Progress 10/01/10 to 09/30/15

Outputs
Target Audience:The main target audiences include industries in animal production, crop (corn, wheat, etc.) production, and renewable energy production as well as environmental protection agencies or industry, scientists, engineers, students, and government agents in waste management and renewable energy production fields. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three doctoral students, three Master's students, two post-doctoral researchers, and fourvisiting scholars from Research Triangle Institute, Research Triangle Park, NC,Nanjing University of Technology, Nanjing, China, Shanghai Univeristy, Shanghai, China, and Wuhan University of Science and Technology, Wuhan, China have been trained in this project. How have the results been disseminated to communities of interest?The results obtained from this project have been published in a technicalbook andscientific journals as well as presented in professional conferences. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Dilute sulfuric acid was used to pretreat coastal Bermuda grass at high temperature prior to enzymatic hydrolysis. After both pretreatment and enzymatic hydrolysis processes, the highest yield of total sugars (combined xylose and glucose) was 97% of the theoretical value. Accounting for the formation of the inhibitory compounds, a pretreatment with 1.2% acid at 140 C for 30 min with a total sugar yield of 94% of the theoretical value may be more favorable for fermentation. Dilute sulfuric acid pretreatment can be successfully applied to coastal Bermuda grass to achieve high yields of monomeric glucose and xylose with acceptable levels of inhibitory compound formation. Microwave-based alkali pretreatmentof switchgrass and coastal bermudagrass was investigated in this study. Pretreatments were carried out by immersing the biomass in dilute alkali reagents and exposing the slurry to microwave radiation at 250 W for residence times ranging from 5 to 20 min. Simons' stain method was used to quantify changes in biomass porosity as a result of the pretreatment. Pretreatments were evaluated based on yields of total reducing sugars, glucose, and xylose. An evaluation of different alkalis identified sodium hydroxide as the most effective alkali reagent for microwave-based pretreatment of switchgrass and coastal bermudagrass. 82% glucose and 63% xylose yields were achieved for switchgrass and 87% glucose and 59% xylose yields were achieved for coastal bermudagrass following enzymatic hydrolysis of biomass pretreated under optimal conditions. Overcoming biomass recalcitrance to bioconversion is crucial for cellulosic biofuels commercialization. In this study, Alamo switchgrass (Panicum virgatum L.) was genetically transformed to suppress the expression of 4-coumarate-CoA ligase (4CL). The transgenic plants were determined to have lignin content reductions of up to 5.8%. The ratios of acid soluble lignin (ASL) to acid insoluble lignin (AIL) and syringyl/ guaiacyl (S/G) in transgenic plants were 21.4-64.3% and 11.8-164.5%, respectively, higher than those of conventional biomass. Both conventional and transgenic plants were pretreated with 0.5%, 1%, and 2% (w/v) NaOH for 15, 30, and 60 min at 121 C, followed by enzymatic hydrolysis with commercial cellulases and xylanases. At the optimal conditions, the glucan and xylan conversion efficiency in the best transgenic plants were 16% and 18% higher than the conventional plant, respectively. The results show that down-regulation of 4CL gene promoted enzymatic hydrolysis of plant cell walls following a mild alkali pretreatment. 