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Anaerobic digester (AD) microbiomes harbor complex, interacting microbial populations to achieve biomass reduction and biogas production, however how they are influenced by operating conditions and feed sludge microorganisms remain unclear. These were addressed by analyzing the microbial communities of 90 full-scale digesters at 51 municipal wastewater treatment plants from five countries. Heterogeneity detected in community structures suggested that no single AD microbiome could be defined. Instead, the AD microbiomes were classified into eight clusters driven by operating conditions ( e.g. , pretreatment, temperature range, and salinity), whereas geographic location of the digesters did not have significant impacts. Comparing digesters populations with those present in the corresponding feed sludge led to the identification of a hitherto overlooked feed-associated microbial group ( i.e. , the residue populations). They accounted for up to 21.4% of total sequences in ADs operated at low temperature, presumably due to ineffective digestion, and as low as 0.8% in ADs with pretreatment. Within each cluster, a core microbiome was defined, including methanogens, syntrophic metabolizers, fermenters, and the newly described residue populations. Our work provides insights into the key factors shaping full-scale AD microbiomes in a global scale, and draws attentions to the overlooked residue populations. [ABSTRACT FROM AUTHOR]

The ability of sludge, lignin and humic acid to support the growth and production of antimicrobial substances by 19 microorganism strains was tested. Organisms from seven genera: Bacillus, Pseudomonas, Streptomyces, Beauveria, Paecilomyces, Trichoderma and Trichosporon grew on the tested media. On these media, they were also examined for the production of anti-phytopathogenic activity against Fusarium oxysporum P1 BIM, Botrytis cinerea B1 BIM and Pseudomonas syringae. pv. glicinea B-280 BIM. Strains Pseudomonas aurantiaca S-1, Bacillus sp. 19 and Streptomyces sp. 11 synthesize antimicrobial metabolites on the different media. Protease, cellulase, α-amylase, xylanase and peroxidase were also produced by the same microorganisms, which can explain their ability to grow on sludge, and laccase was produced only by P. aurantiaca S-1. HPLC analysis of the lignin culture media before and after P. aurantiaca S-1 growth has shown that the major lignin peak in the culture broth disappeared. [ABSTRACT FROM AUTHOR]