@article{ernest-saunders_pawlak_lee_2014, title={Properties of surface acetylated microfibrillated cellulose relative to intra- and inter-fibril bonding}, volume={21}, ISSN={["1572-882X"]}, DOI={10.1007/s10570-014-0177-7}, number={3}, journal={CELLULOSE}, author={Ernest-Saunders, Rachel and Pawlak, Joel J. and Lee, Jung Myoung}, year={2014}, month={Jun}, pages={1541–1552} }
 @article{lee_pawlak_heitmann_2012, title={Dimensional and hygroexpansive behaviors of cellulose microfi brils (MFs) from kraft pulp-based fibers as a function of relative humidity}, volume={66}, ISSN={["1437-434X"]}, DOI={10.1515/hf-2011-0129}, abstractNote={Abstract Cellulose aggregate fibrils (CAFs) with dimensions of 100,000×3000×300 nm from unbleached kraft pulp (KP), oxygen delignified KP (KP ox.del ), and fully bleached kraft pulp (BKP) were liberated by a series of high shear and fractionation operations. The CAFs served as microfibril model material to evaluate their dimensional and hygroexpansive behaviors when submitted to variable relative humidities (RHs). The atomic force microscopy images of CAFs from different sources of kraft fibers were obtained during a RH cycle from 50% RH to 78% RH and then to 21% RH while being kept at 23°C. The resulting images were analyzed to determine dimensional changes in length, its concurrent cross-sectional area, width, and height. The mean value of changes in length and width was in the range of 2.3–3.2% and 1.9–3.3%, respectively. The changes in area and height were in the range of 14.5–18.2% and 12.4–17.3%, respectively. The length of CAFs showed a negative correlation with RH, whereas cross-sectional area, width, and height changes correlated positively with RHs. In the out-of-plane direction, such as area and height, the hygroexpansivity was one order of magnitude larger than the in-plane hygroexpansivity, i.e., in terms of length and width.}, number={8}, journal={HOLZFORSCHUNG}, author={Lee, Jung Myoung and Pawlak, Joel J. and Heitmann, John A.}, year={2012}, month={Dec}, pages={1001–1008} }
 @article{santos_treasure_gonzalez_phillips_lee_jameel_chang_2012, title={Impact of hardwood species on production cost of second generation ethanol}, volume={117}, ISSN={["1873-2976"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84861134453&partnerID=MN8TOARS}, DOI={10.1016/j.biortech.2012.04.083}, abstractNote={The present work targeted the understanding of the influence of nine different hardwood species as feedstock on ethanol production yield and costs. It was found that the minimum ethanol revenue (MER) ($ per gallon to the producer) to achieve a 12% internal rate of return (IRR) on invested capital was smaller for low lignin content samples and the influence of species characteristics remained restricted to high residual lignin content. We show that if the pretreatment being applied to the feedstock targets or is limited to low lignin removal, one can expect the species to have a significant impact on overall economics, playing important role to project success. This study also showed a variation of up to 40% in relative MER among hardwood species, where maple, globulus and sweet gum varied the least. Sensitivity analysis showed ethanol yield per ton of feedstock had the largest influence in MER, followed by CAPEX.}, journal={BIORESOURCE TECHNOLOGY}, author={Santos, Ricardo B. and Treasure, Trevor and Gonzalez, Ronalds and Phillips, Richard and Lee, Jung Myoung and Jameel, Hasan and Chang, Hou-min}, year={2012}, month={Aug}, pages={193–200} }
 @article{lee_venditti_jameel_kenealy_2011, title={Detoxification of woody hydrolyzates with activated carbon for bioconversion to ethanol by the thermophilic anaerobic bacterium Thermoanaerobacterium saccharolyticum}, volume={35}, ISSN={0961-9534}, url={http://dx.doi.org/10.1016/j.biombioe.2010.10.021}, DOI={10.1016/j.biombioe.2010.10.021}, abstractNote={Autohydrolysis is a simple, green method of recovering sugars from biomass, using only hot water. One potential drawback is that byproducts are formed during the autohydrolysis process that could interfere with subsequent hydrolysis and fermentation to ethanol. In the present work, autohydrolysis