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Genome-Wide and Functional View of Proteolytic and Lipolytic Bacteria for Efficient Biogas Production Through Enhanced Sewage Sludge Hydrolysis

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Genome-Wide and Functional View of Proteolytic and Lipolytic Bacteria for Efficient Biogas Production Through Enhanced Sewage Sludge Hydrolysis

Krzysztof Poszytek et al. Molecules.

Abstract

In this study, we used a multifaceted approach to select robust bioaugmentation candidates for enhancing biogas production and to demonstrate the usefulness of a genome-centric approach for strain selection for specific bioaugmentation purposes. We also investigated the influence of the isolation source of bacterial strains on their metabolic potential and their efficiency in enhancing anaerobic digestion. Whole genome sequencing, metabolic pathway reconstruction, and physiological analyses, including phenomics, of phylogenetically diverse strains, Rummeliibacillus sp. POC4, Ochrobactrum sp. POC9 (both isolated from sewage sludge) and Brevundimonas sp. LPMIX5 (isolated from an agricultural biogas plant) showed their diverse enzymatic activities, metabolic versatility and ability to survive under varied growth conditions. All tested strains display proteolytic, lipolytic, cellulolytic, amylolytic, and xylanolytic activities and are able to utilize a wide array of single carbon and energy sources, as well as more complex industrial by-products, such as dairy waste and molasses. The specific enzymatic activity expressed by the three strains studied was related to the type of substrate present in the original isolation source. Bioaugmentation with sewage sludge isolates-POC4 and POC9-was more effective for enhancing biogas production from sewage sludge (22% and 28%, respectively) than an approach based on LPMIX5 strain (biogas production boosted by 7%) that had been isolated from an agricultural biogas plant, where other type of substrate is used.

Keywords: anaerobic digestion; bioaugmentation; biogas; metabolic pathway reconstruction; phenomic analysis; sewage sludge hydrolysis; whole genome sequencing.

Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

Figure 1
Figure 1
Number of genes of the LPMIX5 and POC4 strains classified into particular COG functional categories.
Figure 2
Figure 2
Fatty acid β-oxidation (A) and glutathione (B) degradation pathways of the LPMIX5, POC4 and POC9 strains.
Figure 3
Figure 3
Mapping of the predicted proteins from the three investigated strains to the MEROPS peptidase database clan groups. Aspartic: clans of aspartic peptidases, Cysteine: clans of cysteine peptidases, Glutamic: clans of glutamic peptidases, Metallo: clans of metallo peptidases, Asparagine: clans of asparagine peptide lyases, Mixed: clans of mixed (C, S, T) catalytic type, Serine: clans of serine peptidases, Threonine: clans of threonine peptidases, Unknown: clans of peptidases of unknown catalytic type.

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