Review Articles and Book Chapters
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: Bhargava Nemmaru, Antonio DeChellis, Nivedita Patil, Shishir Chundawat
Article Link: Link
Abstract: Lignocellulosic biomass is composed primarily of cellulose (homopolysaccharide of glucose), hemicellulose (heteropolysaccharide of glucose, xylose, and/or mannose), and lignin (phenolic organic polymer). Biochemical deconstruction of biomass to fermentable sugar monomers for biofuel production requires application of cocktails of synergistic enzymes belonging to several different families of Carbohydrate Active enZymes (CAZymes). Among these, cellulolytic enzymes are well-known to catalyze hydrolysis of glycosidic linkages within cellulose and can be categorized as exocellulases (or cellobiohydrolases) or endocellulases (or endoglucanases). These cellulases differ in substrate binding site preference, hydrolysis products formed, and mechanistic mode of action and often contain linked substrate-specific carbohydrate binding modules (CBMs). Other, accessory CAZymes such as xylanases and Lytic Polysaccharide Monooxygenases (LPMOs) act synergistically along with cellulases to break down cellulose and hemicellulose into fermentable sugars. Here we discuss the structure, catalytic mechanisms, rate-limitations, and relevant enzyme engineering studies that have been completed in recent years for several different CAZyme families with a focus on the most well-studied enzymes from industrially relevant microbes such as Trichoderma reesei and Thermobifida fusca.
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Authors: Erin Tiwold, Aron Gyorgypal, Shishir Chundawat
Article Link: Link
Abstract: Post-translational modification such as N-Glycosylation on biologics during the production of monoclonal antibody (mAb) based therapeutics is a critical quality attribute that dictates safety and efficacy. Variability is introduced in the cell culture process which influences, the glycosylation pattern which is known to be highly heterogenous and must be tightly controlled during the manufacturing process. Techniques have been developed for glycan screening through the use of new denaturation techniques; deglycosylation, fluorescent labeling, and analysis coupled to state-of-the-art tools consisting of multi attribute methods and multi attribute chromatography. In this review, we delve into advances within sample preparation techniques that allow for rapid and robust sample preparation as well as how these techniques are being used for innovative at-line high-throughput screening and PAT focused systems. Finally, we foresee how these advances will influence current manufacturing practices and enable bioprocess automation. The future state of biomanufacturing looks to decrease process costs while increasing process understanding and quality for novel biologic candidates and biosimilars.
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Authors: Shyamal Roy, Shishir PS Chundawat
Article Link: Link
Abstract: The shifting of crude oil–based refinery to biomass-based biorefinery has enticed compelling scientific interest which focuses on the development of cellulosic ethanol as an alternative transportation fuel to fossil fuels. Therefore, conversion of plentiful lignocellulosic biomass to biofuel as transportation fuels will be a feasible alternative for boosting energy security and abating greenhouse gas emissions. Strong intra- and inter-molecular hydrogen bonds in cellulose make it highly recalcitrant to enzyme or catalyst catalyzed deconstruction to fuels and chemicals. Decrystallization of cellulose using solvents like anhydrous ammonia or ionic liquids can overcome biomass recalcitrance to deconstruction. Here, review of various chemicals and related pretreatment processes used to decrystallize/solubilize cellulose that facilitates rapid downstream processing of biomass into biofuels. Here, we will mostly focus on recent advances made in the use of non-derivatizing ionic liquids for biomass pretreatment. We explore the role of solvent-substrate molecular properties (e.g., hydrophobicity, hydrogen bonding) on decrystallization/dissolution mechanism of cellulose as well as the operational challenges (e.g., viscosity, toxicity, recyclability) of using such solvent systems in commercially relevant biorefinery processes.
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Authors: Viki Chopda, Aron Gyorgypal, Ou Yang, Ravendra Singh, Rohit Ramachandran, Haoran Zhang, George Tsilomelekis, Shishir PS Chundawat, Marianthi G Ierapetritou
Article Link: Link
Abstract: Continuous bioprocessing is significantly changing the biological drugs (or biologics) manufacturing landscape by potentially improving product quality, process stability, and overall profitability, as was similarly seen during the adoption of advanced manufacturing processes for small molecule drugs in the past decade. However, the implementation of continuous manufacturing for biological processes producing protein-based drug molecules, such as monoclonal antibodies (mAbs), is facing several new hurdles. The barriers to continuous bioprocessing can be overcome through improved process understanding via better predictive capabilities enabled by hybrid modeling that can also lead to robust process control. This review article summarizes the recent advances and ongoing obstacles faced during the use of advanced process analytical technologies (PAT), process modeling, and control strategies to enable continuous manufacturing of mAbs. In addition, this review also discusses the process strategies and future directions of advanced continuous manufacturing approaches that have been adapted by other industries and that could be implemented for mAbs production soon.
