Isolation and characterization of potential aerobic bacteria capable for pyridine degradation in presence of picoline,phenol and formaldehyde as co-pollutants

Pyridine, heterocyclic aromatic compound is known to be toxic, carcinogenic and teratogenic to several living organisms. In this study, two aerobic bacteria ITRCEM1 and ITRCEM2 capable for pyridine degradation were isolated and characterized as Bacillus cereus (DQ435020) and Alcaligenes faecalis (DQ435021), respectively. For pyridine degradation, mixed bacterial culture was found more effective compared to axenic culture ITRCEM1 and ITRCEM2 degrading 94.23, 67.84, and 83.35% pyridine, respectively, at 144 h incubation period at pH 7.0 ± 0.1, temp 37 ± 2°C and shaking rate 125 rpm in MSM containing 1% glucose and 0.2% peptone as carbon and nitrogen source, respectively. The presence of phenol and formaldehyde in MSM has shown inhibitory effect on pyridine degradation whereas picoline has favored the bacterial growths and pyridine degradation. Further, the HPLC analysis has shown the reduction in peaks compared to controls, indicating that reduction in peak area might be largely attributed to the bacterial degradation of pyridine by bacterial catabolic enzymes.     

Biodegradation of pyridine raffinate by two bacterial co-cultures of Bacillus cereus (DQ435020) and Alcaligenes faecalis (DQ435021)

This study deals with the optimization of bacterial degradation of pyridine raffinate by previously isolated two aerobic bacteria ITRCEM1 (Bacillus cereus) and ITRCEM2 (Alcaligens faecalis) with accession number DQ4335020 and DQ435021, respectively. The degradation of pyridine raffinate was studied by axenic and mixed bacterial consortium at different nutritional and environmental conditions after the removal of formaldehyde from pyridine raffinate (FPPR). Results revealed that the optimum degradation of pyridine raffinate was observed by mixed bacterial culture in presence of glucose (1% w/v) and peptone (0.2% w/v) at 20% FPPR, pH 7.0, temperature 30°C and 120 rpm at 168 h incubation period . The HPLC analysis of degraded pyridine raffinate samples has indicated the complete removal of α, β and γ picoline. Further, the GC–MS analysis of FPPR pyridine raffinate has shown the presence of pyrazine acetonitrile (6.74), 1,3-dioxepin (8.68), 2-pyridine carboxaldehyde (11.26), propiolactone (12.06), 2-butanol (13.10), benzenesulfonic acid (16.22) and 1,4-dimethyl pyperadine while phenol (17.64) and 3,4-dimethyl benzaldehyde as metabolic products of FPPR.     

Isolation and characterization of novel Serratia marcescens (AY927692) for pentachlorophenol degradation from pulp and paper mill waste

Seven aerobic bacterial strains were isolated from pulp paper mill waste and screened for pentachlorophenol (PCP) tolerance on PCP containing mineral salt agar medium (MSM). The organism was characterized by 16S rDNA sequencing which showed 99.7% sequence similarity with Serratia marcescens. PCP degradation was routinely monitored with spectrophotometric analysis and further confirmed by HPLC analysis. Among seven strains, ITRC S₇ was found to degrade up to 90.33% of 1.127 mM (300 mg/l) of PCP and simultaneous release of chloride ion (2.435 mM) emphasized the bacterial dechlorination in the medium in presence of glucose as an additional carbon and energy source under optimized condition within 168 h incubation. In absence of glucose bacterium was unable to utilize PCP indicating the phenomenon of co-metabolism. Bacterium was identified as S. marcescens (AY927692), was a novel and potential aerobic bacterial strain capable of degrading PCP in axenic condition. Further, this strain may be used for bioremediation of PCP containing pulp paper mill waste in the environment.     

