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Wardman JF, Withers SG. Carbohydrate-active enzyme (CAZyme) discovery and engineering via (Ultra)high-throughput screening. RSC Chem Biol 2024; 5:595-616. [PMID: 38966674 PMCID: PMC11221537 DOI: 10.1039/d4cb00024b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 05/16/2024] [Indexed: 07/06/2024] Open
Abstract
Carbohydrate-active enzymes (CAZymes) constitute a diverse set of enzymes that catalyze the assembly, degradation, and modification of carbohydrates. These enzymes have been fashioned into potent, selective catalysts by millennia of evolution, and yet are also highly adaptable and readily evolved in the laboratory. To identify and engineer CAZymes for different purposes, (ultra)high-throughput screening campaigns have been frequently utilized with great success. This review provides an overview of the different approaches taken in screening for CAZymes and how mechanistic understandings of CAZymes can enable new approaches to screening. Within, we also cover how cutting-edge techniques such as microfluidics, advances in computational approaches and synthetic biology, as well as novel assay designs are leading the field towards more informative and effective screening approaches.
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Affiliation(s)
- Jacob F Wardman
- Department of Biochemistry and Molecular Biology, University of British Columbia Vancouver BC V6T 1Z3 Canada
- Michael Smith Laboratories, University of British Columbia Vancouver BC V6T 1Z4 Canada
| | - Stephen G Withers
- Department of Biochemistry and Molecular Biology, University of British Columbia Vancouver BC V6T 1Z3 Canada
- Michael Smith Laboratories, University of British Columbia Vancouver BC V6T 1Z4 Canada
- Department of Chemistry, University of British Columbia Vancouver BC V6T 1Z1 Canada
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2
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Li S, Cao L, Yang X, Wu X, Xu S, Liu Y. Simultaneously optimizing multiple properties of β-glucosidase Bgl6 using combined (semi-)rational design strategies and investigation of the underlying mechanisms. BIORESOURCE TECHNOLOGY 2023; 374:128792. [PMID: 36842511 DOI: 10.1016/j.biortech.2023.128792] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 02/20/2023] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
The performance of β-glucosidase during cellulose saccharification is determined by thermostability, activity and glucose tolerance. However, conflicts between them make it challenging to simultaneously optimize three properties. In this work, such a case was reported using Bgl6-M3 as a starting point. Firstly, four thermostability-enhancing mutations were obtained using computer-aided engineering strategies (mutant M7). Secondly, substrate binding pocket of M7 was reshaped, generating two mutations that increased activity but decreased glucose tolerance (mutant M9). Then a key region lining active site cavity was redesigned, resulting in three mutations that boosted glucose tolerance and activity. Finally, mutant M12 with simultaneously improved thermostability (half-life of 20-fold), activity (kcat/Km of 5.6-fold) and glucose tolerance (ΔIC50 of 200 mM) was obtained. Mechanisms for property improvement were elucidated by structural analysis and molecular dynamics simulations. Overall, the strategies used here and new insights into the underlying mechanisms may provide guidance for multi-property engineering of other enzymes.
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Affiliation(s)
- Shuifeng Li
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Lichuang Cao
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Xiangpeng Yang
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Xiangrui Wu
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Shujing Xu
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Yuhuan Liu
- School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, PR China.
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3
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Wei T, Xu Q, Zou C, He Z, Tang Y, Gao T, Han M, Dai Z. A boronate-modified renewable nanointerface for ultrasensitive electrochemical assay of cellulase activity. CHINESE CHEM LETT 2021. [DOI: 10.1016/j.cclet.2020.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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4
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Ghosh S, Godoy L, Anchang KY, Achilonu CC, Gryzenhout M. Fungal Cellulases: Current Research and Future Challenges. Fungal Biol 2021. [DOI: 10.1007/978-3-030-85603-8_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Liu S, Wang J, Zhu Z, Shi T, Zhang YHPJ. Efficient secretory production of large-size heterologous enzymes in Bacillus subtilis: A secretory partner and directed evolution. Biotechnol Bioeng 2020; 117:2957-2968. [PMID: 32589796 DOI: 10.1002/bit.27478] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 06/25/2020] [Indexed: 12/20/2022]
Abstract
Secretory production of recombinant proteins provides a simple approach to the production and purification of target proteins in the enzyme industry. We developed a combined strategy for the secretory production of three large-size heterologous enzymes with a special focus on 83-kDa isoamylase (IA) from an archaeon Sulfolobus tokodaii in a bacterium Bacillus subtilis. First, a secretory protein of the B. subtilis family 5 glycoside hydrolase endoglucanase (Cel5) was used as a fusion partner, along with the NprB signal peptide, to facilitate secretory production of IA. This secretory partner strategy was effective for the secretion of two other large enzymes: family 9 glycoside hydrolase from Clostridium phytofermentas and cellodextrin phosphorylase from Clostridium thermocellum. Second, the secretion of Cel5-IA was improved by directed evolution with two novel double-layer Petri-dish-based high-throughput screening (HTS) methods. The high-sensitivity HTS relied on the detection of high-activity Cel5 on the carboxymethylcellulose/Congo-red assay. The second modest-sensitivity HTS focused on the detection of low-activity IA on the amylodextrin-I2 assay. After six rounds of HTS, a secretory Cel5-IA level was increased to 234 mg/L, 155 times the wild-type IA with the NprB signal peptide only. This combinatory strategy could be useful to enhance the secretory production of large-size heterologous proteins in B. subtilis.
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Affiliation(s)
- Shan Liu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Juan Wang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Zhiguang Zhu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Ting Shi
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Yi-Heng P Job Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
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6
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Tyr320 is a molecular determinant of the catalytic activity of β-glucosidase from Neosartorya fischeri. Int J Biol Macromol 2020; 151:609-617. [DOI: 10.1016/j.ijbiomac.2020.02.117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 02/09/2020] [Accepted: 02/11/2020] [Indexed: 11/23/2022]
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7
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Yoav S, Stern J, Salama-Alber O, Frolow F, Anbar M, Karpol A, Hadar Y, Morag E, Bayer EA. Directed Evolution of Clostridium thermocellum β-Glucosidase A Towards Enhanced Thermostability. Int J Mol Sci 2019; 20:E4701. [PMID: 31547488 PMCID: PMC6801902 DOI: 10.3390/ijms20194701] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 09/19/2019] [Accepted: 09/20/2019] [Indexed: 12/27/2022] Open
Abstract
β-Glucosidases are key enzymes in the process of cellulose utilization. It is the last enzyme in the cellulose hydrolysis chain, which converts cellobiose to glucose. Since cellobiose is known to have a feedback inhibitory effect on a variety of cellulases, β-glucosidase can prevent this inhibition by hydrolyzing cellobiose to non-inhibitory glucose. While the optimal temperature of the Clostridium thermocellum cellulosome is 70 °C, C. thermocellum β-glucosidase A is almost inactive at such high temperatures. Thus, in the current study, a random mutagenesis directed evolutionary approach was conducted to produce a thermostable mutant with Kcat and Km, similar to those of the wild-type enzyme. The resultant mutant contained two mutations, A17S and K268N, but only the former was found to affect thermostability, whereby the inflection temperature (Ti) was increased by 6.4 °C. A17 is located near the central cavity of the native enzyme. Interestingly, multiple alignments revealed that position 17 is relatively conserved, whereby alanine is replaced only by serine. Upon the addition of the thermostable mutant to the C. thermocellum secretome for subsequent hydrolysis of microcrystalline cellulose at 70 °C, a higher soluble glucose yield (243%) was obtained compared to the activity of the secretome supplemented with the wild-type enzyme.
