Filamentous cyanobacteria and hydrophobic protein in extracellular polymeric substances facilitate algae-bacteria aggregation during partial nitrification.

In algae-bacteria symbiotic wastewater treatment, the excellent settling performance of algae-bacteria aggregates is critical for biomass separation and recovery. Here, the composition of extracellular polymeric substances (EPS), microbial profiles, and functional genes of algae-bacteria aggregates were investigated at different solid retention times (SRTs) (10, 20, and 40 d) during partial nitrification in photo sequencing bioreactors (PSBRs). Results showed that SRTs greatly influenced the nitrogen transformation and the formation and morphological structure of algae-bacteria aggregates. The highest nitrite accumulation, the largest particle size (~1.54 mm) and the best settling performance were observed for the algae-bacteria aggregates in the PSBR with an SRT of 10 d, where the abundant occurrence of filamentous cyanobacteria with the highest ratio of chlorophyll a/b and the lowest EPS amount with the highest protein-to-polysaccharide ratio were observed. In particular, the EPS at 10 d of SRT contained a higher amount of protein-related hydrophobic groups and a lower ratio of α-helix/(ß-sheet + random coil), indicating a looser protein structure, which might facilitate the formation and stabilization of algae-bacteria aggregates. Moreover, algal-bacterial aggregation greatly depended on the composition and evolution of filamentous cyanobacteria (unclassified _o__Oscillatoriales and Phormidium accounted for 56.29 % of the identified algae at SRT 10 d). The metagenomic analysis further revealed that functional genes related to amino acid metabolism (e.g., genes of phenylalanine, tyrosine, and tryptophan biosynthesis) were expressed at high levels within 10 d of SRT. Overall, this study demonstrates the influence of EPS structures and filamentous cyanobacteria on algae-bacteria aggregation and reveals the biological mechanisms driving photogranule structure and function.

Evaluating the impacts of biochemical processes on nitrogen dynamics in a tide gate-controlled river flowing into the South China Sea.

This study aimed to evaluate the nitrogen (N) dynamics in Lijiang River, a tide gate-controlled river flowing into South China Sea, and to quantify the biochemical processes affecting nitrate fate and transport during the closed-tide gate period. The continuous on-line water monitoring indicates a chemostatic NH4+-N pattern with respect to variable discharges in the upstream section. The survey via daily grab water sampling from July to December 2020 at four equidistant locations in the lower stretch showed that a gradual increase in NO3--N and decrease in NH4+-N concentrations occurred along the river from upstream to downstream sections and with the time from September to December (the closed-tide gate period). The mean difference between nitrification and denitrification rate peaked at 0.43 mg L-1 d-1 in October in the upper section and gradually reduced to -0.26 mg L-1 d-1 in December in the middle section, indicating the increased advantage of denitrification over nitrification with time. A gradual increase in the mean NO3--N assimilatory uptake rate with time and a decrease from upstream to downstream were also observed. These results show that the closed-tide gate promoted N biotransformation in Laingian River and significant N removal was achieved through coupled nitrification-denitrification.

Metagenomics and network analysis decipher profiles and co-occurrence patterns of bacterial taxa in soils amended with biogas slurry.

Microbial community and interaction play crucial roles in ecological functions of soil including nutrient cycling carbon storage, and water maintenance etc. Numerous studies have shown that the application of fertilizers alters bacterial diversity; However, it remains unknown whether and how the continuous application of biogas slurry from anaerobic digestion affects the spatiotemporal heterogeneity of soil layers, complexity and stability of microbial networks, and functions related to C and N cycling. Here, we investigated the bacterial taxa of purple soils treated with swine biogas slurry for four different periods (0, 1, 3 and 8 years) and five different soil depths (20, 40, 60, 80 and 100 cm). The results showed that the application period of biogas slurry and soil depth were two powerful drivers of bacterial diversity and communities. Biogas slurry input resulted in marked changes in the bacterial diversity and composition at the soil depths of 0-60 cm. The relative abundances of Acidobacteriota, Myxococcot, and Nitrospirota decreased, while Actinobacteria, Chloroflexi, and Gemmatimonadota increased with repeated biogas slurry input. The decreasing complexity and stability of the bacterial network with decreasing nodes, links, robustness, and cohesions were found with increasing years of biogas slurry application, suggesting that the bacterial network of soils treated by the biogas slurry became more vulnerability compared with the control. Also, the linkages between the keystone taxa and soil properties were weakened after biogas slurry input, leading to the cooccurrence patterns being less affected by the keystones in the high level of nutrients. Metagenomic analysis confirmed that biogas slurry input increased the relative abundance of liable-C degradation and denitrification genes, which could highly impact the network properties. Overall, our study could give comprehensive understandings on the impacts of biogas slurry amendment on soils, which could be useful for maintaining sustainable agriculture and soil health with liquid fertilization.