Bacterial decolorization of black liquor in axenic and mixed condition and characterization of metabolites

The pulping byproducts (black liquor) cause serious environmental problem due to its high pollution load. In order to search the degradability of black liquor, the potential bacterial strains Citrobacter freundii (FJ581026) and Citrobacter sp. (FJ581023) were applied in axenic and mixed condition. Results revealed that the mixed bacterial culture are more effective than axenic condition and can reduce 82% COD, 79% AOX, 79% color and 60% lignin after 144 h of incubation period. Additionally, the optimum activity of lignin degrading enzyme was noted at 96 h and characterized as manganese peroxidase (MnP) by SDS–PAGE analysis. Further, the HPLC analysis of control and bacterial degraded sample has shown the reduction as well as shifting of peaks compared to control indicating the degradation as well as transformation of compounds of black liquor. The comparative GC–MS analysis of control and degraded black liquor revealed that along with lignin fragment some chlorophenolic compounds 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol and pentachlorophenol were detected in black liquor degraded by axenic culture whereas these chlorophenolic compounds were completely absent in black liquor degraded by mixed bacterial culture. These chlorophenol inhibit the oxidative degradation which seems a major reason behind the low degradability of axenic degradation compared to mixed culture. The innovation of this aerobic treatment of alkaline black liquor opens additional possibilities for the better treatment of black liquor along with its metabolic product.     

Synergistic biodegradation of pentachlorophenol by <Emphasis Type="Italic">Bacillus cereus</Emphasis> (DQ002384), <Emphasis Type="Italic">Serratia marcescens</Emphasis> (AY927692) and <Emphasis Type="Italic">Serratia marcescens</Emphasis> (DQ002385)

The consortium of Bacillus cereus (DQ002384), Serratia marcescens (AY927692) and Serratia marcescens (DQ002385) were used for pentachlorophenol (PCP) degradation. The consortia showed better overall removal efficiencies than single strains by utilization of PCP as a carbon and energy source confirmed by pH dependent dye indicator bromocresol purple (BCP) in mineral salt media (MSM). Mixed culture was found to degrade up to 93% of PCP (300 mg/l) as compared to single strains (62.75–90.33%), at optimized conditions (30 ± 1°C, pH 7 ± 0.2, 120 rpm) at 168 h incubation. PCP degradation was also recorded at 20°C (62.75%) and 37°C (83.33%); pH 6 (70%) and pH 9 (75.16%); 50 rpm (73.33%) and 200 rpm (91.63%). The simultaneous release of chloride ion up to 90.8 mg/l emphasized the bacterial dechlorination in the medium. GC–MS analysis revealed the formation of low molecular weight compound, i.e., 6-chlorohydroxyquinol, 2,3,4,6-tetrachlorophenol and tetrachlorohydroquinone, from degraded sample as compared to control.     

Characterization of sucrose–glutamic acid Maillard products (SGMPs) degrading bacteria and their metabolites

Two aerobic bacteria RNBS1 and RNBS3 capable to degrade and utilize sucrose–glutamic acid Maillard products (SGMPs) as carbon, nitrogen and energy source were isolated and characterized as Alcaligenes faecalis (DQ659619) and Bacillus cereus (DQ659620) respectively by 16S rRNA gene sequence analysis. In present study, mixed bacterial culture was found more effective compared to axenic culture RNBS1 and RNBS3 decolourizing 73.79%, 66.80% and 62.56% SGMPs, respectively. The SGMPs catabolizing enzyme was characterized as manganese dependent peroxidase (MnP) by SDS–PAGE yielding a single band of 43 KDa. Further, the LC-MS–MS and other spectrophotometric analysis have revealed that most of the SGMPs detected in control were diminished from bacteria treated samples. The disappearance of SGMPs from bacteria treated samples could be related with the degradation of SGMPs.     

Isolation and characterization of four novel Gram-positive bacteria associated with the rhizosphere of two endemorelict plants capable of degrading a broad range of aromatic substrates

Four new Gram-positive, phenol-degrading strains were isolated from the rhizospheres of endemorelict plants Ramonda serbica and Ramonda nathaliae known to exude high amounts of phenolics in the soil. Isolates were designated Bacillus sp. PS1, Bacillus sp. PS11, Streptomyces sp. PS12, and Streptomyces sp. PN1 based on 16S rDNA sequence and biochemical analysis. In addition to their ability to tolerate and utilize high amounts of phenol of either up to 800 or up to 1,400 mg l⁻¹ without apparent inhibition in growth, all four strains were also able to degrade a broad range of aromatic substrates including benzene, toluene, ethylbenzene, xylenes, styrene, halogenated benzenes, and naphthalene. Isolates were able to grow in pure culture and in defined mixed culture on phenol and on the mixture of BTEX (benzene, toluene, ethylbenzene, and xylenes) compounds as a sole source of carbon and energy. Pure culture of Bacillus sp. PS11 yielded 1.5-fold higher biomass amounts in comparison to mixed culture, under all conditions. Strains successfully degraded phenol in the soil model system (2 g kg⁻¹) within 6 days. Activities of phenol hydroxylase, catechol 1,2-dioxygenase, and catechol 2,3-dioxygenase were detected and analyzed from the crude cell extract of the isolates. While all four strains use ortho degradation pathway, enzyme indicative of meta degradation pathway (catechol 2,3-dioxygenase) was also detected in Bacillus sp. PS11 and Streptomyces sp. PN1. Phenol degradation activities were induced 2 h after supplementation by phenol, but not by catechol. Catechol slightly inhibited activity of catechol 2,3-dioxygenase in strains PS11 and PN1.     

