Production of D-xylonic acid from hemicellulose using artificial enzyme complexes (original) (raw)
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Novel perspectives for evolving enzyme cocktails for lignocellulose hydrolysis in biorefineries
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Optimization of enzyme complexes for lignocellulose hydrolysis
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The ability of a commercial Trichoderma reesei cellulase preparation (Celluclast 1.5L), to hydrolyze the cellulose and xylan components of pretreated corn stover (PCS) was significantly improved by supplementation with three types of crude commercial enzyme preparations nominally enriched in xylanase, pectinase, and b-glucosidase activity. Although the well-documented relief of product inhibition by b-glucosidase contributed to the observed improvement in cellulase performance, significant benefits could also be attributed to enzymes components that hydrolyze non-cellulosic polysaccharides. It is suggested that socalled ''accessory'' enzymes such as xylanase and pectinase stimulate cellulose hydrolysis by removing non-cellulosic polysaccharides that coat cellulose fibers. A high-throughput microassay, in combination with response surface methodology, enabled production of an optimally supplemented enzyme mixture. This mixture allowed for a $twofold reduction in the total protein required to reach glucan to glucose and xylan to xylose hydrolysis targets (99% and 88% conversion, respectively), thereby validating this approach towards enzyme improvement and process cost reduction for lignocellulose hydrolysis.
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Recent Advances in Bioethanol Production from Lignocelluloses: A comprehensive focus on enzyme engineering and designer biocatalysts Yogita Lugani1,!, Rohit Rai2,!, Ashish A. Prabhu3, Poonam Maan4, Meenu Hans5, Vinod, Kumar3, Sachin Kumar5,*, Anuj K. Chandel6, R.S. Sengar4 1Department of Biotechnology, Punjabi University, Patiala-147002, Punjab, India 2Faculty of Applied Medical Sciences, Lovely Professional University, Phagwara-144411, Punjab, India
Production of Glucaric Acid from Hemicellulose Substrate by Rosettasome Enzyme Assemblies
Molecular biotechnology, 2016
Hemicellulose biomass is a complex polymer with many different chemical constituents that can be utilized as industrial feedstocks. These molecules can be released from the polymer and transformed into value-added chemicals through multistep enzymatic pathways. Some bacteria produce cellulosomes which are assemblies composed of lignocellulolytic enzymes tethered to a large protein scaffold. Rosettasomes are artificial engineered ring scaffolds designed to mimic the bacterial cellulosome. Both cellulosomes and rosettasomes have been shown to facilitate much higher rates of biomass hydrolysis compared to the same enzymes free in solution. We investigated whether tethering enzymes involved in both biomass hydrolysis and oxidative transformation to glucaric acid onto a rosettasome scaffold would result in an analogous production enhancement in a combined hydrolysis and bioconversion metabolic pathway. Three different enzymes were used to hydrolyze birchwood hemicellulose and convert the...
Applied Microbiology and Biotechnology, 2014
An essential step in the conversion of lignocellulosic biomass to ethanol and other biorefinery products is conversion of cell wall polysaccharides into fermentable sugars by enzymatic hydrolysis. The objective of the present study was to understand the mode of action of hemicellulolytic enzyme mixtures for pretreated sugarcane bagasse (PSB) deconstruction and wheat arabinoxylan (WA) hydrolysis on target biotechnological applications. In this study, five hemicellulolytic enzymes-two endo-1,4xylanases (GH10 and GH11), two α-L-arabinofuranosidases (GH51 and GH54), and one β-xylosidase (GH43)-were submitted to combinatorial assays using the experimental design strategy, in order to analyze synergistic and antagonistic effects of enzyme interactions on biomass degradation. The xylooligosaccharides (XOSs) released from hydrolysis were analyzed by capillary electrophoresis and quantified by highperformance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Based on this analysis, it was possible to define which enzymatic combinations favor xylose (X1) or XOS production and thus enable the development of target biotechnological applications. Our results demonstrate that if the objective is X1 production from WA, the best enzymatic combination is GH11 +GH54+ GH43, and for xylobiose (X2) production from WA, it is best to combine GH11+GH51. However, if the goal is to produce XOS, the five enzymes used in WA hydrolysis are important, but for PSB hydrolysis, only GH11 is sufficient. If the final objective is bioethanol production, GH11 is responsible for hydrolyzing 64.3 % of hemicellulose from PSB. This work provides a basis for further studies on enzymatic mechanisms for XOS production, and the development of more efficient and less expensive enzymatic mixtures, targeting commercially viable lignocellulosic ethanol production and other biorefinery products.
