Mixed Bacterial Consortium Research Articles

Bioremediation of Petroleum Polluted Soils using Consortium Bacteria

This study was carried out to isolate opportunistic hydrocarbons oil-degrading bacteria and develop a consortium or a mixture of bacteria with high biodegradation capabilities which can be used in biological treatment units of the contaminated water before release. The biological processes in general are environmentally friendly and cost effective, as they are easy to design and apply; as such they are more appropriate to the public.
 The location of the study was in Al-Dora refinery sludge holes area. The samples were collected for three seasons (winter, spring and summer) each consisted of three months. The sludge samples were analyzed for various physical and chemical parameters. Temperature values of the sludge were at maximum in summer season, reaching 32˚C, whereas they were at minimum in winter (24 ˚C). The values of sludge pH were at maximum in summer (9.70) and minimum in winter (9.20). Turbidity levels were 382 NTU in spring and 353 NUT in winter. Biological oxygen demand (BOD5) was at maximum in summer (760) and (690 mg/l) in winter. The maximum dissolved oxygen (DO) value of 5.20 mg/l was recorded in winter, while the minimum was 3.80 mg/l recorded in summer. The maximum electrical conductivity (EC) was 17130 μs/cm recorded in summer, while the minimum was 16150 μs/cm recorded in winter. The maximum total dissolved solids (TDS) values were 10335 mg/l recorded in summer, while the minimum (10015 mg/l) was recorded in winter. The maximum total petroleum hydrocarbon (TPH) value (431 mg/l) was recorded in summer, while the minimum (367 mg/l) was recorded in spring. Finally, the maximum salinity value (9.90%) was recorded in spring, while the minimum (9.30%) was recorded in winter. Also, hydrocarbon compounds in sludge samples were measured using Gas Chromatography - Mass Spectrometry (GC-MS), and the result showed that they were composed of 31 hydrocarbon compounds.In the present work, nineteen sludge degrading bacterial strains were isolated from the soil near Al-Dora refinery hole by primary and secondary screenings using a modified mineral salt medium supplemented with 1% (v/v) sludge as a carbon source. The most efficient two sludge degraded isolates identified by VITIK 2 compact were Kocuria rosea and Bacillus amyloliquefaciens. The tow isolates and there mixture showed best growth at 30°C for 12 days, as shown by the measurement of the optical density of the liquid culture and the final oil concentration by spectrophotometer.
 The bacterial isolates in liquid media with 2% (v/v) sludge showed best growth and the maximum biodegradation percentage after 12-day incubation period, as determined by gas chromatographic (GC). The degradation values were 68.9, 93.8 and 95.5% for Bacillus amyloliquefaciens, Kocuria rosea and the mixture of the tow isolates, respectively. In optimum conditions of pH 7, 40°C, 12 days incubation, the mixed bacterial consortium showed maximum sludge degradation.

Effectiveness of ozone pretreatment on bioconversion of oily bilge water into biopolymer

Oily bilge water (OBW) is complex wastewater generated from ship operation. In the present study, the application of ozonation pretreatment before the sequential batch reactor (SBR) for removing organics and polyhydroxyalkanoates (PHA) production from complex OBW were investigated. OBW was subjected to lab-scale ozone pretreatment under the various experimental conditions such as a specific reaction time (0 min–120 min), inlet ozone dose (0.5 g/L–2.5 g/L) and solution pH (4–8). Pretreatment of OBW by ozone improved biodegradability index (BDI) from 0.36 to 0.52. The GC–MS analysis revealed that the BDI enhancement was due to the formation of water-soluble carboxylic groups after 75 min of ozonation operated at solution pH 6 and 2 g/ L of O3 dose. The CODs removal efficiency was 68 % and 92 % for SBR and ozonized SBR respectively. Also, the biopolymer production rate was increased by 4.5 folds for ozonized SBR as the bioconversion of carboxylic compounds by using a mixed bacterial consortium (MBC) was stress-free. The functional groups and thermal property of the produced PHA were tested by various analytical techniques. These results confirmed that the bioconversion of ozonized OBW into valuable biological polyesters using MBC.

Biodegradation of Reactive Orange 16 Dye in Microbial Fuel Cell: An Innovative Way to Minimize Waste Along with Electricity Production.