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Affiliation(s)
- Shahar Yoav
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, the Advanced School for Environmental Studies, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Johanna Stern
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Orly Salama-Alber
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Felix Frolow
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 6997801, Israel.
| | - Michael Anbar
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Alon Karpol
- CelDezyner, 2 Bergman St, Tamar Science Park, Rehovot 7670504, Israel.
| | - Yitzhak Hadar
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, the Advanced School for Environmental Studies, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
| | - Ely Morag
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Edward A Bayer
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 7610001, Israel.
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Zhou Y, Li X, Yan D, Addai Peprah F, Ji X, Fletcher EE, Wang Y, Wang Y, Gu J, Lin F, Shi H. Multifunctional elastin-like polypeptide renders β-glucosidase enzyme phase transition and high stability. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:157. [PMID: 31249620 PMCID: PMC6589881 DOI: 10.1186/s13068-019-1497-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Accepted: 06/11/2019] [Indexed: 05/10/2023]
Abstract
BACKGROUND In the enzymatic conversion of biomass, it becomes an important issue to efficiently and cost-effectively degrade cellulose into fermentable glucose. β-Glucosidase (Bgluc), an essential member of cellulases, plays a critical role in cellulosic biomass degradation. The difficulty in improving the stability of Bgluc has been a bottleneck in the enzyme-dependent cellulose degradation. The traditional method of protein purification, however, leads to higher production cost and a decrease in activity. To simplify and efficiently purify Bgluc with modified special properties, Bgluc-tagged ELP and His with defined phase transitions was designed to facilitate the process. RESULTS Here, a novel binary ELP and His tag was fused with Bgluc from termite Coptotermes formosanus to construct a Bgluc-linker-ELP-His recombinant fusion protein (BglucLEH). The recombinant plasmid Bgluc expressing a His tag (BglucH) was also constructed. The BglucLEH and BglucH were expressed in E. coli BL21 and purified using inverse transition cycling (ITC) or Ni-NTA resin. The optimum salt concentration for the ITC purification of BglucLEH was 0.5 M (NH4)2SO4 and the specific activity of BglucLEH purified by ITC was 75.5 U/mg for substrate p-NPG, which was slightly higher than that of BglucLEH purified by Ni-NTA (68.2 U/mg). The recovery rate and purification fold of BglucLEH purified by ITC and Ni-NTA were 77.8%, 79.1% and 12.60, 11.60, respectively. The results indicated that purification with ITC was superior to the traditional Ni-NTA. The K m of BglucLEH and BglucH for p-NPG was 5.27 and 5.73 mM, respectively. The K ca t/K m (14.79 S-1 mM-1) of BglucLEH was higher than that of BglucH (12.10 S-1 mM-1). The effects of ELP tag on the enzyme activity, secondary structure and protein stability were also studied. The results showed that ELP tag did not affect the secondary structure or enzyme activity of Bgluc. More importantly, ELP improved the protein stability in harsh conditions such as heating and exposure to denaturant. CONCLUSION The Bgluc-linker-ELP-His system shows wide application prospect in maintaining the activity, efficient purification and improving the stability of Bgluc. These properties of BglucLEH make it an interesting tool to reduce cost, to improve the efficiency of biocatalyst and potentially to enhance the degradation of lignocellulosic biomass.
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Affiliation(s)
- Yang Zhou
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Xiaofeng Li
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Dandan Yan
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Frank Addai Peprah
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Xingqi Ji
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Emmanuella Esi Fletcher
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Yanwei Wang
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Yingying Wang
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Jie Gu
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
| | - Feng Lin
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture, Zhejiang Institute of Freshwater Fisheries, Huzhou, 313001 People’s Republic of China
| | - Haifeng Shi
- Institute of Life Sciences, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, 212013 People’s Republic of China
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9
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Cao L, Li S, Huang X, Qin Z, Kong W, Xie W, Liu Y. Enhancing the Thermostability of Highly Active and Glucose-Tolerant β-Glucosidase Ks5A7 by Directed Evolution for Good Performance of Three Properties. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:13228-13235. [PMID: 30488698 DOI: 10.1021/acs.jafc.8b05662] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A high-performance β-glucosidase for efficient cellulose hydrolysis needs to excel in thermostability, catalytic efficiency, and resistance to glucose inhibition. However, it is challenging to achieve superb properties in all three aspects in a single enzyme. In this study, a hyperactive and glucose-tolerant β-glucosidase Ks5A7 was employed as the starting point. Four rounds of random mutagenesis were then performed, giving rise to a thermostable mutant 4R1 with five amino acid substitutions. The half-life of 4R1 at 50 °C is 8640-fold that of Ks5A7 (144 h vs 1 min). Meanwhile, 4R1 had a higher specific activity (374.26 vs 243.18 units·mg-1) than the wild type with a similar glucose tolerance. When supplemented to Celluclast 1.5L, the mutant significantly enhanced the hydrolysis of pretreated sugar cane bagasse, improving the released glucose concentration by 44%. With excellent performance in thermostability, activity, and glucose tolerance, 4R1 will serve as an exceptional catalyst for industrial applications.