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Authors: Chandra Kanth Bandi, Ayushi Agrawal, Shishir PS Chundawat
Article Link: Link
Abstract: One of the stumbling blocks to advance the field of glycobiology has been the difficulty in synthesis of bespoke carbohydrate-based molecules like glycopolymers (e.g. human milk oligosaccharides) and glycoconjugates (e.g. glycosylated monoclonal antibodies). Recent strides towards using engineered Carbohydrate-Active enZymes (CAZymes) like glycosyl transferases, transglycosidases, and glycosynthases for glycans synthesis has allowed production of diverse glycans. Here, we discuss enzymatic routes for glycans biosynthesis and recent advances in protein engineering strategies that enable improvement of CAZyme specificity and catalytic turnover. We focus on rational and directed evolution methods that have been developed to engineer CAZymes. Finally, we discuss how improved CAZymes have been used in recent years to remodel and synthesize glycans for biotherapeutics and biotechnology related applications.
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Authors: Chao Zhao, Qianjun Shao, Shishir PS Chundawat
Article Link: Link
Abstract: Ammonia-based pretreatments have been extensively studied in the last decade as one of the leading pretreatment technologies for lignocellulose biorefining. Here, we discuss the key features and compare performances of several leading ammonia-based pretreatments (e.g., soaking in aqueous ammonia or SAA, ammonia recycled percolation or ARP, ammonia fiber expansion or AFEX, and extractive ammonia or EA). We provide detailed insight into the distinct physicochemical mechanisms employed during ammonia-based pretreatments and its impact on downstream bioprocesses (e.g., enzymatic saccharification); such as modification of cellulose crystallinity, lignin/hemicellulose structure, and other ultrastructural changes such as cell wall porosity. Lastly, a brief overview of process technoeconomics and environmental impacts are discussed, along with recommendations for future areas of research on ammonia-based pretreatments.
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Authors: Chandel, A. K., Albarelli, J. Q., Santos, D. T., Chundawat, S. P. S.*, Puri, M., and Meireles, M. A. A.
Book Title: Biofuels, Bioproducts and Biorefining, vol. 13, Mar. 2019, p. bbb.1990. DOI: 10.1002/bbb.1990
Article Link: Link
Abstract: Biorefineries can upgrade waste lignocellulosic biomass (LB) into soluble (C5 and C6) sugars that can be fermented into second-generation (2G) ethanol-based biofuels and a range of valuable byproducts derived from lignin. Research advances made in various laboratories worldwide have not been easy to translate into large-scale operations. Here, we performed a simple economic analysis of cellulosic ethanol production from a stand-alone 100ton dry sugarcane bagasse per day process, from a Brazilian market perspective, based on current state-of-the-art biorefinery process technologies. Economic analysis reveals that the cost of manufacturing (COM) of 2G ethanol in an annexed Brazilian facility is close to USD 1.33 L−1. Fixed and variable costs contributed 57% and 24% in COM of 2G ethanol with a high payback period of ~31 years and a negative net present value (NPV). Further cost reduction can be realized by continuous R&D efforts aiming for innovation in new processing paradigms for cellulosic biorefineries. The key market players (Poet-DSM, DuPont, Abengoa, Beta Renewables, Raizen, Granbio, Praj, etc.) and other new emerging players (Global Yeast, Taurus Energy, Leaf, Mascoma-Lallemand) working on ethanologen development, and cellulase producers (Novozyme, Metgen), should also develop partnerships / joint ventures to establish a sustainable business model to develop cost-competitive 2G ethanol production from bagasse in Brazil. This paper presents additional commentary and analysis with pertinent information about the commercialization of integrated 2G ethanol biorefineries processing sugarcane bagasse, from a Brazilian perspective.
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Authors: Ong RG*, Chundawat SPS, Hodge DH, Keskar S, Dale BE
Book Title: Plants and Bioenergy (Advances in Plant Biology). 2014, 4, 231-253
Article Link: Link
Abstract: In order to more economically process cellulosic feedstocks using a biochemical pathway for fuel production, it is necessary to develop a detailed understanding of plant cell wall characteristics, pretreatment reaction chemistry, and their complex interactions. However given the large number of thermochemical pretreatment methods that are currently being researched and the extreme diversity of plant cell wall structure and composition, this prospect is extremely challenging. Here we present the current state of research at the interface between plant biology and pretreatment chemistry. The first two sections discuss the chemistry of the secondary plant cell wall and how different pretreatment methods alter the overall cell wall structure. The third section addresses how the characteristics of the cell wall and pretreatment efficacy are impacted by different factors such as plant maturity, classification, and plant fraction. The fourth section summarizes current directions in the development of novel plant materials for improved biochemical conversion. And the final section discusses the use of chemical pretreatments as a screening and analysis tool for rapid identification of amenable plant materials, and for expansion of the fundamental understanding of plant cell walls.