Microbial fuel cell (MFC) is an attractive green technology which harnesses the power of microorganism for the production of electricity along with bioremediation of waste. However, the bioremediation of the high concentration of dye wastewater in MFC remains unclear. In present study, double-chambered MFC inoculated with mixed bacterial consortium was used for bioremediation of reactive orange 16 (RO-16) dyes at a very high and variable concentration range of 100 to 1000ppm. Maximum voltage was obtained for 100ppm of dye and was found to be 0.5791V along with a power density of 0.0851W/m3. Till 500 ppm concentration of dye COD removal efficiency remains in range of 40 to 100% thereafter it decreases. The maximum concentration of CO2 was found to be 2% at 1000ppm which confirms the biodegradation phenomena in MFC. Kinetics of biodegradation of reactive orange 16 were studied using Haldane inhibitory kinetic model and kinetic constants μmax, Ks, and Ki were calculated and found to be 0.417day-1, 206.2ppm, and 447.12ppm respectively. The experimental results showed inhibitory condition in the MFC after 500ppm and it was supported by the value of inhibitory kinetic constant Ki= 447.12ppm. This study opened the possibility of bioremediation of dyes at high concentrations in MFCs.

Evaluation of mass transfer effect and response surface optimization for abatement of phenol and cyanide using immobilized carbon alginate beads in a fixed bio‐column reactor

AbstractCoke oven sectors dispense phenol and cyanide into the circumferential ecosystem, which becomes a serious concern to the subsistence of the flora and fauna. The current study investigates phenol–cyanide treatment using carbon alginate beads immobilized with mixed bacterial consortium. Response surface using central composite design was contrived for the batch and packed bed bio‐column optimization study. The optimal removal conditions obtained in batch study were 89.77% and 82.33% for phenol and cyanide, respectively, with 10‐g/L adsorbent dosage, time 2 hr, and particle diameter 0.3 cm, whereas 87.22% and 90.97% with 22‐cm column height, column diameter 3 cm, 10‐ml/min flow rate, and 1‐hr operation time. The actual exposure time of the pollutants in the bio‐column reactor was calculated to be 22.15 min. Analysis of variance and model statistics predicted a high coefficient of determination for column operation with R2 = .9950 (phenol), R2 = .9976 (cyanide), and p values < .0001 stating significant model. The quantitative estimation of the combined external mass transfer and biodegradation effect was performed to evaluate correlation as (phenol) and (cyanide) with km = 0.052 and km = 0.055 cm/hr, respectively. The surface morphological study was executed by field emission scanning electron microscopy and Brunauer–Emmett–Teller surface area analysis depicting bacterial film development on the porous carbon matrix for effective treatment of binary system.

Improving dark fermentative hydrogen production through zero-valent iron/copper (Fe/Cu) micro-electrolysis.

To investigate the effect of zero-valent iron and copper (Fe/Cu) micro-electrolysis on dark fermentative hydrogen production from glucose by a mixed bacterial consortium and the possible mechanisms of increasing hydrogen yield. Compared to zero-valent iron and activated carbon (Fe/C) micro-electrolysis, Fe/Cu micro-electrolysis could increase hydrogen yield by 32.2%, hydrogen production potential by 27.1%, and the maximum hydrogen production rate by 62.0%. Meanwhile, the number of ferrous ions released into the liquid phase with Fe/Cu micro-electrolysis was about 27.0% greater than that released by Fe/C micro-electrolysis, because the dispersion of copper on the surface of iron could markedly improve electrochemical corrosion activity. Metabolic analysis revealed that Fe/C micro-electrolysis promoted acetate formation, which may have been responsible for the observed improvement in fermentative hydrogen production. Further investigation indicated that Fe/Cu micro-electrolysis increased the activity of hydrogenases and stimulated the expression of the [FeFe]-hydrogenase gene. Fe/Cu micro-electrolysis is better than Fe/C micro-electrolysis or Fe corrosion alone for dark fermentative hydrogen production.

Development of a sulfidogenic bioreactor system for removal of co-existent selenium, iron and nitrate from drinking water sources

The present study showed for the first time that selenium, iron, and nitrate could be simultaneously removed in a sulfidogenic bioreactor to meet drinking water standards. A bioreactor inoculated with mixed bacterial consortium was operated for around 330 days in anoxic environment at 30 °C under varying combination of influent selenate (200–1000 μg/L as selenium), and iron (3–10 mg/L) in presence of 50 mg/L of nitrate. Required amount of acetic acid (as carbon source) and sulfate were supplied and the reactor was operated at different empty bed contact time (EBCT) of 45–120 min. Along with complete removal of nitrate, the reactor removed both selenium and iron to meet the drinking water standards. Field emission transmission electron microscopy (FETEM) and X-ray diffraction (XRD) analyses confirmed the formation of selenium sulfide (SeS), achavalite (FeSe) and pyrite (FeS2), which were the possible removal mechanisms of selenium and iron. Thus, this study exhibited that selenium, iron, and nitrate can be simultaneously removed to meet the drinking water standards in a sulfidogenic bioreactor.