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Affiliation(s)
- Lichuang Cao
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Shuifeng Li
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Xin Huang
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Zongmin Qin
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Wei Kong
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Wei Xie
- Ministry of Education Key Laboratory of Gene Function and Regulation, State Key Laboratory for Biocontrol, School of Life Sciences , Sun Yat-Sen University , Guangzhou , Guangdong 510006 , People's Republic of China
| | - Yuhuan Liu
- School of Life Sciences, Institute of Aquatic Economic Animals and Guangdong Provincial Key Laboratory for Aquatic Economic Animals, National Engineering Center for Marine Biotechnology of South China Sea , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
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10
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Mukherjee I, Sinha SK, Datta S, De P. Recyclable Thermoresponsive Polymer−β-Glucosidase Conjugate with Intact Hydrolysis Activity. Biomacromolecules 2018; 19:2286-2293. [DOI: 10.1021/acs.biomac.8b00258] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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Huang R, Chen H, Zhou W, Ma C, Zhang YHP. Engineering a thermostable highly active glucose 6-phosphate dehydrogenase and its application to hydrogen production in vitro. Appl Microbiol Biotechnol 2018; 102:3203-3215. [DOI: 10.1007/s00253-018-8798-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/16/2018] [Accepted: 01/18/2018] [Indexed: 10/17/2022]
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12
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You C, Huang R, Wei X, Zhu Z, Zhang YHP. Protein engineering of oxidoreductases utilizing nicotinamide-based coenzymes, with applications in synthetic biology. Synth Syst Biotechnol 2017; 2:208-218. [PMID: 29318201 PMCID: PMC5655348 DOI: 10.1016/j.synbio.2017.09.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 09/08/2017] [Accepted: 09/22/2017] [Indexed: 01/01/2023] Open
Abstract
Two natural nicotinamide-based coenzymes (NAD and NADP) are indispensably required by the vast majority of oxidoreductases for catabolism and anabolism, respectively. Most NAD(P)-dependent oxidoreductases prefer one coenzyme as an electron acceptor or donor to the other depending on their different metabolic roles. This coenzyme preference associated with coenzyme imbalance presents some challenges for the construction of high-efficiency in vivo and in vitro synthetic biology pathways. Changing the coenzyme preference of NAD(P)-dependent oxidoreductases is an important area of protein engineering, which is closely related to product-oriented synthetic biology projects. This review focuses on the methodology of nicotinamide-based coenzyme engineering, with its application in improving product yields and decreasing production costs. Biomimetic nicotinamide-containing coenzymes have been proposed to replace natural coenzymes because they are more stable and less costly than natural coenzymes. Recent advances in the switching of coenzyme preference from natural to biomimetic coenzymes are also covered in this review. Engineering coenzyme preferences from natural to biomimetic coenzymes has become an important direction for coenzyme engineering, especially for in vitro synthetic pathways and in vivo bioorthogonal redox pathways.
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Affiliation(s)
- Chun You
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Avenue, Tianjin Airport Economic Area, Tianjin, 300308, People's Republic of China
| | - Rui Huang
- Biological Systems Engineering Department, Virginia Tech, 304 Seitz Hall, Blacksburg, VA 24061, USA
| | - Xinlei Wei
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Avenue, Tianjin Airport Economic Area, Tianjin, 300308, People's Republic of China
| | - Zhiguang Zhu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Avenue, Tianjin Airport Economic Area, Tianjin, 300308, People's Republic of China
| | - Yi-Heng Percival Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Avenue, Tianjin Airport Economic Area, Tianjin, 300308, People's Republic of China.,Biological Systems Engineering Department, Virginia Tech, 304 Seitz Hall, Blacksburg, VA 24061, USA
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Parisutham V, Chandran SP, Mukhopadhyay A, Lee SK, Keasling JD. Intracellular cellobiose metabolism and its applications in lignocellulose-based biorefineries. BIORESOURCE TECHNOLOGY 2017; 239:496-506. [PMID: 28535986 DOI: 10.1016/j.biortech.2017.05.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/27/2017] [Accepted: 05/01/2017] [Indexed: 05/28/2023]
Abstract
Complete hydrolysis of cellulose has been a key characteristic of biomass technology because of the limitation of industrial production hosts to use cellodextrin, the partial hydrolysis product of cellulose. Cellobiose, a β-1,4-linked glucose dimer, is a major cellodextrin of the enzymatic hydrolysis (via endoglucanase and exoglucanase) of cellulose. Conversion of cellobiose to glucose is executed by β-glucosidase. The complete extracellular hydrolysis of celluloses has several critical barriers in biomass technology. An alternative bioengineering strategy to make the bioprocessing less challenging is to engineer microbes with the abilities to hydrolyze and assimilate the cellulosic-hydrolysate cellodextrin. Microorganisms engineered to metabolize cellobiose rather than the monomeric glucose can provide several advantages for lignocellulose-based biorefineries. This review describes the recent advances and challenges in engineering efficient intracellular cellobiose metabolism in industrial hosts. This review also describes the limitations of and future prospectives in engineering intracellular cellobiose metabolism.
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Affiliation(s)
- Vinuselvi Parisutham
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Sathesh-Prabu Chandran
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Aindrila Mukhopadhyay
- Joint BioEnergy Institute, Emeryville, CA 94608, USA; Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Sung Kuk Lee
- School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea; School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
| | - Jay D Keasling
- Joint BioEnergy Institute, Emeryville, CA 94608, USA; Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Chemical and Biomolecular Engineering & Department of Bioengineering, UC Berkeley, Berkeley, CA 94720, USA; Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, KogleAllé, DK2970 Hørsholm, Denmark; Synthetic Biology Engineering Research Center (Synberc), Berkeley, CA 94720, USA
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14
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Goswami S, Das S, Datta S. Understanding the role of residues around the active site tunnel towards generating a glucose-tolerant β-glucosidase from Agrobacterium tumefaciens 5A. Protein Eng Des Sel 2017; 30:523-530. [DOI: 10.1093/protein/gzx039] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 07/10/2017] [Indexed: 12/18/2022] Open
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15
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Guo W, Sheng J, Feng X. Mini-review: In vitro Metabolic Engineering for Biomanufacturing of High-value Products. Comput Struct Biotechnol J 2017; 15:161-167. [PMID: 28179978 PMCID: PMC5288458 DOI: 10.1016/j.csbj.2017.01.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 01/12/2017] [Accepted: 01/15/2017] [Indexed: 11/23/2022] Open
Abstract
With the breakthroughs in biomolecular engineering and synthetic biology, many valuable biologically active compound and commodity chemicals have been successfully manufactured using cell-based approaches in the past decade. However, because of the high complexity of cell metabolism, the identification and optimization of rate-limiting metabolic pathways for improving the product yield is often difficult, which represents a significant and unavoidable barrier of traditional in vivo metabolic engineering. Recently, some in vitro engineering approaches were proposed as alternative strategies to solve this problem. In brief, by reconstituting a biosynthetic pathway in a cell-free environment with the supplement of cofactors and substrates, the performance of each biosynthetic pathway could be evaluated and optimized systematically. Several value-added products, including chemicals, nutraceuticals, and drug precursors, have been biosynthesized as proof-of-concept demonstrations of in vitro metabolic engineering. This mini-review summarizes the recent progresses on the emerging topic of in vitro metabolic engineering and comments on the potential application of cell-free technology to speed up the “design-build-test” cycles of biomanufacturing.
