Consolidated bioprocessing (CBP), which merges enzyme production, biomass hydrolysis, and fermentation into a single step, has the potential to become an efficient and economic strategy for the bioconversion of lignocellulosic feedstocks to transportation fuels or chemicals. In this study, we evaluated <
i>
Clostridium thermocellum<
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, <
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Caldicellulosiruptor bescii<
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, and <
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Caldicellulosiruptor obsidiansis<
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, three , thermophilic,cellulolytic, mixed-acid fermenting candidate CBP microorganisms, for their fermentation capabilities using dilute acid pretreated <
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Populus<
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as a model biomass feedstock. Under pH controlled, anaerobic fermentation conditions, each candidate successfully digested a minimum of 75% of the cellulose from dilute acid pretreated <
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Populus<
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, as indicated by an increase in planktonic cells and end-product metabolites and a concurrent decrease in glucan content. <
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C. thermocellum<
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, which employs a cellulosomal approach to biomass degradation, required 120 hours to achieve 75% cellulose utilization. In contrast, the non-cellulosomal, secreted hydrolytic enzyme system of the <
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Caldicellulosiruptor<
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sp. required 300 hours to achieve similar results. End-point fermentation conversions for <
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C. thermocellum<
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, <
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C. bescii<
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, and <
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C. obsidiansis<
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were determined to be 0.29, 0.34, and 0.38 grams of total metabolites per gram of loaded glucan, respectively. This data provide a starting point for future strain engineering efforts that can serve to improve the biomass fermentation capabilities of these three promising candidate CBP platforms.