New insights into multi-strategies of sludge granulation in up-flow anaerobic sludge blanket reactors from community succession and interaction.

This study aimed to elucidate the multiple strategies employed by anaerobes during granulation in a laboratory upflow anaerobic sludge blanket reactor, based on microbial succession and interactions. The anaerobic granulation process featured staged dominance of microbial genera, corresponding well with the environmental traits. Across the stages (selection, seeding, expansion, and maturation), chemotaxis attraction of nitrogen and/or carbon sources and flagellar motion were the primary strategy of microbial assembly. The second messengers - cyclic adenosine and guanosine monophosphates - partially regulated the agglomeration of filamentous Euryachaeota and Chloroflexi as the inner cores, while quorum sensing mediated the expansion of granules prior to maturation. Antagonism or competition governed the interactions within the phylogenetic molecular ecological network during sludge granulation, which were largely driven by the low-abundance (<1%) taxa. These new insights suggest that better engineering solutions to enhance chemotaxis attraction and species selection could achieve more efficient anaerobic granular sludge processes.

Biofouling control potential of quorum quenching anaerobes in lab-scale anaerobic membrane bioreactors: Foulants profile and microbial dynamics.

Indigenously isolated anaerobes encoding four quorum quenching (QQ) enzymes were applied in immobilized- and bioaugmented forms for their implications on membrane foulants, microbial taxa, and biofouling control. Two identical anaerobic membrane bioreactors (AnMBRs) with different immobilizing media, i.e. silica-alginate (AnMBR-Si) and hollow fiber-alginate (AnMBR-Hf), were sequentially operated for two conventional and three QQ based phases. The synergistic addition of QQ anaerobes in free cells and the immobilized form prolonged the membrane filtration operation by 172 ± 29% and 284 ± 12% in AnMBR-Si and AnMBR-Hf, respectively. Biocake with low surface coverage was prominent during QQ application compared to conventional phases. Despite the better control of AHLs (3OC6-, C6-, 3OC8, C8, and C10-HSL) and AI-2 at various points of QQ phases, the QQ consortium could not maintain a low concentration of signals for longer period. Therefrom, quenching of targeted signal molecules instigate the dominance of microbial species bearing non-targeted quorum sensing mechanism. The QQ significantly altered the biofilm-forming community in mixed liquor, while the members with robust signal transduction systems became dominant to counteract the QQ mechanism and were the ultimate cause of biofouling. The improved methane content in biogas and increased methanogens composition during QQ phases demonstrated the synergism of exogenous and immobilized QQ as the most viable option for long-term AnMBR operation.

Resuscitation-Promoting Factor Accelerates Enrichment of Highly Active Tetrachloroethene/Polychlorinated Biphenyl-Dechlorinating Cultures.

