Renewable Biomass Utilization: A Way Forward to Establish Sustainable Chemical and Processing Industries

Lignocellulosic biomass-based glycoconjugates for diverse biotechnological applications

Glycoconjugates are the ubiquitous components of mammalian cells, mainly synthesized by covalent bonds of carbohydrates to other biomolecules such as proteins and lipids, with a wide range of potential applications in novel vaccines, therapeutic peptides and antibodies (Ab). Considering the emerging developments in glycoscience, renewable production of glycoconjugates is of importance and lignocellulosic biomass (LCB) is a potential source of carbohydrates to produce synthetic glycoconjugates in a sustainable pathway. In this review, recent advances in glycobiology aiming on glycoconjugates production is presented together with the recent and cutting-edge advances in the therapeutic properties and application of glycoconjugates, including therapeutic glycoproteins, glycosaminoglycans (GAGs), and nutraceuticals, emphasizing the integral role of glycosylation in their function and efficacy. Special emphasis is given towards the potential exploration of carbon neutral feedstocks, in which LCB has an emerging role. Techniques for extraction and recovery of mono- and oligosaccharides from LCB are critically discussed and influence of the heterogeneous nature of the feedstocks and different methods for recovery of these sugars in the development of the customized glycoconjugates is explored. Although reports on the use of LCB for the production of glycoconjugates are scarce, this review sets clear that the potential of LCB as a source for the production of valuable glycoconjugates cannot be underestimated and encourages that future research should focus on refining the existing methodologies and exploring new approaches to fully realize the potential of LCB in glycoconjugate production.

Characterization and structural analysis of the endo-1,4-β-xylanase GH11 from the hemicellulose-degrading Thermoanaerobacterium saccharolyticum useful for lignocellulose saccharification

Xylanases are important for the enzymatic breakdown of lignocellulose-based biomass to produce biofuels and other value-added products. We report functional and structural analyses of TsaGH11, an endo-1,4-β-xylanase from the hemicellulose-degrading bacterium, Thermoanaerobacterium saccharolyticum. TsaGH11 was shown to be a thermophilic enzyme that favors acidic conditions with maximum activity at pH 5.0 and 70 °C. It decomposes xylans from beechwood and oat spelts to xylose-containing oligosaccharides with specific activities of 5622.0 and 3959.3 U mg-1, respectively. The kinetic parameters, Km and kcat towards beechwood xylan, are 12.9 mg mL-1 and 34,015.3 s-1, respectively, resulting in kcat/Km value of 2658.7 mL mg-1 s-1, higher by 102-103 orders of magnitude compared to other reported GH11s investigated with the same substrate, demonstrating its superior catalytic performance. Crystal structures of TsaGH11 revealed a β-jelly roll fold, exhibiting open and close conformations of the substrate-binding site by distinct conformational flexibility to the thumb region of TsaGH11. In the room-temperature structure of TsaGH11 determined by serial synchrotron crystallography, the electron density map of the thumb domain of the TsaGH11 molecule, which does not affect crystal packing, is disordered, indicating that the thumb domain of TsaGH11 has high structural flexibility at room temperature, with the water molecules in the substrate-binding cleft being more disordered than those in the cryogenic structure. These results expand our knowledge of GH11 structural flexibility at room temperature and pave the way for its application in industrial biomass degradation.

