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Water Science and Technology : a... Jul 2020Aerobic granular sludge process as a promising biotechnology has been one of the research hotspots in the area of wastewater treatment during the last two decades. In...
Aerobic granular sludge process as a promising biotechnology has been one of the research hotspots in the area of wastewater treatment during the last two decades. In our study, after around 60 days' operation, filamentous granular sludge (FGS) was formed under low aeration (SAV = 0.085 cm/s) and multi-feeding conditions. The characteristics of FGS and the performance of the FGS system for organic matter and nutrients removal were investigated. The results showed that chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were relatively stable, while COD removal efficiency increased from 82% to 94% in the presence of sulfamethoxazole (SMZ) at low concentration (1 mg/L). At the same time, the TP removal efficiency could be improved and maintained at around 75%, while TN removal efficiency was flocculated at around 50%. The analysis of microbial diversity showed that Thiothrix and Trichococcus as typical filamentous species were detected and dominant in the FGS system. The abundance of Thiothrix increased from 15% to 34%, while Trichococcus decreased from 23% to 3% in the presence of SMZ.
Topics: Aerobiosis; Biological Oxygen Demand Analysis; Bioreactors; Nitrogen; Sewage; Waste Disposal, Fluid; Wastewater
PubMed: 32941177
DOI: 10.2166/wst.2020.278 -
Studies in History and Philosophy of... Aug 2016Biological evolution is a fundamentally historical phenomenon in which intertwined stochastic and deterministic processes shape lineages with long, continuous histories...
Biological evolution is a fundamentally historical phenomenon in which intertwined stochastic and deterministic processes shape lineages with long, continuous histories that exist in a changing world that has a history of its own. The degree to which these characteristics render evolution historically contingent, and evolutionary outcomes thereby unpredictably sensitive to history has been the subject of considerable debate in recent decades. Microbial evolution experiments have proven among the most fruitful means of empirically investigating the issue of historical contingency in evolution. One such experiment is the Escherichia coli Long-Term Evolution Experiment (LTEE), in which twelve populations founded from the same clone of E. coli have evolved in parallel under identical conditions. Aerobic growth on citrate (Cit(+)), a novel trait for E. coli, evolved in one of these populations after more than 30,000 generations. Experimental replays of this population's evolution from various points in its history showed that the Cit(+) trait was historically contingent upon earlier mutations that potentiated the trait by rendering it mutationally accessible. Here I review this case of evolutionary contingency and discuss what it implies about the importance of historical contingency arising from the core processes of evolution.
Topics: Aerobiosis; Biological Evolution; Citric Acid; Escherichia coli; Selection, Genetic
PubMed: 26787098
DOI: 10.1016/j.shpsc.2015.12.007 -
Water Research May 2021The aerobic granular sludge (AGS) process is an effective wastewater treatment technology for organic matter and nutrient removal that has been introduced in the market...
The aerobic granular sludge (AGS) process is an effective wastewater treatment technology for organic matter and nutrient removal that has been introduced in the market rapidly. Until now, limited information is available on AGS regarding the removal of bacterial and viral pathogenic organisms present in sewage. This study focussed on determining the relation between reactor operational conditions (plug flow feeding, turbulent aeration and settling) and physical and biological mechanisms on removing two faecal surrogates, Escherichia coli and MS2 bacteriophages. Two AGS laboratory-scale systems were separately fed with influent spiked with 1.0 × 10 CFU/100 mL of E. coli and 1.3 × 10 PFU/100 mL of MS2 bacteriophages and followed during the different operational phases. The reactors contained only granular sludge and no flocculent sludge. Both systems showed reductions in the liquid phase of 0.3 Log during anaerobic feeding caused by a dilution factor and attachment of the organisms on the granules. Higher removal efficiencies were achieved during aeration, approximately 1 Log for E. coli and 0.6 Log for the MS2 bacteriophages caused mainly by predation. The 18S sequencing analysis revealed high operational taxonomic units (OTUs) of free-living protozoa genera Rhogostoma and Telotrochidium concerning the whole eukaryotic community. Attached ciliates propagated after the addition of the E. coli, an active contribution of the genera Epistylis, Vorticella, and Pseudovorticella was found when the reactor reached stability. In contrast, no significant growth of predators occurred when spiking the system with MS2 bacteriophages, indicating a low contribution of protozoa on the phage removal. Settling did not contribute to the removal of the studied bacterial and viral surrogates.
