Aerobic Heterotrophic Microorganisms Research Articles

Fast development of purple nonsulfur bacteria (PNSB) in a bubble column photobioreactor: Influence of carbon source and dissolved O2 availability on wastewater treatment performance

Photobioreactors with purple nonsulfur bacteria (PNSB) constitute a promising technology for wastewater treatment, gas purification, and high value-added bioproducts. In this work, different operational strategies were tested to investigate their impacts on photobioreactor performance, biomass properties, and microbial community. It showed that the operational conditions significantly influence the performance and microbial composition of PNSB photobioreactors. Anaerobic conditions favored the dominance of Rhodopseudomonas spp. and moderate COD removal efficiency (36.7 %), while aerobic conditions significantly enhanced COD removal efficiency (91.7 %) but altered the microbial community composition from PNSB to aerobic heterotrophic microorganisms, such as Delftia sp. and Microbacterium sp.. The removal ratio of chemical oxygen demand (COD):N:P was 100:10:2 under anaerobic conditions with continuous CO2 supply, while it was 100:1:1 under aerobic conditions with continuous supply of a CO2/O2 mixture. Net CO2 removal efficiencies of 2.8 % and 5.4 % were recorded under anaerobic conditions with and without the addition of organic carbon, respectively. The outlet CO2 concentration showed that CO2 uptake occurred under dark and anaerobic conditions without organic carbon. The reduced production of extracellular polymeric substances (EPS) was observed after COD was removed from the influent, preventing granule formation.

The Use of Lawn Grasses for Purification of Soil From Toxic Cr(VI)

Background. Environmental pollution with toxic compounds poses a danger to nature and humans. Various technologies for soil purification from toxic metals are being developed. Objective. The work was aimed to study the possibility of lawn grass using for soil purification from Cr(VI). Methods. Plant seeds (Festuca rubra L. 45%, Festuca arundinacea Schreb. 25%, Lolium perenne L. 20%, Poa pratensis L. 10%) were sown in a container at 24 °C and grown for two months to obtain a lawn. K2CrO4 was added to the soil (400 g) (variants: 1.0 g, No. 1 and 2.5 g, No. 2) The following parameters were determined in two, five and ten days after Cr(VI) addition to the soil: the content of Cr(VI) in the roots, aerial part, and the soil; the coefficient of Cr(VI) content reduction; total content of aerobic heterotrophic microorganisms (CFU/g). Results. In 2 days after Cr(VI) adding the roots accumulated Cr(VI) in more significant amounts than the leaves (16.6 and 15 times in No. 1 and No. 2). In 5 days, an increase in Cr(VI) concentration in the plants was detected. Cr(VI) concentration in the soil decreased in 5 days by 45.8 and 13.57 times in variants No. 1 and No. 2, respectively. Inhibition of soil microorganisms growth was detected. CFU number in the control sample was 7.2×108, and in experimental variants No. 1 and No. 2 – 5×106 and 1×106, respectively. Conclusions. The addition of K2CrO4 inhibited the growth of soil microorganisms. Lawn grasses composition was successfully used for Cr(VI) extraction from the soil. A notable (13.8 and 9.3 times) reduction in Cr(VI) content in the soil was observed in two days. This reduction progressed greatly in five days as well (91.8 and 85.0 times). Cr(VI) was accumulated in the root system and the leaves of the plants. Thus, the selected grasses can be used in bioremediation technologies to purify contaminated soil.

Saccharomyces exiguus Uses Kerosene as a Source of Carbon and Energy

Kerosene is a fuel derived from petroleum, a mixture of aliphatic and aromatic hydrocarbons, which eventually cause environmental pollution. In nature, there are genera and species of aerobic heterotrophic microorganisms, native to all environments, that have the potential capacity to degrade kerosene, such as some genera and species of yeast, to synthesize protein of unicellular origin or to bioaugment the negative environmental impact of kerosene. for the above. The objective of this work was to analyze the ability of Saccharomyces exiguus to use kerosene as a carbon and energy source. For this, S. exiguus was isolated from oil wells, it was grown in 5% kerosene with 1.2% NH4Cl and 50 ppm yeast extract. The growth of S. exiguus in kerosene was analyzed using the response variables: dry weight, protein quantification, and gas chromatography showed the use of kerosene components as a carbon and energy source. The results showed that S. exiguus can use the aliphatic and aromatic hydrocarbons of kerosene as the only source of carbon and energy, this potential is applicable to synthesize unicellular protein or in the recovery of environments impacted by kerosene.