Whole-Genome Sequence and Fermentation Characteristics of Enterobacter hormaechei UW0SKVC1: A Promising Candidate for Detoxification of Lignocellulosic Biomass Hydrolysates and Production of Value-Added Chemicals

Enterobacter hormaechei is part of the Enterobacter cloacae complex (ECC), which is widespread in nature. It is a facultative Gram-negative bacterium of medical and industrial importance. We assessed the metabolic and genetic repertoires of a new Enterobacter isolate. Here, we report the whole-genome sequence of a furfural- and 5-hydroxymethyl furfural (HMF)-tolerant strain of E. hormaechei (UW0SKVC1), which uses glucose, glycerol, xylose, lactose and arabinose as sole carbon sources. This strain exhibits high tolerance to furfural (IC50 = 34.2 mM; ~3.3 g/L) relative to Escherichia coli DH5α (IC50 = 26.0 mM; ~2.5 g/L). Furfural and HMF are predominantly converted to their less-toxic alcohols. E. hormaechei UW0SKVC1 produces 2,3-butanediol, acetoin, and acetol, among other compounds of industrial importance. E. hormaechei UW0SKVC1 produces as high as ~42 g/L 2,3-butanediol on 60 g/L glucose or lactose. The assembled genome consists of a 4,833,490-bp chromosome, with a GC content of 55.35%. Annotation of the assembled genome revealed 4586 coding sequences and 4516 protein-coding genes (average length 937-bp) involved in central metabolism, energy generation, biodegradation of xenobiotic compounds, production of assorted organic compounds, and drug resistance. E. hormaechei UW0SKVC1 shows considerable promise as a biocatalyst and a genetic repository of genes whose protein products may be harnessed for the efficient bioconversion of lignocellulosic biomass, abundant glycerol and lactose-replete whey permeate to value-added chemicals.

Effective hydrolysis for waste plant biomass impacts sustainable fuel and reduced air pollution generation: A comprehensive review

Among various natural biowastes availability in the environment, agricultural residues showed great impacts. It is due to huge availability and cheap carbon source, creating big challenges for their utility and systematic reduction. Objective of this review is to address the waste biomass availability and huge quantities issues and also put effort to minimize this nutrient load via biotransforming into value-added products. Different wastes (organic/inorganic) generation with their negative issues are due to numbers of developmental and social activities, reported. Currently, various efforts are found for these wastes minimization via generation of different types of value-added products (biogas, bioH₂, alcoholic fuel, organic acids and others products) and these wastes in municipal cities are also reported with production of advanced biofuels as promising outcomes. For hydrolysis of complex organic resources including lignocellulosic biomasses, physicochemical, structural or compositional changes are needed that aid in conversion into sugar and organic compounds such as biofuels. So, efficient and effective pretreatment processes selection (physical, biological, chemical or combined one) is critical to achieve these hydrolysis goals and resultant cellulose or hemicellulose components can be accessible by biological catalysis. These can achieve final hydrolysis and fermentative or monomer sugars. And later, synthesis of fuels or value-added products during microbial fermentation or biotransformation processes can be achieved. This review discusses pretreatment techniques for improved hydrolysis for fermentative sugar with emphasis on reduced quantities of toxic compounds (furfural compound) in hydrolyzed biomasses. Minimum deterioration fuel economy also reported with production of different bioproducts including biofuels. Additionally, impacts of toxic products and gasses emission are also discussed with their minimization.

One pot bioprocessing in lignocellulosic biorefinery: A review

Practically, high-yield conversion of biomass into value-added products at low cost is a primary goal for any lignocellulosic refinery. In the industrial context, the limitation in the practical adaptation of the conventional techniques practically involves multiple reactors for the conversion of biomass to bioproducts. Therefore, the present manuscript critically reviewed the advancements in one-pot reaction systems with a major focus on the scientific production of value-added products from lignocellulosic biomass. In view of that, the novelty of one-pot reactions is shown during the fractionation of biomass into their individual constituents. The importance of the direct conversion of cellulose and lignin into a range of valuable products including organic acids and platform chemicals are separately discussed. Finally, the article is concluded with the opportunities, existing troubles, and possible solutions to overcome the challenges in lignocellulosic biorefinery. This article will assist the readers to identify the economic-friendly-one-pot conversion of lignocellulosic biomass.

