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Increasing the Conversion Efficiency of Biomass Into n-caproate With Reactor Microbiomes


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We envision producing medium-chain carboxylic acids from organic feed stocks with open cultures of microbial consortia (reactor microbiomes) via a bioprocess that is called chain elongation. Our vision is based on the carboxylate platform and combines two fermentation steps into one bioprocess: 1. producing short-chain carboxylic acids from variable feed stocks; 2. chain elongating these acids into hydrophobic, extractable medium-chain carboxylic acids (n-caproic acid and n-caprylic acid). We proposed three different objectives:1. To understand how hydrogen partial pressures can influence the production efficiencies of n-caproic acid at mesophilic temperatures; 2.To investigate whether changes in the hydrogen partial pressures alter the microbiome composition; and 3. To ascertain if reactor microbiomes that operate at thermophilic temperatures can produce n-caproic acid at sufficient rates. We found that hydrogen gas did influence the production rates of medium-chain carboxylic acids, and therefore also likely the microbiome (analysis still in progress), but that a higher temperature would not be advisable. At a lower temperature of 30 degrees C we found that lactic acid was converted efficientlyt o n-caproic acid in a continuously fed bioreactor that was operated at mildly acid conditions and with product extraction. This is opening the way to chain elongation with lactic acid.



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