Lignocellulose solubilization and conversion by extremely thermophilic Caldicellulosiruptor bescii improves by maintaining metabolic activity.

Authors:
Christopher T Straub
Christopher T Straub
North Carolina State University Raleigh
Raleigh | United States
Piyum A Khatibi
Piyum A Khatibi
Virginia Polytechnic Institute and State University
United States
Michael W W Adams
Michael W W Adams
Korey Stringer Institute
Robert M Kelly
Robert M Kelly
North Carolina State University

Biotechnol Bioeng 2019 Apr 14. Epub 2019 Apr 14.

Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina.

The extreme thermophile Caldicellulosiruptor bescii solubilizes and metabolizes the carbohydrate content of lignocellulose, a process that ultimately ceases because of biomass recalcitrance, accumulation of fermentation products, inhibition by lignin moieties, and reduction of metabolic activity. Deconstruction of low loadings of lignocellulose (5 g/L), either natural or transgenic, whether unpretreated or subjected to hydrothermal processing, by C. bescii typically results in less than 40% carbohydrate solubilization. Mild alkali pretreatment (up to 0.09 g NaOH/g biomass) improved switchgrass carbohydrate solubilization by C. bescii to over 70% compared to less than 30% for no pretreatment, with two-thirds of the carbohydrate content in the treated switchgrass converted to acetate and lactate. C. bescii grown on high loadings of unpretreated switchgrass (50 g/L) retained in a pH-controlled bioreactor slowly purged (τ = 80 hr) with growth media without a carbon source improved carbohydrate solubilization to over 40% compared to batch culture at 29%. But more significant was the doubling of solubilized carbohydrate conversion to fermentation products, which increased from 40% in batch to over 80% in the purged system, an improvement attributed to maintaining the bioreactor culture in a metabolically active state. This strategy should be considered for optimizing solubilization and conversion of lignocellulose by C. bescii and other lignocellulolytic microorganisms.

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http://dx.doi.org/10.1002/bit.26993DOI Listing
April 2019
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References

(Supplied by CrossRef)
Thermophilic lignocellulose deconstruction
Blumer‐Schuette S. E. et al.
FEMS Microbiology Reviews 2014
Direct conversion of plant biomass to ethanol by engineered Caldicellulosiruptor bescii
Chung D. et al.
Proceedings of the National Academy of Sciences of the USA 2014

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