Development of miniaturized agar based assays in 96-well microplates applicable to high-throughput screening of industrially valuable microorganisms

High-throughput screening (HTS) is a present-day approach for assaying thousands of cultures in parallel. This miniaturization allows rapid screening of large number of microorganims capable of producing bio-based materials thereby meeting the demands of the ever evolving food, pharmaceutical and cosmetic industry. In this study, agar-based assays for phosphate solubilization, cellulose degradation and lactic acid production were developed in 96-well microplates using Biomek FX^P Automated Liquid Handling system. Techno-economic analysis from this study reveals the lower overall cost per assay using HTS as compared to conventional Petri plate assays. Though automated liquid handling workstations have been used to perform liquid-based assays, there are very few studies which report their use for agar-based microplate assays. These findings thus corroborate the establishment of rapid and efficient miniaturized, qualitative agar-based screening methods for identifying microorganisms with potential for commercial application.

Mathematical Model of a Thermophilic Anaerobic Digestion for Methane Production of Wheat Straw

This paper presents a newly created mathematical model of thermophilic anaerobic digestion of wheat straw carried out in a 2 dm3 bioreactor for methane production. Two batch processes, with 30 mL/dm3 and 35 mL/dm3 organic load, are carried out—one set for parameter identification and one set for model verification. The identification of model parameter values is based on dynamical experiments. It is fulfilled using two different techniques: deterministic sequential quadratic programming algorithm and metaheuristic genetic algorithm. Verification of the developed mathematical models is conducted based on the different data sets of the process. Both models predict the set of the experimental data for all considered process variables well. Genetic algorithm visually fits the data with a higher degree of accuracy, as confirmed by the numerical results for the objective function value.

Genome-wide association study for lignocellulosic compounds and fermentable sugar in rice straw

Cellulose and lignin are the two main components of secondary plant cell walls with substantial impact on stalk in the field and on straw during industrial processing. The amount of fermentable sugar that can be accessed is another important parameter affecting various industrial applications. In the present study, genetic variability of rice (Oryza sativa L.) genotypes for cellulose, lignin, and fermentable sugars contents was analyzed in rice straw. A genome-wide association study of 33,484 single nucleotide polymorphisms (SNPs) with a minor allele frequency (MAF) >0.05 was performed. The genome-wide association study identified seven, three, and three genomic regions to be significantly associated with cellulose, lignin, and fermentable sugar contents, respectively. Candidate genes in the associated genomic regions were enzymes mainly involved in cell wall metabolism. Novel SNP markers associated with cellulose were tagged to GH16, peroxidase, GT6, GT8, and CSLD2. For lignin content, Villin protein, OsWAK1/50/52/53, and GH16 were identified. For fermentable sugar content, UTP-glucose-1-phosphate uridylyltransferase, BRASSINOSTEROID INSENSITIVE 1, and receptor-like protein kinase 5 were found. The results of this study should improve our understanding of the genetic basis of the factors that might be involved in biosynthesis, turnover, and modification of major cell wall components and saccharides in rice straw.

Simulation and optimization of organosolv based lignocellulosic biomass refinery: A review

Organosolv pretreatment can be considered as the core of the lignocellulosic biomass fractionation within the biorefinery concept. Organosolv facilitates the separation of the major fractions (cellulose, hemicelluloses, lignin), and their use as renewable feedstocks to produce bioenergy, biofuels, and added-value biomass derived chemicals. The efficient separation of these fractions affects the economic feasibility of the biorefinery complex. This review focuses on the simulation of the organosolv pretreatment and the optimization of (i) feedstock delignification, (ii) sugars production (mainly from hemicelluloses), (iii) enzymatic digestibility of the cellulose fraction and (iv) quality of lignin. Simulation is used for the technoeconomic optimization of the biorefinery complex. Simulation and optimization implement a holistic approach considering the efficient technological, economic, and environmental performance of the biorefinery operational units. Consequently, an optimized organosolv stage is the first step for a sustainable, economically viable biorefinery complex in the concept of industrial ecology and zero waste circular economy.