Bioremediation of Fungicides by Spent Mushroom Substrate and Its Associated Microflora

Experiments were conducted both under in vitro and in situ conditions to determine the biodegradation potential of button mushroom spent substrate (SMS) and its dominating microbes (fungi and bacteria) for carbendazim and mancozeb, the commonly used agricultural fungicides. During 6 days of incubation at 30 ± 2°C under broth culture conditions, highest degradation of carbendazim (17.45%) was recorded with B-1 bacterial isolate, while highest degradation of mancozeb (18.05%) was recorded with Trichoderma sp. In fungicide pre-mixed sterilized SMS, highest degradation of carbendazim (100.00–66.50 μg g⁻¹) was recorded with mixed inoculum of Trichoderma sp. and Aspergillus sp., whereas highest degradation of mancozeb (100.00–50.50 μg g⁻¹) was with mixed inoculum of Trichoderma sp., Aspergillus sp. and B–I bacterial isolate in 15 days of incubation at 30 ± 2°C. All these microbes both individually as well as in different combinations grew well and produced extracellular lignolytic enzymes on SMS, which helped in fungicides degradation. Under in situ conditions, among three different proportions of SMS (10, 20 and 30%, w/w) mixed with fungicide pre-mixed soil (100 μg g⁻¹ of soil), the degradation of carbendazim was highest in 30% SMS treatment, while for mancozeb it was in 20% SMS treatment. The residue levels of both fungicides decreased to half of their initial concentration after 1 month of SMS mixing.     

Cellulose synthesis by Komagataeibacter rhaeticus strain P 1463 isolated from Kombucha

Isolate B17 from Kombucha was estimated to be an efficient producer of bacterial cellulose (BC). The isolate was deposited under the number P 1463 and identified as Komagataeibacter rhaeticus by comparing a generated amplified fragment length polymorphism (AFLP™) DNA fingerprint against a reference database. Static cultivation of the K. rhaeticus strain P 1463 in Hestrin and Schramm (HS) medium resulted in 4.40 ± 0.22 g/L BC being produced, corresponding to a BC yield from glucose of 25.30 ± 1.78 %, when the inoculum was made with a modified HS medium containing 10 g/L glucose. Fermentations for 5 days using media containing apple juice with analogous carbon source concentrations resulted in 4.77 ± 0.24 g/L BC being synthesised, corresponding to a yield from the consumed sugars (glucose, fructose and sucrose) of 37.00 ± 2.61 %. The capacity of K. rhaeticus strain P 1463 to synthesise BC was found to be much higher than that of two reference strains for cellulose production, Komagataeibacter xylinus DSM 46604 and Komagataeibacter hansenii DSM 5602^T, and was also considerably higher than that of K. hansenii strain B22, isolated from another Kombucha sample. The BC synthesised by K. rhaeticus strain P 1463 after 40 days of cultivation in HS medium with additional glucose supplemented to the cell culture during cultivation was shown to have a degree of polymerization of 3300.0 ± 122.1 glucose units, a tensile strength of 65.50 ± 3.27 MPa and a length at break of 16.50 ± 0.83 km. For the other strains, these properties did not exceed 25.60 ± 1.28 MPa and 15.20 ± 0.76 km.