prehydrolyzate from mixed hardwood chips was detoxified with activated carbon and the removal efficiency of byproducts as well as the loss of sugars determined. The resulting detoxified prehydrolyzate was evaluated for the fermentation to ethanol with a thermophilic anaerobic bacterium. Activated carbon at a 2.5 wt % level on the prehydrolyzate was able to remove 42% of formic acid, 14% of acetic acid, 96% of hydroxymethylfurfural (HMF) and 93% of the furfural. However, 8.9% of sugars were also removed. The removal of HMF and furfural follow expected adsorption isotherms but formic acid, acetic acid, and sugars did not. Autohydrolysis prehydrolyzates from mixed hardwood detoxified with activated carbon can be fermented with Thermoanaerobacterium saccharolyticum strain MO1442 with an essentially 100% yield. T. saccharolyticum strain MO1442 is able to metabolize the glucose, xylose, and arabinose in the hydrolyzate. The results showed the detoxification process with activated carbon improved the ethanol yields by the removal of toxic compounds, mainly HMF and furfural, with moderate loss of fermentable sugars.}, number={1}, journal={Biomass and Bioenergy}, publisher={Elsevier BV}, author={Lee, Jung Myoung and Venditti, Richard A. and Jameel, Hasan and Kenealy, William R.}, year={2011}, month={Jan}, pages={626–636} }
 @article{lee_jameel_venditti_2010, title={A comparison of the autohydrolysis and ammonia fiber explosion (AFEX) pretreatments on the subsequent enzymatic hydrolysis of coastal Bermuda grass}, volume={101}, ISSN={0960-8524}, url={http://dx.doi.org/10.1016/j.biortech.2010.02.055}, DOI={10.1016/j.biortech.2010.02.055}, abstractNote={Two distinct pretreatment technologies, autohydrolysis and AFEX, have been applied to coastal Bermuda grass (CBG) followed by enzymatic hydrolysis in order to compare the effects of pretreatment on the subsequent sugar generation. Furthermore, the influence of structural features from each pretreatment on biomass digestibility was characterized with SEM, ATR-FTIR, and XRD. Enzymatic conversion of pretreated solids from the pretreatments increased with elevated temperature and longer residence times. AFEX pretreatment at 100 degrees C for 30 min produced a sugar yield of 94.8% of theoretical possible with 30 FPU/g enzymatic loading, the maximum achieved with AFEX. It was also shown that with autohydrolysis at 170 degrees C for 60 min that 55.4% sugar yield of the theoretical possible was produced with a 30 FPU/g enzymatic loading, the maximum with autohydrolysis. AFEX pretreatment does not change the chemical composition of CBG but autohydrolysis reduces hemicellulose content in the pretreated solids. Both pretreatments cause re-localization of lignin components. There was no observed correlation between crystallinity and enzyme digestibility of the pretreated solids. AFEX pretreatment developed more enzymatic accessibility to pretreated solids of CBG than did autohydrolysis pretreatment, leading to more sugar generation through the whole process. The total amount of sugars accounted for with autohydrolysis decreases with increasing temperature, consistent with increased byproduct generation via thermal degradation reactions.}, number={14}, journal={Bioresource Technology}, publisher={Elsevier BV}, author={Lee, Jung Myoung and Jameel, Hasan and Venditti, Richard A.}, year={2010}, month={Jul}, pages={5449–5458} }
 @article{lee_jameel_venditti_2010, title={Effect of ozone and autohydrolysis pretreatments on enzymatic digestibility of coastal bermuda grass}, volume={5}, DOI={10.15376/biores.5.2.1084-1101}, abstractNote={Coastal Bermuda grass (CBG) has been shown to have potential as a biomass feedstock for sugar production. In this study, the effectiveness of ozone pretreatment for CBG to improve the sugar recovery via enzyme hydrolysis was investigated. Raw CBG and autohydrolysis-treated CBG were pretreated with ozone at ozone consumption of 1.8 to 26.4 % (w/w) at room temperature. Lignin degradation and hemicellulose solubilization increased with increased ozone consumption. At 26.4% ozone consumption by weight on CBG the amount of lignin in the CBG was reduced by 34%. Autohydrolysis of CBG increased the reactivity of cellulose, hemicellulose, and lignin with ozone. The maximum total sugar recovery after enzymatic hydrolysis was 32% for a 14.0% consumption of ozone on raw CBG. For CBG samples pretreated with autohydrolysis followed by a 3.1% ozone consumption pretreatment the maximum total sugar recovery after enzyme hydrolysis was 40.1%. Autohydrolysis pretreatment followed by enzyme hydrolysis yielded a 36.4% sugar recovery, indicating that the application and benefits of ozone after autohydrolysis with the conditions studied herein are marginally better than autohydrolysis alone.