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. Anaerobic digestion process to treat organic wastes has become attractive because of environmental and economic reasons. The process not only reduces the amount of material to be disposed, but also is a source of energy by producing biogas. An interesting option to improve yields of anaerobic digestion is the treatment of different substrates in a process called anaerobic co-digestion. This is a promising technology to enhance biogas production and stabilize the process. In most of the cases addition of co-substrates improves the biogas yield due to a better balance of nutrients and positive synergisms in the digestion medium. The overall goal of this research is to gain new insight into the impact of anaerobic co-digestion of swine manure and agricultural residues on biogas production. In this study, the performance of anaerobic co-digestion of swine manure and corn stover in two 14 liters continuous stirred tank reactors (CSTR) under mesophilic conditions (35 C) with a hydraulic retention time (HRT) of 25 days was investigated. One reactor (Reactor 1) was fed with swine manure alone (C:N ratio of 2.3) and the other reactor (Reactor 2) was fed with swine manure and corn stover (C:N ratio 10). When corn stover was co-digested with swine wastewater, methane production increased 11 times compared to methane production from swine wastewater alone (1980 versus 186 ml of CH4 per day). However, there was no significant difference on methane yield (0.19 versus 0.18 m3CH4/kg CODremoved). Because of the better balance of nutrients during co-digestion the ammonium accumulation in the Reactor 2 decreased, reducing the risk of inhibition. The effect of alkali pretreatment (solution of 5% NaOH and 5% CaO) and additional enzymes (cellulase complex) on biogas production from anaerobic co-digestion of swine wastewater and corn stover was investigated in the same reactors under mesophilic conditions (35 C) with a HRT of 25 days. While both reactors were fed with 560 ml of swine manure and 14 g of corn stover, three different treatments where applied only to reactor 2 (1: addition of 140 mg per day of cellulase; 2: pretreated corn stover; and 3: pretreated corn stover and addition of 140 mg per day of cellulase). Even though all the treatments improved methane yield compared, the best result was obtained with treatment 3 (31.9% of increase), followed by treatment 2 (21.8% increase) showing that alkali pretreatment was effective improving methane generation. Cellulase complex also showed to be effective, increasing methane production by 10.4%. However, cost analysis showed that, for all the treatments studied, the benefit obtained because of the extra methane produced is lower than the cost implied by the addition of either chemicals or enzymes because of the low price of methane. International collaborative study on biofuel production was conducted during my sabbatical leave at Peking University-Shenzhen Graduate School from January 1 through June 30, 2014. A study on screening of microalgal strains from the Peking University Algae Collection and heterotrophic cultivation for biodiesel production of a selected microalgal strain was conducted. Among 89 strains, only five were capable of growing under heterotrophic conditions in liquid cultures and Chlorella sp. PKUAC 102 was found the best for the production of heterotrophic algal biodiesel.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2011 Citation: Wang, Z., J.J. Cheng, R. Li, R. Qu. (2011) Alkaline Pretreatment of Genetically-Engineered Switchgrass for Improved Carbohydrates Conversion Efficiency. Presented at the 33rd Symposium on Biotechnology for Fuels and Chemicals, 2  5 May 2011, Seattle, Washington, USA.
• Type: Journal Articles Status: Published Year Published: 2011 Citation: Wang, Z.#, Xu, J #, Cheng, J.J.* (2011) Modeling biochemical conversion of lignocellulosic materials for sugar production: a review. BioResources. 6(4), 5282-5306.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Darwin, M., Gontupil, J., Liu, Z., Cheng, J.J. (2013) Potential of methane production from anaerobic co-digestion of swine manure with rice straw and cocoa husk. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Gontupil, J., Liu, Z., Darwin, M., Cheng, J.J. (2013) Anaerobic Co-Digestion of Swine Manure and Corn Stover with Additional Enzymes for Enhancing Biogas Production. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Liu, Z., Gontupil, J., Darwin, M., Pura, A., Cheng, J.J. (2013) Mesophilic Anaerobic Co-Digestion of Swine Manure with Switchgrass and Wheat Straw for Methane Production. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.
