Archaeal and Bacterial Content in a Two-Stage Anaerobic System for Efficient Energy Production from Agricultural Wastes

Abstract

Anaerobic digestion (AD) is a microbially-driven process enabling energy production. Microorganisms are the core of anaerobic digesters and play an important role in the succession of hydrolysis, acidogenesis, acetogenesis, and methanogenesis processes. The diversity of participating microbial communities can provide new information on digester performance for biomass valorization and biofuel production. In this study anaerobic systems were used, operating under mesophilic conditions that realized biodegradation processes of waste wheat straw pretreated with NaOH—a renewable source for hydrogen and methane production. These processes could be managed and optimized for hydrogen and methane separately but combining them in a two-stage system can lead to higher yields and a positive energy balance. The aim of the study was to depict a process of biohydrogen production from lignocellulosic waste followed by a second one leading to the production of biomethane. Archaeal and bacterial consortia in a two-stage system operating with wheat straw were identified for the first time and the role of the most important representatives was elucidated. The mixed cultures were identified by the molecular-biological methods of metagenomics. The results showed that biohydrogen generation is most probably due to the presence of Proteiniphilum saccharofermentans, which was 28.2% to 45.4% of the microbial community in the first and the second bioreactor, respectively. Archaeal representatives belonging to Methanobacterium formicicum (0.71% of the community), Methanosarcina spelaei (0.03%), Methanothrix soehngenii (0.012%), and Methanobacterium beijingense (0.01%) were proven in the methane-generating reactor. The correlation between substrate degradation and biogas accumulation was calculated, together with the profile of fatty acids as intermediates produced during the processes. The hydrogen concentration in the biogas reached 14.43%, and the Methane concentration was 69%. Calculations of the energy yield during the two-stage process showed 1195.89 kWh·t−1 compared to a 361.62 kWh·t−1 cumulative yield of energy carrier for a one-stage process.

Evaluating the performance of an integrated membrane-aerated biofilm reactor (MABR) system for high-strength brewery wastewater treatment

“…39 On the other hand, Prevotella , Caproiciproducens and Ruminiclostridium were found to be beneficial together for the degradation of polysaccharides and protein, such as cellulose and hemicellulose and contribute to the acidification process. 40–42 Taken together, these results suggested that the above-mentioned genera preferred to live in high strength wastewater and were the key degraders in biofilms under anaerobic conditions, which was inconsistent with their highly positive associations with COD loading rate and influent COD concentration as identified by the CCA analysis (Fig. 6a).…”

Biogas Production Potential of Thermophilic Anaerobic Biodegradation of Organic Waste by a Microbial Consortium Identified with Metagenomics

“…Stage-specific bacterial and archaeal populations were found to reside in thermophilic or mesophilic AD bioreactors [ 55 ]. Several metagenomic studies revealed high functional redundancy in AD bioreactors [ 56 ], explained by taxonomic variations under certain changing operational conditions, while biogas production remained relatively stable.…”

Implications of a short carbon pulse on biofilm formation on mica schist in microcosms with deep crystalline bedrock groundwater

“…However, no methane usage-related genes have been described in Proteiniphilum genomes, and it is not considered a methanotroph ( Wu et al, 2021 ). Instead, Proteiniphilum has been shown to produce acetate, formate, and multiple volatiles, as well as a variety of extracellular enzymes ( Kabaivanova et al, 2022 ). Similarly, analysis of our previous mica schist-derived Proteiniphilum MAG (OKU04) suggested the genetic potential for a wide enzyme pool and the potential for acetogenesis and nitric oxide reduction in the deep subsurface ( Nuppunen-Puputti et al, 2022 ).…”