Topics: Aerobiosis; Bioreactors; Escherichia coli; Sewage; Waste Disposal, Fluid; Water Purification
PubMed: 33714012
DOI: 10.1016/j.watres.2021.116992 -
Biotechnology and Bioengineering Feb 2023Floccules are another major form of microbial aggregates in aerobic granular sludge systems. Previous studies mainly attributed the persistence of floccules to their...
Floccules are another major form of microbial aggregates in aerobic granular sludge systems. Previous studies mainly attributed the persistence of floccules to their relatively faster nutrient uptake and higher growth rate over aerobic granules; however, they failed to unravel the underlying mechanism of the long-term coexistence of these two aggregates. In this work, the existence and function of the floccules in an aerobic granule-dominated sequencing batch reactor were investigated from the view of quorum sensing (QS) and quorum quenching (QQ). The results showed that though the floccules were closely associated with the granules in terms of similar community structures (including the QS- and QQ-related ones), they exhibited a relatively higher QQ-related activity but a lower QS-related activity. A compatible proportion of floccules might be helpful to maintain the QS-related activity and keep the granules stable. In addition, the structure difference was demonstrated to diversify the QS- and QQ-related activities of the floccules and the aerobic granules. These findings could broaden our understanding of the interactions between the coexistent floccules and granules in aerobic granule-dominated systems and would be instructive for the development of the aerobic granular sludge process.
Topics: Quorum Sensing; Sewage; Bioreactors; Biological Transport; Aerobiosis
PubMed: 36303067
DOI: 10.1002/bit.28275 -
Water Science and Technology : a... Aug 2020Despite aerobic granular sludge wastewater treatment plants operating around the world, our understanding of internal granule structure and its relation to treatment...
Despite aerobic granular sludge wastewater treatment plants operating around the world, our understanding of internal granule structure and its relation to treatment efficiency remains limited. This can be attributed in part to the drawbacks of time-consuming, labor-intensive, and invasive microscopy protocols which effectively restrict samples sizes and may introduce artefacts. Time-domain nuclear magnetic resonance (NMR) allows non-invasive measurements which describe internal structural features of opaque, complex materials like biofilms. NMR was used to image aerobic granules collected from five full-scale wastewater treatment plants in the Netherlands and United States, as well as laboratory granules and control beads. T and T relaxation-weighted images reveal heterogeneous structures that include high- and low-density biofilm regions, water-like voids, and solid-like inclusions. Channels larger than approximately 50 μm and connected to the bulk fluid were not visible. Both cluster and ring-like structures were observed with each granule source having a characteristic structural type. These structures, and their NMR relaxation behavior, were stable over several months of storage. These observations reveal the complex structures within aerobic granules from a range of sources and highlight the need for non-invasive characterization methods like NMR to be applied in the ongoing effort to correlate structure and function.
Topics: Aerobiosis; Bioreactors; Magnetic Resonance Spectroscopy; Netherlands; Sewage; Waste Disposal, Fluid
PubMed: 32970616
DOI: 10.2166/wst.2020.341 -
Nature Communications Nov 2020The spontaneous self-assembly of multicellular ensembles into living materials with synergistic structure and function remains a considerable challenge in biotechnology...
