US scientists have used beer fermentation broth to upgrade ethanol to higher value products for the fuel industry, rather than distilling the ethanol itself.
Distilling ethanol in the biofuel industry is energetically expensive because ethanol is completely miscible in water. So, the team decided to upgrade it into a hydrophobic chemical that’s easier to separate, and of higher value.
They did it by shaping a reactor microbiome to sequentially elongate carboxylic acids with 2-carbon units from dilute ethanol in yeast fermentation beer. The continuous bioprocess produced n-caproic acid, a 6-carbon chain carboxylic acid that’s more valuable than ethanol.
In-line product extraction achieved an n-caproic acid production rate exceeding two grams per litre of reactor volume per day, which is comparable to established bioenergy systems with microbiomes, they say. Incorporation of other organics found in beer increased the mass of carbon in n-caproic acid by 10% compared to ethanol, they add.
Read this ‘HOT’ EES Communication:
Chain elongation with reactor microbiomes: upgrading dilute ethanol to medium-chain carboxylates
Matthew T Agler, Catherine M Spirito, Joseph G Usack, Jeffrey J Werner and Lars Angenent
Energy Environ. Sci., 2012, DOI: 10.1039/C2EE22101B