Coupling enhancement of Chromium(VI) bioreduction in groundwater by phosphorus minerals

Groundwater contaminated by hexavalent chromium (Cr(VI)) has posed severe threat to the environment and public health. Although heterotrophic bioremediation has been known as an efficient approach, little is explored on mineral nutrient source addition such as phosphorus minerals. In this study, the stabilization and sustainability of phosphorus minerals for providing phosphorus has been investigated, and the enhancement of Cr(VI) removal by mixed bacterial consortium coupled with phosphorus minerals was also observed and further verified, with 1.4–3.9 times K values (first-order) increase under different conditions. We demonstrated that the applied of phosphorus minerals facilitated the reduction of Cr(VI) and the removal of Cr(III), promoted the resistance of Cr(VI) and the generation of antioxidase, and engendered the evolution of microbial community structures and functional genes. These findings provide a new insight for enhancement of Cr(VI)-contaminated groundwater in-situ remediation.

Microbial Corrosion of C1018 mild steel by a halotolerant consortium of sulfate reducing bacteria isolated from an Egyptian oil field

In this study, a consortium of halotolerant sulfate reducing bacteria (SRB) was obtained from a water sample collected from an Egyptian oil-field. North Bahreyia Petroleum Company (NORPETCO) is one of the petroleum companies that suffer from severe corrosion. The present study aim to investigate the microbial structures of this consortium and their potential contributed to microbial corrosion. Dissimilatory sulfite reductase dsrAB gene sequences analysis indicated that the mixed bacterial consortium contained two main phylotypes: members of the Proteobacteria (Desulfomicrobium sp., Desulforhopalus sp., and Desulfobulbus sp.) and Firmicutes (Desulfotomaculum sp.). Mild steel C1018 coupons were incubated in the presence of SRB consortium for a period of 35 days, the evolution of corrosion was studied using weight loss and dissolved sulfide production of SRB consortium. Results indicated that, the corrosion rate in the presences of SRB was approximately 15 times of that for the control. Furthermore, sessile cells (biofilm) and subsequent corrosion products that developed were characterized by scanning electron microscope coupled with energy dispersive X-ray spectroscopy (EDX).

Efficient decolorization and detoxification of sulphonated azo dye Ponceau 4R by using single and mixed bacterial consortia

The decolorization of toxic azo dye Ponceau 4R by three strains of bacteria Bacillus sp. strain AK1, Lysinibacillus sp. strain AK2 and Kerstersia sp. strain VKY1 individually and in consortia was studied. At optimal conditions, up to 95%, 93% and 87% of the dye was decolorized by the strains AK1, AK2 and VKY1, respectively, in 24 h at 200 mg/L of the dye. Decolorization of the dye was optimized for different parameters such as the concentration of dye, pH, temperature and NaCl concentration. These strains were able to decolorize Ponceau 4R up to an initial concentration of 800 mg/L in the pH range of 5–10, temperature 25–55 °C and NaCl concentration up to 30 g/L. The dye decolorization efficiency of these strains was further enhanced by using different consortia of AK1, AK2 and VKY1 in various combinations. The complete decolorization of the dye by a consortium was achieved within 18 h at 200 mg/L. The cell-free extract of these strains grown on this dye exhibited a remarkable activity of azoreductase which is involved in the breakage of the azo bond. The steady-state kinetics of azoreductase, validated the ping pong Bi-Bi mechanism of enzyme action. UV–Vis spectra, HPLC, FTIR and LC-MS analysis of the dye decolorized samples showed the formation of 4-aminonaphthalene-1-sulphonic acid and 5-amino-6-hydroxynaphthalene-2, 4-disulphonic acid as the products of azo bond breakage. The phytotoxicity test of decolorized sample revealed a considerable reduction in the toxicity in comparison with the parent dye.