}, number={2}, journal={BioResources}, author={Lee, J. M. and Jameel, H. and Venditti, R. A.}, year={2010}, pages={1084–1101} }
 @article{lee_pawlak_heitmann_2010, title={Longitudinal and concurrent dimensional changes of cellulose aggregate fibrils during sorption stages}, volume={61}, ISSN={["1873-4189"]}, DOI={10.1016/j.matchar.2010.02.007}, abstractNote={Abstract Atomic force microscopy (AFM) studies of the dimensional changes of cellulose microfibril materials, called cellulose aggregate fibrils (approx. 100 µm × 3 µm × 300 nm), exposed to two distinct relative humidities of 80% and 23% for 24 h and then suddenly subjected to 50% RH and 23 °C show that the fibrils are responsive to the surrounding environments in a nonspecific fashion. AFM images (10 µm × 10 µm) of the individual straight cellulose aggregate fibrils were taken as a function of elapsed time during both desorption and adsorption of moisture. The longitudinal distance between discrete natural defects observed on the cellulose aggregate fibrils as well as the width, cross-sectional area, and height of the cellulose aggregate fibril were measured from the AFM images. The length of the cellulose aggregate fibrils was found to have reduced after exposure to either high or low relative humidity, and then placement in ambient conditions. Over time in ambient conditions, the cellulose aggregate fibrils progressively relaxed to their original length during both desorption and adsorption of moisture. However, the relaxation rate during adsorption was faster than that during desorption. The possible explanations for this phenomenon are discussed including the sample preparation method, volume conservation, entropy elasticity, and free volume theory. The changes in the width, height, and cross-sectional area are also discussed.}, number={5}, journal={MATERIALS CHARACTERIZATION}, author={Lee, Jung Myoung and Pawlak, Joel J. and Heitmann, John A.}, year={2010}, month={May}, pages={507–517} }
 @article{lee_shi_venditti_jameel_2009, title={Autohydrolysis pretreatment of Coastal Bermuda grass for increased enzyme hydrolysis}, volume={100}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2008.12.068}, abstractNote={Coastal Bermuda grass (GBG) was pretreated using an autohydrolysis process with different temperatures and times, and the pretreated materials were enzymatically hydrolyzed using a mixture of cellulase, xylanase and beta-glucosidase with different enzyme loadings to evaluate sugar yields. Compared with untreated CBG, autohydrolysis pretreatments at all elevated temperatures and residence times tested enhanced enzymatic digestibility of both cellulose and hemicellulose. Increasing the temperature and residence time also helps to solubilize hemicelluloses, with 83.3% of the hemicelluloses solubilized at 170 degrees C for 60 min treatment. However, higher temperatures and longer times resulted in an overall lower sugar recovery when considering monosaccharides in the prehydrolyzate combined with the enzyme hydrolyzate. Autohydrolysis at 150 degrees C for 60 min provided the highest overall sugar yield for the entire process. A total of 43.3 g of sugars, 70% of the theoretical sugar yield, can be generated from 100g CBG, 15.0 g of monosaccharide in the prehydrolyzate and 28.3 g in the enzyme hydrolyzate. The conversion efficiency could be further improved by optimizing enzyme dosages and xylanases:cellulases ratio and pretreatment conditions to minimize sugar degradation.}, number={24}, journal={BIORESOURCE TECHNOLOGY}, author={Lee, Jung Myoung and Shi, Jian and Venditti, Richard A. and Jameel, Hasan}, year={2009}, month={Dec}, pages={6434–6441} }
