1
|
Gufe C, Jambwa P, Marumure J, Makuvara Z, Khunrae P, Kayoka-Kabongo PN. Are phenolic compounds produced during the enzymatic production of prebiotic xylooligosaccharides (XOS) beneficial: a review. JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH 2024; 26:867-882. [PMID: 38594834 DOI: 10.1080/10286020.2024.2328723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 03/05/2024] [Indexed: 04/11/2024]
Abstract
Phenolics produced during xylooligosaccharide production might inhibit xylanases and enhance the antioxidant and antimicrobial activities of XOS. The effects of phenolic compounds on xylanases may depend on the type and concentration of the compound, the plant biomass used, and the enzyme used. Understanding the effects of phenolic compounds on xylanases and their impact on XOS is critical for developing viable bioconversion of lignocellulosic biomass to XOS. Understanding the complex relationship between phenolic compounds and xylanases can lead to the development of strategies that improve the efficiency and cost-effectiveness of XOS manufacturing processes and optimise enzyme performance.
Collapse
Affiliation(s)
- Claudious Gufe
- Department of Veterinary Technical Services, Central Veterinary Laboratories, Borrowdale Road, Harare, Zimbabwe
| | - Prosper Jambwa
- Department of Veterinary Biosciences, Faculty of Veterinary Science, University of Zimbabwe, Mount Pleasant, Harare, Zimbabwe
| | - Jerikias Marumure
- School of Natural Sciences, Great Zimbabwe University, Masvingo, Zimbabwe
| | - Zakio Makuvara
- School of Natural Sciences, Great Zimbabwe University, Masvingo, Zimbabwe
| | - Pongsak Khunrae
- Department of Microbiology, Faculty of Science, King Mongkut's University of Technology Thonburi (KMUTT), Bang Mod, Thung Khru, Bangkok, Thailand
| | | |
Collapse
|
2
|
Wongleang S, Premjet D, Premjet S. Physicochemical Pretreatment of Vietnamosasa pusilla for Bioethanol and Xylitol Production. Polymers (Basel) 2023; 15:3990. [PMID: 37836039 PMCID: PMC10575274 DOI: 10.3390/polym15193990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 09/28/2023] [Accepted: 09/28/2023] [Indexed: 10/15/2023] Open
Abstract
The consumption of fossil fuels has resulted in severe environmental consequences, including greenhouse gas emissions and climate change. Therefore, transitioning to alternative energy sources, such as cellulosic ethanol, is a promising strategy for reducing environmental impacts and promoting sustainable low-carbon energy. Vietnamosasa pusilla, an invasive weed, has been recognized as a high potential feedstock for sugar-based biorefineries due to its high total carbohydrate content, including glucan (48.1 ± 0.3%) and xylan (19.2 ± 0.4%). This study aimed to examine the impact of NaOH pretreatment-assisted autoclaving on V. pusilla feedstock. The V. pusilla enzymatic hydrolysate was used as a substrate for bioethanol and xylitol synthesis. After treating the feedstock with varying concentrations of NaOH at different temperatures, the glucose and xylose recovery yields were substantially higher than those of the untreated material. The hydrolysate generated by enzymatic hydrolysis was fermented into bioethanol using Saccharomyces cerevisiae TISTR 5339. The liquid byproduct of ethanol production was utilized by Candida tropicalis TISTR 5171 to generate xylitol. The results of this study indicate that the six- and five-carbon sugars of V. pusilla biomass have great potential for the production of two value-added products (bioethanol and xylitol).