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Affiliation(s)
- Weihua Guo
- Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States
| | - Jiayuan Sheng
- Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States
| | - Xueyang Feng
- Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States
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High-Throughput Screening of Coenzyme Preference Change of Thermophilic 6-Phosphogluconate Dehydrogenase from NADP(+) to NAD(.). Sci Rep 2016; 6:32644. [PMID: 27587230 PMCID: PMC5009329 DOI: 10.1038/srep32644] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 08/10/2016] [Indexed: 11/09/2022] Open
Abstract
Coenzyme engineering that changes NAD(P) selectivity of redox enzymes is an important tool in metabolic engineering, synthetic biology, and biocatalysis. Here we developed a high throughput screening method to identify mutants of 6-phosphogluconate dehydrogenase (6PGDH) from a thermophilic bacterium Moorella thermoacetica with reversed coenzyme selectivity from NADP+ to NAD+. Colonies of a 6PGDH mutant library growing on the agar plates were treated by heat to minimize the background noise, that is, the deactivation of intracellular dehydrogenases, degradation of inherent NAD(P)H, and disruption of cell membrane. The melted agarose solution containing a redox dye tetranitroblue tetrazolium (TNBT), phenazine methosulfate (PMS), NAD+, and 6-phosphogluconate was carefully poured on colonies, forming a second semi-solid layer. More active 6PGDH mutants were examined via an enzyme-linked TNBT-PMS colorimetric assay. Positive mutants were recovered by direct extraction of plasmid from dead cell colonies followed by plasmid transformation into E. coli TOP10. By utilizing this double-layer screening method, six positive mutants were obtained from two-round saturation mutagenesis. The best mutant 6PGDH A30D/R31I/T32I exhibited a 4,278-fold reversal of coenzyme selectivity from NADP+ to NAD+. This screening method could be widely used to detect numerous redox enzymes, particularly for thermophilic ones, which can generate NAD(P)H reacted with the redox dye TNBT.
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Serdiuk IE, Reszka M, Myszka H, Krzymiński K, Liberek B, Roshal AD. Flavonol-based fluorescent indicator for determination of β-glucosidase activity. RSC Adv 2016. [DOI: 10.1039/c6ra06062e] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A flavonol-based ESIPT fluorescence probe for evaluation of β-glucosidase activity was synthesized and tested for sensitivity to enzymatic cleavage at different conditions.
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Affiliation(s)
- Illia E. Serdiuk
- Department of Chemistry
- University of Gdańsk
- 80-308 Gdańsk
- Poland
- Institute of Chemistry
| | - Milena Reszka
- Department of Chemistry
- University of Gdańsk
- 80-308 Gdańsk
- Poland
| | - Henryk Myszka
- Department of Chemistry
- University of Gdańsk
- 80-308 Gdańsk
- Poland
| | | | - Beata Liberek
- Department of Chemistry
- University of Gdańsk
- 80-308 Gdańsk
- Poland
| | - Alexander D. Roshal
- Institute of Chemistry
- V. N. Karazin Kharkiv National University
- Kharkiv
- 61022 Ukraine
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18
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Fungal Biotechnology for Industrial Enzyme Production: Focus on (Hemi)cellulase Production Strategies, Advances and Challenges. Fungal Biol 2016. [DOI: 10.1007/978-3-319-27951-0_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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19
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Xia W, Xu X, Qian L, Shi P, Bai Y, Luo H, Ma R, Yao B. Engineering a highly active thermophilic β-glucosidase to enhance its pH stability and saccharification performance. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:147. [PMID: 27446236 PMCID: PMC4955127 DOI: 10.1186/s13068-016-0560-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 07/11/2016] [Indexed: 05/07/2023]
Abstract
BACKGROUND β-Glucosidase is an important member of the biomass-degrading enzyme system, and plays vital roles in enzymatic saccharification for biofuels production. Candidates with high activity and great stability over high temperature and varied pHs are always preferred in industrial practice. To achieve cost-effective biomass conversion, exploring natural enzymes, developing high level expression systems and engineering superior mutants are effective approaches commonly used. RESULTS A newly identified β-glucosidase of GH3, Bgl3A, from Talaromyces leycettanus JCM12802, was overexpressed in yeast strain Pichia pastoris GS115, yielding a crude enzyme activity of 6000 U/ml in a 3 L fermentation tank. The purified enzyme exhibited outstanding enzymatic properties, including favorable temperature and pH optima (75 °C and pH 4.5), good thermostability (maintaining stable at 60 °C), and high catalytic performance (with a specific activity and catalytic efficiency of 905 U/mg and 9096/s/mM on pNPG, respectively). However, the narrow stability of Bgl3A at pH 4.0-5.0 would limit its industrial applications. Further site-directed mutagenesis indicated the role of excessive O-glycosylation in pH liability. By removing the potential O-glycosylation sites, two mutants showed improved pH stability over a broader pH range (3.0-10.0). Besides, with better stability under pH 5.0 and 50 °C compared with wild type Bgl3A, saccharification efficiency of mutant M1 was improved substantially cooperating with cellulase Celluclast 1.5L. And mutant M1 reached approximately equivalent saccharification performance to commercial β-glucosidase Novozyme 188 with identical β-glucosidase activity, suggesting its great prospect in biofuels production. CONCLUSIONS In this study, we overexpressed a novel β-glucosidase Bgl3A with high specific activity and high catalytic efficiency in P. pastoris. We further proved the negative effect of excessive O-glycosylation on the pH stability of Bgl3A, and enhanced the pH stability by reducing the O-glycosylation. And the enhanced mutants showed much better application prospect with substantially improved saccharification efficiency on cellulosic materials.
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Affiliation(s)
- Wei Xia
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
- />College of Animal Science, Zhejiang University, Hangzhou, 310058 People’s Republic of China
| | - Xinxin Xu
- />Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081 People’s Republic of China
| | - Lichun Qian
- />College of Animal Science, Zhejiang University, Hangzhou, 310058 People’s Republic of China
| | - Pengjun Shi
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
| | - Yingguo Bai
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
| | - Huiying Luo
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
| | - Rui Ma
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
| | - Bin Yao
- />Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguancun South Street, Beijing, 100081 People’s Republic of China
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20
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Zhang J, Shi H, Xu L, Zhu X, Li X. Site-Directed Mutagenesis of a Hyperthermophilic Endoglucanase Cel12B from Thermotoga maritima Based on Rational Design. PLoS One 2015. [PMID: 26218520 PMCID: PMC4517919 DOI: 10.1371/journal.pone.0133824] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
To meet the demand for the application of high activity and thermostable cellulases in the production of new-generation bioethanol from nongrain-cellulose sources, a hyperthermostable β-1,4-endoglucase Cel12B from Thermotoga maritima was selected for further modification by gene site-directed mutagenesis method in the present study, based on homology modeling and rational design. As a result, two recombinant enzymes showed significant improvement in enzyme activity by 77% and 87%, respectively, higher than the parental enzyme TmCel12B. Furthermore, the two mutants could retain 80% and 90.5% of their initial activity after incubation at 80°C for 8 h, while only 45% for 5 h to TmCel12B. The Km and Vmax of the two recombinant enzymes were 1.97±0.05 mM, 4.23±0.15 μmol·mg(-1)·min(-1) of TmCel12B-E225H-K207G-D37V, and 2.97±0.12 mM, 3.15±0.21 μmol·mg(-1)·min(-1) of TmCel12B-E225H-K207G, respectively, when using CMC-Na as the substrate. The roles of the mutation sites were also analyzed and evaluated in terms of electron density, hydrophobicity of the modeled protein structures. The recombinant enzymes may be used in the hydrolysis of cellulose at higher temperature in the future. It was concluded that the gene mutagenesis approach of a certain active residues may effectively improve the performance of cellulases for the industrial applications and contribute to the study the thermostable mechanism of thermophilic enzymes.