• Type: Book Chapters Status: Published Year Published: 2014 Citation: Cheng, J.J., Timilsina, G.R., Zilberman, D. (2014) Biofuel technologies and potential. In Timilsina & Zilberman (eds.) The Impacts of Biofuels on the Economy, Environment, and Poverty. Springer New York ? Heidelberg ? Dordrecht ? London.
• Type: Journal Articles Status: Published Year Published: 2011 Citation: Wang, Z., # Cheng, J.J. * (2011) Lime Pretreatment of Coastal Bermuda Grass for Bioethanol Production. Energy & Fuels, 25(4): 1830-1836.
• Type: Journal Articles Status: Published Year Published: 2011 Citation: Redding, A.P. #, Z. Wang#, D.R. Keshwani#, and J.J. Cheng*. (2011) High Temperature Dilute Acid Pretreatment of Coastal Bermuda Grass for Enzymatic Hydrolysis. Bioresource Technology, 102(2), 1415-1424.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Wang, Z., Li, R., Xu, J., Marita, J.M., Hatfield, R.D., Qu, R., Cheng, J.J. (2012) Sodium hydroxide pretreatment of genetically modified switchgrass. Bioresource Technology. 110(4): 364-370.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Zhou, X., Xu, J., Wang, Z., Cheng, J.J. , Li, R., Qu, R. (2012) Dilute Sulfuric Acid Pretreatment of Transgenic Switchgrass for Sugar Production. Bioresource Technology. 104(1): 823-827.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Redding, A., Chen, Y., Fu, S., Zhan, H., Cheng, J.J. (2012) Bioethanol production and dilute acid pretreatment of lignocellulosic materials: a review. Journal of South China University of Technology. 40(3): 1-9.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Xu, J., Zhao, H., Stomp, A-M., Cheng, J.J. (2012) Production of duckweed as a source of biofuels. Biofuels. 3(5): 589-601.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Mota, C.R., Head, M.A., Williams, J.C., Eland, L., Cheng, J.J., de los Reyes III, F.L. (2014) Structural integrity affects nitrogen removal activity of granules in semi-continuous reactors. Biodegradation. 25(6): 923-934.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Cui, Y., Yuan, W., Cheng, J.J. (2014) Understanding pH and ionic strength effects on aluminum sulfate-induced microalgae flocculation. Applied Biochemistry and Biotechnology. 173(7): 16921702.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: You, Z.Y., Wei, T.Y., Cheng, J.J. (2014) Improving anaerobic co-digestion of corn stover using sodium hydroxide pretreatment. Energy & Fuels, 28, 549?554.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Ansanay, Y., Kolar, P., Sharma-Shivappa, R., Cheng, J. (2014) Niobium oxide catalyst for delignification of switchgrass for fermentable sugar production. Industrial Crops and Products, 52,790-795.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Liu, Y., Tang, J., Li, J., Daroch, M., Cheng, J.J. (2014) Efficient production of triacylglycerols rich in docosahexaenoic acid (DHA) by osmo-heterotrophic marine protists. Applied Microbiology and Biotechnology. 98: 9643-9652.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Jia, Z., Liu Y., Daroch, M., Geng, S., Cheng, J.J. (2014) Screening, growth medium optimisation and heterotrophic cultivation of microalgae for biodiesel production. Applied Biochemistry and Biotechnology. 173(7): 1667-1679.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Yang, X., Zhang, R., Fu, J., Geng, S., Cheng, J.J., Sun, Y. (2014) Pyrolysis kinetic and product analysis of different microalgal biomass by distributed activation energy model and pyrolysisgas chromatographymass spectrometry. Bioresource Technology, 163, 335342.