Collapse
Affiliation(s)
- Suwanan Wongleang
- Department of Biology, Faculty of Science, Naresuan University, Muang, Phitsanulok 65000, Thailand;
| | - Duangporn Premjet
- Department of Agricultural Science, Faculty of Agriculture, Natural Resources and Environment, Naresuan University, Muang, Phitsanulok 65000, Thailand
| | - Siripong Premjet
- Department of Biology, Faculty of Science, Naresuan University, Muang, Phitsanulok 65000, Thailand;
| |
Collapse
|
3
|
Liu B, Liu L, Deng B, Huang C, Zhu J, Liang L, He X, Wei Y, Qin C, Liang C, Liu S, Yao S. Application and prospect of organic acid pretreatment in lignocellulosic biomass separation: A review. Int J Biol Macromol 2022; 222:1400-1413. [PMID: 36195224 DOI: 10.1016/j.ijbiomac.2022.09.270] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 08/20/2022] [Accepted: 09/28/2022] [Indexed: 11/28/2022]
Abstract
As a clean and efficient method of lignocellulosic biomass separation, organic acid pretreatment has attracted extensive research. Hemicellulose or lignin is selectively isolated and the cellulose structure is preserved. Effective fractionation of lignocellulosic biomass is achieved. The separation characteristics of hemicellulose or lignin by different organic acids were summarized. The organic acids of hemicellulose were separated into hydrogen ionized, autocatalytic and α-hydroxy acids according to the separation mechanism. The separation of lignin depends on the dissolution mechanism and spatial effect of organic acids. In addition, the challenges and prospects of organic acid pretreatment were analyzed. The separation of hemicellulose and enzymatic hydrolysis of cellulose were significantly affected by the polycondensation of lignin, which is effectively inhibited by the addition of green additives such as ketones or alcohols. Lignin separation was improved by developing a deep eutectic solvent treatment based on organic acid pretreatment. This work provides support for efficient cleaning of carbohydrate polymers and lignin to promote global carbon neutrality.
Collapse
Affiliation(s)
- Baojie Liu
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Lu Liu
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Baojuan Deng
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Caoxing Huang
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, PR China
| | - Jiatian Zhu
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Linlin Liang
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Xinliang He
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Yuxin Wei
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Chengrong Qin
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China.
| | - Chen Liang
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China
| | - Shijie Liu
- Department of Paper and Bioprocess Engineering, SUNY College of Environmental Science and Forestry,1 Forestry Drive, Syracuse, NY 13210, United States
| | - Shuangquan Yao
- Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, School of Light Industrial and Food Engineering, Guangxi University, Nanning 530004, PR China.
| |
Collapse
|
4
|
Zhai R, Hu J, Jin M. Towards efficient enzymatic saccharification of pretreated lignocellulose: Enzyme inhibition by lignin-derived phenolics and recent trends in mitigation strategies. Biotechnol Adv 2022; 61:108044. [PMID: 36152893 DOI: 10.1016/j.biotechadv.2022.108044] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 08/24/2022] [Accepted: 09/19/2022] [Indexed: 01/01/2023]
Abstract
Lignocellulosic biorefinery based on its sugar-platform has been considered as an efficient strategy to replace fossil fuel-based refinery. In the bioconversion process, pretreatment is an essential step to firstly open up lignocellulose cell wall structure and enhance the accessibility of carbohydrates to hydrolytic enzymes. However, various lignin and/or carbohydrates degradation products (e.g. phenolics, 5-hydroxymethylfurfural, furfural) also generated during pretreatment, which severely inhibit the following enzymatic hydrolysis and the downstream fermentation process. Among them, the lignin derived phenolics have been considered as the most inhibitory compounds and their inhibitory effects are highly dependent on the source of biomass and the type of pretreatment strategy. Although liquid-solid separation and subsequent washing can remove the lignin derived phenolics and other inhibitors, this is undesirable in the realistic industrial application where the whole slurry of pretreated biomass need to be directly used in the hydrolysis process. This review summarizes the phenolics formation mechanism for various commonly applied pretreatment methods and discusses the key factors that affect the inhibitory effect of phenolics on cellulose hydrolysis. In addition, the recent achievements on the rational design of inhibition mitigation strategies to boost cellulose hydrolysis for sugar-platform biorefinery are also introduced. This review also provides guidance for rational design detoxification strategies to facilitate whole slurry hydrolysis which helps to realize the industrialization of lignocellulose biorefinery.
