A. M.}, year={2012}, pages={181–185} }
 @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} }
 @misc{xu_wang_cheng_2011, title={Bermuda grass as feedstock for biofuel production: A review}, volume={102}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2011.05.070}, abstractNote={Bermuda grass is a promising feedstock for the production of fuel ethanol in the Southern United States. This paper presents a review of the significant amount of research on the conversion of Bermuda grass to ethanol and a brief discussion on the factors affecting the biomass production in the field. The biggest challenge of biomass conversion comes from the recalcitrance of lignocellulose. A variety of chemical, physico-chemical, and biological pretreatment methods have been investigated to improve the digestibility of Bermuda grass with encouraging results reported. The subsequent enzymatic hydrolysis and fermentation steps have also been extensively studied and effectively optimized. It is expected that the development of genetic engineering technologies for the grass and fermenting organisms has the potential to greatly improve the economic viability of Bermuda grass-based fuel ethanol production systems. Other energy applications of Bermuda grass include anaerobic digestion for biogas generation and pyrolysis for syngas production.}, number={17}, journal={BIORESOURCE TECHNOLOGY}, author={Xu, Jiele and Wang, Ziyu and Cheng, Jay J.}, year={2011}, month={Sep}, pages={7613–7620} }
 @article{xu_chen_cheng_sharma-shivappa_burns_2011, title={Delignification of switchgrass cultivars for bioethanol production}, volume={6}, number={1}, journal={BioResources}, author={Xu, J. L. and Chen, Y. and Cheng, J. J. and Sharma-Shivappa, R. R. and Burns, J. C.}, year={2011}, pages={707–720} }
 @article{zhou_xu_wang_cheng_li_qu_2012, title={Dilute sulfuric acid pretreatment of transgenic switchgrass for sugar production}, volume={104}, ISSN={["0960-8524"]}, DOI={10.1016/j.biortech.2011.11.051}, abstractNote={Conventional Alamo switchgrass and its transgenic counterparts with reduced/modified lignin were subjected to dilute sulfuric acid pretreatment for improved sugar production. At 150 °C, the effects of acid concentration (0.75%, 1%, 1.25%) and residence time (5, 10, 20, 30 min) on sugar productions in pretreatment and enzymatic hydrolysis were investigated, with the optimal pretreatment conditions determined for each switchgrass genotype based on total sugar yield and the amounts of sugar degradation products generated during the pretreatment. The results show that genetic engineering, although did not cause an appreciable lignin reduction, resulted in a substantial increase in the ratio of acid soluble lignin:acid insoluble lignin, which led to considerably increased sugar productions in both pretreatment and enzymatic hydrolysis. At an elevated threshold concentration of combined 5-hydroxyfuranmethal and furfural (2.0 g/L), the overall carbohydrate conversions of conventional switchgrass and its transgenic counterparts, 10/9-40 and 11/5-47, reached 75.9%, 82.6%, and 82.2%, respectively.}, journal={BIORESOURCE TECHNOLOGY}, author={Zhou, Xu and Xu, Jiele and Wang, Ziyu and Cheng, Jay J. and Li, Ruyu and Qu, Rongda}, year={2012}, month={Jan}, pages={823–827} }
 @article{xu_shen_2011, title={Effects of harvest regime and water depth on nutrient recovery from swine wastewater by growing Spirodela oligorrhiza}, volume={83}, number={11}, journal={Water Environment Research}, author={Xu, J. L. and Shen, G. X.}, year={2011}, pages={2049–2056} }
 @article{xu_wang_sharma-shivappa_cheng_2011, title={Enzymatic hydrolysis of switchgrass and coastal bermuda grass pretreated using different chemical methods}, volume={6}, number={3}, journal={BioResources}, author={Xu, J. L. and Wang, Z. Y. and Sharma-Shivappa, R. R. and Cheng, J. J.}, year={2011}, pages={2990–3003} }
 @article{xu_shen_2011, title={Growing duckweed in swine wastewater for nutrient recovery and biomass production}, volume={102}, number={2}, journal={Bioresource Technology}, author={Xu, J. L. and Shen, G. X.}, year={2011}, pages={848–853} }
 @misc{wang_xu_cheng_2011, title={Modeling biochemical conversion of lignocellulosic materials for sugar production: a Review}, volume={6}, number={4}, journal={BioResources}, author={Wang, Z. Y. and Xu, J. L. and Cheng, J. J.}, year={2011}, pages={5282–5306} }
 @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} }