     

Phenol biodegradation by the thermoacidophilic archaeon <Emphasis Type="Italic">Sulfolobus solfataricus</Emphasis> 98/2 in a fed-batch bioreactor

Toxic at low concentrations, phenol is one of the most common organic pollutants in air and water. In this work, phenol biodegradation was studied in extreme conditions (80°C, pH = 3.2) in a 2.7 l bioreactor with the thermoacidophilic archaeon Sulfolobus solfataricus 98/2. The strain was first acclimatized to phenol on a mixture of glucose (2000 mg l⁻¹) and phenol (94 mg l⁻¹) at a constant dissolved oxygen concentration of 1.5 mg l⁻¹. After a short lag-phase, only glucose was consumed. Phenol degradation then began while glucose was still present in the reactor. When glucose was exhausted, phenol was used for respiration and then for biomass build-up. After several batch runs (phenol < 365 mg l⁻¹), specific growth rate (μ_X) was 0.034 ± 0.001 h⁻¹, specific phenol degradation rate (q_P) was 57.5 ± 2 mg g⁻¹ h⁻¹, biomass yield (Y_X/P) was 52.2 ± 1.1 g mol⁻¹, and oxygen yield factor ( \textY_{\textX/\textO 2} ) \left( {{\text{Y}}_{{{\text{X}}/{\text{O}}_{ 2} }} } \right) was 9.2 ± 0.2 g mol⁻¹. A carbon recovery close to 100% suggested that phenol was exclusively transformed into biomass (35%) and CO₂ (65%). Molar phenol oxidation constant ( \textY_{\textO 2 /\textP} ) \left( {{\text{Y}}_{{{\text{O}}_{ 2} /{\text{P}}}} } \right) was calculated from stoichiometry of phenol oxidation and introducing experimental biomass and CO₂ conversion yields on phenol, leading to values varying between 4.78 and 5.22 mol mol⁻¹. Respiratory quotient was about 0.84 mol mol⁻¹, very close to theoretical value (0.87 mol mol⁻¹). Carbon dioxide production, oxygen demand and redox potential, monitored on-line, were good indicators of growth, substrate consumption and exhaustion, and can therefore be usefully employed for industrial phenol bioremediation in extreme environments.     

A study of the efficiency of edible oils degraded in alkaline conditions by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> SS-219 and <Emphasis Type="Italic">Acinetobacter</Emphasis> sp. SS-192 bacteria isolated from Japanese soil

High lipid concentration contained in wastewater inhibits the activity of microorganisms in biological wastewater treatment systems such as activated sludge and methane fermentation. To reduce the inhibitory effects, microorganisms capable of efficiently degrading edible oils were screened from various environmental sources. From Japanese soil, we isolated 2 bacteria strains with high degradation abilities at an alkaline pH without consumption of biological oxygen demand (BOD) constituents. Acinetobacter sp. strain SS-192 and Pseudomonas aeruginosa strain SS-219 degraded 77.5 ± 0.6% and 89.5 ± 1.5%, respectively, of 3,000 ppm of mixed oil consisting of salad oil/lard/beef tallow (1/1/1, w/w/w) at 37°C and pH 9.0 in 24 h. Efficient degradation by the two strains occurred at pH 8–9 and 25–40°C. Strain SS-219 degraded lipids even at pH 3. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-192 was 79.9 ± 2.6%, 63.6 ± 1.9%, and 70.1 ± 1.2%, respectively, during a 24-h cultivation. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-219 was 82.3 ± 2.1%, 71.9 ± 2.2%, and 71.0 ± 1.1%, respectively, during a 24-h cultivation. After mixed oil degradation by both strains, the BOD value of the cell culture increased from 2,100 ppm to 3,200–4,000 ppm. The fact that neither strain utilizes BOD ingredients will be beneficial to pretreatment of methane fermentation systems such as upflow anaerobic sludge blanket reactors. In addition, the growth of usual heterotrophic microorganisms utilizing soluble BOD can be suppressed under alkaline pH.     

Identification and antifungal activity analysis of two biocontrol antagonists to Colletotrichum musae

