J. Y. Zhu

Energy Product Options for Eucalyptus Species Grown as Short Rotation Woody Crops

Eucalyptus species are native to Australia but grown extensively worldwide as short rotation hardwoods for a variety of products and as ornamentals. We describe their general importance with specific emphasis on existing and emerging markets as energy products and the potential to maximize their productivity as short rotation woody crops. Using experience in Florida USA and similar locations, we document their current energy applications and assess their productivity as short-term and likely long-term energy and related products.

Lignosulfonate-mediated cellulase adsorption: enhanced enzymatic saccharification of lignocellulose through weakening nonproductive binding to lignin

BackgroundThermochemical pretreatment of lignocellulose is crucial to bioconversion in the fields of biorefinery and biofuels. However, the enzyme inhibitors in pretreatment hydrolysate make solid substrate washing and hydrolysate detoxification indispensable prior to enzymatic hydrolysis. Sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL) is a relatively new process, but has demonstrated robust performance for sugar and biofuel production from woody biomass in terms of yield and energy efficiency. This study demonstrated the advantage of SPORL pretreatment whereby the presentation of lignosulfonate (LS) renders the hydrolysate non-inhibitory to cellulase (Cel) due to the formation of lignosulfonate-cellulase complexes (LCCs) which can mediate the Cel adsorption between lignin and cellulose, contrary to the conventional belief that pretreatment hydrolysate inhibits the enzymatic hydrolysis unless detoxified.ResultsParticular emphasis was made on the formation mechanisms and stability phase of LCCs, the electrostatic interaction between LCCs and lignin, and the redistributed Cel adsorption between lignin and cellulose. The study found that LS, the byproduct of SPORL pretreatment, behaves as a polyelectrolyte to form LCCs with Cel by associating to the oppositely charged groups of protein. Compared to Cel, the zeta potential of LCCs is more negative and adjustable by altering the molar ratio of LS to Cel, and thereby LCCs have the ability to mitigate the nonproductive binding of Cel to lignin because of the enlarged electrostatic repulsion. Experimental results showed that the benefit from the reduced nonproductive binding outweighed the detrimental effects from the inhibitors in pretreatment hydrolysate. Specifically, the glucan conversions of solid substrate from poplar and lodgepole pine were greatly elevated by 25.9% and 31.8%, respectively, with the complete addition of the corresponding hydrolysate. This contradicts the well-acknowledged concept in the fields of biofuels and biorefinery that the pretreatment hydrolysate is inhibitory to enzymes.ConclusionsThe results reported in this study also suggest significant advantages of SPORL pretreatment in terms of water consumption and process integration, that is, it should abolish the steps of solid substrate washing and pretreatment hydrolysate detoxification for direct simultaneous saccharification and combined fermentation (SSCombF) of enzymatic and pretreatment hydrolysate, thereby facilitating bioprocess consolidation. Furthermore, this study not only has practical significance to biorefinery and bioenergy, but it also provides scientific importance to the molecular design of composite enzyme-polyelectrolyte systems, such as immobilized enzymes and enzyme activators, as well as to the design of enzyme separation processes using water-soluble polyelectrolytes.

Enzymatic hydrolysis of loblolly pine: effects of cellulose crystallinity and delignification

Abstract Hydrolysis experiments with commercial cellulases have been performed to understand the effects of cell wall crystallinity and lignin on the process. In the focus of the paper are loblolly pine wood samples, which were systematically delignified and partly ball-milled, and, for comparison, Whatman CC31 cellulose samples with different crystallinities. In pure cellulose samples, the percentage of cellulose hydrolysis was inversely proportional to the degree of crystallinity. For the loblolly pine samples, the extent of hydrolysis was low for the fraction with 74- to 149-μm particle size, but the ball-milled fraction was hydrolyzed easily. The impact of lignin removal was also influential as demonstrated on progressively delignified wood, i.e., the degree of saccharification increased with lignin removal. On the basis of data of 72 h hydrolysis time on materials with similar crystallinity, the cell wall was found to be eight times less hydrolyzable than Whatman CC31 cellulose. Taken together, cellulose crystallinity and composition are not as important as the ultrastructural changes caused by the disruption of the tightly packed regions of the cell wall that ensued upon acid chlorite delignification.

Ethanol production from non-detoxified whole slurry of sulfite-pretreated empty fruit bunches at a low cellulase loading.

Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) was applied to an empty fruit bunches (EFB) for ethanol production. SPORL facilitated delignification through lignin sulfonation and dissolution of xylan to result in a highly digestible substrate. The pretreated whole slurry was enzymatically saccharified at a solids loading of 18% using a relatively low cellulase loading of 15 FPU/g glucan and simultaneously fermented without detoxification using Saccharomyces cerevisiae of YRH400. An ethanol yield of 217 L/tonne EFB was achieved at titer of 32 g/L. Compared with literature studies, SPORL produced high ethanol yield and titer with much lower cellulase loading without detoxification.

Using a combined hydrolysis factor to optimize high titer ethanol production from sulfite-pretreated poplar without detoxification.

Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) was applied to poplar NE222 chips in a range of chemical loadings, temperatures, and times. The combined hydrolysis factor (CHF) as a pretreatment severity accurately predicted xylan dissolution by SPORL. Good correlations between CHF and pretreated solids enzymatic digestibility, sugar yield, and the formations of furfural and acetic acid were obtained. Therefore, CHF was used to balance sugar yield with the formation of fermentation inhibitors for high titer ethanol production without detoxification. The results indicated that optimal sugar yield can be achieved at CHF=3.1, however, fermentation using un-detoxified whole slurries of NE222 pretreated at different severities by SPORL indicated CHF≈2 produced best results. An ethanol titer of 41 g/L was achieved at total solids of approximately 20 wt% without detoxification with a low cellulase loading of 15 FPU/g glucan (27 mL/kg untreated wood).