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Comments: Must Read Primer on Ammonia Based Biomass Pretreatment Technology!
Authors: Chundawat SPS*, Bals B, Campbell T, Sousa L, Gao D, Jin M, Eranki P, Garlock R, Teymouri F, Balan V, Dale BE
Book Title: Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and Chemicals
Edited By: Charles Wyman: Wiley-Blackwell Publishing; 2013, 169-200
Article Link: Link
Abstract: We provide an extensive review of ammonia fiber expansion (AFEX) pretreatment from a techno-economical and environmental sustainability perspective. A brief historical perspective on concentrated ammonia-based pretreatments is provided followed by a detailed overview of the AFEX process and its physicochemical impact on lignocellulosic plant cell walls. AFEX is unique in terms of leaving biomass composition virtually intact after pretreatment, unlike other aqueous pretreatments. The impact of AFEX pretreatment on enzymatic digestibility and microbial fermentability for a diverse selection of feedstocks is reviewed. The utility of using transgenic plants as feedstocks for an AFEX process are highlighted. Recent developments of the AFEX process (e.g., extractive vs. non-extractive AFEX) are discussed along with a focus on commercialization efforts to develop cheap, hybrid AFEX reactors with in-built, low-cost ammonia recovery systems. Integration of the AFEX process into a regional biomass processing depot is discussed along with its ramifications on plant protein extraction, animal feed production, on-site enzyme production, and biomass fractionation. Finally, we discuss various techno-economic and life-cycle analysis modeling efforts that have centered on systems employing the AFEX process.
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Authors: Balan V*, Sousa L, Chundawat SPS, Humpula J, Dale BE
Book Title: Dynamic Biochemistry, Process Biotechnology and Molecular Biology, 2012, 6 (Special Issue 2): 1-11
Article Link: Link
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Authors: Balan V*, Bals B, Chundawat SPS, Jin M, Kumar S, Dale B
Book Title: Switchgrass: A Valuable Biomass Crop for Energy
Edited By: Andrea Monti: Springer-Verlag London Ltd; 2012
Article Link: Link
Abstract: With dwindling oil reserves and growing environmental concerns, researchers are looking at producing sustainable biofuels and chemicals from renewable resources like switchgrass. Biofuels and biochemicals will be produced in the near future from switchgrass in biorefineries using both biochemical and thermochemical platforms. We have summarized recent literature pertaining to different processing steps within the biochemical platform (pretreatment, enzyme hydrolysis, microbial fermentation, protein extraction) and thermochemical platform (pyrolysis, bio-oil, gasification, combustion, hydrothermal process) in this chapter. Though we have improved our fundamental understanding on the different processing steps to produce biofuels, several challenges still have to be overcome to create a bioeconomy and produce fuels and chemicals from biomass in an economic and sustainable manner.
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Comments: Most Cited and Top 10 Downloaded Review Article for Annual Review of Chemical and Biomolecular Engineering!
Authors: Chundawat SPS*, Beckham GT*, Himmel ME, Dale BE
Book Title: Annual Review of Chemical and Biomolecular Engineering 2011, 2, 121-145.
Article Link: Link
Abstract: Plants represent a vast, renewable resource and are well suited to provide sustainably for humankind’s transportation fuel needs. To produce infrastructure-compatible fuels from biomass, two challenges remain: overcoming plant cell wall recalcitrance to extract sugar and phenolic intermediates, and reduction of oxygenated intermediates to fuel molecules. To compete with fossil-based fuels, two primary routes to deconstruct cell walls are under development, namely biochemical and thermochemical conversion. Here, we focus on overcoming recalcitrance with biochemical conversion, which uses low-severity thermochemical pretreatment followed by enzymatic hydrolysis to produce soluble sugars. Many challenges remain, including understanding how pretreatments affect the physicochemical nature of heterogeneous cell walls; determination of how enzymes deconstruct the cell wall effectively with the aim of designing superior catalysts; and resolution of issues associated with the co-optimization of pretreatment, enzymatic hydrolysis, and fermentation. Here, we highlight some of the scientific challenges and open questions with a particular focus on problems across multiple length scales.