The anaerobic bioremediation of polychlorinated biphenyls (PCBs) is largely impeded by difficulties in massively enriching PCB dechlorinators in short periods of time. Tetrachloroethene (PCE) is often utilized as an alternative electron acceptor to preenrich PCB-dechlorinating bacteria. In this study, resuscitation promoting factor (Rpf) was used as an additive to enhance the enrichment of the microbial communities involved in PCE/PCBs dechlorination. The results indicated that Rpf accelerates PCE dechlorination 3.8 to 5.4 times faster than control cultures. In Aroclor 1260-fed cultures, the amendment of Rpf enables significantly more rapid and extensive dechlorination of PCBs. The residual high-chlorinated PCB congeners (≥5 Cl atoms) accounted for 36.7% and 59.8% in the Rpf-amended cultures and in the corresponding controls, respectively. This improvement was mainly attributed to the enhanced activity of the removal of meta-chlorines (47.7 mol % versus 14.7 mol %), which did not appear to affect dechlorination pathways. The dechlorinators, including Dehalococcoides in Chloroflexi and Desulfitobacterium in Firmicutes, were greatly enriched via Rpf amendment. The abundance of nondechlorinating populations, including Methanosarcina, Desulfovibrio, and Bacteroides, was also greatly enhanced via Rpf amendment. These results suggest that Rpf serves as an effective additive for the rapid enrichment of active dechlorinating cultures so as to provide a new approach by which to massively cultivate bioinoculants for accelerated in situ anaerobic bioremediation. IMPORTANCE The resuscitation promoting factor (Rpf) of Micrococcus luteus has been reported to resuscitate and stimulate the growth of functional microorganisms that are involved in the aerobic degradation of polychlorinated biphenyls (PCBs). However, few studies have been conducted to investigate the role of Rpf on anaerobic microbial populations. In this study, the enhancement of Rpf on the anaerobic microbial dechlorination of PCE/PCBs was discovered. Additionally, the Rpf-responsive populations underlying the enhanced dechlorination were uncovered. This report reveals the rapid enrichment of active dechlorinating cultures via Rpf amendment, and this sheds light on massively enriching PCB dechlorinators in short periods of time. The enhanced in situ anaerobic bioremediation of PCBs could be expected by supplementing Rpf.

Molecular transformations of dissolved organic matter during UV/O3-assisted membrane filtration of UASB-treated real textile wastewater.

A ceramic membrane reactor (CMR) integrated with in-situ UV/O3 was assessed for post-treatment of the effluent out of an up-flow anaerobic sludge blanket (UASB) reactor treating real textile wastewater, focusing on the transformation of dissolved organic matter (DOM). Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) revealed the transformation of heteroatomic DOM containing S, N or both to simpler DOM containing mainly C, H, and O atoms. The decreased N contents in products (N/C = 0.0249) compared to precursors (N/C = 0.0311) and the higher O/C ratios in the N-containing products suggest the removal of R-NH2 groups accompanying DOM oxidation. While, S-containing compounds in the products had lower O/C and H/C ratios, suggesting a reduced state and the transformation of R-SO3 to R-S-R. H-abstraction and OH addition were identified as the primary oxidation mechanisms, thus enhancing the dominance of highly unsaturated and phenolic DOM in the effluent (70.3%) compared to the feed (56.6%). The double bond equivalent (DBE) was also increased by 26% in the effluent compared to the feed and by 33% in products compared to precursors. These findings help understand the DOM transformation in UV/O3-assisted ceramic membrane reactors and call for comprehensive toxicity analyses of effluents from the advanced oxidation processes.

Effective partial denitrification of biological effluent of landfill leachate for Anammox process: Start-up, influencing factors and stable operation.

Partial denitrification combined with Anammox is a promising approach for simultaneous removal of ammonium and nitrate from wastewaters. In this study, the start-up, influencing factors and stable operation of partial denitrification for treating biological effluent from landfill leachate were investigated. High nitrate loads (3.85 kg N m-3 d-1) and short hydraulic retention time (0.66 h) were obtained in the partial denitrification process, yielding a suitable ratio of NO2--N/NH4+-N in the effluent for downstream Anammox process. The study also revealed the importance of carbon sources, COD/NO3--N ratio and salinity in the partial denitrification. Acetate-type carbon source, COD/NO3--N ratio of about 3.0 and salinity lower than 1% favored high-efficient partial denitrification. The endogenous carbon sources from high-rate partial denitrification sludge contributed to low COD consumption in the process. During the partial denitrification, the dominant genus of Thauera was enriched, and shifted to Pseudomonas with the increase of organic removal rates.

Genetic insights unraveling quorum quenching potential of indigenous isolates from an anaerobic membrane bioreactor.