Effect of Different Immersion Tank Water Temperatures on the Microbiological Quality of Rabbit Carcasses

The pre-chilling of rabbit carcasses in an immersion tank directly interferes with microbial control. Therefore, this study was developed to examine the influence of different pre-chill tank water temperatures (4, 7, and 10 °C) on the microbiological quality of rabbit carcasses. Samples of rabbit carcasses and water and ice from the pre-chiller tank were collected; mesophilic aerobic heterotrophic microorganisms (MES), enterobacteria (EC), and coagulase-positive Staphylococcus (CPS) were counted; and the presence of Salmonella spp. was investigated. After the carcasses were immersed in the pre-chiller, there was a significant increase (p < 0.05) in MES (38.69 and 88.06 Log CFU·mL−1 at 4 and 10 °C, respectively) and EC (3.20, 4.15, and 4.84 Log CFU·mL−1 at 4, 7, and 10 °C, respectively). The average EC count tended to increase after the carcasses were immersed in the pre-chiller at different temperatures, but this increase was not significant. Water samples showed MES, EC, and CPS counts only after the immersion of the carcasses; however, the presence of these microorganisms was not detected in any of the ice samples. Salmonella spp. was not identified in the analyzed samples. The microorganisms analyzed at the three pre-chiller water temperatures evaluated did not multiply on the surface of the rabbit carcasses or in the pre-chiller water after carcass immersion. This study showed that none of the three pre-chilling temperatures were able to reduce the count of indicator microorganisms in the carcasses of rabbits. These data provide scientific support to discuss the need for specific norms and guidelines for rabbit meat production.

Microbiological analysis of technozems of the Abagura agglomeration and concentration factory tailings dump

Microorganisms participate in the processes of restoration of contaminated soil ecosystems. Analysis of the processes is important for the biomonitoring of reclaimed territories and can improve the accuracy of forecasts of detoxification processes of the formed technozems. In the process of study of the microbiological state of the technozems of the Abagur agglomeration and concentration plant tailings dump, Novokuznetsk, changes in the group and species composition of soil aerobic heterotrophic microorganisms were studied and a quantitative assessment of the saprotrophic microflora content was presented. A microbiological analysis of the original sewage sludge (WWS) shows their initially high biological contamination by a wide taxonomic spectrum of microorganisms. It was shown, that the use of WWS for the enrichment of iron ore wastes by an organic substance contributes to the microbiological saturation of the latter at the level of ecological trophic diversity. The overall level of microbial population increases sharply compared with the control man-caused option, regardless of the way the WWS placing and its “quality”. At that, the WWS material neutralized by quicklime is most available to microorganisms, as evidenced by stimulation of the growth of representatives of various taxonomic affiliations and a high mineralization coefficient of the organic substance of the used ameliorant. The control man-caused substrate - soil mixture without organic additives is characterized by weak microbiological contamination. A microbiological analysis shows that small amounts of ammonifying microorganisms of various taxonomic affiliations, as well as bacteria and proactinomycetes with a trophic strategy for utilization of mineral forms of nitrogen, can be found in small amounts on the surface of the tailings dump. Biological testing of microbiological samples showed that in rehabilitated ecosystems with WWS during the microbiological mineralization of organic substance by active pathogens, actinomycetes and fungi participate in the destruction of protein compounds along with bacteria.

