Acetotrophic Activity Facilitates Methanogenesis from LCFA at Low Temperatures: Screening from Mesophilic Inocula

Abstract

The inoculum source plays a crucial role in the anaerobic treatment of wastewaters. Lipids are present in various wastewaters and have a high methanogenic potential, but their hydrolysis results in the production of long chain fatty acids (LCFAs) that are inhibitory to anaerobic microorganisms. Screening of inoculum for the anaerobic treatment of LCFA-containing wastewaters has been performed at mesophilic and thermophilic conditions. However, an evaluation of inocula for producing methane from LCFA-containing wastewater has not yet been conducted at low temperatures and needs to be undertaken. In this study, three inocula (one granular sludge and two municipal digester sludges) were assessed for methane production from LCFA-containing synthetic dairy wastewater (SDW) at low temperatures (10 and 20°C). A methane yield (based on mL-CH4/g-CODadded) of 86-65% with acetate and 45-20% with SDW was achieved within 10 days using unacclimated granular sludge, whereas the municipal digester sludges produced methane only at 20°C but not at 10°C even after 200 days of incubation. The acetotrophic activity in the inoculum was found to be crucial for methane production from LCFA at low temperatures, highlighting the role of Methanosaeta (acetoclastic archaea) at low temperatures. The presence of bacterial taxa from the family Syntrophaceae (Syntrophus and uncultured taxa) in the inoculum was found to be important for methane production from SDW at 10°C. This study suggests the evaluation of acetotrophic activity and the initial microbial community characteristics by high-throughput amplicon sequencing for selecting the inoculum for producing methane at low temperatures (up to 10°C) from lipid-containing wastewaters.

The Geochemical Drivers of Bacterial Community Diversity in the Watershed Sediments of the Heihe River (Northern China)

“…Gelria is a thermophilic, anaerobic, obligately syntrophic, glutamate-degrading genus, usually found in granular sludge within anaerobic sludge bed reactors [53]. The genus Syntrophus (positively influenced by Al-p-value = 0.004, Fe-0.030, Cr-0.016, Ni-0.004, and Co-0.027) is responsible for methane production and was found to be correlated to Gelria for treating the mixed-LCFA (long-chain fatty acids) at low temperature in municipal wastewater plants [54]. Syntrophus-associated sequences have been identified in anoxic sediments and sewage sludge [48].…”

Biogas Production and Metagenomic Analysis in a New Hybrid Anaerobic Labyrinth-Flow Bioreactor Treating Dairy Wastewater

“…The abundance of Synergistates represents the same tendency as Actinobacteria (3% in V1, 3.9% in V3, and 1.3% in V5) (Figure 6). This phylum was dominated by Synergistia, to which belong syntrophic acido-and acetogens involved in amino acid fermentation [94]. Probably due to interspecies hydrogen transfer between Synergistia and methanogens, Nakasaki and co-workers [95] observed that the abundance of Synergistales highly correlated with the rate of methane production from oil during the anaerobic digestion for treatment of synthetic lipid-rich wastewater.…”

A review of nature-based solutions for resource recovery in cities

“…Dairy wastewaters contain lipids that are hydrolysed into long-chain fatty acids (LCFA) that may be inhibitory to anaerobic microorganisms. Anaerobic conversion of LCFAs to methane was reported for the first time at 10°C and 20°C (with lipid content of .1%) in batch bottles, where the role of acetoclastic methanogens from the genus Methanosaeta was highlighted (Singh et al 2019). In the pulp industry, recovery of chemicals from black liquor results in the production of condensates that contain methanol up to 46 g/L.…”