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Agricultural and environmental researchers and engineers; bioenergy researchers and producers; governmental agents in agriculture, environment and bioenergy areas; swine and crop farmers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? A doctoral student, a visiting scholar from Nanjing University, Nanjing, China, and a visiting scholar from Research Triangle Institute, Research Triangle Park, NC have been trained in this project. How have the results been disseminated to communities of interest? The results from this project have been published in a scientific book and technical journals. What do you plan to do during the next reporting period to accomplish the goals? Further studies on anaerobic co-digestion of animal manure and agricultural residues such as corn stover, wheat straw, and switchgrass under thermophilic conditions will be conducted to understand the fundamentals of the co-digestion

Impacts
What was accomplished under these goals? NaOH pretreatment of corn stover was investigated for anaerobic co-digestion of corn stover with swine manure to shorten digestion time and improve biogas yield. Different NaOH concentration (2%, 4%, and 6%) at various temperatures (20 °C, 35 °C, and 55 °C) and 3 h of pretreatment time were tested for corn stover pretreatment. A C/N ratio of 25:1 in the substrates (corn stover to swine manure) was employed in the co-digestion test. The results showed that the lignin removal rate of 54.57% to 79.49% was achieved through the NaOH pretreatment. The highest biogas production rate was obtained from the corn stover pretreated at 6% NaOH at 35 °C produced for 3 h, which was 34.59% higher than that from the untreated raw corn stover. The increase of methane yield was from 276 to 350 mL/g VS. On the average, the reducing sugar content of corn stover decreased to 126.7 mg/g after digestion. Digestion time (T80) of pretreated corn stover was shortened from 18 days to 12−13 days. NaOH pretreatment not only effectively shortened the digestion time for anaerobic codigestion of corn stover with swine manure by removing the lignin from the corn stover but also improved biogas yield of corn stover. The pretreatment condition of 6% NaOH at 35 °C for 3 h is recommended for the pretreatment of corn stover. International collaborative study on biofuel production was conducted during my sabbatical leave at Peking University-Shenzhen Graduate School from January 1 through June 30, 2014. A study on screening of microalgal strains from the Peking University Algae Collection and heterotrophic cultivation for biodiesel production of a selected microalgal strain was conducted. Among 89 strains, only five were capable of growing under heterotrophic conditions in liquid cultures and Chlorella sp. PKUAC 102 was found the best for the production of heterotrophic algal biodiesel. Composition of the growth medium was optimised using response surface methodology and optimised growth conditions were successfully used for cultivation of the strain in a fermentor. Conversion of algal lipids to fatty acid methyl esters (FAMEs) showed that the lipid profile of the heterotrophically cultivated Chlorella sp. PKUAC 102 contains fatty acids suitable for biodiesel production. To assess the energy potential of different microalgae, Chlorella sorokiniana and Monoraphidium were selected for studying the pyrolytic behavior at different heating rates with the analytical method of thermogravimetric analysis (TG), distributed activation energy model (DAEM) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Results presented that Monoraphidium 3s35 showed superiority for pyrolysis at low heating rate. Calculated by DAEM, during the conversion rate range from 0.1 to 0.7, the activation energies of C. sorokiniana 21 were much lower than that of Monoraphidium 3s35. Both C. sorokiniana 21 and Monoraphidium 3s35 can produce certain amount (up to 20.50%) of alkane compounds, with 9-Octadecyne (C18H34) as the primary compound. Short-chain alkanes (C7-C13) with unsaturated carbon can be released in the pyrolysis at 500 °C for both microalgal biomass. It was also observed that the pyrolysis of C. sorokiniana 21 released more alcohol compounds, while Monoraphidium 3s35 produced more saccharides.

