Biology subjects

Kougias, P. G.

Publications and source records attributed to Kougias, P. G..

2 recordsLinked to original sources

bioRxiv2023

Bioaugmentation strategies based on bacterial and methanogenic cultures to relieve stress in anaerobic digestion of protein-rich substrates

Anaerobic co-digestion of protein-rich substrates is a prominent strategy for converting valuable feedstocks into methane, but it releases ammonia, which can inhibit methanogenesis. This study developed a cutting-edge combined culturomic and metagenomic approach to investigate the microbial composition of an ammonia-tolerant biogas plant. Newly-isolated microorganisms were used for bioaugmentation of stressed batch reactors fed with casein, maize silage and their combination. A co-culture enriched with proteolytic bacteria was isolated, selected and compared with the proteolytic collection strain Pseudomonas lundensis DSM6252. The co-culture and P. lundensis were combined with the ammonia-resistant archaeon Methanoculleus bourgensis MS2 to boost process stability. A microbial population pre-adapted to casein was also tested for evaluating the digestion of protein-rich feedstock. The promising results suggest combining proteolytic bacteria and M. bourgensis could exploit microbial co-cultures to improve anaerobic digestion stability and ensure stable productivity even under the harshest of ammonia conditions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/571062v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@623848org.highwire.dtl.DTLVardef@5d2311org.highwire.dtl.DTLVardef@a95f70org.highwire.dtl.DTLVardef@1b8beb6_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- High ammonia release from protein-rich substrates inhibits anaerobic digestion - Newly isolated bacterial strains from anaerobic digester were obtained - Proper bioaugmentation alleviates stress in casein and maize silage co-digestion - Bioaugmentation with a hydrolytic/hydrogenotrophic co-culture enhances CH4 yields

bioengineering↗

bioRxiv2019

The anaerobic digestion microbiome: a collection of 1600 metagenome-assembled genomes shows high species diversity related to methane production

BackgroundMicroorganisms in biogas reactors are essential for degradation of organic matter and methane production through anaerobic digestion process. However, a comprehensive genome-centric comparison, including relevant metadata for each sample, is still needed to identify the globally distributed biogas community members and serve as a reliable repository.\n\nResultsHere, 134 publicly available datasets derived from different biogas reactors were used to recover 1,635 metagenome-assembled genomes (MAGs) representing different bacterial and archaeal species. All genomes were estimated to be >50% complete and nearly half were [≥]90% complete with [≤]5% contamination. In most samples, specialized microbial communities were established, while only a few taxa were widespread among the different reactor systems. Metabolic reconstruction of the MAGs enabled the prediction of functional traits related to biomass degradation and methane production from waste biomass. An extensive evaluation of the replication index provided an estimation of the growth rate for microbes involved in different steps of the food chain. The recovery of many MAGs belonging to Candidate Phyla Radiation and other underexplored taxa suggests their specific involvement in the anaerobic degradation of organic matter.\n\nConclusionsThe outcome of this study highlights a high flexibility of the biogas microbiome. The dynamic composition and adaptability to the environmental conditions, including temperatures and a wide range of substrates, were demonstrated. Our findings enhance the mechanistic understanding of anaerobic digestion microbiome and substantially extend the existing repository of genomes. The established database represents a relevant resource for future studies related to this engineered ecosystem.

microbiology↗