Evaluation energy efficiency of bioconversion knot rejects to ethanol in comparison to other thermochemically pretreated biomass

Rejects from sulfite pulp mill that otherwise would be disposed of by incineration were converted to ethanol by a combined physical-biological process that was comprised of physical refining and simultaneous saccharification and fermentation (SSF). The energy efficiency was evaluated with comparison to thermochemically pretreated biomass, such as those pretreated by dilute acid (DA) and sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL). It was observed that the structure deconstruction of rejects by physical refining was indispensable to effective bioconversion but more energy intensive than that of thermochemically pretreated biomass. Fortunately, the energy consumption was compensated by the reduced enzyme dosage and the elevated ethanol yield. Furthermore, adjustment of disk-plates gap led to reduction in energy consumption with negligible influence on ethanol yield. In this context, energy efficiency up to 717.7% was achieved for rejects, much higher than that of SPORL sample (283.7%) and DA sample (152.8%).

Direct production of lignin nanoparticles (LNPs) from wood using p-toluenesulfonic acid in an aqueous system at 80°C: characterization of LNP morphology, size, and surface charge

Abstract Lignin nanoparticles (LNPs) from renewable lignocelluloses can be a valuable building block for a variety of applications and could contribute to the economic development in rural agricultural communities. Current technologies for producing LNPs are not cost effective and use toxic solvents. In this study, LNPs were produced by fractionating poplar wood at ≤80°C with a recyclable hydrotrope p-toluenesulfonic acid (p-TsOH) in an aqueous system. The dissolved lignin was separated as LNPs simply by diluting the spent liquor (SL) to the minimal hydrotrope concentration (HCmin) of 11.5%. The p-TsOH, a solid acid, can be easily recycled by re-concentrating the diluted SL after lignin separation. The LNP size, morphology, and surface charge were controlled by the dilution ratio, speed, pH, and ionic strength of the LNP sol. The LNPs were analyzed by dynamic light scattering (DLS) and found to be fairly stable in terms of mean particle size and surface charge over a period of 2 weeks. Fractionation conditions also affected LNP properties.

Bioenergy Special Issue: International Conference on Bioenergy Technologies and Joint Symposium with AIChE Forest Products Division, Nanjing, China, October 2012

Lignocellulosic biomass, such as agriculture residue, historically has been an energy source in many rural areas. This is especially true in China, where not many years ago rural families relied on rice and wheat straw or corn stover as energy sources for cooking. Agriculture residue has also been used for biogas production in China for several decades, and combustion and gasification of municipal waste have also been a source of energy. Rapid economic development in the past two decades has raised concerns over energy supply and the environmental impact of fossil fuel, which has led the Chinese government to invest heavily in research and development for bioenergy production from lignocellulloses. Since 1990, total investment has been more than 1 billion RMB. Chinese Academy of Sciences (CAS) established the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) with an initial investment of US

Lignosulfonate To Enhance Enzymatic Saccharification of Lignocelluloses: Role of Molecular Weight and Substrate Lignin

50 million. The QIBEBT focuses on biomass energy research and technical explorations, complementing the bioenergy research efforts at the Guangzhou Institute of Energy Conversion of CAS, which focuses on process engineering. The QIBEBT has recently expanded to a second phase with more investments. This special issue is based on selected papers presented at the 2012 International Conference on Bioenergy Technologies and Joint Symposium with the American Institute of Chemical Engineers (AIChE) Forest Products Division held in Nanjing, China. The biannual conference sponsored by the Biomass Energy Technical Committee of China Renewable Energy Society is one of the largest showcases of bioenergy research and development in China. Co-sponsorship by the Forest Products Division of AIChE enhanced participation in the conference. This special issue reveals that current bioenergy research in China is no longer limited to traditional biogas, combustion, and gasification. It also involves biochemical, catalytic conversion, and new plant breeding. Also ongoing is research involving coproduct development through the biorefinery concept. Yang et al. from Capital Normal University (Beijing China) reported onestep saccharification and fermentation by expressingAGA1 gene of native а-agglutinin into the genomes of Saccharomyces cerevisiae Y5. Mu et al. from Georgia Institute of Technology conducted a review on upgrading lignin pyrolysis oil. Hu et al. of Northeastern Forestry University discussed thermal energy storage using nanocapsules with carboxymethyl cellulose. We hope that through this special issue, readers get a glimpse of bioenergy research in China. We also hope that this issue can help promote international research collaboration in bioenergy. Finally, we hope that readers consider using BioEnergy Research as their primary source for research and publication.We see tremendous growth of the journal in terms of both numbers and quality of papers published as it enters its sixth year of publication. We thank the authors for contributing to BioEnergy Research in a timely manner. We also thank the following Guest Associate Editors for overseeing and editing manuscripts for the issue: Prof. Yulin Deng of Georgia Institute of Technology, Dr. Bruce Dien of USDA Agriculture Research Service, Prof. Zhen Fan of the Chinese Academy of Sciences, Profs. Troy Runge and Xuejun Pan of University of Wisconsin, Prof. Sunkyu Park of North Carolina State University, Profs. Xiao Zhang and Jinwen Zhang of Washington State University, Prof. Nathan Mosier of Purdue University, Prof. Xuebing Zhao of Tsinghua University, Prof. Jie Bao of East China University of Technology, Dr. Ronald Zalesny, Jr., of USDA Forest Service, Prof. Peter van Walsum of University of Maine, and Prof. Donald Rockwood of University of Florida. J. Y. Zhu (*) Forest Products Laboratory, USDA Forest Service, Madison, WI, USA e-mail: jzhu@fs.fed.us