Postharvest anthracnose of banana caused by Colletotrichum musae is one of the major diseases resulting in huge economic losses worldwide. To control this disease using biocontrol agents, two antagonistic strains SD7 and NB20 with significant inhibitory effects on mycelial growth and conidial germination of C. musae were identified and evaluated in this study. The inhibitory effects of cell‐free culture filtrates of SD7 and NB20 on conidial germination of C. musae were both 100%, and those on mycelial growth of C. musae were 97.7 ± 0.9% and 95.0 ± 0.6%, respectively. The antifungal activities of cell‐free culture filtrates of both strains were still stable after they were stored at 4°C for 6 months. The control efficacies of cell‐free culture filtrates of SD7 and NB20 on postharvest anthracnose of banana were 55.9 ± 4.1% and 33.2 ± 3.9%, respectively. The disease severity (mean scale value) in banana fruit fingers was significantly lower after the treatment with a cultural suspension of the bacterial strain SD7 (1.4 ± 0.49) or actinomycete strain NB20 (2.0 ± 0.63), compared to that in the control (4.8 ± 0.40). After subculturing for 10 generations, the antifungal efficiency of NB20 remained stable, whereas that of strain SD7 declined obviously. Lastly, based on the morphological, physio‐biochemical and molecular characteristics, the bacterial strain SD7 was identified as Burkholderia cepacia, while the actinomycete strain NB20 was identified as Streptomyces katrae. The results from this study will provide the basis for developing an effective and novel biofungicide to control banana anthracnose disease.     

Degradation of 3-chlorobenzoate and phenol singly and in mixture by a mixed culture of two ortho-pathway-following <Emphasis Type="Italic">Pseudomonas</Emphasis> strains

The compatibility and efficiency of two ortho-cleavage pathway-following pseudomonads viz. the 3-chlorobenzoate (3-CBA)-degrader, Pseudomonas aeruginosa 3mT (3mT) and the phenol-degrader, P. stutzeri SPC-2 (SPC-2) in a mixed culture for the degradation of these substrates singly and simultaneously in mixtures was studied. Another phenol-degrading strain, Pseudomonas sp. SoPC-5 (SoPC-5) that utilizes a meta-cleavage mode also was tried in co-culture with 3mT. The former combination was found to be a better degrader of both the substrates when present alone. But, with inoculum levels of 0.15 mg cell dry wt each of 3mT/SPC-2 or 3mT/SoPC-5 growth with 2 mM each of 3-CBA and phenol was slow with a lag of 24 h and degradation being incomplete. However, with higher inocula in the ratios 1:1, 1:2, and 2:1, i.e., 0.3 + 0.3, 0.3 + 0.6, and 0.6 + 0.3 mg cell dry wt of 3mT and SPC-2, respectively complete degradation of both the substrates occurred. Degradation of 3-CBA was complete with the release of stoichiometric amounts of chloride (Cl⁻) when concentrations of phenol/3-CBA were varied as 2:2, 2:4, and 4:2 mM, i.e., even when the concentration of the more toxic co-substrate 3-CBA was higher than phenol effective simultaneous degradation occurred at the inoculums ratio of 1:1 (0.3 mg dry cell wt. of each strain). These studies clearly indicated the better suitability of ortho-cleavage-utilizing strains as partners in a mixed culture than those follow different modes.     

Efficacy of bacterial consortium-AIE2 for contemporaneous Cr(VI) and azo dye bioremediation in batch and continuous bioreactor systems, monitoring steady-state bacterial dynamics using qPCR assays

Bacterial consortium-AIE2 with a capability of contemporaneous Cr(VI) reduction and azo dye RV5 decolourization was developed from industrial wastewaters by enrichment culture technique. The 16S rRNA gene based molecular analyses revealed that the consortium bacterial community structure consisted of four bacterial strains namely, Alcaligenes sp. DMA, Bacillus sp. DMB, Stenotrophomonas sp. DMS and Enterococcus sp. DME. Cumulative mechanism of Cr(VI) reduction by the consortium was determined using in vitro Cr(VI) reduction assays. Similarly, the complete degradation of Reactive Violet 5 (RV5) dye was confirmed by FTIR spectroscopic analysis. Consortium-AIE2 exhibited simultaneous bioremediation efficiencies of (97.8 ± 1.4) % and (74.1 ± 1.2) % in treatment of both 50 mg l⁻¹ Cr(VI) and RV5 dye concentrations within 48 h of incubation at pH 7 and 37°C in batch systems. Continuous bioreactor systems achieved simultaneous bioremediation efficiencies of (98.4 ± 1.5) % and (97.5 ± 1.4) % after the onset of steady-state at 50 mg l⁻¹ input Cr(VI) and 25 mg l⁻¹ input RV5 concentrations, respectively, at medium dilution rate (D) of 0.014 h⁻¹. The 16S rRNA gene copy numbers in the continuous bioreactor as determined by real-time PCR assay indicated that Alcaligenes sp. DMA and Bacillus sp. DMB dominated consortium bacterial community during the active continuous bioremediation process.     