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Affiliation(s)
- Jinfeng Zhang
- Jiangsu Provincial Engineering Laboratory for Biomass Conversion and Process Integration, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- School of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
| | - Hao Shi
- Jiangsu Provincial Engineering Laboratory for Biomass Conversion and Process Integration, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
| | - Linyu Xu
- Jiangsu Provincial Engineering Laboratory for Biomass Conversion and Process Integration, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- School of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
| | - Xiaoyan Zhu
- Jiangsu Provincial Engineering Laboratory for Biomass Conversion and Process Integration, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- School of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- Jiangsu Key Laboratory for Biomass-based Energy and Enzyme Technology, Huaiyin Normal University, Huaian, Jiangsu 223300, P. R. China
| | - Xiangqian Li
- Jiangsu Provincial Engineering Laboratory for Biomass Conversion and Process Integration, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- School of Life Science and Chemical Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P. R. China
- * E-mail:
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Weiss PHE, Álvares ACM, Gomes AA, Miletti LC, Skoronski E, da Silva GF, de Freitas SM, Magalhães MLB. Beta glucosidase from Bacillus polymyxa is activated by glucose-6-phosphate. Arch Biochem Biophys 2015; 580:50-6. [PMID: 26116788 DOI: 10.1016/j.abb.2015.06.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/19/2015] [Accepted: 06/21/2015] [Indexed: 01/10/2023]
Abstract
Optimization of cellulose enzymatic hydrolysis is crucial for cost effective bioethanol production from lignocellulosic biomass. Enzymes involved in cellulose hydrolysis are often inhibited by their end-products, cellobiose and glucose. Efforts have been made to produce more efficient enzyme variants that are highly tolerant to product accumulation; however, further improvements are still necessary. Based on an alternative approach we initially investigated whether recently formed glucose could be phosphorylated into glucose-6-phosphate to circumvent glucose accumulation and avoid inhibition of beta-glucosidase from Bacillus polymyxa (BGLA). The kinetic properties and structural analysis of BGLA in the presence of glucose-6-phosphate (G6P) were investigated. Kinetic studies demonstrated that enzyme was not inhibited by G6P. In contrast, the presence of G6P activated the enzyme, prevented beta glucosidase feedback inhibition by glucose accumulation and improved protein stability. G6P binding was investigated by fluorescence quenching experiments and the respective association constant indicated high affinity binding of G6P to BGLA. Data reported here are of great impact for future design strategies for second-generation bioethanol production.
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Affiliation(s)
- Paulo H E Weiss
- Biochemistry Laboratory, Department of Food and Animal Production, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil
| | - Alice C M Álvares
- Biophysics Laboratory, Department of Cellular Biology, University of Brasília, Brasília 70910-900, Brazil
| | - Anderson A Gomes
- Water Treatment Laboratory, Department of Environmental Engineering, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil
| | - Luiz C Miletti
- Biochemistry Laboratory, Department of Food and Animal Production, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil
| | - Everton Skoronski
- Water Treatment Laboratory, Department of Environmental Engineering, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil
| | - Gustavo F da Silva
- Biochemistry Laboratory, Department of Food and Animal Production, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil
| | - Sonia M de Freitas
- Biophysics Laboratory, Department of Cellular Biology, University of Brasília, Brasília 70910-900, Brazil
| | - Maria L B Magalhães
- Biochemistry Laboratory, Department of Food and Animal Production, Center of Agroveterinary Sciences, State University of Santa Catarina, Lages, Santa Catarina 88520-000, Brazil.
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Identification and Characterization of Two Endogenous β-Glucosidases from the Termite Coptotermes formosanus. Appl Biochem Biotechnol 2015; 176:2039-52. [PMID: 26054618 DOI: 10.1007/s12010-015-1699-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 05/28/2015] [Indexed: 10/23/2022]
Abstract
Coptotermes formosanus is a well-known wood-feeding termite that can degrade lignocellulose polysaccharides efficiently with its unique multi-enzyme catalysis system. β-glucosidase (BG) is one of the important cellulases in its enzyme system. However, there may present multiple endogenous BGs in termite digestive system for various properties and functions. This study aims to characterize two BG homologs and reveal their potential coordinative effect. In this study, two endogenous BG homologs (CfGlu1B and CfGlu1C) from C. formosanus showed different substrate specificity. CfGlu1B favors cellobiose while CfGlu1C favors sucrose. Besides, CfGlu1C exhibited higher alkali resistance than CfGlu1B. Kinetic analysis revealed that CfGlu1B enzyme's activity toward p-NP-β-D-glucopyranoside (p-NPG) was higher than that of CfGlu1C, and the difference mainly attributes to the turnover number (K cat). In addition, the activity assay showed significant synergistic action of CfGlu1B and CfGlu1C in degrading D-lactosum. For effect of metals, Cu(2+) inhibited both enzymes and Ca(2+) increased the activity of CfGlu1C but not CfGlu1B. Site-directed mutagenesis analysis indicated that both enzymes lost activities when residues E190 of CfGlu1B and E168 of CfGlu1C were mutated to alanine, respectively, which were essential active centers of the GHF1 enzymes. Moreover, mutation H252N increased the activity of enzyme CfGlu1C by 2.1-fold. This study implies interesting possibilities for better practical biotechnological use in green energy production.