Effect of variations in heterotrophic plate count methods on bacterial estimation in some sachet water in Calabar Metropolis

Heterotrophic plate count (HPC) or standard plate count is a standardized method for determining the density of aerobic and facultative anaerobic heterotrophic microorganisms in water. In this study, water samples were analyzed to ascertain the effects of temperature, media, and incubation time in HPC methods of bacterial estimation. The samples were analyzed using the membrane filtration and direct plating methods. No faecal coliform was detected in all the samples and at all temperature. However, some coliforms and heterotrophic bacteria were present in the water samples. The organisms were isolated at 4 °C, 28 °C and 37 °C after 24-72 h. The heterotrophic bacterial isolates include: Enterobacter spp., Staphylococcus aureus, S. epidermidis, Bacillus sphericus, B. cereus, Micrococcus roseus, Pseudomonas aeruginosa and Klebsiella pneumonia. It was observed that yeast extract agar gave a higher heterotrophic plate count at 28 °C while EMB agar yielded the highest total coliform count at 37 °C. The result of the physicochemical analysis showed that the water samples met the World Health Organization (WHO) and Standards Organization of Nigeria (SON) standards for drinking water while the bacteriological quality based on the total coliform count result indicates the need for improvement in the treatment systems.

Biofloc formation improves water quality and fish yield in a freshwater pond aquaculture system

High-throughput sequencing of the 16S rRNA gene of microbial communities was used to investigate how biofloc technology (BFT) improved water quality and fish yield in freshwater pond aquaculture. Three treatments included conventional treatment (CT), biofloc treatment (BT) and biofloc systems augmented with floc-forming bacterium (Zoogloea resiniphila MMB) treatment (BZT). The feeding trial lasted for 8 weeks with triplicate groups of cyprinid species in nine enclosures, which were placed in an outdoor pond to simulate a real aquaculture environment. Biofloc was generated by adding organic carbon and continuous aeration, which resulted in reducing dissolved nitrogen from 22% to 14% and sedimentary nitrogen from 49% to 5% and increasing nitrogen accumulation in biofloc and fish biomass. Nitrogen content in fish biomass increased from 28% in a CT to 42% when BFT was applied. Changes in the bacterial community and stimulation of biofloc formation played a central part in transferring nitrogen from remaining food, excreta and feces to bacteria and fish biomass. Z. resiniphila MMB did not outcompete indigenous communities and had no impact on floc formation by direct addition to the pond. Filamentous bacteria comprised the major structure of biofloc, while the proportion of zoogloea-forming microorganisms was very low. The proportion of aerobic heterotrophic microorganisms increased in both BFT treatments. Actinobacteria promoted the formation of floc and could have secondary benefits of protecting against fish pathogens, such as Aeromonas sp., though may increase the accumulation of off-flavor in the water and fish tissue.

Abundance and diversity of aerobic heterotrophic microorganisms and their interaction with cyanobacteria in the oxic layer of an intertidal hypersaline cyanobacterial mat.

Aerobic heterotrophic microorganisms (AH) play a significant role in carbon cycling in cyanobacterial mats; however, little is known about their abundance, diversity and interaction with cyanobacteria. Using catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), bacterial counts in the mat's oxic layer reached a mean of 2.23±0.4×1010 cells g-1. Cultivation of AH yielded strains belonging to Actinobacteria, Bacteroidetes, Firmicutes, Gammaproteobacteria and Haloarchaea. 16S rRNA bacterial sequences retrieved from the mat's oxic layer were related to Bacteroidetes, Chloroflexi and Proteobacteria, whereas archaeal sequences belonged to Crenarchaeota and Haloarchaea. Monocultures of cyanobacteria from the same mat were associated with different AH, although Bacteroidetes were found in most cultures. CARD-FISH showed that Bacteroidetes- and Chloroflexi-related bacteria were closely associated with filaments of Microcoleus chthonoplastes. The growth of an axenic culture of M. chthonoplastes PCC7420 was stimulated on the addition of a filtrate obtained from a non-axenic Microcoleus culture and containing only AH and released substances. In contrast, a similar filtrate from a non-axenic Cyanothece-related culture killed Cyanothece PCC 7418. We conclude that a diverse community of AH exist in close association with cyanobacteria in microbial mats and the interactions between AH and cyanobacteria are species-specific and involve the release of substances.