Collapse
Affiliation(s)
- Rui Zhai
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China
| | - Jianguang Hu
- Department of Chemical and Petroleum Engineering, University of Calgary, Calgary T2N 1N4, Canada
| | - Mingjie Jin
- School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing 210094, China.
| |
Collapse
|
5
|
Aarti C, Khusro A, Agastian P. Saccharification of alkali pre-treated aquatic weeds biomass using partially purified cellulase immobilized on different matrices. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2022. [DOI: 10.1016/j.bcab.2022.102283] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
6
|
Zafar A, Aftab MN, Asif A, Karadag A, Peng L, Celebioglu HU, Afzal MS, Hamid A, Iqbal I. Efficient biomass saccharification using a novel cellobiohydrolase from Clostridium clariflavum for utilization in biofuel industry. RSC Adv 2021; 11:9246-9261. [PMID: 35423428 PMCID: PMC8695235 DOI: 10.1039/d1ra00545f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/18/2021] [Accepted: 02/23/2021] [Indexed: 11/30/2022] Open
Abstract
The present study describes the cloning of the cellobiohydrolase gene from a thermophilic bacterium Clostridium clariflavum and its expression in Escherichia coli BL21(DE3) utilizing the expression vector pET-21a(+). The optimization of various parameters (pH, temperature, isopropyl β-d-1-thiogalactopyranoside (IPTG) concentration, time of induction) was carried out to obtain the maximum enzyme activity (2.78 ± 0.145 U ml−1) of recombinant enzyme. The maximum expression of recombinant cellobiohydrolase was obtained at pH 6.0 and 70 °C respectively. Enzyme purification was performed by heat treatment and immobilized metal anionic chromatography. The specific activity of the purified enzyme was 57.4 U mg−1 with 35.17% recovery and 3.90 purification fold. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the molecular weight of cellobiohydrolase was 78 kDa. Among metal ions, Ca2+ showed a positive impact on the cellobiohydrolase enzyme with increased activity by 115%. Recombinant purified cellobiohydrolase enzyme remained stable and exhibited 77% and 63% residual activity in comparison to control in the presence of n-butanol and after incubation at 80 °C for 1 h, respectively. Our results indicate that our purified recombinant cellobiohydrolase can be used in the biofuel industry. Successful expression of a novel cellobiohydrolase enzyme from Clostridium clariflavum with efficient saccharification potential of plant biomass for the biofuel industry.![]()
Collapse
Affiliation(s)
- Asma Zafar
- Faculty of Life Sciences
- University of Central Punjab
- Lahore
- Pakistan
| | | | - Anam Asif
- Institute of Industrial Biotechnology
- GC University
- Lahore
- Pakistan
| | - Ahmet Karadag
- Department of Chemistry
- Faculty of Arts and Sciences
- Yozgat Bozok University
- Yozgat
- Turkey
| | - Liangcai Peng
- Biomass and Bioenergy Research Center
- Huazhong Agriculture University
- Wuhan
- China
| | | | - Muhammad Sohail Afzal
- Department of Life Sciences
- School of Science
- University of Management and Technology (UMT)
- Lahore
- Pakistan
| | - Attia Hamid
- Institute of Industrial Biotechnology
- GC University
- Lahore
- Pakistan
| | - Irfana Iqbal
- Department of Zoology
- Lahore College for Women University
- Lahore
- Pakistan
| |
Collapse
|
7
|
Alokika, Anu, Kumar A, Kumar V, Singh B. Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective. Int J Biol Macromol 2020; 169:564-582. [PMID: 33385447 DOI: 10.1016/j.ijbiomac.2020.12.175] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/29/2020] [Accepted: 12/23/2020] [Indexed: 12/01/2022]
Abstract
Sugarcane bagasse is a rich source of cellulose (32-45%), hemicellulose (20-32%) and lignin (17-32%), 1.0-9.0% ash and some extractives. Huge amount of the generation of sugarcane bagasse has been a great challenge to industries and environment at global level for many years. Though cellulosic and hemicellulosic fractions in bagasse makes it a potential raw substrate for the production of value-added products at large scale, the presence of lignin hampers its saccharification which further leads to low yields of the value-added products. Therefore, an appropriate pretreatment strategy is of utmost importance that effectively solubilizes the lignin that exposes cellulose and hemicellulose for enzymatic action. Pretreatment also reduces the biomass recalcitrance i.e., cellulose crystallinity, structural complexity of cell wall and lignification for its effective utilization in biorefinery. Sugarcane bagasse served as nutrient medium for the cultivation of diverse microorganisms for the production of industrially important metabolites including enzymes, reducing sugars, prebiotic, organic acids and biofuels. Sugarcane bagasse has been utilized in the generation of electricity, syngas and as biosorbant in the bioremediation of heavy metals. Furthermore, the ash generated from bagasse is an excellent source for the synthesis of high strength and light weight bricks and tiles. Present review describes the utility of sugarcane bagasse as sustainable and renewable lignocellulosic substrate for the production of industrially important multifarious value-added products.