 @article{xu_cui_cheng_stomp_2011, title={Production of high-starch duckweed and its conversion to bioethanol}, volume={110}, ISSN={["1537-5110"]}, DOI={10.1016/j.biosystemseng.2011.06.007}, abstractNote={Growing high-starch duckweed for its conversion to bioethanol was investigated as a novel technology to supplement maize-based ethanol production. Under the fall (autumn) climate conditions of North Carolina, the biomass accumulation rate of Spirodela polyrrhiza grown in a pilot-scale culture pond using diluted pig effluent was 12.4 g dry weight m−2 day−1. Through simple transfer of duckweed plants into well water for 10 days, the duckweed starch content increased by 64.9%, resulting in a high annual starch yield of 9.42 × 103 kg ha−1. After enzymatic hydrolysis and yeast fermentation of high-starch duckweed biomass in a 14-l fermentor, 94.7% of the theoretical starch conversion was achieved. The ethanol yield of duckweed reached 6.42 × 103 l ha−1, about 50% higher than that of maize-based ethanol production, which makes duckweed a competitive starch source for fuel ethanol production.}, number={2}, journal={BIOSYSTEMS ENGINEERING}, author={Xu, Jiele and Cui, Weihua and Cheng, Jay J. and Stomp, Anne-M.}, year={2011}, month={Oct}, pages={67–72} }
 @article{xu_cheng_2011, title={Pretreatment of switchgrass for sugar production with the combination of sodium hydroxide and lime}, volume={102}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2010.12.038}, abstractNote={Sodium hydroxide (NaOH) and lime (Ca(OH)2) were innovatively used together in this study to improve the cost-effectiveness of alkaline pretreatment of switchgrass at ambient temperature. Based on the sugar production in enzymatic hydrolysis, the best pretreatment conditions were determined as: residence time of 6 h, NaOH loading of 0.10 g/g raw biomass, NaOH addition at the beginning, Ca(OH)2 loading of 0.02 g/g raw biomass, and biomass wash intensity of 100 ml water/g raw biomass, at which the glucose and xylose yields were respectively 59.4% and 57.3% of the theoretical yields. The sugar yield of the biomass pretreated using the combination of 0.10 g NaOH/g raw biomass and 0.02 g Ca(OH)2/g raw biomass was found comparable with that of the biomass pretreated using 0.20 g NaOH/g raw biomass at the same conditions, while the chemical expense was remarkably reduced due to the low cost of lime and the reduced loading of NaOH.}, number={4}, journal={BIORESOURCE TECHNOLOGY}, author={Xu, Jiele and Cheng, Jay J.}, year={2011}, month={Feb}, pages={3861–3868} }
 @article{xu_cheng_sharma-shivappa_burns_2010, title={Sodium Hydroxide Pretreatment of Switchgrass for Ethanol Production}, volume={24}, ISSN={["1520-5029"]}, DOI={10.1021/ef9014718}, abstractNote={Lignocellulose-to-ethanol conversion is a promising technology to supplement corn-based ethanol production. However, the recalcitrant structure of lignocellulosic material is a major obstacle to the efficient conversion. To improve the enzymatic digestibility of switchgrass for the fermentable sugar production in hydrolysis, sodium hydroxide pretreatment of the biomass feedstock was investigated. At 121, 50, and 21 °C, raw switchgrass biomass at a solid/liquid ratio of 0.1 g/mL was pretreated, respectively, for 0.25−1, 1−48, and 1−96 h at different NaOH concentrations (0.5, 1.0, and 2.0%, w/v). Pretreatments were evaluated based on the yields of lignocellulose-derived sugars in the subsequent enzymatic hydrolysis. At the best pretreatment conditions (50 °C, 12 h, and 1.0% NaOH), the yield of total reducing sugars was 453.4 mg/g raw biomass, which was 3.78 times that of untreated biomass, and the glucan and xylan conversions reached 74.4 and 62.8%, respectively. Lignin reduction was closely related to the ...}, number={3}, journal={ENERGY & FUELS}, author={Xu, Jiele and Cheng, Jay J. and Sharma-Shivappa, Ratna R. and Burns, Joseph C.}, year={2010}, month={Mar}, pages={2113–2119} }
 @article{xu_cheng_sharma-shivappa_burns_2010, title={Lime pretreatment of switchgrass at mild temperatures for ethanol production}, volume={101}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2009.12.015}, abstractNote={To improve the enzymatic digestibility of switchgrass at mild temperatures, lime pretreatment of switchgrass was explored at 50 and 21 degrees Celsius, and compared with that at 121 degrees Celsius. The effects of residence time, lime loading, and biomass washing on the sugar production efficiency were investigated. Pretreatments were evaluated based on the yields of biomass-derived sugars in the subsequent enzymatic hydrolysis. Under the best pretreatment conditions (50 degrees Celsius, 24 h, 0.10 g Ca(OH)(2)/g raw biomass, and wash intensity of 100 ml water/g raw biomass), the yields of glucose, xylose, and total reducing sugars reached 239.6, 127.2, and 433.4 mg/g raw biomass, which were respectively 3.15, 5.78, and 3.61 times those of untreated biomass. The study on calcium-lignin bonding showed that calcium ions crosslinked lignin molecules under alkaline conditions, which substantially decreased lignin solubilization during pretreatment, but the resulting high lignin contents of the pretreated biomass did not compromise the improvement of enzymatic digestibility.}, number={8}, journal={BIORESOURCE TECHNOLOGY}, author={Xu, Jiele and Cheng, Jay J. and Sharma-Shivappa, Ratna R. and Burns, Joseph C.}, year={2010}, month={Apr}, pages={2900–2903} }