Evaluation of Quality Parameters in the Meat of Pintado Amazônico, Female Pseudoplatystoma fasciatum × Male Leiarius marmoratus, Subjected to Different Slaughter Methods

AbstractThe objective of this study was to check the effect of different stunning methods on the meat quality of Pintado Amazônico, female Pseudoplatystoma fasciatum × male Leiarius marmoratus, stored on ice for 18 d. A total of 90 specimens (2.5 ± 0.45 kg and 58.21 ± 6.20 cm) were divided into three groups and subjected to stunning by: water saturated with CO2, hypothermia on ice, or asphyxia in air. Subsequently, samples were removed to be analyzed after (times) 0, 2, 4, 6, 8, 10, 12, 14, 16, and 18 d. At the established times, aerobic mesophilic heterotrophic microorganisms and aerobic psychrotrophic heterotrophic microorganisms were quantified, and the pH, total volatile base nitrogen, color (L*a*b*), and sensory traits were analyzed. The stunning method significantly affected (P < 0.05) the meat quality. The group stunned on ice showed the best results compared with the other treatments.

Research of Processes of a Deep Aerobic Mineralization of Activated Sludge

The article describes the process of deep aerobic mineralization of activated sludge in municipal wastewater treatment plants using a complex of aerobic heterotrophic and autotrophic microorganisms, including denitrifiers.

Microbiological and biogeochemical properties of the Caspian Sea sediments and water column

The work presents the results of investigation of microbial and biogeochemical processes at the water-sediment interface in the samples of three Caspian Sea profiles obtained during the 39th cruise of RV “Rift” in May–June 2012. The decrease in suspended Corg content from the surface to the bottom resulted from the activity of aerobic heterotrophic microorganisms. Autotrophic methanogenesis occurred in anoxic water of deep-sea depressions, where methane concentrations were up to 2.2–3.75 μL CH4 L−1, which was an order of magnitude higher than in the aerobic water column (0.04–0.32 μL CH4 L−1). Methanogenesis was accompanied by a considerable decrease in δ13C of suspended Corg (−26 to −30‰). The numbers of microbial cells in the water column varied from 40 to 3200 × 103 cells mL−1. The results of microbiological and biogeochemical investigation demonstrated that, in spite of the absence of connection with the ocean and other specific features, the Caspian Sea has the characteristics of a typical marine basin.

Estudio de la influencia microbiológica en la corrosión de latones (UNS C68700, UNS C443) y acero inoxidable AISI 316;

Microorganisms may play an important role in the corrosion process and generate conditions which affect the rate and/or the mechanism of deterioration. They become visible by the formation of biofilms: clusters of microorganisms and extracellular polymers. These biofilms affect not only the durability of the material, but also reduce the heat transfer. The present work studied the growth of aerobic and anaerobic heterotrophic microorganisms and sulfate reducing bacteria on aluminum brass (UNS C68700), admiralty brass (UNS C443) and stainless steel AISI 316 in exposure experiments held in the Bay of Montevideo (Uruguay). The influence of the biofilm growth on the corrosion behavior was studied by electrochemical techniques: polarization curves and Electrochemical Impedance Spectroscopy (EIS). The selection of the most suitable material for the exposure conditions is discussed and hypotheses of the corrosion mechanism are presented. Although stainless steel AISI 316 presented the lowest corrosion rate it showed localized deterioration.

Effects of leaching from alkaline red mud on soil biota: modelling the conditions after the Hungarian red mud disaster

A soil column experiment was set up to investigate the effect of red mud from Ajka (Hungary) on a typical soil profile from the affected area. The chemical changes caused by the red mud leachate and the effects of these changes on living organisms were assessed. Ecotoxicological tests were performed with Vibrio fischeri, Sinapis alba and Folsomia candida and the number of aerobic heterotrophic microorganisms was determined. The total, plant-available, exchangeable and water-soluble fractions of Na, Mo, Cu and Cr increased in the soil, mostly owing to their leaching from the red mud layer, but partly to the increase in the pH and DOC concentration. The chemical changes only had significant effects on the test organisms in the 0–30 cm soil layer, except for F. candida, which also had a lower survival rate in the 30–50 cm soil layer. No severe toxic effects were detected in the test organisms; in fact a stimulating effect was revealed for the aerobic heterotrophic cell number and for S. alba germination. However, the red mud itself was toxic, so the ecotoxicological tests justified the removal of red mud from the soil surface after the disaster.