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Cao LC, Wang ZJ, Ren GH, Kong W, Li L, Xie W, Liu YH. Engineering a novel glucose-tolerant β-glucosidase as supplementation to enhance the hydrolysis of sugarcane bagasse at high glucose concentration. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:202. [PMID: 26628916 PMCID: PMC4666061 DOI: 10.1186/s13068-015-0383-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 11/16/2015] [Indexed: 05/02/2023]
Abstract
BACKGROUND Most β-glucosidases reported are sensitive to the end product (glucose), making it the rate limiting component of cellulase for efficient degradation of cellulose through enzymatic route. Thus, there are ongoing interests in searching for glucose-tolerant β-glucosidases, which are still active at high glucose concentration. Although many β-glucosidases with different glucose-tolerance levels have been isolated and characterized in the past decades, the effects of glucose-tolerance on the hydrolysis of cellulose are not thoroughly studied. RESULTS In the present study, a novel β-glucosidase (Bgl6) with the half maximal inhibitory concentration (IC 50) of 3.5 M glucose was isolated from a metagenomic library and characterized. However, its poor thermostability at 50 °C hindered the employment in cellulose hydrolysis. To improve its thermostability, random mutagenesis was performed. A thermostable mutant, M3, with three amino acid substitutions was obtained. The half-life of M3 at 50 °C is 48 h, while that of Bgl6 is 1 h. The K cat/K m value of M3 is 3-fold higher than that of Bgl6. The mutations maintained its high glucose-tolerance with IC 50 of 3.0 M for M3. In a 10-h hydrolysis of cellobiose, M3 completely converted cellobiose to glucose, while Bgl6 reached a conversion of 80 %. Then their synergistic effects with the commercial cellulase (Celluclast 1.5 L) on hydrolyzing pretreated sugarcane bagasse (SCB) were investigated. The supplementation of Bgl6 or mutant M3 to Celluclast 1.5 L significantly improved the SCB conversion from 64 % (Celluclast 1.5 L alone) to 79 % (Bgl6) and 94 % (M3), respectively. To further evaluate the application potential of M3 in high-solids cellulose hydrolysis, such reactions were performed at initial glucose concentration of 20-500 mM. Results showed that the supplementation of mutant M3 enhanced the glucose production from SCB under all the conditions tested, improving the SCB conversion by 14-35 %. CONCLUSIONS These results not only clearly revealed the significant role of glucose-tolerance in cellulose hydrolysis, but also showed that mutant M3 may be a potent candidate for high-solids cellulose refining.
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Affiliation(s)
- Li-chuang Cao
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Zhi-jun Wang
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Guang-hui Ren
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Wei Kong
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Liang Li
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Wei Xie
- />State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
| | - Yu-huan Liu
- />School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
- />South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, Sun Yat-sen University, Guangzhou, 510275 People’s Republic of China
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Xiao H, Bao Z, Zhao H. High Throughput Screening and Selection Methods for Directed Enzyme Evolution. Ind Eng Chem Res 2014; 54:4011-4020. [PMID: 26074668 PMCID: PMC4461044 DOI: 10.1021/ie503060a] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 02/08/2023]
Abstract
Successful
evolutionary enzyme engineering requires a high throughput
screening or selection method, which considerably increases the chance
of obtaining desired properties and reduces the time and cost. In
this review, a series of high throughput screening and selection methods
are illustrated with significant and recent examples. These high throughput
strategies are also discussed with an emphasis on compatibility with
phenotypic analysis during directed enzyme evolution. Lastly, certain
limitations of current methods, as well as future developments, are
briefly summarized.
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Affiliation(s)
- Han Xiao
- Department of Chemical and Biomolecular Engineering, Department of Biochemistry, and Departments of Chemistry and Bioengineering and Institute for Genomic Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Zehua Bao
- Department of Chemical and Biomolecular Engineering, Department of Biochemistry, and Departments of Chemistry and Bioengineering and Institute for Genomic Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Huimin Zhao
- Department of Chemical and Biomolecular Engineering, Department of Biochemistry, and Departments of Chemistry and Bioengineering and Institute for Genomic Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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Sahoo DK, Maiti IB. Biomass derived from transgenic tobacco expressing the Arabidopsis CESA3ixr1-2 gene exhibits improved saccharification. ACTA BIOLOGICA HUNGARICA 2014; 65:189-204. [PMID: 24873912 DOI: 10.1556/abiol.65.2014.2.7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Studies in Arabidopsis thaliana and Nicotiana tabacum L. variety Samsun NN demonstrated that expression of the CESA3 cellulose synthase gene that contains a point mutation, named ixr1-2, results in greater conversion of plant-derived cellulose to fermentable sugars. The present study was designed to examine the improved enzymatic saccharification efficiency of lignocellulosic biomass of tobacco plants expressing AtCESA3ixr1-2. Three-month-old AtCESA3ixr1-2 transgenic and wild-type tobacco plants (Nicotiana tabacum L. variety Samsun NN) were grown in the presence and absence of isoxaben. Biomass obtained from leaf, stem, and root tissues were analyzed for enzymatic saccharification rates. During enzymatic saccharification, 45% and 25% more sugar was released from transgenic leaf and stem samples, respectively, when compared to the wild-type samples. This gain in saccharification efficiency was achieved without chemical or heat pretreatment. Additionally, leaf and stem biomass from transgenic AtCESA3ixr1-2 requires a reduced amount of enzyme for saccharification compared to biomass from wild-type plants. From a practical standpoint, a similar strategy could be employed to introduce the mutated CESA into energy crops like poplar and switchgrass to improve the efficiency of biomass conversion.
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Affiliation(s)
- Dipak Kumar Sahoo
- University of Kentucky KTRDC, College of Agriculture, Food and Environment Lexington KY 40546-0236 USA
| | - Indu B Maiti
- University of Kentucky KTRDC, College of Agriculture, Food and Environment Lexington KY 40546-0236 USA
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Batra J, Mishra S. Organic solvent tolerance and thermostability of a β-glucosidase co-engineered by random mutagenesis. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.molcatb.2013.07.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fatehi P. Recent advancements in various steps of ethanol, butanol, and isobutanol productions from woody materials. Biotechnol Prog 2013; 29:297-310. [DOI: 10.1002/btpr.1688] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 11/30/2012] [Indexed: 01/24/2023]
Affiliation(s)
- Pedram Fatehi
- Chemical Engineering Dept.; Lakehead University; Thunder Bay ON Canada P7B5E1
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Liu M, Gu J, Xie W, Yu H. Directed co-evolution of an endoglucanase and a β-glucosidase in Escherichia coli by a novel high-throughput screening method. Chem Commun (Camb) 2013; 49:7219-21. [DOI: 10.1039/c3cc42485e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Mutations in the substrate entrance region of -glucosidase from Trichoderma reesei improve enzyme activity and thermostability. Protein Eng Des Sel 2012; 25:733-40. [DOI: 10.1093/protein/gzs073] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Goldsmith M, Tawfik DS. Directed enzyme evolution: beyond the low-hanging fruit. Curr Opin Struct Biol 2012; 22:406-12. [DOI: 10.1016/j.sbi.2012.03.010] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 03/14/2012] [Accepted: 03/14/2012] [Indexed: 12/26/2022]
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31
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You C, Percival Zhang YH. Easy preparation of a large-size random gene mutagenesis library in Escherichia coli. Anal Biochem 2012; 428:7-12. [PMID: 22659340 DOI: 10.1016/j.ab.2012.05.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 11/17/2022]
Abstract
A simple and fast protocol for the preparation of a large-size mutant library for directed evolution in Escherichia coli was developed based on the DNA multimers generated by prolonged overlap extension polymerase chain reaction (POE-PCR). This protocol comprised the following: (i) a linear DNA mutant library was generated by error-prone PCR or shuffling, and a linear vector backbone was prepared by regular PCR; (ii) the DNA multimers were generated based on these two DNA templates by POE-PCR; and (iii) the one restriction enzyme-digested DNA multimers were ligated to circular plasmids, followed by transformation to E. coli. Because the ligation efficiency of one DNA fragment was several orders of magnitude higher than that of two DNA fragments for typical mutant library construction, it was very easy to generate a mutant library with a size of more than 10(7) protein mutants per 50 μl of the POE-PCR product. Via this method, four new fluorescent protein mutants were obtained based on monomeric cherry fluorescent protein. This new protocol was simple and fast because it did not require labor-intensive optimizations in restriction enzyme digestion and ligation, did not involve special plasmid design, and enabled constructing a large-size mutant library for directed enzyme evolution within 1 day.
