Publications
Dr. Chundawat’s complete list of publications is available here and at . Current h-index is 39, i10-index is 72, and total citations are 8284 (updated 2024/01). Corresponding author/s highlighted by an asterisk (*). Peer-reviewed papers are available on the publisher’s website, RUcore, and some older papers are also posted on Dr. Chundawat’s personal ResearchGate account. Original preprints are available on the bioRxiv and chemRxiv websites. Patents are available on Google Patents website.
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Authors: Chundawat SPS*, Balan V, Dale B.
Journal Link: Link
Abstract: Several factors will influence the viability of a biochemical platform for manufacturing lignocellulosic based fuels and chemicals, for example, genetically engineering energy crops, reducing pre-treatment severity, and minimizing enzyme loading. Past research on biomass conversion has focused largely on acid based pre-treatment technologies that fractionate lignin and hemicellulose from cellulose. However, for alkaline based (e.g., AFEX) and other lower severity pre-treatments it becomes critical to co-hydrolyze cellulose and hemicellulose using an optimized enzyme cocktail. Lignocellulosics are appropriate substrates to assess hydrolytic activity of enzyme mixtures compared to conventional unrealistic substrates (e.g., filter paper, chromogenic, and fluorigenic compounds) for studying synergistic hydrolysis. However, there are few, if any, high-throughput lignocellulosic digestibility analytical platforms for optimizing biomass conversion. The 96-well Biomass Conversion Research Lab (BCRL) microplate method is a high-throughput assay to study digestibility of lignocellulosic biomass as a function of biomass composition, pre-treatment severity, and enzyme composition. The most suitable method for delivering milled biomass to the microplate was through multi-pipetting slurry suspensions. A rapid bio-enzymatic, spectrophotometric assay was used to determine fermentable sugars. The entire procedure was automated using a robotic pipetting workstation. Several parameters that affect hydrolysis in the microplate were studied and optimized (i.e., particle size reduction, slurry solids concentration, glucan loading, mass transfer issues, and time period for hydrolysis). The microplate method was optimized for crystalline cellulose (Avicel) and ammonia fiber expansion (AFEX) pre-treated corn stover.
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Authors: Balan V*, da Costa Sousa L, Chundawat SPS, Vismeh R, Jones AD, Dale BE
Paper Link: Link
Journal Link: Link
Abstract: Rice straw (RS) is important lignocellulosic biomass with nearly 800 million dry tons produced annually worldwide. RS has immense potential as a lignocellulosic feedstock for making renewable fuels and chemicals in a biorefinery. However, because of its natural recalcitrance, RS needs thermochemical treatment prior to further biological processing. Ammonia fiber expansion (AFEX) is a leading biomass pretreatment process utilizing concentrated/liquefied ammonia to pretreat lignocellulosic biomass at moderate temperatures (70-140 degrees C). Previous research has shown improved cellulose and hemicellulose conversions upon AFEX treatment of RS at 2:1 ammonia to biomass (w/w) loading, 40% moisture (dwb), and 90 degrees C. However, there is still scope for further improvement. Fungal pretreatment of lignocellulosics is an important biological pretreatment method that has not received much attention in the past. A few reasons for ignoring fungal-based pretreatments are substantial loss in cellulose and hemicellulose content and longer pretreatment times that reduce overall productivity. However, the sugar loss can be minimized through use of white-rot fungi (e.g. Pleutorus ostreatus) over a much shorter duration of pretreatment time. It was found that mushroom spent RS prior to AFEX allowed reduction in thermochemical treatment severity, while resulting in 15% higher glucan conversions than RS pretreated with AFEX alone. In this work, we report the effect of fungal conditioning of RS followed by AFEX pretreatment and enzymatic hydrolysis. The recovery of other byproducts from the fungal conditioning process such as fungal enzymes and mushrooms are also discussed.