Antimicrobial action and effects on beef quality attributes of a gaseous ozone treatment at refrigeration temperatures

The effects of gaseous ozone treatment at refrigeration temperatures, on microbial counts (total aerobic mesophilic heterotrophic microorganisms and inoculated Escherichia coli) in culture media and in beef samples were analyzed. The influence of ozone on beef quality properties such as surface color and rancidity was measured.The effect of gaseous ozone (154 × 10−6 kg m−3) in culture media inoculated with E. coli after 3- or 24-h treatment at 0° and 4 °C caused a total inactivation of this microorganism.For beef samples treated with the same gaseous ozone concentration, the highest microbial inhibition was observed at 0 °C and after 24-h exposure, producing a decrease of 0.7 and 2.0 log10 cycles in E. coli and total aerobic mesophilic heterotrophic microorganism counts respectively; however, both the surface color and lipid oxidation of these beef samples were unacceptable. Shorter exposure times (3 h) to the tested ozone concentration at both temperatures (0–4 °C), reduced 0.5 log10 cycles the counts of total aerobic mesophilic heterotrophic microorganisms and 0.6–1.0 log10 cycles the counts of E. coli, without changing the color or producing rancidity in beef.

Environmental Impact after 30 to 60 Years of Remediation: Microbial Investigation of Hard Coal Mining Dumps in Germany

Important groups of microbes were investigated in three hard coal mining dumps in Saxonia/ Germany. In the particular dumps, different chemophysical and geochemical conditions are existing, depending on the kind of remediation up to six decades ago. Thiobacillus denitrificans, iron and sulfate reducers, and general aerobic heterotrophs and fungi were counted by MPN and CFU methods. Samples were taken from drilling cores in different depths out of the dumps, from seepage-, surface- and ground waters and from sediments. Similarities and significant differences were found between the microbial populations of the three dumps, depending on the appropriate environmental conditions. As a result, enhanced counts of T. denitrificans were detected at all three sites, originating from fertilizers (agricul-ture, gardens) and atmospheric precipitations. Sulfate reducers and aerobic heterotrophic microorganisms are suited indicators for the ongoing biogeochemical processes in the dumps

Distribution of microorganisms in the oil-polluted ground of vadose and saturation zones

The ground polluted with oil products was analyzed at a depth of 0.5–7.8 m (loamy soil), 11.5–13.0 m (gravelstone), 13.0–15.0 m (siltstone). It was shown that the distribution of oil products and microorganisms in the ground over the profile depends on the hydrogeological properties of the rock (porosity, hydraulic conductivity). The number of aerobic heterotrophic microorganisms varied from 106–107 CFU/g, the fraction of hydrocarbon-oxidizing ones increased with depth from 30 to 85%. The number of anaerobic microorganisms was comparable to the number of aerobic ones. The number of psychrotrophs and psychrophiles increases with depth; in the lower horizon these organisms prevail over the number of mesophiles.

Alkylphenol Polyethoxylate Removal in a Pilot‐Scale Reed Bed and Phenotypic Characterization of the Aerobic Heterotrophic Community

The removal of the non-ionic surfactant Triton X-100, dosed at 30 and 300 mg/L in a pilot-scale subsurface horizontal flow reed bed, and the aerobic heterotrophic cultivable community associated with the roots and with the substrate gravel in both absence and presence of Triton X-100 were investigated. t-Octylphenol (OP) and its mono-, di- and tri-ethoxyl derivatives, among others, were found in the outlet. A mass balance allowed us to calculate that approximately 40% of the Triton X-100 metabolites OP and octylphenol polyethoxylate derivatives flowed out of the reed bed during the dosage and postdosage experiments. More aerobic heterotrophic microorganisms adhered to the roots than to the gravel. The appearance of new strains (Aeromonas, Flavobacterium, and Aquaspirillum) and the increased presence of others (Pseudomonas) during the dosage of Triton may be linked to the capacity of these bacteria to adapt to the presence of the surfactant or to use it as a nourishment.