Collapse
Affiliation(s)
- Alokika
- Laboratory of Bioprocess Technology, Department of Microbiology, Maharshi Dayanand University, Rohtak 124001, Haryana, India
| | - Anu
- Laboratory of Bioprocess Technology, Department of Microbiology, Maharshi Dayanand University, Rohtak 124001, Haryana, India
| | - Anil Kumar
- Department of Botany, Pt. N.R.S. Govt. College, Rohtak 124001, Haryana, India
| | - Vinod Kumar
- Department of Chemistry, Central University of Haryana, Jant-Pali, Mahendergarh 123031, Haryana, India
| | - Bijender Singh
- Laboratory of Bioprocess Technology, Department of Microbiology, Maharshi Dayanand University, Rohtak 124001, Haryana, India; Department of Biotechnology, Central University of Haryana, Jant-Pali, Mahendergarh 123031, Haryana, India.
| |
Collapse
|
8
|
Zhang H, Zhang J, Xie J, Qin Y. Effects of NaOH-catalyzed organosolv pretreatment and surfactant on the sugar production from sugarcane bagasse. BIORESOURCE TECHNOLOGY 2020; 312:123601. [PMID: 32502887 DOI: 10.1016/j.biortech.2020.123601] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/25/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
In this study, NaOH-catalyzed organosolv pretreatment with different loading of NaOH (0-10%) was proposed to disrupt the recalcitrant structure by degrading lignin, reserve the majority of cellulose and hemicellulose, and improve the enzymatic efficiency of sugarcane bagasse. It was found that the higher loading of NaOH during organosolv pretreatment yielded more glucose, and the synergistic performance of NaOH and ethanol on enzymolysis was superior to that pretreated with only NaOH and only ethanol during two-step pretreatment. Furthermore, Tween 80 was added to determine its influence on enzymolysis after NaOH-catalyzed organosolv pretreatment, leading to the highest glucose yield of 95.1% at 24 h, which saved 2/3 hydrolysis time while generating the similar glucose yield comparing with that without Tween 80. However, the increased yields of glucose by adding Tween 80 were decreased as hydrolysis time was prolonged from 6 h to 24 h.
Collapse
Affiliation(s)
- Hongdan Zhang
- College of Forestry and Landscape Architecture, Key Laboratory of Energy Plants Resource and Utilization, Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou 510642, PR China; CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Guangzhou 510640, PR China.
| | - Jiajie Zhang
- College of Forestry and Landscape Architecture, Key Laboratory of Energy Plants Resource and Utilization, Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou 510642, PR China
| | - Jun Xie
- College of Forestry and Landscape Architecture, Key Laboratory of Energy Plants Resource and Utilization, Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou 510642, PR China
| | - Yanlin Qin
- Guangdong University of Technology, School of Chemical Engineering and Light Industry, Guangzhou 510006, PR China.
| |
Collapse
|
9
|
Ladeira Ázar RIS, Bordignon-Junior SE, Laufer C, Specht J, Ferrier D, Kim D. Effect of Lignin Content on Cellulolytic Saccharification of Liquid Hot Water Pretreated Sugarcane Bagasse. Molecules 2020; 25:molecules25030623. [PMID: 32023910 PMCID: PMC7037451 DOI: 10.3390/molecules25030623] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 01/22/2020] [Accepted: 01/28/2020] [Indexed: 11/16/2022] Open
Abstract
Lignin contributes to the rigid structure of the plant cell wall and is partially responsible for the recalcitrance of lignocellulosic materials to enzymatic digestion. Overcoming this recalcitrance is one the most critical issues in a sugar-flat form process. This study addresses the effect of low lignin sugarcane bagasse on enzymatic hydrolysis after liquid hot water pretreatment at 190 °C and 20 min (severity factor: 3.95). The hydrolysis of bagasse from a sugarcane line selected for a relatively low lignin content, gave an 89.7% yield of cellulose conversion to glucose at 40 FPU/g glucan versus a 68.3% yield from a comparably treated bagasse from the high lignin bred line. A lower enzyme loading of 5 FPU/g glucan (equivalent to 3.2 FPU/g total solids) resulted in 31.4% and 21.9% conversion yields, respectively, for low and high lignin samples, suggesting the significance of lignin content in the saccharification process. Further increases in the enzymatic conversion of cellulose to glucose were achieved when the bagasse sample was pre-incubated with a lignin blocking agent, e.g., bovine serum albumin (50 mg BSA/g glucan) at 50 °C for 1 h prior to an actual saccharification. In this work, we have demonstrated that even relatively small differences in lignin content can result in considerably increased sugar production, which supports the dissimilarity of bagasse lignin content and its effects on cellulose digestibility. The increased glucose yields with the addition of BSA helped to decrease the inhibition of non-productive absorption of cellulose enzymes onto lignin and solid residual lignin fractions.