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Affiliation(s)
- Chun You
- Biological Systems Engineering Department, Virginia Tech, Blacksburg, VA 24061, USA
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Ye X, Zhang C, Zhang YHP. Engineering a large protein by combined rational and random approaches: stabilizing the Clostridium thermocellum cellobiose phosphorylase. MOLECULAR BIOSYSTEMS 2012; 8:1815-23. [DOI: 10.1039/c2mb05492b] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Camarillo-Cadena M, Garza-Ramos G, Peimbert M, Pérez-Hernández G, Zubillaga RA. Thermal denaturation of β-glucosidase B from Paenibacillus polymyxa proceeds through a Lumry-Eyring mechanism. Protein J 2011; 30:318-23. [PMID: 21626159 DOI: 10.1007/s10930-011-9334-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
β-glucosidase B (BglB), 1,4-β-D: -glucanohydrolase, is an enzyme with various technological applications for which some thermostable mutants have been obtained. Because BglB denatures irreversibly with heating, the stabilities of these mutants are assessed kinetically. It, therefore, becomes relevant to determine whether the measured rate constants reflect one or several elementary kinetic steps. We have analyzed the kinetics of heat denaturation of BglB from Paenibacillus polymyxa under various conditions by following the loss of secondary structure and enzymatic activity. The denaturation is accompanied by aggregation and an initial reversible step at low temperatures. At T ≥ T ( m ), the process follows a two-state irreversible mechanism for which the kinetics does not depend on the enzyme concentration. This behavior can be explained by a Lumry-Eyring model in which the difference between the rates of the irreversible and the renaturation steps increases with temperature. Accordingly, at high scan rates (≥1 °C min(-1)) or temperatures (T ≥ T ( m )), the measurable activation energy involves only the elementary step of denaturation.
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Zhang YHP. Simpler Is Better: High-Yield and Potential Low-Cost Biofuels Production through Cell-Free Synthetic Pathway Biotransformation (SyPaB). ACS Catal 2011. [DOI: 10.1021/cs200218f] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Y.-H. Percival Zhang
- Biological Systems Engineering Department, Virginia Tech, 210-A Seitz Hall, Blacksburg, Virginia 24061, United States
- Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech, Virginia 24061, United States
- DOE Bioenergy Science Center, Oak Ridge, Tennessee 37831, United States
- Gate Fuels Inc., 3107 Alice Dr., Blacksburg, Virginia 24060, United States
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Fusion of a family 9 cellulose-binding module improves catalytic potential of Clostridium thermocellum cellodextrin phosphorylase on insoluble cellulose. Appl Microbiol Biotechnol 2011; 92:551-60. [DOI: 10.1007/s00253-011-3346-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/02/2011] [Accepted: 05/03/2011] [Indexed: 10/18/2022]
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Pei XQ, Yi ZL, Tang CG, Wu ZL. Three amino acid changes contribute markedly to the thermostability of β-glucosidase BglC from Thermobifida fusca. BIORESOURCE TECHNOLOGY 2011; 102:3337-42. [PMID: 21129951 DOI: 10.1016/j.biortech.2010.11.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 11/06/2010] [Indexed: 05/07/2023]
Abstract
Thermostability of β-glucosidase was enhanced by family shuffling, site saturation mutagenesis, and site-directed mutagenesis. Family shuffling was carried out based on β-glucosidase BglC from Thermobifida fusca and β-glucosidase BglB from Paebibacillus polymxyxa with the help of synthetic primers. High-throughput screening revealed mutants with higher thermostability than both parental enzymes. The most thermostable mutant VM2 containing three key amino acid changes in L444Y/G447S/A433V had a 144-fold increase in half-life of inactivation as compared to the parental enzyme BglC. The mutant VM2 showed 28% and 94% increase in k(cat) towards p-nitrophenyl-β-D-glucopyranoside (pNPG) and cellobiose, respectively. The mutant with enhanced stability would facilitate the recycle of β-glucosidase in the bioconversion of cellulosic biomass.
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Affiliation(s)
- Xiao-Qiong Pei
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan, China
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Renewable Hydrogen Carrier — Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy. ENERGIES 2011. [DOI: 10.3390/en4020254] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Rollin JA, Zhu Z, Sathitsuksanoh N, Zhang YHP. Increasing cellulose accessibility is more important than removing lignin: A comparison of cellulose solvent-based lignocellulose fractionation and soaking in aqueous ammonia. Biotechnol Bioeng 2010; 108:22-30. [DOI: 10.1002/bit.22919] [Citation(s) in RCA: 268] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Dashtban M, Maki M, Leung KT, Mao C, Qin W. Cellulase activities in biomass conversion: measurement methods and comparison. Crit Rev Biotechnol 2010; 30:302-9. [DOI: 10.3109/07388551.2010.490938] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Yeoman CJ, Han Y, Dodd D, Schroeder CM, Mackie RI, Cann IKO. Thermostable enzymes as biocatalysts in the biofuel industry. ADVANCES IN APPLIED MICROBIOLOGY 2010; 70:1-55. [PMID: 20359453 DOI: 10.1016/s0065-2164(10)70001-0] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Lignocellulose is the most abundant carbohydrate source in nature and represents an ideal renewable energy source. Thermostable enzymes that hydrolyze lignocellulose to its component sugars have significant advantages for improving the conversion rate of biomass over their mesophilic counterparts. We review here the recent literature on the development and use of thermostable enzymes for the depolymerization of lignocellulosic feedstocks for biofuel production. Furthermore, we discuss the protein structure, mechanisms of thermostability, and specific strategies that can be used to improve the thermal stability of lignocellulosic biocatalysts.