Enhanced crude oil depletion by constructed bacterial consortium comprising bioemulsifier producer and petroleum hydrocarbon degraders

The aim of this work was to study the production of bioemulsifier by Rhodococcus erythropolis OSDS1, and the improvement of crude oil depletion efficiency using a consortium of petroleum hydrocarbon degraders and OSDS1. The results showed that R. erythropolis OSDS1 produced highly stable bioemulsifier under various salinity (0–35 g/L NaCl) and pH (5.0–9.0) conditions; more than 90% of the initial emulsification activity was retained after 168 h. Emulsification capacity of the bioemulsifier on different petroleum hydrocarbons was diesel > mineral oil/crude oil > gasoline. A mixed bacterial consortium combining OSDS1 and four other petroleum hydrocarbon degraders was constructed. GC–MS results revealed that the constructed consortium achieved 85.26% depletion efficiency of crude oil in 15 days, which was significantly higher than that of individual strains. During the process, alkane hydroxylase gene (alkB) was successfully amplified from the consortium, confirming presence of crude oil degrading enzymes.

Microbial reduction fate of chromium (Cr) in aqueous solution by mixed bacterial consortium

Groundwater contaminated by Cr(VI) requires effective remediation to prevent adverse environmental impacts. The biodegradation of Cr(VI) has been documented for several decades, but little remains known about the removal fate of chromium, including the main species of reductase (sites) and functional genes involved in Cr(VI) reduction in mixed bacterial consortium. Cr(VI) reduction in this study was verified to be an enzyme-mediated process. Meanwhile, Cr(VI) reduction of different cell components demonstrated that the extracellular enzyme was the main active substance, and the distribution of Cr after experiment was quantified using mass balance calculation. Furthermore, the optimal pH for reduction was 8.0, with the reduction rate decreasing with increasing initial Cr(VI) concentrations. The co-existing oxyanions had little effect on Cr(VI) reduction, while the presence of other heavy metals had a relatively significant influence. The evolutionary behavior of microbial community structure and functional genes affected by Cr(VI) were also analyzed, which provided new insights on the underlying mechanisms involved in bioreduction in this study. These results generated new understanding of the reduction mechanisms on the Cr-relevant bacterial species and genes, which would be helpful in designing strategies for the bioremediation of Cr(VI) contaminated water.

Organic removal and synthesis of biopolymer from synthetic oily bilge water using the novel mixed bacterial consortium

Synthetic oily bilge water (OBW) treatment and subsequent production of biopolymer were studied by using a sequential batch reactor (SBR). The effect of various influencing parameters such as solids retention time (SRT), cycle time (CT), substrate concentration, pH level on the organic removal and synthesis of polyhydroxyalkanoates (PHA) was examined by novel soil bacteria isolated from hydrocarbon contaminated site near Karaikal port, India. The isolates were identified as Pseudomonas tuomuerensis and Pseudomonas nitroreducens using 16S rRNA. Sudan Black B staining was performed to visualize the presence of PHA. The experimental results showed that a decrease in substrate concentration to 5000 mg/L of soluble COD (CODs) showed maximum organic removal (81%) and maximum PHA yields of its cell dry mass (81%). The PHA yield was maximum at SRT of 5 d, pH = 7 and CT of 24 h. The produced PHA was characterized by using FTIR, XRD and SEM analysis.

A New Approach of Rpf Addition to Explore Bacterial Consortium for Enhanced Phenol Degradation Under High Salinity Conditions.

Only a small fraction of salt-tolerant phenol-degrading bacteria can be isolated by conventional plate separation methods, because most bacteria in nature are in a viable but non-culturable (VBNC) state. The aims of this study were to screen out more effective functional bacteria using resuscitation-promoting factor (Rpf), and to determine whether a mixed bacterial consortium possesses better phenol-degrading capabilities under high salinity conditions. The results indicated that three strains unique to treatment group with Rpf addition were obtained. A mixed bacterial consortium consisting of two high-efficient strains which belonged to genera Bacillus and Corynebacterium was capable of utilizing phenol as a sole source of carbon at high salinity. Complete degradation of 100mg/L phenol at 2% NaCl concentration was achieved within 8h. This study provides new insights into resuscitation of VBNC bacteria for enhanced treatment of phenol-laden saline wastewater.

Surfactant-enhanced biodegradation of crude oil by mixed bacterial consortium in contaminated soil.

