Long-chain fatty acid feeding frequency in anaerobic codigestion impacts syntrophic community structure and biokinetics

Abstract

This study investigated the impacts of long-chain fatty acid (LCFA) feeding frequencies on microbial community structure, bioconversion kinetics, and process stability during anaerobic codigestion. Parallel laboratory-scale anaerobic codigesters fed with dairy cattle manure were either pulse-fed every two days or continuously-fed daily, respectively, with oleate (C) in incremental step increases over 200 days up to 64% of the influent chemical oxygen demand (COD). The effluent acetate concentration exceeded 3000 mg/L in the continuous-fed codigester at the highest oleate loading rate, but remained below 100 mg/L in the pulse-fed codigester at the end of its 48-hr oleate feed cycle. Maximum substrate conversion rates of oleate (q) and acetate (q) were significantly higher in the pulse-fed codigester compared to the continuous-fed codigester. 16S rRNA gene amplicon sequencing showed that Bacteria and Archaea community profiles diverged based on the codigester LCFA feeding pattern and loading rate. LCFA-degrading Syntrophomonas bacteria were significantly enriched in both LCFA codigesters relative to the control digester. The pulse-fed codigester had the highest community fraction of Syntrophomonas 16S rRNA genes by the end of the experiment with 43% of Bacteria amplicon sequences. q and q values were both significantly correlated to absolute concentrations of Syntrophomonas and Methanosaeta 16S rRNA genes, respectively. Multiple-linear regression models based on the absolute abundance of Syntrophomonas and Methanosaeta taxa provided improved predictions of oleate and acetate bioconversion kinetics, respectively. These results collectively suggest that pulse feeding rather than continuous feeding LCFA during anaerobic codigestion selected for higher microbial bioconversion kinetics and functional stability, which were related to changes in the physiological diversity and adaptive capacity of syntrophic and methanogenic communities.

Microbial rRNA gene expression and co‐occurrence profiles associate with biokinetics and elemental composition in full‐scale anaerobic digesters

“…S3). Higher concentrations of Syntrophomonas have previously been correlated with higher degradation rates of LCFA in anaerobic digestion (Ziels et al ., , , ). Recently, 16S rRNA gene expression of Syntrophomonas was correlated with methane production from LCFA‐rich waste (Amha et al ., ).…”

“…S4). Lower Hill numbers with codigestion have been observed in prior works (Ziels et al ., ) and may be caused by the enrichment of specialized microorganisms on influent substrates with certain organic matter compositions. Higher diversity in the SS digesters could also have been attributed to immigration of populations from the PS+WAS feed source, as was shown to occur in other biological wastewater treatment processes (Wells et al ., ).…”

“…The high representation of syntrophs and methanogens in the co‐occurrence network may also be attributed to their metabolic specialization (Sieber et al ., ), suggesting that their ecological niches are not easily filled by other taxa (Werner et al ., ). Yet, recent work has shown high strain variability within digester syntrophic communities under different feeding strategies (Ziels et al ., , ), indicating that selective forces may still govern the syntrophic community structure in different digester environments.…”

“…Many factors can impact the digester efficiency as well as the microbial community structure, such as temperature (De Vrieze et al, 2015;Westerholm et al, 2015), the hydraulic and solids retention times (Lee et al, 2011;Hao et al, 2016), salinity (De Vrieze et al, 2016b), free ammonia (Westerholm et al, 2015), feeding regime (Conklin et al, 2006;De Vrieze et al, 2013;Mulat et al, 2016;Ziels et al, 2017) and micronutrients (Karlsson et al, 2012). Among these important parameters, macroand micronutrient levels are gaining attention because they are necessary for many biological and enzymemediated processes in methanogenic communities, and they can be controlled via supplementation (Demirel and Scherer, 2011).…”

Effect of Temperature on Biohydrogen and Biomethane Productions by Anaerobic Digestion of Sugar Beet by-Products

“…Among the intermediates compounds of the anaerobic digestion process, long chain fatty acids (LCFAs) could be found. It should be noted that LCFAs present an inhibitory effect on the process, particularly for methanogens and acetogens [17], [18]. Fig.…”