Publications

• Type: Book Chapters Status: Published Year Published: 2014 Citation: Cheng, J.J., Timilsina, G.R., Zilberman, D. (2014) Biofuel technologies and potential. In Timilsina & Zilberman (eds.) The Impacts of Biofuels on the Economy, Environment, and Poverty. Springer New York ? Heidelberg ? Dordrecht ? London.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: You, Z.Y., Wei, T.Y., Cheng, J.J. (2014) Improving anaerobic co-digestion of corn stover using sodium hydroxide pretreatment. Energy & Fuels, 28, 549?554.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Mota, C.R., Head, M.A., Williams, J.C., Eland, L., Cheng, J.J., de los Reyes III, F.L. (2014) Structural integrity affects nitrogen removal activity of granules in semi-continuous reactors. Biodegradation. 25(6): 923-934.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Ansanay, Y., Kolar, P., Sharma-Shivappa, R., Cheng, J. (2014) Niobium oxide catalyst for delignification of switchgrass for fermentable sugar production. Industrial Crops and Products, 52,790-795.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Liu, Y., Tang, J., Li, J., Daroch, M., Cheng, J.J. (2014) Efficient production of triacylglycerols rich in docosahexaenoic acid (DHA) by osmo-heterotrophic marine protists. Applied Microbiology and Biotechnology. 98: 9643-9652.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Jia, Z., Liu Y., Daroch, M., Geng, S., Cheng, J.J. (2014) Screening, growth medium optimisation and heterotrophic cultivation of microalgae for biodiesel production. Applied Biochemistry and Biotechnology. 173(7): 1667-1679.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Yang, X., Zhang, R., Fu, J., Geng, S., Cheng, J.J., Sun, Y. (2014) Pyrolysis kinetic and product analysis of different microalgal biomass by distributed activation energy model and pyrolysisgas chromatographymass spectrometry. Bioresource Technology, 163, 335342.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Cui, Y., Yuan, W., Cheng, J.J. (2014) Understanding pH and ionic strength effects on aluminum sulfate-induced microalgae flocculation. Applied Biochemistry and Biotechnology. 173(7): 16921702.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Agricultural and environmental researchers and engineers; bioenergy researchers and producers; governmental agents in agriculture, environment and bioenergy areas; swine and crop farmers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Three graduate students have been trained in this project. How have the results been disseminated to communities of interest? The results from this project have been published in scientific journals and presented in professional conferences. What do you plan to do during the next reporting period to accomplish the goals? Further studies on anaerobic co-digestion of animal manure and agricultural residues such as corn stover, wheat straw, and switchgrass will be conducted to understand the fundamentals of the co-digestion.

Impacts
What was accomplished under these goals? Anaerobic digestion process to treat organic wastes has become attractive because of environmental and economic reasons. The process not only reduces the amount of material to be disposed, but also is a source of energy by producing biogas. An interesting option to improve yields of anaerobic digestion is the treatment of different substrates in a process called anaerobic co-digestion. This is a promising technology to enhance biogas production and stabilize the process. In most of the cases addition of co-substrates improves the biogas yield due to a better balance of nutrients and positive synergisms in the digestion medium. The overall goal of this research is to gain new insight into the impact of anaerobic co-digestion of swine manure and agricultural residues on biogas production. In this study, the performance of anaerobic co-digestion of swine manure and corn stover in two 14 liters continuous stirred tank reactors (CSTR) under mesophilic conditions (35 C) with an hydraulic retention time (HRT) of 25 days was investigated. One reactor (Reactor 1) was fed with swine manure alone (C:N ratio of 2.3) and the other reactor (Reactor 2) was fed with swine manure and corn stover (C:N ratio 10). When corn stover was co-digested with swine wastewater, methane production increased 11 times compared to methane production from swine wastewater alone (1980 versus 186 ml of CH4 per day). However, there was no significant difference on methane yield (0.19 versus 0.18 m3CH4/kg CODremoved). Because of the better balance of nutrients during co-digestion the ammonium accumulation in the Reactor 2 decreased, reducing the risk of inhibition. The effect of alkali pretreatment (solution of 5% NaOH and 5% CaO) and additional enzymes (cellulase complex) on biogas production from anaerobic co-digestion of swine wastewater and corn stover was investigated in the same reactors under mesophilic conditions (35 C) with a HRT of 25 days. While both reactors were fed with 560 ml of swine manure and 14 g of corn stover, three different treatments where applied only to reactor 2 (1: addition of 140 mg per day of cellulase; 2: pretreated corn stover; and 3: pretreated corn stover and addition of 140 mg per day of cellulase). Even though all the treatments improved methane yield compared, the best result was obtained with treatment 3 (31.9% of increase), followed by treatment 2 (21.8% increase) showing that alkali pretreatment was effective improving methane generation. Cellulase complex also showed to be effective, increasing methane production by 10.4%. However, cost analysis showed that, for all the treatments studied, the benefit obtained because of the extra methane produced is lower than the cost implied by the addition of either chemicals or enzymes because of the low price of methane.