This study evaluated the effects of two surfactants (i.e., Tween 80 and SDS) on biodegradation of crude oil by mixed bacterial consortium in soil-aqueous system. The mixed bacterial consortium was domesticated from the activated sludge of cooking plant through a progressive domestication process. High-throughput sequencing analysis revealed that Rhodanobacter sp. was the dominant bacteria. The higher CMCeff value for two surfactants was observed in soil-aqueous system compared with that in aqueous system, which was likely due to their adsorption onto soil particles. Either Tween 80 or SDS can be utilized as carbon source and promote the growth of mixed bacterial consortium. Further findings evidenced that the degradation of crude oil can be enhanced by adding either Tween 80 or SDS. The performance of Tween 80 was generally superior to SDS for the crude oil degradation. The highest crude oil degradation efficiency was 42.2 and 31.0% under the conditions of 5 CMCeff of Tween 80 and 2 CMCeff of SDS, respectively. Furthermore, the degradation efficiency of crude oil in remediation experiment (i.e., 77%) evidenced that the integration of adding Tween 80 and inoculating mixed bacterial consortium was effective for crude oil-contaminated soil decontamination.

Biodegradation of Diesel Contaminated Soil Using Single Bacterial Strains and a Mixed Bacterial Consortium

This study was conducted to assess the hydrocarbon degradation abilities of Sphingomonas paucimobilis, Pentoae species, Staphylococcus aureus, and Enterobacter cloacae, which isolated from diesel contaminated soil samples. Single strains and mixed bacterial consortia have been investigated their ability to degrade 1.0 % (v/v) of diesel oil in Bushnell- Haas medium as sole.carbon.and.energy.source. At temperature 30∘C, the individual.bacterial.isolates exhibited low growth and low degradation.than did the.mixed. bacterial.culture. After 28 days.of incubation the.combination.of four isolates degraded.an upper limit.of diesel 88.4%. This was. continued.by 85.1% by S. paucimobilis, 84 % by Pentoae sp., 79% by S.aureus, and 74% by E. cloacae. For further evidence of the biodegradation effect of these isolates individually and as a mixed culture, which was supported by the use of technology chromatography confirming the occurrence of biodegradation. The results showed that the isolated bacteria are effective in biodegradation of diesel spills when used separately. It also confirmed the better biodegradability when used together in a mixed -culture.

Biodegradation of Diesel Contaminated Soil Using Single Bacterial Strains and a Mixed Bacterial Consortium

This study was conducted to assess the hydrocarbon degradation abilities of Sphingomonas paucimobilis, Pentoae species, Staphylococcus aureus, and Enterobacter cloacae, which isolated from diesel contaminated soil samples. Single strains and mixed bacterial consortia have been investigated their ability to degrade 1.0 % (v/v) of diesel oil in Bushnell- Haas medium as sole.carbon.and.energy.source. At temperature 30∘C, the individual.bacterial.isolates exhibited low growth and low degradation.than did the.mixed. bacterial.culture. After 28 days.of incubation the.combination.of four isolates degraded.an upper limit.of diesel 88.4%. This was. continued.by 85.1% by S. paucimobilis, 84 % by Pentoae sp., 79% by S.aureus, and 74% by E. cloacae. For further evidence of the biodegradation effect of these isolates individually and as a mixed culture, which was supported by the use of technology chromatography confirming the occurrence of biodegradation. The results showed that the isolated bacteria are effective in biodegradation of diesel spills when used separately. It also confirmed the better biodegradability when used together in a mixed -culture.

MICROBIAL BIODEGRADATION POTENTIAL OF PETROLEUM-AND NATURE OILS BY INDIGENOUS HYDROCARBON DEGRADING BACTERIA ISOLATED FROM PETRO-CONTAMINATED SITES

The study was carried out as an effort at developing active natural petroleum hydrocarbon degraders that could be of relevance of bioremoval of petro-and non-petro oil pollutants from contaminated sites, a collection of 10 bacterial isolates as well as 3 yeast strains and Enterobacter clocace spp. disssolvens strain as efficient petro-hydrocarbon degraders were employed in this study to reach to this target. These bacterial isolates were identified to genus and species level using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALD-TOF-MS) with high degree of precision (2.111-3.361) as an efficient approach for unambiguous identification process in real sample within minutes. Two experimental techniques, namely respirometric method (CO2 production) and the redox indicator 2,6-dichlorophenol indophenol (DCPIP) test were carried out to evaluate the capacity of the tested organisms to utilize monoaromatic hydrocacbons (BTEX-mixture) and/or n-hexadecane as an excellent substrates in the study of hydrocarbon biodegradation in the tested media, individual and/or mixed bacterial and yeast consortium. The results indicated that the tested organisms showed different rate and extent of growth as well as mixed bacterial–or yeast consortium showed more growth and degradation. Also, some growth condition factors that affect the success of biodegradation were determined, and obtained results revealed that pH (7.0), temperature (30-35˚C), salinity (0.0% and 0.5% NaCl) and incubation period (11 days) were suitable for the most tested bacteria. The results showed also that only five bacterial strains out of 10 strains namely: Sphingobacterium thalpophilum QBII-6, Pseudomonas nitroreducens RdI-14, Bacillus subtilis ssp subtilis GH-5, B. atrophaeus GH-6 and B. licheniformis RdI-17 as well as Ent. clocace spp. disssolvens exhibited the highest capability to metabolize a diverse range petroleum oils (crude oil, diesel oil, engine oil, used engine oil) and natural oils (corn oil, used corn oil, sunflower oil and used sunflower oil), and these five bacterial types could be applicable in bioremediation process of pollutants after carrying out future studies in field condition as a final goal.