The spontaneous self-assembly of multicellular ensembles into living materials with synergistic structure and function remains a considerable challenge in biotechnology and synthetic biology. Here, we exploit the aqueous two-phase separation of dextran-in-PEG emulsion micro-droplets for the capture, spatial organization and immobilization of algal cells or algal/bacterial cell communities to produce discrete multicellular spheroids capable of both aerobic (oxygen producing) and hypoxic (hydrogen producing) photosynthesis in daylight under air. We show that localized oxygen depletion results in hydrogen production from the core of the algal microscale reactor, and demonstrate that enhanced levels of hydrogen evolution can be achieved synergistically by spontaneously enclosing the photosynthetic cells within a shell of bacterial cells undergoing aerobic respiration. Our results highlight a promising droplet-based environmentally benign approach to dispersible photosynthetic microbial micro-reactors comprising segregated cellular micro-niches with dual functionality, and provide a step towards photobiological hydrogen production under aerobic conditions.
Topics: Aerobiosis; Bioreactors; Cell Hypoxia; Chlorella; Escherichia coli; Hydrogen; Industrial Microbiology; Microbiota; Oxygen; Photosynthesis; Renewable Energy
PubMed: 33239636
DOI: 10.1038/s41467-020-19823-5 -
Environmental Research Nov 2022A thermotolerant strain isolated from sewage sludge (SS) composting was identified as Brevibacillus Agri N2, which showed the efficient capability for heterotrophic...
A thermotolerant strain isolated from sewage sludge (SS) composting was identified as Brevibacillus Agri N2, which showed the efficient capability for heterotrophic nitrification under high-temperature conditions. Incubation at 60 °C, strain N2 could utilize 45.47% of ammonium nitrogen (99.64 mg/L), 68.89% of hydroxylamine nitrogen (51.14 mg/L) and 76.77% of nitrite nitrogen (55.20 mg/L), with a minor part of nitrogen loss for 1.64%, 2.82% and 5.01%, respectively. The successful detection of ammonia monooxygenase, hydroxylamine oxidase, and nitrate oxidoreductase and PCR amplification of amoA, hao and nxrA genes provided evidence of nitrification ability by strain N2. Furthermore, single-factor experiments indicated that the optimal conditions for efficient nitrification performance by strain N2 were succinate as carbon source, 50 °C, C/N 12, pH 8 and 200 r/min. Strain N2 could perform the complete nitrification process, with minimal nitrogen loss at high temperature conditions, which indicated it had the potential for practical application for reducing nitrogen loss of SS composting.
Topics: Aerobiosis; Brevibacillus; Composting; Denitrification; Nitrification; Nitrogen; Sewage
PubMed: 35863446
DOI: 10.1016/j.envres.2022.113903 -
Food Microbiology Dec 2018Heterofermentative lactic acid bacteria (76 strains) belonging to Lactobacillus, Leuconostoc and Weissella species which are important in fermentation, spoilage or as...
Heterofermentative lactic acid bacteria (76 strains) belonging to Lactobacillus, Leuconostoc and Weissella species which are important in fermentation, spoilage or as probiotics were screened in a factorial experiment for their ability to grow, produce catalase and consume oxygen in aerobiosis or in anaerobiosis, with or without supplementation with hemin and/or menaquinone in a medium containing glucose as a carbohydrate source. Aerobiosis improved growth with a few exceptions. The effect of supplementation with heme and/or menaquinone was strain specific and clear evidence of heme-boosted respiration was found in some cases. Heme-catalase was produced by strains of L. brevis, W. minor and Leuc. mesenteroides; some strains of the latter species produced non-heme catalase. Shaken flasks experiments showed that aerobic growth resulted in increased maximum growth rate and in a limited increase in biomass. Heme supplementation during aerobic growth resulted in a further increase in growth rate and final biomass only for a few strains; this was often related to catalase, which was also responsible for increased tolerance of HO. In both experiments we found evidence of heme toxicity, especially in anaerobiosis and in absence of menaquinone. Dose response curves for aerobic growth in the presence of combinations of hemin and menaquinone were non-monotonic, with growth stimulation at low doses of heme (<2.5 mg/l) and toxicity at higher doses. Menaquinone at 0.25-8 mg/l increased growth stimulation and partially reduced toxicity.