 @article{lee_heitmann_pawlak_2007, title={Local morphological and dimensional changes of enzyme-degraded cellulose materials measured by atomic force microscopy}, volume={14}, ISSN={["0969-0239"]}, DOI={10.1007/s10570-007-9172-6}, number={6}, journal={CELLULOSE}, author={Lee, Jung Myoung and Heitmann, John A. and Pawlak, Joel J.}, year={2007}, month={Dec}, pages={643–653} }
 @article{lee_heitmann_pawlak_2007, title={Rheology of carboxymethyl cellulose solutions treated with cellulases}, volume={2}, number={1}, journal={BioResources}, author={Lee, J. M. and Heitmann, J. A. and Pawlak, J. J.}, year={2007}, pages={20–33} }
 @article{park_venditti_abrecht_jameel_pawlak_lee_2007, title={Surface and pore structure modification of cellulose fibers through cellulase treatment}, volume={103}, ISSN={["0021-8995"]}, DOI={10.1002/app.25457}, abstractNote={The surface and pore structure of cellulose fibers have a significant impact on the properties and performance in applications. Cellulase enzymatic hydrolysis of cellulose fibers can result in changes to the surface and pore structure, thus providing a useful tool for fiber modification. This research characterizes these changes using various test methods such as fiber dimension, water retention value (WRV), hard-to-remove (HR) water content, freezing and nonfreezing bound water content, polymer adsorption, and crystallinity index. For a high-dosage cellulase treatment (600 U/g dry solid), the fiber length was significantly decreased and the fibers were “cut” in the cross direction, not in the axial direction. The swelling capacities as measured by the WRV and HR water content increased for the high-dosage treatment. Three independent measurements (nonfreezing bound water, polymer adsorption, and crystallinity index) are in good agreement with the statement that the amorphous regions of cellulose fibers are a more readily available substrate relative to crystalline regions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3833–3839, 2007}, number={6}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Park, Sunkyu and Venditti, Richard A. and Abrecht, David G. and Jameel, Hasan and Pawlak, Joel J. and Lee, Jung M.}, year={2007}, month={Mar}, pages={3833–3839} }
 @article{lee_heitmann_pawlak_2007, title={Technique for the measurement of dimensional changes of natural microfibril materials under variable humidity environments}, volume={445}, DOI={10.1016/j.msea.2006.09.096}, abstractNote={Abstract An algorithm was developed to analyze the dimensions of line scan data of step-shaped disconitunities acquired with an atomic force microscope. The effect of a number of AFM parameters on the quantitative imaging of step features was discussed. Quantitiative imaging using AFM was shown to be very reproducible as five successive scans of a standard step height grating produced less than 3% variation in measured parameters. A cellulose microfibril, called cellulose aggregate fibril (CAF), with dimensions of ∼50,000 nm × 2000 nm × 300 nm derived from papermaking fibers was scanned under cyclic relative humdity conditions with the relative humidity starting at 50% then raising to 80% followed by a decrease in the relative humidity to 28%. Changes in the width of the CAF were weakly correlated with changes in the relative humdity, while changes in the height and area of the CAF were positively correlated with the relative humdity. The length of the CAF was negatively correlated with the given relative humdity cycle. These findings have significant implications in paper dimensional stability and the engineering of cellulose micro and nano-fiber composites.}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Lee, J. M. and Heitmann, J. A. and Pawlak, Joel}, year={2007}, pages={632–640} }
 @article{park_lee_eom_2004, title={The control of sticky contaminant with enzymes in the recycling of wastepaper}, volume={10}, number={1}, journal={Journal of Industrial and Engineering Chemistry}, author={Park, S. B. and Lee, J. M. and Eom, T. J.}, year={2004}, pages={72–77} }