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Authors: Murnen HK, Balan V*, Chundawat SPS, Bals B, Sousa LD, Dale BE
Paper Link: Link
Journal Link: Link
Abstract: Miscanthus x giganteus is a tall perennial grass whose suitability as an energy crop is presently being appraised. There is very little information on the effect of pretreatment and enzymatic saccharification of Miscanthus to produce fermentable sugars. This paper reports sugar yields during enzymatic hydrolysis from ammonia fiber expansion (AFEX) pretreated Miscanthus. Pretreatment conditions including temperature, moisture, ammonia loading, residence time, and enzyme loadings are varied to maximize hydrolysis yields. In addition, further treatments such as soaking the biomass prior to AFEX as well as washing the pretreated material were also attempted to improve sugar yields. The optimal AFEX conditions determined were 160 degrees C, 2:1 (w/w) ammonia to biomass loading, 233% moisture (dry weight basis), and 5 min reaction time for water-soaked Miscanthus. Approximately 96% glucan and 81% xylan conversions were achieved after 168 h enzymatic hydrolysis at 1% glucan loading using 15 FPU/(g of glucan) of cellulase and 64 p-NPGU/(g of glucan) of beta-glucosidase along with xylanase and tween-80 supplementation. A mass balance for the AFEX pretreatment and enzymatic hydrolysis process is presented.
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Authors: Huda MS, Balan V, Drzal LT, Chundawat SPS, Dale BE, Misra M*
Paper Link: Link
Journal Link: Link
Abstract: Development of economically and ecologically attractive composite technologies is possible through the use of renewable biomass based resources such as polymeric matrices and reinforcement filler materials. The processability and physical properties of these composite materials are very important parameters for product performance. This study develops the enabling technology needed to transform corncobs, an abundant agricultural residue from the corn grain industry, into reinforcement filler material for manufacturing biocomposites. We have successfully fabricated biocomposite materials from poly(lactic acid) (PLA) and corncob granules (CCG) that were produced by a microcompounding molding system. To ensure appropriate interfacial interactions between the matrix and composite material, surface properties of the biocomposite filler must be modified accordingly. CCG-matrix adhesion was promoted by surface modifications using ammonia fiber expansion (AFEX), liquid ammonia treatment, and silane treatment. The final composite materials have improved mechanical and thermomechanical properties such as high flexural properties, high impact strength, and modulus at higher temperature. The surface morphology, as indicated by scanning electron microscopy (SEM), showed good dispersion of CCG in the PLA matrix. Modification of the CCG surface showed an improved adhesion and dispersion within the matrix. Overall, the results demonstrated the potential of CCG as reinforcement filler material for a renewable source based polymeric matrix.
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Authors: Chundawat SPS*, Balan V, Dale B.
Paper Link: Link
Abstract: Particle size and compositional variance are found to have a substantial influence on ammonia fiber explosion (AFEX) pretreatment and enzymatic hydrolysis of lignocellulosic biomass. Corn stover was milled and fractionated into particle sizes of varying composition. The larger particle size fractions (rich in corn cob and stalk portions) were found to be more recalcitrant to hydrolysis compared to the smaller size fractions (rich in leaves and husk portion). Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR) were used for biomass surface and bulk compositional analysis, respectively. The ESCA results showed a 15–30% decrease in the O/C (oxygen to carbon) ratio after the pretreatment indicating an increase in the hydrophobic nature of biomass surface. FTIR results confirmed cleavage of the lignin–carbohydrate complex (LCC) for the AFEX-treated fractions. The spectroscopic results indicate the extraction of cleaved lignin phenolic fragments and other cell wall extractives to the biomass surface upon AFEX. Water washing of AFEX-treated fractions removed some of the hydrophobic extractives resulting in a 13% weight loss (dry weight basis). Phenolic content of wash stream was evaluated by the modified Prussian blue (MPB) method. Removal of ligno-phenolic extractives from the AFEX-treated biomass by water washing vastly improved the glucan conversion as compared to the unwashed samples. Reduction in substrate particle size was found to affect the AFEX process and rate of hydrolysis as well. Implications of the stover particle size, composition, and inhibitory role of the phenolic fragments on an integrated biorefinery are discussed. Biotechnol. Bioeng. 2007;96: 219–231.