Publications

• Type: Journal Articles Status: Published Year Published: 2012 Citation: Redding, A., Chen, Y., Fu, S., Zhan, H., Cheng, J.J. (2012) Bioethanol production and dilute acid pretreatment of lignocellulosic materials: a review. Journal of South China University of Technology. 40(3): 1-9.
• Type: Journal Articles Status: Published Year Published: 2012 Citation: Xu, J., Zhao, H., Stomp, A-M., Cheng, J.J. (2012) Production of duckweed as a source of biofuels. Biofuels. 3(5): 589-601.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Darwin, M., Gontupil, J., Liu, Z., Cheng, J.J. (2013) Potential of methane production from anaerobic co-digestion of swine manure with rice straw and cocoa husk. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.
• Type: Journal Articles Status: Published Year Published: 2013 Citation: Gontupil, J., Liu, Z., Darwin, M., Cheng, J.J. (2013) Anaerobic Co-Digestion of Swine Manure and Corn Stover with Additional Enzymes for Enhancing Biogas Production. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Liu, Z., Gontupil, J., Darwin, M., Pura, A., Cheng, J.J. (2013) Mesophilic Anaerobic Co-Digestion of Swine Manure with Switchgrass and Wheat Straw for Methane Production. IBE Annual Meeting, 7-9 March 2013, Raleigh, North Carolina.

Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Overcoming biomass recalcitrance to bioconversion is crucial for cellulosic biofuels commercialization. In this study, Alamo switchgrass (Panicum virgatum L.) was genetically transformed to suppress the expression of 4-coumarate-CoA ligase (4CL). The transgenic plants were determined to have lignin content reductions of up to 5.8%. The ratios of acid soluble lignin (ASL) to acid insoluble lignin (AIL) and syringyl/ guaiacyl (S/G) in transgenic plants were 21.4-64.3% and 11.8-164.5%, respectively, higher than those of conventional biomass. Both conventional and transgenic plants were pretreated with 0.5%, 1%, and 2% (w/v) NaOH for 15, 30, and 60 min at 121 C, followed by enzymatic hydrolysis with commercial cellulases and xylanases. At the optimal conditions, the glucan and xylan conversion efficiency in the best transgenic plants were 16% and 18% higher than the conventional plant, respectively. The results show that down-regulation of 4CL gene promoted enzymatic hydrolysis of plant cell walls following a mild alkali pretreatment. 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. PARTICIPANTS: Ziyu Wang, Graduate Student; Xu Zhou, Graduate Student; Jiele Xu, Post-Doctoral Researcher; Ruyu Li, Post-Doctoral Researcher; Rongda Qu, Professor TARGET AUDIENCES: Agricultural and environmental researchers and engineers; bioenergy researchers and producers; governmental agents in agriculture, environment and bioenergy areas; swine and crop farmers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Renewable energy production to reduce our dependency on foreign oil is very important to the national security. Bioenergy plays an important role in renewable energy production. Biogas, bioethanol, and biodiesel can all make substantial contribution to the bioenergy production. Transgenic switchgrass is a promising feedstock for biofuel production. However, it is critical to develop cost-effective technologies to convert the transgenic switchgrass into biofuel.

Publications

• Wang, Z., Li, R., Xu, J., Marita, J.M., Hatfield, R.D., Qu, R., Cheng, J.J. (2012) Sodium hydroxide pretreatment of genetically modified switchgrass. Bioresource Technology. 110(4): 364-370.
• Zhou, X., Xu, J., Wang, Z., Cheng, J.J. , Li, R., Qu, R. (2012) Dilute Sulfuric Acid Pretreatment of Transgenic Switchgrass for Sugar Production. Bioresource Technology. 104(1): 823-827.
• Wang, Z., Xu, J., Cheng, J.J. (2011) Modeling biochemical conversion of lignocellulosic materials for sugar production: a review. BioResources. 6(4), 5282-5306.

Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Dilute sulfuric acid was used to pretreat coastal Bermuda grass at high temperature prior to enzymatic hydrolysis. After both pretreatment and enzymatic hydrolysis processes, the highest yield of total sugars (combined xylose and glucose) was 97% of the theoretical value. The prehydrolyzate liquor was analyzed for inhibitory compounds (furfural, hydroxymethylfurfural (HMF)) in order to assess potential risk for inhibition during the following fermentation. Accounting for the formation of the inhibitory compounds, a pretreatment with 1.2% acid at 140 C for 30 min with a total sugar yield of 94% of the theoretical value may be more favorable for fermentation. From this study, it can be concluded that dilute sulfuric acid pretreatment can be successfully applied to coastal Bermuda grass to achieve high yields of monomeric glucose and xylose with acceptable levels of inhibitory compound formation. Microwave-based alkali pretreatment of switchgrass and coastal bermudagrass was investigated in this study. Pretreatments were carried out by immersing the biomass in dilute alkali reagents and exposing the slurry to microwave radiation at 250 W for residence times ranging from 5 to 20 min. Simons' stain method was used to quantify changes in biomass porosity as a result of the pretreatment. Pretreatments were evaluated based on yields of total reducing sugars, glucose, and xylose. An evaluation of different alkalis identified sodium hydroxide as the most effective alkali reagent for microwave-based pretreatment of switchgrass and coastal bermudagrass. 82% glucose and 63% xylose yields were achieved for switchgrass and 87% glucose and 59% xylose yields were achieved for coastal bermudagrass following enzymatic hydrolysis of biomass pretreated under optimal conditions. Dielectric properties for dilute sodium hydroxide solutions were measured and compared with solid losses, lignin reduction, and reducing sugar levels in hydrolyzates. Results indicate that dielectric loss tangent of alkali solutions is a potential indicator of the severity of microwave-based pretreatments. PARTICIPANTS: Jiele Xu, Graduate student; Deepak Keshwani, Graduate student; Ziyu Wang, Graduate student; Arthur Redding, Graduate student TARGET AUDIENCES: Agricultural and environmental researchers and engineers; bioenergy researchers and producers; governmental agents in agriculture, environment and bioenergy areas; swine and crop farmers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Renewable energy production to reduce our dependency on foreign oil is very important to the national security. Bioenergy plays an important role in renewable energy production. Biogas, bioethanol, and biodiesel can all make substantial contribution to the bioenergy production. Switchgrass and coastal Bermuda grass are promising feedstocks for biofuel production. It is critical to develop cost-effective technologies to convert these feedstocks into biofuel.

Publications

• Wang, Z., J.J. Cheng, R. Li, R. Qu. (2011) Alkaline Pretreatment of Genetically-Engineered Switchgrass for Improved Carbohydrates Conversion Efficiency. Presented at the 33rd Symposium on Biotechnology for Fuels and Chemicals, 2-5 May 2011, Seattle, Washington, USA.
• Wang, Z., Xu, J , Cheng, J.J. (2011) Modeling biochemical conversion of lignocellulosic materials for sugar production: a review. BioResources. 6(4), 5282-5306.
• Wang, Z., Cheng, J.J. (2011) Lime Pretreatment of Coastal Bermuda Grass for Bioethanol Production. Energy & Fuels, 25(4): 1830-1836.
• Redding, A.P., Z. Wang, D.R. Keshwani, and J.J. Cheng. (2011) High Temperature Dilute Acid Pretreatment of Coastal Bermuda Grass for Enzymatic Hydrolysis. Bioresource Technology, 102(2), 1415-1424.
• Keshwani, D.R. and J.J. Cheng. (2010) Microwave-Based Alkali Pretreatment of Switchgrass and Coastal Bermudagrass for Bioethanol Production. Biotechnology Progress. 26(3), 644-652.
• Wang, Z., D.R. Keshwani, A.P. Redding and J.J. Cheng*. (2010) Sodium Hydroxide Pretreatment and Enzymatic Hydrolysis of Coastal Bermuda Grass. Bioresource Technology, 101(10), 3583-3585.