Lignocellulolytic enzymes: Biomass to biofuel
Lignocellulosic biomass is an inexhaustible, renewable, and ubiquitous organic material on the Earth. It is present in huge amount as agricultural and forestry residues and wastes generated from different industries including solid municipal wastes. Lignocellulosic biomass is an alternative, economical and eco-friendly source for biofuel production and other bio-based products. Lignocellulose biomass is mainly comprised of cellulose, lignocellulose, and lignin polymers. Each of the structural components of lignocellulose is degraded specifically by a battery of enzymes, such as cellulase, hemicellulase and ligninase enzyme system, and these constituents in turn can be utilized as a sustainable source of energy. In this communication, we are presenting an overview on the enzymes involved in the degradation of most abundant polysaccharide on earth, and other structural components of the lignocellulosic biomass and their application in conversion of biomass to biofuel.
Biomacromolecules, 2009
Endo--1,4-xylanases (EC 3.2.1.8) are the main enzymes involved in the hydrolysis of xylans, the most abundant hemicelluloses in plant biomass. However, the development of efficient endoxylanases for use in biorefinery processes is currently hampered by insufficient knowledge regarding the impact of the cell wall network organization on the action of the enzyme at the supramolecular level. The action pattern of a GH11 endoxylanase from Thermobacillus xylanilyticus (Tx-xyl) was investigated by means of in vitro reconstituted model systems which can mimic certain cell wall structures. The action of Tx-xyl was evaluated on polymer assemblies displaying increasing complexity using delignified glucuronoarabinoxylan (GAX), then GAX-DHP model complexes obtained by oxidative polymerization of coniferyl alcohol into dehydrogenation polymers (DHP: lignin model compounds) in the presence of GAX. At a high concentration of GAX, interchain associations are formed leading to high molecular weight aggregates. These structures did not appear to affect the action of endoxylanase, which induces disaggregation of the self-aggregates along with polymer depolymerization. To mimic lignin-carbohydrate interactions, two different GAX-DHP nanocomposites were prepared and incubated with endoxylanase. In both cases, free GAX was hydrolyzed, while the GAX-DHP complexes appeared to be resistant. In the case of the noncovalently linked GAX-DHP ZL complexes, enzyme action favored a decrease in particle size, owing to the removal of their relatively exposed carbohydrate chains, whereas the complex supramolecular organization of the covalently linked GAX-DHP ZT complexes severely hampers the enzyme's access to carbohydrate. Overall, these results establish the negative impact of DHP on the endoxylanase action and provide new knowledge regarding the limitations of the enzyme action in the lignocellulose bioconversion processes. Figure 8. Hydrolysis rates of GAX ((), GAX-DHP ZL (9), and GAX-DHP ZT (2) by Tx-Xyl (2 IU/mg GAX) as a function of reaction time.
Lignocellulosic biomasses as sources of fermentable sugars and biocatalysts for biorefinery
2016
The lignocellulosic biomasses constitute the Earth’s most abundant repository of carbon, thus the future development of processes that exploit this raw materials as sources of fermentable sugars represents a key challenge for a bio-based economy. Because of the complex macromolecular structure, the lignocellulose conversion requires a pretreatment step and an effective hydrolysis. The attention is mainly focusing on the enzymatic hydrolysis, carried out by a tailor-made enzyme cocktail, due to the increasing concerns regarding the environmental impact. A several number of works exploit the autochthonous microbial community involved in lignocellulose decomposition as reservoir of novel lignocellulose-degrading enzymes. The overall goal of this PhD project was the valorization of selected lignocellulosic biomasses as source of both fermentable sugars and novel biocatalysts for the production of biobased products via fermentation. Two different lignocellulosic biomasses (the perennial ...