Semi-continuous fermentation of unpretreated corn stover in a novel high solids bioreactor by a coculture of Clostridium thermocellum and Thermoanaerobacterium thermosaccharolyticum.

Thermophilic anaerobic bacteria have potential for production of fuels and chemicals from cellulosic biomass via one-step consolidated bioprocessing (CBP) without added enzymes. Studies of thermophilic CBP have thus far featured solids loadings at or below the maximum levels practical in batch culture, which are about half that required for economic viability in stand-alone plants. Moreover, a "solids effect" consisting of a pronounced decline in fractional carbohydrate solubilization with increasing solids loading has been observed for thermophilic CBP in batch mode. This study reports a lab-scale fermentation system capable of semi-continuous, aseptic, metered feeding of moist biomass, believed to be the first such system described in the literature. This system was used to establish semi-continuously fed co-cultures of Clostridium thermocellum and Thermoanaerobacterium thermosaccharolyticum fermenting unpretreated corn stover for periods of up to 10 residence times. Replicate steady state cocultures, one fed 30 g stover/L at a 72-hour residence time and one fed 120 g stover/L at a 48-hour residence time, exhibited similar fractional carbohydrate solubilization at 0.640 ± 0.021 and 0.601 ± 0.025 respectively. The volumetric rate of carbohydrate solubilization (Cs) of 0.856 g/L/h observed at 120 g/L solids loading is to our knowledge the highest reported thus far for a cellulosic feedstock fermented by a defined culture and approaches rates seen for the rumen. Cs divided by the solids loading decreased markedly with increasing solids loading for batch cocultures but not for semi-continuous cocultures, suggesting that the "solids effect" may be avoided by continuous cultivation.

• Publication year

  2025

• Venue

  Bioresource Technology

• Publication date

  2025-09-01

• Fields of study

  Medicine, Engineering, Environmental Science

• Identifiers
  DOI 10.1016/j.biortech.2025.133309PMID 40972838
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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