Mixed Acid Fermentation of Carbohydrate-Rich Dairy Manure Hydrolysate

Abstract

Dairy manure (DM) is an abundant agricultural residue that is largely composed of lignocellulosic biomass. The aim of this study was to investigate if carbon derived from DM fibers can be recovered as medium-chain fatty acids (MCFAs), which are mixed culture fermentation products of economic interest. DM fibers were subjected to combinations of physical, enzymatic, chemical, and thermochemical pretreatments to evaluate the possibility of producing carbohydrate-rich hydrolysates suitable for microbial fermentation by mixed cultures. Among the pretreatments tested, decrystalization dilute acid pretreatment (DCDA) produced the highest concentrations of glucose and xylose, and was selected for further experiments. Bioreactors fed DCDA hydrolysate were operated. Acetic acid and butyric acid comprised the majority of end products during operation of the bioreactors. MCFAs were transiently produced at a maximum concentration of 0.17 mg CODMCFAs/mg CODTotal. Analyses of the microbial communities in the bioreactors suggest that lactic acid bacteria, Megasphaera, and Caproiciproducens were involved in MCFA and C4 production during DCDA hydrolysate metabolism.

Thermophilic caproic acid production from grass juice by sugar-based chain elongation

“…It is also described that mesophilic chain elongators like Caproicibacterium lactatifermentans (Wang et al, 2022) can often use both sugars and lactic acid as substrates. A similar observation was made by Ingle et al (2021), where during fermentation of hydrolyzed dairy manure under mesophilic conditions (35°C, pH 5.0) lactic acid was first produced and subsequently consumed together with the remaining sugars, and the abundance of Caproiciproducens (and Clostridium_sensu_stricto_12) was positively correlated with butyric acid production.…”

Metagenome-Assembled Genomes from a Microbiome Grown in Dairy Manure Hydrolysate

“…We are investigating microbial fermentation to valorize agroindustrial residues ( 1 – 5 ). Previously, we reported on the fermentation product profile produced when feeding dairy manure (DM) hydrolysate to an anaerobic bioreactor ( 3 ), and here, we report on the microbial community. The bioreactor was inoculated with acid-phase anaerobic digester sludge from the Nine Springs Wastewater Treatment Plant (Madison, WI, USA) ( 2 – 5 ).…”

“…Previously, we reported on the fermentation product profile produced when feeding dairy manure (DM) hydrolysate to an anaerobic bioreactor ( 3 ), and here, we report on the microbial community. The bioreactor was inoculated with acid-phase anaerobic digester sludge from the Nine Springs Wastewater Treatment Plant (Madison, WI, USA) ( 2 – 5 ). DNA was extracted from the inoculum and at multiple time points during bioreactor operation using a phenol-chloroform extraction method ( 4 ) that excluded a bead-beating step so that the DNA fragment lengths were appropriate for long-read sequencing.…”

Metagenomes and Metagenome-Assembled Genomes from Microbiomes Metabolizing Thin Stillage from an Ethanol Biorefinery

“…We are investigating how to use anaerobic microbial communities for valorizing agroindustrial residues ( 1 – 5 ). We reported on fermentation products when thin stillage (TS) from starch bioethanol production was fed to a set of bioreactors ( 4 ).…”