Treatment of wastewater by mixed bacterial consortium in continuous reactors packed with solid waste

Phenol is one of the priority pollutants as declared by EPA (USA). Very few comparative studies have been carried out with continuous packed bed reactors (PBR) for bacterial degradation of phenol and applying the result in real time situation. The present study compared the performance of a co-current and a counter-current continuous PBR in degrading phenol by a mixed consortium of bacteria isolated from the East Calcutta Wetlands based on both rate of phenol degradation and phenol removal efficiency. Different process parameters like air flow rate, hydraulic retention time and temperature were varied for both the systems. Performance of the co-current continuous PBR was found to be more efficient. To validate the performance of this system in actual application in industry a real time phenolic industrial effluent was fed to this system. Phenol degradation rate was 1.43mg/lmin and the phenol removal efficiency of this co-current continuous PBR was 72.85%.

Performance of low temperature Microbial Fuel Cells (MFCs) catalyzed by mixed bacterial consortia

Microbial Fuel Cells (MFCs) are a promising technology for treating wastewater in a sustainable manner. In potential applications, low temperatures substantially reduce MFC performance. To better understand the effect of temperature and particularly how bioanodes respond to changes in temperature, we investigated the current generation of mixed-culture and pure-culture MFCs at two low temperatures, 10°C and 5°C. The results implied that the mixed-culture MFC sustainably performed better than the pure-culture (Shewanella) MFC at 10°C, but the electrogenic activity of anodic bacteria was substantially reduced at the lower temperature of 5°C. At 10°C, the maximum output voltage generated with the mixed-culture was 540–560mV, which was 10%–15% higher than that of Shewanella MFCs. The maximum power density reached 465.3±5.8mW/m2 for the mixed-culture at 10°C, while only 68.7±3.7mW/m2 was achieved with the pure-culture. It was shown that the anodic biofilm of the mixed-culture MFC had a lower overpotential and resistance than the pure-culture MFC. Phylogenetic analysis disclosed the prevalence of Geobacter and Pseudomonas rather than Shewanella in the mixed-culture anodic biofilm, which mitigated the increase of resistance or overpotential at low temperatures.

Isopropanol biodegradation by immobilized Paracoccus denitrificans in a three-phase fluidized bed reactor

ABSTRACTA three-phase bed bioreactor including a mix of immobilized microbes was used to degrade isopropanol (IPA). The immobilization method was studied and cells immobilized with calcium alginate, polyvinyl alcohol, activated carbon, and SiO2 were demonstrated to be the best immobilization method for the degradation of 90% of 2 g/L IPA in just 4 days, 1 day earlier than with free cells. Acetone was monitored as an indicator of microbial IPA utilization as the major intermediate of aerobic IPA biodegradation. The bioreactor was operated at hydraulic retention time (HRT) values of 32, 24, 16, 12, and 10 hr, which correspond to membrane fluxes of 0.03, 0.04, 0.06, 0.08, and 0.10 L/m2/hr, respectively. The chemical oxygen demand (COD) removal efficiencies were maintained at 98.0, 97.8, 89.1, 80.6, and 71.1% at a HRT of 32, 24, 16, 12, and 10 hr, respectively, while the IPA degradations were 98.6, 98.3, 90.3, 81.6, and 73.3%, respectively. With a comprehensive consideration of COD removal and economy, the optimal HRT was 24 hr. The results demonstrate the potential of immobilized mixed bacterial consortium in a three-phase fluidized bed reactor system for the aerobic treatment of wastewater containing IPA.