Pretreatment of waste-activated sludge (WAS) is an effective way to destabilize sludge floc structure and release organic matter for improving sludge digestion efficiency. Nonetheless, information on the impact of WAS pretreatment on digestion sludge microbiomes, as well as mechanistic insights into how sludge pretreatment improves digestion performance, remains elusive. In this study, a genome-centric metagenomic approach was employed to investigate the digestion sludge microbiome in four sludge digesters with different types of feeding sludge: WAS pretreated with 0.25 mol/liter alkaline/acid (APAD), WAS pretreated with 0.8 mol/liter alkaline/acid (HS-APAD), thermally pretreated WAS (thermal-AD), and fresh WAS (control-AD). We retrieved 254 metagenome-assembled genomes (MAGs) to identify the key functional populations involved in the methanogenic digestion process. These MAGs span 28 phyla, including 69 yet-to-be-cultivated lineages, and 30 novel lineages were characterized with metabolic potential associated with hydrolysis and fermentation. Interestingly, functional populations involving carbohydrate digestion were enriched in APAD and HS-APAD, while lineages related to protein and lipid fermentation were enriched in thermal-AD, corroborating the idea that different substrates are released from alkaline/acid and thermal pretreatments. Among the major functional populations (i.e., fermenters, syntrophic acetogens, and methanogens), significant correlations between genome sizes and abundance of the fermenters were observed, particularly in APAD and HS-APAD, which had improved digestion performance.

中文翻译：

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以基因组为中心的宏基因组学见解，可了解碱/酸和热污泥预处理对消化污泥微生物组的影响。

废物活性污泥（WAS）的预处理是使污泥絮凝结构不稳定并释放有机物以提高污泥消化效率的有效方法。尽管如此，有关WAS预处理对消化污泥微生物组的影响的信息，以及有关污泥预处理如何改善消化性能的机制性见解仍然难以捉摸。在这项研究中，采用了以基因组为中心的宏基因组学方法来研究四种不同类型进料污泥的污泥消化器中的消化污泥微生物组：WAS预先用0.25 mol / L碱/酸（APAD）预处理，WAS预先用0.8 mol / L预处理碱/酸（HS-APAD），经过热处理的WAS（热AD）和新鲜的WAS（对照AD）。我们检索了254个元基因组组装的基因组（MAG），以确定参与产甲烷消化过程的关键功能种群。这些MAG跨越28个门，包括69个尚待培养的谱系，并且表征了30个具有与水解和发酵相关的代谢潜能的新谱系。有趣的是，涉及碳水化合物消化的功能性群体富含APAD和HS-APAD，而与蛋白质和脂质发酵相关的谱系富含热AD，从而证实了碱/酸和热预处理释放出不同底物的想法。在主要功能种群（即发酵罐，营养型产乙酸菌和产甲烷菌）中，尤其是在APAD和HS-APAD中，观察到了基因组大小与发酵罐丰度之间的显着相关性，