New insights into mycelial pellets for aerobic sludge granulation in membrane bioreactor: Bio-functional interactions among metazoans, microbial communities and protein expression. (1st January 2023)

• Record Type: Journal Article
• Authors: Xiao, Xiao; Guo, Haijuan; Ma, Fang; Zhang, Jinna; Ma, Xiping; You, Shijie
• Is Part Of: Water research. Volume 228(2023)Part A
• Publication Date: 2023-01-01
• Subjects: Mycelial pellets -- Aerobic granular sludge -- Metazoans -- Microbial communities -- Proteomics; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.119361
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Metazoans enjoyed grazing on the hyphae of MPs with abundant secretions. MPs adsorbed bacteria to form sludge aggregates to prevent predation by metazoans. MPs-induced granulation inhibited Thiothrix overgrowth and enriched NOBs/DNBs. Thiothrix and Nitrospira were the main contributors to the DEPs. Enhanced energy/amino acid/N- metabolisms led to functional superiority of MPs-AGS. Abstract: Direct cultivation of aerobic granular sludge (AGS) in membrane bioreactor (MBR) has gained increasing attention. Mycelial pellets (MPs) has been shown capable of promoting rapid granulation of aerobic sludge in MBR, yet mechanisms remain unclear and in-depth insight into cross-scale interactions between MPs and indigenous microbiota as well as the corresponding protein expression functions is necessary. Herein, we found that the addition of MPs in MBR resulted in massive growth of metazoans with 40–400 /mL for rotifers, 20–140 /mL for nematodes and 2–420 /mL for oligochaetes in the initial phase of granulation. This facilitated the MPs to rapidly aggregate with bacteria to form defensive granules for physical protection from predation by metazoans, which inhibited the overgrowth of filamentous bacteria Thiothrix and promoted the reproduction of functional bacteria related to nitrogen removal ( Nitrospira, Trichococcus and Acinetobacter ). Proteomic analysis demonstrated that the upregulation of functional proteins was mainly ascribed to the decrease of Thiothrix and the increase of Nitrospira, resulting in the enhancement of metabolic pathways involved in glycolysis/gluconeogenesis, citrate (TCA) cycle, oxidative phosphorylation, pyruvate metabolism, nitrogen metabolism and biosynthesis of amino acids, which was responsible for MPs-induced AGS with denser structure, more abundant proteins and β-polysaccharides, higher species diversity, significant nitrogen removal (33.12–42.33%) and lower membrane fouling potential. This study provided a novel and comprehensive insight into the enhanced granulation of aerobic sludge by MPs and the functional superiority of MPs-induced AGS in MBR system. Graphical abstract: Image, graphical abstract