1
|
Chou KJ, Croft T, Hebdon SD, Magnusson LR, Xiong W, Reyes LH, Chen X, Miller EJ, Riley DM, Dupuis S, Laramore KA, Keller LM, Winkelman D, Maness PC. Engineering the cellulolytic bacterium, Clostridium thermocellum, to co-utilize hemicellulose. Metab Eng 2024; 83:193-205. [PMID: 38631458 DOI: 10.1016/j.ymben.2024.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 03/15/2024] [Accepted: 03/29/2024] [Indexed: 04/19/2024]
Abstract
Consolidated bioprocessing (CBP) of lignocellulosic biomass holds promise to realize economic production of second-generation biofuels/chemicals, and Clostridium thermocellum is a leading candidate for CBP due to it being one of the fastest degraders of crystalline cellulose and lignocellulosic biomass. However, CBP by C. thermocellum is approached with co-cultures, because C. thermocellum does not utilize hemicellulose. When compared with a single-species fermentation, the co-culture system introduces unnecessary process complexity that may compromise process robustness. In this study, we engineered C. thermocellum to co-utilize hemicellulose without the need for co-culture. By evolving our previously engineered xylose-utilizing strain in xylose, an evolved clonal isolate (KJC19-9) was obtained and showed improved specific growth rate on xylose by ∼3-fold and displayed comparable growth to a minimally engineered strain grown on the bacteria's naturally preferred substrate, cellobiose. To enable full xylan deconstruction to xylose, we recombinantly expressed three different β-xylosidase enzymes originating from Thermoanaerobacterium saccharolyticum into KJC19-9 and demonstrated growth on xylan with one of the enzymes. This recombinant strain was capable of co-utilizing cellulose and xylan simultaneously, and we integrated the β-xylosidase gene into the KJC19-9 genome, creating the KJCBXint strain. The strain, KJC19-9, consumed monomeric xylose but accumulated xylobiose when grown on pretreated corn stover, whereas the final KJCBXint strain showed significantly greater deconstruction of xylan and xylobiose. This is the first reported C. thermocellum strain capable of degrading and assimilating hemicellulose polysaccharide while retaining its cellulolytic capabilities, unlocking significant potential for CBP in advancing the bioeconomy.
Collapse
Affiliation(s)
- Katherine J Chou
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA.
| | - Trevor Croft
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Skyler D Hebdon
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Lauren R Magnusson
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Wei Xiong
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Luis H Reyes
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA; Grupo de Diseño de Productos y Procesos, Department of Chemical and Food Engineering, Universidad de los Andes, Bogotá, Colombia
| | - Xiaowen Chen
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Emily J Miller
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Danielle M Riley
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Sunnyjoy Dupuis
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Kathrin A Laramore
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Lisa M Keller
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Dirk Winkelman
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| | - Pin-Ching Maness
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO, 80228, USA
| |
Collapse
|
2
|
Akdemir H, Liu Y, Zhuang L, Zhang H, Koffas MAG. Utilization of microbial cocultures for converting mixed substrates to valuable bioproducts. Curr Opin Microbiol 2022; 68:102157. [DOI: 10.1016/j.mib.2022.102157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/26/2022] [Accepted: 04/21/2022] [Indexed: 11/03/2022]
|
3
|
Biorefinery Gets Hot: Thermophilic Enzymes and Microorganisms for Second-Generation Bioethanol Production. Processes (Basel) 2021. [DOI: 10.3390/pr9091583] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with feed production. For this reason, lignocellulosic biomasses (LCBs) have been recognized as important alternatives for bioethanol production. Because LCBs supply is sustainable, abundant, widespread, and cheap, LCBs-derived bioethanol currently represents one of the most viable solutions to meet the global demand for liquid fuel. However, the cost-effective conversion of LCBs into ethanol remains a challenge and its implementation has been hampered by several bottlenecks that must still be tackled. Among other factors related to the challenging and variable nature of LCBs, we highlight: (i) energy-demanding pretreatments, (ii) expensive hydrolytic enzyme blends, and (iii) the need for microorganisms that can ferment mixed sugars. In this regard, thermophiles represent valuable tools to overcome some of these limitations. Thus, the aim of this review is to provide an overview of the state-of-the-art technologies involved, such as the use of thermophilic enzymes and microorganisms in industrial-relevant conditions, and to propose possible means to implement thermophiles into second-generation ethanol biorefineries that are already in operation.
Collapse
|