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Title: Cellulosic ethanol production via consolidated bioprocessing at 75 °C by engineered Caldicellulosiruptor bescii

Journal Article · · Biotechnology for Biofuels

In this paper, we report that the C. bescii genome does not encode an acetaldehyde/alcohol dehydrogenase or an acetaldehyde dehydrogenase and no ethanol production is detected in this strain. The recent introduction of an NADH-dependent AdhE from C. thermocellum (Fig. 1a) in an ldh mutant of this strain resulted in production of ethanol from un-pretreated switchgrass, but the thermolability of the C. thermocellum AdhE at the optimum growth temperature of C. bescii (78 °C) meant that ethanol was not produced above 65 °C. The adhB and adhE genes from Thermoanaerobacter pseudethanolicus 39E, an anaerobic thermophile that produces ethanol as a major fermentation product at 70 °C, were cloned and expressed in an ldh deletion mutant of C. bescii. The engineered strains produced ethanol at 75 °C, near the ethanol boiling point. The AdhB expressing strain produced ethanol (1.4 mM on Avicel, 0.4 mM on switchgrass) as well as acetate (13.0 mM on Avicel, 15.7 mM on switchgrass). The AdhE expressing strain produced more ethanol (2.3 mM on Avicel, 1.6 mM on switchgrass) and reduced levels of acetate (12.3 mM on Avicel, 15.1 mM on switchgrass). These engineered strains produce cellulosic ethanol at the highest temperature of any microorganism to date. In addition, the addition of 40 mM MOPS to the growth medium increased the maximal growth yield of C. bescii by approximately twofold. In conclusion, the utilization of thermostable enzymes will be critical to achieving high temperature CBP in bacteria such as C. bescii. The ability to produce ethanol at 75 °C, near its boiling point, raises the possibility that process optimization could allow in situ product removal of this end product to mitigate ethanol toxicity.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1618875
Alternate ID(s):
OSTI ID: 1260585; OSTI ID: 1324147
Journal Information:
Biotechnology for Biofuels, Journal Name: Biotechnology for Biofuels Vol. 8 Journal Issue: 1; ISSN 1754-6834
Publisher:
Springer Science + Business MediaCopyright Statement
Country of Publication:
Netherlands
Language:
English
Citation Metrics:
Cited by: 32 works
Citation information provided by
Web of Science

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Cited By (11)

Engineering microbes for direct fermentation of cellulose to bioethanol journal February 2018
Expression of benzoyl-CoA metabolism genes in the lignocellulolytic host Caldicellulosiruptor bescii journal May 2019
Vapor-fed bio-hybrid fuel cell journal March 2017
An iterative computational design approach to increase the thermal endurance of a mesophilic enzyme journal July 2018
Rex in Caldicellulosiruptor bescii : Novel regulon members and its effect on the production of ethanol and overflow metabolites journal April 2018
Genomic and physiological analyses reveal that extremely thermophilic Caldicellulosiruptor changbaiensis deploys uncommon cellulose attachment mechanisms journal August 2019
Ethanol production by the hyperthermophilic archaeon Pyrococcus furiosus by expression of bacterial bifunctional alcohol dehydrogenases journal February 2017
A Highly Thermostable Kanamycin Resistance Marker Expands the Tool Kit for Genetic Manipulation of Caldicellulosiruptor bescii journal May 2016
Heterologous expression of family 10 xylanases from Acidothermus cellulolyticus enhances the exoproteome of Caldicellulosiruptor bescii and growth on xylan substrates journal August 2016
Gene targets for engineering osmotolerance in Caldicellulosiruptor bescii journal March 2020
Utilizing Anaerobic Fungi for Two-stage Sugar Extraction and Biofuel Production from Lignocellulosic Biomass journal April 2017


Figures / Tables (7)