Collapse
Affiliation(s)
- Rafaela I. S. Ladeira Ázar
- Department of Biochemistry and Molecular Biology, BIOAGRO, Federal University of Viçosa, Viçosa, Minas Gerais 36570-000, Brazil;
| | - Sidnei Emilio Bordignon-Junior
- Laboratory of Biochemistry and Applied Microbiology, São Paulo State University (UNESP), IBILCE, 2265 Cristóvão Colombo, São José do Rio Preto 15054-000, São Paulo, Brazil;
| | - Craig Laufer
- Department of Biology, Hood College, 401 Rosemont Avenue, Frederick, MD 21701, USA; (C.L.); (J.S.); (D.F.)
| | - Jordan Specht
- Department of Biology, Hood College, 401 Rosemont Avenue, Frederick, MD 21701, USA; (C.L.); (J.S.); (D.F.)
| | - Drew Ferrier
- Department of Biology, Hood College, 401 Rosemont Avenue, Frederick, MD 21701, USA; (C.L.); (J.S.); (D.F.)
| | - Daehwan Kim
- Department of Biology, Hood College, 401 Rosemont Avenue, Frederick, MD 21701, USA; (C.L.); (J.S.); (D.F.)
- Correspondence: ; Tel.: +1-765-637-8603; Fax: +1-301-696-3667
| |
Collapse
|
10
|
Deciphering the molecular specificity of phenolic compounds as inhibitors or glycosyl acceptors of β-fructofuranosidase from Xanthophyllomyces dendrorhous. Sci Rep 2019; 9:17441. [PMID: 31767902 PMCID: PMC6877581 DOI: 10.1038/s41598-019-53948-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 09/12/2019] [Indexed: 01/09/2023] Open
Abstract
Enzymatic glycosylation of polyphenols is a tool to improve their physicochemical properties and bioavailability. On the other hand, glycosidic enzymes can be inhibited by phenolic compounds. In this work, we studied the specificity of various phenolics (hydroquinone, hydroxytyrosol, epigallocatechin gallate, catechol and p-nitrophenol) as fructosyl acceptors or inhibitors of the β-fructofuranosidase from Xanthophyllomyces dendrorhous (pXd-INV). Only hydroquinone and hydroxytyrosol gave rise to the formation of glycosylated products. For the rest, an inhibitory effect on both the hydrolytic (H) and transglycosylation (T) activity of pXd-INV, as well as an increase in the H/T ratio, was observed. To disclose the binding mode of each compound and elucidate the molecular features determining its acceptor or inhibitor behaviour, ternary complexes of the inactive mutant pXd-INV-D80A with fructose and the different polyphenols were analyzed by X-ray crystallography. All the compounds bind by stacking against Trp105 and locate one of their phenolic hydroxyls making a polar linkage to the fructose O2 at 3.6–3.8 Å from the C2, which could enable the ulterior nucleophilic attack leading to transfructosylation. Binding of hydroquinone was further investigated by soaking in absence of fructose, showing a flexible site that likely allows productive motion of the intermediates. Therefore, the acceptor capacity of the different polyphenols seems mediated by their ability to make flexible polar links with the protein, this flexibility being essential for the transfructosylation reaction to proceed. Finally, the binding affinity of the phenolic compounds was explained based on the two sites previously reported for pXd-INV.
Collapse
|