Despite a few reports of quorum quenching (QQ) in anaerobic membrane bioreactors (AnMBRs), the sensing, regulation and degradation mechanism for quorum sensing (QS) signals by indigenous QQ isolates have been barely studied. This study employed isolation and screening of indigenous QQ strains from anaerobic sludge for acyl-homoserine lactones (AHLs) degradation and membrane biofouling control. High-quality whole genome sequences of Micrococcus luteus anQ-m1, Bacillus pacificus anQ-h4, and Lysinibacillus capsici anQ-h6 were obtained, with a genome size of 2.5, 5.6, and 4.7 Mbp, respectively. Amidase-encoding amiE was the only QQ gene in anQ-m1, while anQ-h6 carries both amiE and lactonase-encoding aiiB genes. Genes responsible for QS autoinducer synthesis were not identified in anQ-m1 and anQ-h6, suggesting low potential of biofilm promotion via QS. Despite a peptidic QS system responsible for biofilm formation, anQ-h4 bears the most comprehensive QQ system, including amiE-amidase, aiiA-lactonase, CYP102A5-cytochrome oxidoreductase, and lsrK-autoinducer-2 kinase. This study elucidates QS and QQ mechanisms of potential anaerobes and provides fundamentals for designing QQ consortia to effectively control biofouling in AnMBRs.

Pyrite-activated persulfate oxidation and biological denitrification for effluent of biological landfill leachate treatment system.

The feasibility of pyrite as catalysts in the persulfate oxidation and electron donor for subsequent bacterial denitrification was investigated. The results demonstrated that pyrite-activated persulfate oxidation could efficiently degrade the organic matter in the effluent of biological landfill leachate treatment system, and COD removal efficiency of about 45% was achieved at the optimum parameters: pH = 6, pyrite dosage = 9.28 mM, dimensionless oxidant dose = 0.25. Among the dissolved organic matter, hydrophobic dissolved organic carbon (HO DOC), humic acids and building blocks were the main components. After the pyrite-activated persulfate oxidation, humic acids and HO DOC were primarily degraded, followed by building blocks, while low molecular weight neutrals were probably the degradation products. In the subsequent biological process, nitrate reduction was satisfactorily accomplished with autotrophic denitrification as the main pathway. When the influent nitrate concentration was about 180 mg L-1, the effluent nitrate concentration was stable below 20 mg L-1 with the nitrogen removal rate of about 108 mg L-1 d-1. To sum up, the pyrite-activated persulfate oxidation and the following biological denitrification was a feasible application in the effluent of biological landfill leachate treatment system.

Viable but Nonculturable State of Yeast Candida sp. Strain LN1 Induced by High Phenol Concentrations.

Microbial degradation plays an important role in environmental remediation. However, most microorganisms' pollutant-degrading capabilities are weakened due to their entry into a viable but nonculturable (VBNC) state. Although there is some evidence for the VBNC state of pollutant-degrading bacteria, limited studies have been conducted to investigate the VBNC state of pollutant degraders among fungi. In this work, the morphological, physiological, and molecular changes of phenol-degrading yeast strain LN1 exposed to high phenol concentrations were investigated. The results confirmed that Candida sp. strain LN1, which possessed a highly efficient capability of degrading 1,000 mg/liter of phenol as well as a high potential for aromatic compound degradation, entered into the VBNC state after 14 h of incubation with 6,000 mg/liter phenol. Resuscitation of VBNC cells can restore their phenol degradation performance. Compared to normal cells, significant dwarfing, surface damage, and physiological changes of VBNC cells were observed. Molecular analysis indicated that downregulated genes were related to the oxidative stress response, xenobiotic degradation, and carbohydrate and energy metabolism, whereas upregulated genes were related to RNA polymerase, amino acid metabolism, and DNA replication and repair. This report revealed that a pollutant-degrading yeast strain entered into the VBNC state under high concentrations of contaminants, providing new insights into its survival status and bioremediation potential under stress. IMPORTANCE The viable but nonculturable (VBNC) state is known to affect the culturability and activity of microorganisms. However, limited studies have been conducted to investigate the VBNC state of other pollutant degraders, such as fungi. In this study, the VBNC state of a phenol-degrading yeast strain was discovered. In addition, comprehensive analyses of the morphological, physiological, and molecular changes of VBNC cells were performed. This study provides new insight into the VBNC state of pollutant degraders and how they restored the activities that were inhibited under stressful conditions. Enhanced bioremediation performance of indigenous microorganisms could be expected by preventing and controlling the formation of the VBNC state.