Topics: Aerobiosis; Anaerobiosis; Biomass; Catalase; Fermentation; Heme; Lactobacillales; Lactobacillus; Oxidative Stress; Probiotics; Vitamin K 2
PubMed: 30166132
DOI: 10.1016/j.fm.2018.02.017 -
Environmental Science & Technology Apr 2017Rapid start-up of partial nitrification is of great significance for subsequent denitrification and the anammox process; however, slow nitritation hinders the...
Rapid start-up of partial nitrification is of great significance for subsequent denitrification and the anammox process; however, slow nitritation hinders the application of these processes. The current study presents a novel strategy for achieving nitritation using aerobic starvation and controlling sludge retention time (SRT). Activated sludge with a high level of complete nitrification was introduced into an aerated reactor without feeding to start the aerobic starvation. The results showed that nitritation was rapidly achieved, while the shorter SRT (15 days) guaranteed the stability of nitritation with an average nitrite accumulation ratio (NAR) of more than 95%. The activity recovery rates of ammonium-oxidizing bacteria (AOB; from 0.20 ± 0.00 d to 0.29 ± 0.08 d) were higher than those of nitrite-oxidizing bacteria (NOB; -0.11 ± 0.02 d to 0.16 ± 0.05 d) during the reactivation periods. Furthermore, the transcriptional responses of amoA and hao mRNA after aerobic starvation were faster than that of the nxrB gene, which explained the fast occurrence of nitritation after the aerobic starvation period. The quantitative real-time PCR (qPCR) analysis showed that the cell number of nitrifying bacteria remained stable during the starvation process, whereas the AOB population gradually became dominant over that of NOB in the reactivation period. These observations strongly supported the feasibility of accelerating the establishment of nitritation using aerobic starvation.
Topics: Aerobiosis; Bacteria; Denitrification; Nitrification; Nitrites; Sewage
PubMed: 28263587
DOI: 10.1021/acs.est.6b04598 -
Journal of Dairy Science Oct 2021There is an increasing recognition throughout the world that many of the feeding problems of dairy herds are linked to the presence of aerobically deteriorated parts on...
There is an increasing recognition throughout the world that many of the feeding problems of dairy herds are linked to the presence of aerobically deteriorated parts on a silo face, causing farmers to pose questions on what amount of silage should be removed daily to feed their animals. Since an adequate feed-out rate helps to prevent silage spoilage, a simple tool is needed to manage the aerobic deterioration of corn silages during feed-out. The aims of this study were to develop an unloading rate index, which we have called the mass feed-out rate (MFR), expressed in kilograms of fresh matter silage unloaded daily per square meter of silo face, to better predict the aerobic deterioration of silage and to offer management solutions to help prevent spoilage, through a survey on 97 commercial dairy farms in Italy and Brazil. Silages were sampled and analyzed for their main microbial, fermentative, and nutritional characteristics, whereas silage temperatures were measured in the core and peripheral areas of the silo working face. Moreover, a detailed questionnaire on silo management and silage utilization was administered to the farmers during each farm visit. The size and silage density of the silos presented a wide variability in the 2 countries, thus indicating that different management practices were adopted during corn harvesting, silo filling, and silage compaction. The differences between pH and temperature in the peripheral areas and in the core of the silage (dpH and dT, respectively) were tested as a single indicator to identify any aerobic deteriorated areas on the silo face, associated with the yeast and mold counts. Both indicators correctly identified aerobic deterioration in 86.6% and 93.8% of the studied silos, respectively. The lactic acid and ethanol increased as the MFR increased, whereas the starch, dT, and the yeast and mold counts decreased with increasing MFR. A daily removal rate of over 250 kg of silage/m markedly reduced the risk of spoilage in corn silages at a farm level in both temperate and tropical environments. The new MFR index can substitute for the commonly used linear feed-out rate as it includes the silage density and can be obtained from 1 single recording.
Topics: Aerobiosis; Animals; Fermentation; Fungi; Silage; Yeasts; Zea mays
PubMed: 34275635
DOI: 10.3168/jds.2021-20419