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Affiliation(s)
- Carl J Yeoman
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
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Zhang YHP. Production of biocommodities and bioelectricity by cell-free synthetic enzymatic pathway biotransformations: challenges and opportunities. Biotechnol Bioeng 2010; 105:663-77. [PMID: 19998281 DOI: 10.1002/bit.22630] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cell-free synthetic (enzymatic) pathway biotransformation (SyPaB) is the assembly of a number of purified enzymes (usually more than 10) and coenzymes for the production of desired products through complicated biochemical reaction networks that a single enzyme cannot do. Cell-free SyPaB, as compared to microbial fermentation, has several distinctive advantages, such as high product yield, great engineering flexibility, high product titer, and fast reaction rate. Biocommodities (e.g., ethanol, hydrogen, and butanol) are low-value products where costs of feedstock carbohydrates often account for approximately 30-70% of the prices of the products. Therefore, yield of biocommodities is the most important cost factor, and the lowest yields of profitable biofuels are estimated to be ca. 70% of the theoretical yields of sugar-to-biofuels based on sugar prices of ca. US$ 0.18 per kg. The opinion that SyPaB is too costly for producing low-value biocommodities are mainly attributed to the lack of stable standardized building blocks (e.g., enzymes or their complexes), costly labile coenzymes, and replenishment of enzymes and coenzymes. In this perspective, I propose design principles for SyPaB, present several SyPaB examples for generating hydrogen, alcohols, and electricity, and analyze the advantages and limitations of SyPaB. The economical analyses clearly suggest that developments in stable enzymes or their complexes as standardized parts, efficient coenzyme recycling, and use of low-cost and more stable biomimetic coenzyme analogs, would result in much lower production costs than do microbial fermentations because the stabilized enzymes have more than 3 orders of magnitude higher weight-based total turn-over numbers than microbial biocatalysts, although extra costs for enzyme purification and stabilization are spent.
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Affiliation(s)
- Y-H Percival Zhang
- Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, 210-A Seitz Hall, Blacksburg, Virginia 24061, USA. USA.
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Liu W, Bevan DR, Zhang YHP. The family 1 glycoside hydrolase from Clostridium cellulolyticum H10 is a cellodextrin glucohydrolase. Appl Biochem Biotechnol 2009; 161:264-73. [PMID: 19816661 DOI: 10.1007/s12010-009-8782-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 09/15/2009] [Indexed: 11/27/2022]
Abstract
The only family 1 glycoside hydrolase in Clostridium cellulolyticum H10 (CcGH1) is annotated as a beta-galactosidase but has high sequence homology with many beta-glucosidases. Given the possible importance of beta-glucosidase in cellulose utilization by C. cellulolyticum, the encoding open reading frame Ccel_0374 was cloned and expressed in E. coli as a soluble fusion protein with thioredoxin. After tag cleavage, the purified enzyme had a molecular mass of 52 kDa and was active in dimeric form on a broad range of substrates, including cellobiose, cellotriose, cellotetraose, p-nitrophenyl-beta-glucopyranoside, lactose, and o-nitrophenyl-beta-galactopyranoside. The enzyme showed lower K(m) and higher catalytic efficiency (k (cat)/K(m)) on cellodextrins with degree of polymerization from 2 to 4 than on lactose, and the k (cat)/K (m) values on cellodextrins increased in the order of cellobiose < cellotriose < cellotetraose, suggesting that CcGH1 was a cellodextrin glucohydrolase (EC 3.2.1.74). The high K(m) (69 mM) on cellobiose implies that CcGH1 likely has a minimal role in the intracellular hydrolysis of cellobiose in C. cellulolyticum. The three-dimensional structure model of CcGH1 generated by homology modeling showed a typical (alpha/beta)(8) barrel topology characteristic of family 1 glycoside hydrolases.
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Affiliation(s)
- Wenjin Liu
- Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University, 210-A Seitz Hall, Blacksburg, VA 24061, USA
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Wang Y, Zhang YHP. Overexpression and simple purification of the Thermotoga maritima 6-phosphogluconate dehydrogenase in Escherichia coli and its application for NADPH regeneration. Microb Cell Fact 2009; 8:30. [PMID: 19497097 PMCID: PMC2701922 DOI: 10.1186/1475-2859-8-30] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 06/04/2009] [Indexed: 11/29/2022] Open
Abstract
Background Thermostable enzymes from thermophilic microorganisms are playing more and more important roles in molecular biology R&D and industrial applications. However, over-production of recombinant soluble proteins from thermophilic microorganisms in mesophilic hosts (e.g. E. coli) remains challenging sometimes. Results An open reading frame TM0438 from a hyperthermophilic bacterium Thermotoga maritima putatively encoding 6-phosphogluconate dehydrogenase (6PGDH) was cloned and expressed in E. coli. The purified protein was confirmed to have 6PGDH activity with a molecular mass of 53 kDa. The kcat of this enzyme was 325 s-1 and the Km values for 6-phosphogluconate, NADP+, and NAD+ were 11, 10 and 380 μM, respectively, at 80°C. This enzyme had half-life times of 48 and 140 h at 90 and 80°C, respectively. Through numerous approaches including expression vectors, hosts, cultivation conditions, inducers, and codon-optimization of the 6pgdh gene, the soluble 6PGDH expression levels were enhanced to ~250 mg per liter of culture by more than 500-fold. The recombinant 6PGDH accounted for >30% of total E. coli cellular proteins when lactose was used as a low-cost inducer. In addition, this enzyme coupled with glucose-6-phosphate dehydrogenase for the first time was demonstrated to generate two moles of NADPH per mole of glucose-6-phosphate. Conclusion We have achieved a more than 500-fold improvement in the expression of soluble T. maritima 6PGDH in E. coli, characterized its basic biochemical properties, and demonstrated its applicability for NADPH regeneration by a new enzyme cocktail. The methodology for over-expression and simple purification of this thermostable protein would be useful for the production of other thermostable proteins in E. coli.
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Affiliation(s)
- Yiran Wang
- Biological Systems Engineering Department, 210-A Seitz Hall, Virginia Polytechnic Institute and State University, Blacksburg, Virgina 24061, USA.
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Zhu Z, Sathitsuksanoh N, Percival Zhang YH. Direct quantitative determination of adsorbed cellulase on lignocellulosic biomass with its application to study cellulase desorption for potential recycling. Analyst 2009; 134:2267-72. [DOI: 10.1039/b906065k] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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