A novel strategy for enhancing anaerobic biodegradation of an anthraquinone dye reactive blue 19 with resuscitation-promoting factors.

Anaerobic process has been widely applied as a cost-effective method for textile wastewater treatment. However, many bacteria exhibit low metabolic activity in unfavorable conditions due to the entry into a viable but non-culturable (VBNC) state. Thus, in this study, a novel method of using resuscitation-promoting factors (Rpfs), which has been proven to resuscitate and stimulate the growth of VBNC bacteria, is explored to enhance the degradation of the anthraquinone dye reactive blue 19 (RB19) in the anaerobic process. The results show that Rpfs could efficiently prompt RB19 decolorization. Compared to the conventional anaerobic condition, RB19 decolorization efficiency was increased by more than 20% with the Rpf addition. UV-visible spectral and gas chromatograph-mass spectrometry analysis indicate that the aromatic amines structures of RB19 was cleaved. More importantly, the Rpf addition appeared to stimulate and/or enrich some dye-degrading species of the family Peptostreptococcaceae, thus leading to a higher RB19 decolorization efficiency.

Enhancement of polychlorinated biphenyl biodegradation by resuscitation promoting factor (Rpf) and Rpf-responsive bacterial community.

The activities of indigenous bacterial communities in polychlorinated biphenyls (PCBs) contaminated environments is closely related to the efficiency of bioremediation processes. Using resuscitation promoting factor (Rpf) from Micrococcus luteus is a promising method for resuscitation and stimulation of functional bacterial populations under stressful conditions. This study aims to use the Rpf to accelerate the biodegradation of Aroclor 1242, and explore putative PCB degraders which were resuscitated by Rpf addition. The Rpf-responsive bacterial populations were investigated using culture-dependent and culture-independent approaches, respectively. The results confirm that Rpf was capable of enhancing PCB degradation of enriched cultures from PCB-contaminated soils, and improving the activities of cultures with low tolerance to PCBs. High-throughput 16S rRNA analysis displays that the Rpf greatly altered the composition and abundance of bacterial populations in the phylum Proteobacteria. Identification of the resuscitated strains further suggests that the Rpf-responsive population was mostly represented by Sphingomonas and Pseudomonas, which are most likely the key PCB-degraders for enhanced biodegradation of PCBs.

The Application of Fluorescence Spectroscopy for the Investigation of Dye Degradation by Chemical Oxidation.

Chemical oxidation is a key technique used in dye wastewater treatment via the formation of hydroxyl radicals. To obtain optimal treatment effects, it is critical to understand the interaction of the molecular structure of the dye with the hydroxyl radical. We evaluated fluorescence excitation-emission matrix spectroscopy to study the decay of an azo-dye (Procion Red MX-5B) by a hydroxyl radical generated from catalytic Fe (III) on H2O2. Results showed that fluorescence signal reliably indicated the variations of the chemical groups and components during degradation, and the degradation could be divided into three stages: initial degradation (decolorisation), rapid intermediate degradation, and final degradation. Under control of uncorrected matrix correlation, the fluorescence fractions could be fitted successfully by parallel factor model (PARAFAC) model: two fluorescence components in initial degradation including mono substituted benzene and mono substituted naphthalene, three components as multi substituted benzene in rapid degradation, and no components could be resolved in the final degradation. The results from the study demonstrate the utility fluorescence characterization of dye degradation mechanisms and enhance the understanding of the degradation mechanisms.

Resuscitation, isolation and immobilization of bacterial species for efficient textile wastewater treatment: A critical review and update.

