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The presence of lignocellulose-derived microbial inhibitory compounds (LDMICs) in lignocellulosic biomass (LB) hydrolysates is a barrier to efficient conversion of LB hydrolysates to fuels and chemicals by fermenting microorganisms. Results from this study provide convincing evidence regarding the effectiveness of metabolically engineered C. beijerinckii NCIMB 8052 for the fermentation of LB-derived hydrolysates to acetone–butanol–ethanol (ABE). The engineered microbial strain ( C. beijerinckii _SDR) was produced by the integration of an additional copy of a short-chain dehydrogenase/reductase (SDR) gene ( Cbei_ 3904) into the chromosome of C. beijerinckii NCIMB 8052 wildtype, where it is controlled by the constitutive thiolase promoter. The C. beijerinckii _SDR and C. beijerinckii NCIMB 8052 wildtype were used for comparative fermentation of non-detoxified and detoxified hydrothermolysis-pretreated switchgrass hydrolysates (SHs) with and without (NH 4 ) 2 CO 3 supplementation. In the absence of (NH 4 ) 2 CO 3 , fermentation of non-detoxified SH with C. beijerinckii _SDR resulted in the production of 3.13- and 2.25-fold greater quantities of butanol (11.21 g/L) and total ABE (20.24 g/L), respectively, than the 3.58 g/L butanol and 8.98 g/L ABE produced by C. beijerinckii _wildtype. When the non-detoxified SH was supplemented with (NH 4 ) 2 CO 3 , concentrations were similar for butanol (9.5 compared with 9.2 g/L) and ABE (14.2 compared with 13.5 g/L) produced by C. beijerinckii _SDR and C. beijerinckii _wildtype, respectively. Furthermore, when C. beijerinckii _SDR and C. beijerinckii _wildtype were cultured in detoxified SH medium, C. beijerinckii _SDR produced 1.11- and 1.18-fold greater quantities of butanol and ABE, respectively, than when there was culturing with C. beijerinckii _wildtype. When the combined results of the present study are considered, conclusions are that the microbial strain and medium modifications of the fermentation milieu resulted in greater production of fuels and chemicals from non-detoxified LB hydrolysates.
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Chromosomal integration of aldo-keto-reductase and short-chain dehydrogenase/reductase genes in Clostridium beijerinckii NCIMB 8052 enhanced tolerance to lignocellulose-derived microbial inhibitory compounds
Abstract In situdetoxification of lignocellulose-derived microbial inhibitory compounds is an economical strategy for the fermentation of lignocellulose-derived sugars to fuels and chemicals. In this study, we investigated homologous integration and constitutive expression ofCbei_3974 andCbei_3904, which encode aldo-keto reductase and previously annotated short chain dehydrogenase/reductase, respectively, inClostridium beijerinckiiNCIMB 8052 (Cb), resulting in two strains:Cb_3974 andCb_3904. Expression ofCbei_3974 led to 2-fold increase in furfural detoxification relative toCb_3904 andCb_wild type. Correspondingly, butanol production was up to 1.2-fold greater in furfural-challenged cultures ofCb_3974 relative toCb_3904 andCb_wild type. With 4-hydroxybezaldehyde and syringaldehyde supplementation,Cb_3974 showed up to 2.4-fold increase in butanol concentration when compared toCb_3904 andCb_wild type. Syringic and vanillic acids were considerably less deleterious to all three strains ofCbtested. Overall,Cb_3974 showed greater tolerance to furfural, 4-hydroxybezaldehyde, and syringaldehyde with improved capacity for butanol production. Hence, development ofCb_3974 represents a significant progress towards engineering solventogenicClostridiumspecies that are tolerant to lignocellulosic biomass hydrolysates as substrates for ABE fermentation.
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- Award ID(s):
- 1803022
- PAR ID:
- 10153922
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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