biostudies-literatureXia YHong Kong Theme-based Research Scheme47https://www.ebi.ac.uk/biostudies/studies/S-EPMC5820786biostudies-literatureUnknown11<h4>Background</h4>Part-stream low-frequency ultrasound (LFUS) was one of the common practices for sludge disintegration in full-scale anaerobic digestion (AD) facilities. However, the effectiveness of part-stream LFUS treatment and its effect on AD microbiome have not been fully elucidated.<h4>Methods</h4>Here we testified the effectiveness of part-stream LFUS pretreatment by treating only a fraction of feed sludge (23% and 33% total solid of the feed sludge) with 20 Hz LFUS for 70 s. State-of-the-art metagenomic and metatranscriptomic analysis was used to investigate the microbial process underpinning the enhanced AD performance by part-stream LFUS pretreatment.<h4>Results</h4>By pretreating 33% total solid of the feed sludge, methane yield was increased by 36.5%, while the volatile solid reduction ratio remained unchanged. RNA-seq of the microbiome at stable stage showed that the continuous dosage of easy-degradable LFUS-pretreated feed sludge had gradually altered the microbial community by selecting <i>Bacteroidales</i> hydrolyzer with greater metabolic capability to hydrolyze cellulosic biomass without substrate attachment. Meanwhile, <i>Thermotogales</i> with excellent cell mobility for nutrient capturing was highly active within the community. Foremost proportion of the methanogenesis was contributed by the dominant <i>Methanomicrobiales</i> via carbon dioxide reduction. More interestingly, a perceivable proportion of the reverse electron flow of the community was input from <i>Methanoculleus</i> species other than syntrophic acetate-oxidizing bacteria. In addition, metagenomic binning retrieved several interesting novel metagenomic-assembled genomes (MAGs): MAG-bin6 of <i>Alistipes shahii</i> showed exceptional transcriptional activities towards protein degradation and MAG-bin11 of Candidatus <i>Cloacimonetes</i> with active cellulolytic GH74 gene detected.<h4>Conclusions</h4>In summary, despite the unchanged sludge digestibility, the applied part-stream LFUS pretreatment strategy was robust in adjusting the microbial pathways towards more effective substrate conversion enabled by free-living hydrolyser and beta-oxidation-capable methanogens.Biotechnology for biofuelsMicrobial effects of part-stream low-frequency ultrasonic pretreatment on sludge anaerobic digestion as revealed by high-throughput sequencing-based metagenomics and metatranscriptomics.PMC5820786T21-711/16-RXia YZhang TYang CfalseMicrobial effects of part-stream low-frequency ultrasonic pretreatment on sludge anaerobic digestion as revealed by high-throughput sequencing-based metagenomics and metatranscriptomics.<h4>Background</h4>Part-stream low-frequency ultrasound (LFUS) was one of the common practices for sludge disintegration in full-scale anaerobic digestion (AD) facilities. However, the effectiveness of part-stream LFUS treatment and its effect on AD microbiome have not been fully elucidated.<h4>Methods</h4>Here we testified the effectiveness of part-stream LFUS pretreatment by treating only a fraction of feed sludge (23% and 33% total solid of the feed sludge) with 20 Hz LFUS for 70 s. State-of-the-art metagenomic and metatranscriptomic analysis was used to investigate the microbial process underpinning the enhanced AD performance by part-stream LFUS pretreatment.<h4>Results</h4>By pretreating 33% total solid of the feed sludge, methane yield was increased by 36.5%, while the volatile solid reduction ratio remained unchanged. RNA-seq of the microbiome at stable stage showed that the continuous dosage of easy-degradable LFUS-pretreated feed sludge had gradually altered the microbial community by selecting <i>Bacteroidales</i> hydrolyzer with greater metabolic capability to hydrolyze cellulosic biomass without substrate attachment. Meanwhile, <i>Thermotogales</i> with excellent cell mobility for nutrient capturing was highly active within the community. Foremost proportion of the methanogenesis was contributed by the dominant <i>Methanomicrobiales</i> via carbon dioxide reduction. More interestingly, a perceivable proportion of the reverse electron flow of the community was input from <i>Methanoculleus</i> species other than syntrophic acetate-oxidizing bacteria. In addition, metagenomic binning retrieved several interesting novel metagenomic-assembled genomes (MAGs): MAG-bin6 of <i>Alistipes shahii</i> showed exceptional transcriptional activities towards protein degradation and MAG-bin11 of Candidatus <i>Cloacimonetes</i> with active cellulolytic GH74 gene detected.<h4>Conclusions</h4>In summary, despite the unchanged sludge digestibility, the applied part-stream LFUS pretreatment strategy was robust in adjusting the microbial pathways towards more effective substrate conversion enabled by free-living hydrolyser and beta-oxidation-capable methanogens.2018-01-01T00:00:00Z20182024-11-13T09:23:53.268Z2019-03-26T23:04:25ZS-EPMC58207862948394010.1186/s13068-018-1042-y