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Nanobiotechnology of Ligninolytic and Cellulolytic Enzymes for Enhanced Bioethanol Production
Published in Madan L. Verma, Nanobiotechnology for Sustainable Bioenergy and Biofuel Production, 2020
Pardeep Kaur, Gurvinder Singh Kocher
Hemicellulose is the second most abundant polymer. Unlike cellulose, hemicellulose has a random and amorphous structure, which is composed of several heteropolymers including xylan, galactomannan, glucuronoxylan, arabinoxylan, glucomannan and xyloglucan. They differ in composition too: hardwood hemicelluloses contain mostly xylans, whereas softwood hemicelluloses contain mostly glucomannans. The heteropolymers of hemicellulose are composed of different 5- and 6-carbon monosaccharide units: pentoses (xylose and arabinose), hexoses (mannose, glucose and galactose) and acetylated sugars. Hemicelluloses are embedded in the plant cell walls to form a complex network of bonds that provide structural strength by linking cellulose fibers into microfibrils and cross-linking with lignin.
Natural enzymes used to convert feedstock to substrate
Published in Ruben Michael Ceballos, Bioethanol and Natural Resources, 2017
AgluAs (e.g., EC 3.2.1.131), of the GH67 and GH115 families of hydrolases, are reported to cleave α-1,2-glycosidic bonds of the 4-O-methyl-d-glucuronic/d-glucuronic acid residues from the terminal nonreducing xyloses of glucuronoxylooligosaccharide or polymeric glucuronoxylan (Tenkanen and Siika-aho, 2000; Nurizzo et al., 2002; Ryabova et al., 2009; Lee et al., 2012a; Lombard et al., 2014; Rogowski et al., 2014; CAZy, 2015).
Bioethanol Production from Jute and Mesta Biomass
Published in Jitendra Kumar Saini, Surender Singh, Lata Nain, Sustainable Microbial Technologies for Valorization of Agro-Industrial Wastes, 2023
A.K. Lavanya, Laxmi Sharma, Gouranga Kar, Pratik Satya, Suman Roy, Srinjoy Ghosh, Bijan Majumdar
The chemical makeup of fibrous agricultural biomass can be split into three categories: cellulose, hemicellulose, and lignin. Cellulose is a polymer made up of D-glucose subunits that are linked by β-1,4 glycosidic linkages. Lignin is an amorphous polymer of phenylpropane, mainly made from p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. Hemicellulose is a heteropolymer xylan, glucuronoxylan, arabinoxylan, or glucomannan made up of pentose and hexose sugars linked by β-1,4 glycosidic linkages. Pectin, protein, ash, extractives such as sugars, nitrogenous material, chlorophyll, and waxes are also present in lower amounts (Hendriks and Zeeman, 2009; Azelee et al., 2014). The cellulose strands are packed together to produce cellulose microfibrils. With varied secondary structure and bonding factors, hemicellulose maintains linkage with cellulose and lignin. About 70% of total plant biomass consists of cellulose and hemicelluloses and are closely attached to the lignin via covalent and hydrogenic interactions, which makes them highly robust and resistant to treatment (Edye et al., 2015; Meents et al., 2018). A network of hemicellulose and lignin surrounds the cellulose fibrils. Cross-linking and constituents can differ depending on the plant species, plant age, and growth stage and other conditions (Hu et al., 2012; Tanmoy et al., 2014). Both crops have higher cellulose and hemicellulose content, with cellulose content ranging from 40 to 63% in jute and 37 to 63% in mesta, and hemicellulose content ranging from 18 to 22% and 14 to 24% in jute and mesta, respectively (Kundu et al., 2012; Song et al., 2017). On maturity, jute and mesta contain 390–568 mg/g and 410–520 mg/g glucose, respectively, higher than tree wood. Jute (121–173 mg/g) and mesta (108–142 mg/g) exhibit high xylan concentrations when compared to other complex hemicellulosic components (mannan, arabinan, etc.) and can be converted to biofuels like ethanol and butanol. Lignin has the lowest solubility of the three biomass components and is the most difficult to treat downstream. As a result, a high lignin content increases the cost of producing ethanol. The lignin concentration of jute (12–24%) and mesta (10–21%) is substantially lower than that of wood (Satya and Maiti, 2013); as a result, low lignin content with other additional properties makes them a suitable option for bioethanol production.
Lignocellulose derived functional oligosaccharides: production, properties, and health benefits
Published in Preparative Biochemistry and Biotechnology, 2019
Latika Bhatia, Ashutosh Sharma, Rakesh K. Bachheti, Anuj K. Chandel
Glucuronoxylan is the major hemicellulose in corn stover. Oligosaccharides (acetyl and feruloyl esters containing XOS) are the products of glucuronoxylan yielded as a result of dilute acid-pretreatment corn fiber.[39] Oligosaccharides with 6 carbon were also found in the sample after hydrolysis and fermentation. Glycoside hydrolases (GHs) cause breakdown of natural polysaccharides to yield mono- and oligosaccharides.[25] Oxidized oligosaccharides and native oligosaccharides containing reducing ends are the outcomes of lytic polysaccharide monooxygenases (LPMOs).[85] AOS can be obtained by the specific enzymatic breakdown of arabinose containing carbohydrate polymers. Arabinan degrading enzymes are categorized into 6 classes viz. α-l-Arabinofuranosidase (EC 3.2.1.55), (not active with polymer), α-l-Arabinofuranosidase (active with polymers), α-l-Arabinofuranohydrolase (specific for arabinoxylans), exo-α-l-Arabinanase, (not active with p-nitrophenyl-α-l-arabinofuranoside), β-l-Arabinopyranosidase and endo-1, 5-α-l-Arabinanase (EC 3.2.1.99).[30] Oligosaccharides may inhibit the enzymatic inhibition during hydrolysis. To overcome this, Xue and coworkers[86] used activated charcoal process followed by size exclusion chromatography to remove these compounds to improve the amenability of cellulases.
Storing of exoelectrogenic anolyte for efficient microbial fuel cell recovery
Published in Environmental Technology, 2019
Johanna M. Haavisto, Aino-Maija Lakaniemi, Jaakko A. Puhakka
In this work, the effect of simple and low-cost MFC anolyte storage for recovering stable power density and lag time required for current production was studied. Anolyte from an operating xylose-fed MFC was freezed (–20°C) or refrigerated (+4°C) with different storing times (from 1 week to 6 months) and compared with fresh anolyte for MFC start-up. To our knowledge, this is the first study on the survival of exoelectrogenic cultures and their ability to regain current production by storing-enriched MFC anolyte. Xylose was used as a substrate, because forest industry wastewaters contain xylose from glucuronoxylan containing wood material [30,31].