Non-phototrophic CO 2 fixation by soil microorganisms

Although soils are generally known to be a net source of CO2 due to microbial respiration, CO2 fixation may also be an important process. The non-phototrophic fixation of CO2 was investigated in a tracer experiment with 14CO2 in order to obtain information about the extent and the mechanisms of this process. Soils were incubated for up to 91 days in the dark. In three independent incubation experiments, a significant transfer of radioactivity from 14CO2 to soil organic matter was observed. The process was related to microbial activity and could be enhanced by the addition of readily available substrates such as acetate. CO2 fixation exhibited biphasic kinetics and was linearly related to respiration during the first phase of incubation (about 20–40 days). The fixation amounted to 3–5% of the net respiration. After this phase, the CO2 fixation decreased to 1–2% of the respiration. The amount of carbon fixed by an agricultural soil corresponded to 0.05% of the organic carbon present in the soil at the beginning of the experiment, and virtually all of the fixed CO2 was converted to organic compounds. Many autotrophic and heterotrophic biochemical processes result in the fixation of CO2. However, the enhancement of the fixation by addition of readily available substrates and the linear correlation with respiration suggested that the process is mainly driven by aerobic heterotrophic microorganisms. We conclude that heterotrophic CO2 fixation represents a significant factor of microbial activity in soils.

Structure of planktonic microbial food web in a brackish stratified Siberian lake

The distribution of primary components of the microbial community (autotrophic pico- and nanoplankton, phototrophic bacteria, heterotrophic bacteria, microscopic fungi, heterotrophic flagellates, ciliates and heliozoa) in the water column of Lake Shira, a steppe brackish-water, stratified lake in Khakasia, Siberia (Russia), were assessed in midsummer. Bacterioplankton was the main component of the planktonic microbial community, accounting for 65.3 to 75.7% of the total microbial biomass. The maximum concentration of heterotrophic bacteria were recorded in the monimolimnion of the lake. Autotrophic microorganisms contributed more significantly to the total microbial biomass in the pelagic zone (20.2–26.5%) than in the littoral zone of the lake (8.7–14.9%). First of all, it is caused by development of phototrophic sulphur bacteria at the oxic-anoxic boundary. The concentrations of most aerobic phototrophic and heterotrophic microorganisms were maximal in the upper mixolimnion. Heterotrophic flagellates dominated the protozoan populations. Ciliates were minor component of the planktonic microbial community of the lake. Heterotrophic flagellates were the most diverse group of planktonic eucaryotes in the lake, which represented by 36 species. Facultative and obligate anaerobic flagellates were revealed in the monimolimnion. There were four species of Heliozoa and only three of ciliates in the lake.

Aerobic granulation in a sequencing batch reactor

In a sequencing batch reactor (SBR) granules of aerobic heterotrophic microorganisms were cultured. The effect of different operational conditions on the formation of these aerobic granules were studied. The time allowed for settling was the main parameter to select for growth of bacteria in well settling granules. Both a short HRT and a relative high shear were found favorable for granulation. A substrate loading rate of 7.5 kg COD/(m 3 day) was applied. This led to formation of granules with an average diameter of 3.3 mm and a biomass density of 11.9 gVSS/l granule. Based on microscopic observations a hypothesis for the granulation process was formulated. The reactor was started up without any carrier material present. At the beginning filamentous fungal pellets dominated the reactor. These pellets functioned as an immobilization matrix in which bacteria could grow out to colonies. After a certain time the fungal pellets fell apart due to lysis in the inner part of the pellets, the bacterial colonies could now remain in the reactor because they were large enough to settle sufficiently fast. These colonies further grew out to granules. This paper shows that granule formation in aerobic reactors is feasible and can be exploited to increase the volumetric conversion capacity of such reactors.