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Authors: Chundawat SPS*, Balan V, Sousa L, Dale BE
Book Title: Bioalcohol production-Biochemical conversion of lignocellulosic biomass
Edited By: Waldron K. Cambridge: Woodhead Publishing; 2010
Article Link: Link
Book Abstract: Bioethanol is one of the main biofuels currently used as a petroleum-substitute in transport applications. However, conflicts over food supply and land use have made its production and utilisation a controversial topic. Second generation bioalcohol production technology, based on (bio)chemical conversion of non-food lignocellulose, offers potential advantages over existing, energy-intensive bioethanol production processes. Food vs. fuel pressures may be reduced by utilising a wider range of lignocellulosic biomass feedstocks, including energy crops, cellulosic residues, and, particularly, wastes.
Bioalcohol production covers the process engineering, technology, modelling and integration of the entire production chain for second generation bioalcohol production from lignocellulosic biomass. Primarily reviewing bioethanol production, the book’s coverage extends to the production of longer-chain bioalcohols which will be elemental to the future of the industry.
Part one reviews the key features and processes involved in the pretreatment and fractionation of lignocellulosic biomass for bioalcohol production, including hydrothermal and thermochemical pretreatment, and fractionation to separate out valuable process feedstocks. Part two covers the hydrolysis (saccharification) processes applicable to pretreated feedstocks. This includes both acid and enzymatic approaches and also importantly covers the development of particular enzymes to improve this conversion step. This coverage is extended in Part three, with chapters reviewing integrated hydrolysis and fermentation processes, and fermentation and co-fermentation challenges of lignocellulose-derived sugars, as well as separation and purification processes for bioalcohol extraction.
Part four examines the analysis, monitoring and modelling approaches relating to process and quality control in the pretreatment, hydrolysis and fermentation steps of lignocellulose-to-bioalcohol production. Finally, Part five discusses the life-cycle assessment of lignocellulose-to-bioalcohol production, as well as the production of valuable chemicals and longer-chain alcohols from lignocellulosic biomass.
With its distinguished international team of contributors, Bioalcohol production is a standard reference for fuel engineers, industrial chemists and biochemists, plant scientists and researchers in this area.
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Authors: Sousa L*, Chundawat SPS, Balan V, Dale BE
Book Title: Current Opinion in Biotechnology 2009; 20:339-347.
Article Link: Link
Abstract: Pretreatment is considered to be a central unit process in a biorefinery to convert lignocellulosic biomass into fuels and chemicals, affecting all other operations in the process. A variety of technologies to pretreat lignocellulosic biomass are available today, which encompass a wide range of physical, chemical, and biological based processes. Among these, chemical based pretreatments are considered to be the most promising for future biorefineries. However, several key criteria regarding technical, economical, and environmental considerations should be critically analyzed when adapting these technologies for the nascent biorefinery industry. This review will discuss the most important pretreatment methods available today and will highlight key criteria for the development of a future ideal pretreatment.
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Authors: Balan V*, Bals B, Chundawat SPS, Marshall D, Dale BE
Book Title: Methods and Protocols. Volume 581; 2009: 61-77: Methods in Molecular Biology
Article Link: Link
Abstract: Although cellulose is the most abundant organic molecule, its susceptibility to hydrolysis is restricted due to the rigid lignin and hemicellulose protection surrounding the cellulose micro fibrils. Therefore, an effective pretreatment is necessary to liberate the cellulose from the lignin–hemicellulose seal and also reduce cellulosic crystallinity. Some of the available pretreatment techniques include acid hydrolysis, steam explosion, ammonia fiber expansion (AFEX), alkaline wet oxidation, and hot water pretreatment. Besides reducing lignocellulosic recalcitrance, an ideal pretreatment must also minimize formation of degradation products that inhibit subsequent hydrolysis and fermentation. AFEX is an important pretreatment technology that utilizes both physical (high temperature and pressure) and chemical (ammonia) processes to achieve effective pretreatment. Besides increasing the surface accessibility for hydrolysis, AFEX promotes cellulose decrystallization and partial hemicellulose depolymerization and reduces the lignin recalcitrance in the treated biomass. Theoretical glucose yield upon optimal enzymatic hydrolysis on AFEX-treated corn stover is approximately 98%. Furthermore, AFEX offers several unique advantages over other pretreatments, which include near complete recovery of the pretreatment chemical (ammonia), nutrient addition for microbial growth through the remaining ammonia on pretreated biomass, and not requiring a washing step during the process which facilitates high solid loading hydrolysis. This chapter provides a detailed practical procedure to perform AFEX, design the reactor, determine the mass balances, and conduct the process safely.