Given highly complex and recalcitrant nature of synthetic dyes, textile wastewater poses a serious challenge on surrounding environments. Until now, biological treatment of textile wastewater using efficient bacterial species is still considered as an environmentally friendly and cost-effective approach. The advances in resuscitating viable but non-culturable (VBNC) bacteria via signaling compounds such as resuscitation-promoting factors (Rpfs) and quorum sensing (QS) autoinducers, provide a vast majority of potent microbial resources for biological wastewater treatment. So far, textile wastewater treatment from resuscitating and isolating VBNC state bacteria has not been critically reviewed. Thus, this review aims to provide a comprehensive picture of resuscitation, isolation and application of bacterial species with this new strategy, while the recent advances in synthetic dye decolorization were also elaborated together with the mechanisms involved. Discussion was further extended to immobilization methods to tackle its application. We concluded that the resuscitation of VBNC bacteria via signaling compounds, together with biochar-based immobilization technologies, may lead to an appealing biological treatment of textile wastewater. However, further development and optimization of the integrated process are still required for their wide applications.

The selective pressure of quorum quenching on microbial communities in membrane bioreactors.

In conventional membrane bioreactor (MBR) treatment systems, Gram-negative bacterial population appears to be always outnumbered Gram-positive community. Thereby, acyl homoserine lactones (AHLs), major signaling molecules utilized by Gram-negative bacteria, have been targeted for biofouling control in quorum quenching (QQ) based studies. This study investigated the impact of AHL and autoinducer-2 (AI-2)-degrading QQ consortium on the selective accumulation of microbial communities in a QQ MBR (MBR-QQb). The results show that addition of the QQ consortium (in the form of beads) increased the filtration time of MBR-QQb by 3.5 times. The distribution of mixed liquor extracellular polymeric substances (EPS), especially the tightly bound (TB) proteinous EPS and the floc size were strongly affected by the QQ activity, and the endless 'battle' between QQ and quorum sensing (QS). More importantly, QQ induced the significant suppression of Gram-negative bacterial community. The average abundance of Gram-positive bacteria at the genus level in the biocake of MBR-QQb (51%) was significantly higher than that of the control MBR (11%) and the MBR with vacant beads (28%). These findings suggest that an unintended condition is created to favor the growth of Gram-positive bacteria in QQ MBRs, resulting in a distinct microbial social network in both bulk sludge and biocake.

Immobilizing a visible light-responsive photocatalyst on a recyclable polymeric composite for floating and suspended applications in water treatment.

A visible light responsive TiO2/Ag3PO4 (10 : 1) nanocomposite was prepared and successfully immobilized (12 wt%) in a spherical polymeric matrix consisting of polysulfone and alginate (10 : 6). The resulted beads featured a sponge-like structure with interconnected macrovoids and micropores, and showed high adsorption and visible-light photocatalytic activity towards various wastewater pollutants, including the widely used dye - methylene blue (k = 0.0321 min-1), and two emerging pharmaceutical contaminants - diclofenac (k = 0.018 min-1) and triclosan (k = 0.052 min-1). As determined, the ˙OH radical and h+ are the primary reactive oxygen species responsible for the photodegradation. The composite photocatalytic beads are also effective in bacterial inactivation and degradation of acyl-homoserine lactones (AHLs), the bacterial quorum sensing autoinducers triggering biofilms, thus exhibiting a promising future in wastewater disinfection and biofilm retardation. Additionally, these beads could be used in inter-switchable suspended or buoyant forms, and be effectively regenerated by H2O2 treatment, and used for multiple cycles without any significant loss in photoactivity. With these unique features, the prepared visible-light photocatalytic beads could be easily applied in large-scale water and wastewater treatment systems.

Aerobic degradation of 3,3',4,4'-tetrachlorobiphenyl by a resuscitated strain Castellaniella sp. SPC4: Kinetics model and pathway for biodegradation.

