Combining chain elongation and oleogel extraction for the production and recovery of caproate from beef cattle manure wastewater

Abstract

Producing and recovering bioproducts from organic wastes is vital for building a circular economy. Livestock waste can serve as a feedstock for bioproduct production, such as medium chain carboxylic acids (MCCAs). This study aims to (1) optimize the conversion of organics in beef cattle manure to caproate and (2) develop an innovative oleogel-based extraction method for caproate recovery. With intrinsic chain elongation bacteria in cattle manure, we achieved a maximum caproate production rate of 8.59 g/L/d and the maximum concentration of 11.09 g/L with ethanol as the electron donor. Chain elongators such as Clostridium, Eubacterium, Caproiciproducens were detected. Oleogel beads were fabricated and enabled high mass transfer rates, achieving a cumulative caproate extraction efficiency of 87.39±0.96 % in 180 min. In subsequent desorption process, caproate accounted for 86.18±0.32 % of all carboxylic acids and alcohols desorbed from oleogel beads. This study demonstrates the technical feasibility of producing bioproducts from an abundant agricultural waste.