Resuscitated strains which were obtained by addition of resuscitation promoting factor (Rpf) could provide a vast majority of microbial source for obtaining highly efficient polychlorinated biphenyl (PCB)-degrading bacteria. In this study, the Castellaniella sp. strain SPC4 which was resuscitated by Rpf addition showed the highest efficiency in degradation of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) among the resuscitated and non-resuscitated isolates. Further investigations on the PCB 77 degradation capability of the resuscitated strain SPC4 showed that SPC4 could efficiently degrade PCB 77 with maximum degradation rate (qmax) of 0.066/h at about 20 mg/L of PCB 77. The maximum growth rate on PCB 77 was 2.663 × 107 CFU/(mL·h) (0.024/h). The most suitable model of Edward demonstrated that the SPC4 could achieve qmax of 0.9315/h, with substrate-affinity of 11.33 mg/L and substrate-inhibition constants of 11.41 mg/L. Meanwhile, the presence of bphA gene expression and chlorine ions release, together with the identification of metabolites, confirmed that the bph-encoded biphenyl pathway was involved in PCB 77 mineralization by SPC4. This report is the first to demonstrate aerobic degradation of PCB 77 by the resuscitated strain Castellaniella sp. SPC4, indicating excellent potential for PCB bioremediation.

Whole-genome sequencing of an acidophilic Rhodotorula sp. ZM1 and its phenol-degrading capability under acidic conditions.

The goal of this work was to investigate the genetics of an acidophilic phenol-degrading yeast strain using whole-genome sequencing (WGS), characterize the growth of the strain and phenol degradation capability as well as degradation pathway under extremely acidic conditions. The result showed that the strain ZM1 isolated from an acid mine drainage (AMD) belongs to basidiomycetous yeast Rhodotorula sp., which possesses some unique genes compared to other four closely related Rhodotorula species. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that ZM1 possessed the degradation potentials for aromatic compounds. ZM1 was acidophilic with the optimum growth at the initial pH of 3.0. It could adjust pH to desired levels probably by acid production during the cultivation. Notably, at pH 3.0, the strain ZM1 showed a high phenol-degrading capability that almost completely degraded 1100 mg/L of phenol in 120 h with the highest degradation rate of 0.074 g/(g cell dry weight h). Under the same pH, the strain could completely degrade 500 mg/L phenol within 48 h at NaCl concentration up to 10 g/L. The identification of the gene catA by the KEGG analysis, together with the presence of metabolic intermediate of cis, cis-muconic acid detected by gas chromatography-mass spectrometry, confirmed that the strain ZM1 degraded phenol via ortho-cleavage pathway. These findings suggest that the indigenous yeasts strain ZM1 could be exploited as an important member for in-situ biodegradation of aromatic compounds in the extremely acidic environments.

Size-dependent microbial diversity of sub-visible particles in a submerged anaerobic membrane bioreactor (SAnMBR): Implications for membrane fouling.

Sub-visible particles, an often-overlooked fine particle (0.45-10 µm) with a size between sludge solids and soluble microbial products (SMP), have recently been identified as a critical foulant in anaerobic membrane bioreactors (AnMBRs), and our recent new insights into the size-fractionation and composition of sub-visible particles in AnMBRs have enabled fouling to be understood in more depth. Here, we investigated the microbial diversity of the sub-visible particles in three size fractions (i.e., 5-10, 1-5, and 0.45-1 µm) from bulk and cake solutions in a lab-scale AnMBR, and their fouling potential was further explored based on their filtration behavior and biofilm formation. Results show that with decreasing particle size, a significant shift in microbial communities was observed for the sub-visible particles in both bulk and cake solutions; (a) with notable decreases in filamentous microbes in the order SJA-15, GCA004, and Anaerolineales of phylum Chloroflexi, and, (b) with substantial increases in sulfate-reducing bacteria (i.e., the family Syntrophobacteraceae, genus DCE29 of family Thermodesulfovibrionaceae, Desulfovibrio, and Geobacter). More importantly, the filamentous microbes associated with micro-particles (5-10 µm) led to higher cake fouling resistances while free living cells in the form of colloidal particles (0.45-1 µm) induced severer pore blocking. Moreover, the micro-particles had an enhanced capacity to favor biofilm formation (OD595 = 1.0-2.5, categorized as highly positive), thus potentially aggravating biofouling. This work advances our knowledge on the effect of particle size on communities and underlying fouling behavior of microbes associated with fine particles in AnMBRs.