Enhanced degradation of phenol by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. CP4 entrapped in agar and calcium alginate beads in batch and continuous processes

Phenol is one of the major toxic pollutants in the wastes generated by a number of industries and needs to be eliminated before their discharge. Although microbial degradation is a preferred method of waste treatment for phenol removal, the general inability of the degrading strains to tolerate higher substrate concentrations has been a bottleneck. Immobilization of the microorganism in suitable matrices has been shown to circumvent this problem to some extent. In this study, cells of Pseudomonas sp. CP4, a laboratory isolate that degrades phenol, cresols, and other aromatics, were immobilized by entrapment in Ca-alginate and agar gel beads, separately and their performance in a fluidized bed bioreactor was compared. In batch runs, with an aeration rate of 1 vol⁻¹ vol⁻¹ min⁻¹, at 30°C and pH 7.0 ± 0.2, agar-encapsulated cells degraded up to 3000 mg l⁻¹ of phenol as compared to 1500 mg l⁻¹ by Ca-alginate-entrapped cells whereas free cells could tolerate only 1000 mg l⁻¹. In a continuous process with Ca-alginate entrapped cells a degradation rate of 200 mg phenol l⁻¹ h⁻¹ was obtained while agar-entrapped cells were far superior and could withstand and degrade up to 4000 mg phenol l⁻¹ in the feed with a maximum degradation rate of 400 mg phenol l⁻¹ h⁻¹. The results indicate a clear possibility of development of an efficient treatment technology for phenol containing waste waters with the agar-entrapped bacterial strain, Pseudomonas sp. CP4.     

Molecular and kinetic characterization of mixed cultures degrading natural and synthetic estrogens

The biodegradation of estradiol (E2), estrone (E1), and ethinylestradiol (EE2) was investigated using mixed bacterial cultures enriched from activated sludge. Enrichments were carried out on E2 or EE2 in batch conditions with acetonitrile as additional carbon source. Degradation experiments were performed both using hormones as sole carbon source or with an additional source. The hormones were completely degraded by these cultures. Estradiol was rapidly converted to E1 within 24 h. Thereafter, E1 degradation began, displaying a lag phase ranging from 3 to 4 days. Estrone depletion took from 48 h to more than 6 days, depending on the culture conditions. For EE2 degradation, when it was the sole carbon source, the lag phase and the time required for its complete removal (7 and 15 days, respectively) were shorter that in cultures with a supplementary carbon source. The specific degradation rates observed for E2 both with and without an additional carbon source were similar. By contrast, the specific degradation rates for E1 and EE2 were, respectively, seven and 20 times faster when these hormones were supplied as the sole carbon source. The bacterial community structure of each culture was characterized by molecular and cultural methods. The mixed cultures were made up of species belonging to Alcaligenes faecalis, Pusillimonas sp., Denitrobacter sp., and Brevundimonas diminuta or related to uncultured Bacteroidetes. The isolated strain B. diminuta achieved the conversion of E2 to E1.     

Modelling and simulation of steady-state phenol degradation in a pulsed plate bioreactor with immobilised cells of Nocardia hydrocarbonoxydans

A novel bioreactor called pulsed plate bioreactor (PPBR) with cell immobilised glass particles in the interplate spaces was used for continuous aerobic biodegradation of phenol present in wastewater. A mathematical model consisting of mass balance equations and accounting for simultaneous external film mass transfer, internal diffusion and reaction is presented to describe the steady-state degradation of phenol by Nocardia hydrocarbonoxydans (Nch.) in this bioreactor. The growth of Nch. on phenol was found to follow Haldane substrate inhibition model. The biokinetic parameters at a temperature of 30 ± 1 °C and pH at 7.0 ± 0.1 are μ _m = 0.5397 h⁻¹, K _S = 6.445 mg/L and K _I = 855.7 mg/L. The mathematical model was able to predict the reactor performance, with a maximum error of 2% between the predicted and experimental percentage degradations of phenol. The biofilm internal diffusion rate was found to be the slowest step in biodegradation of phenol in a PPBR.     

Phenol Biodegradation and Metal Removal by a Mixed Bacterial Consortium

This paper reports the tolerance and biodegradation of phenol by a heavy metal–adapted environmental bacterial consortium, known as consortium culture (CC). At the highest tolerable phenol concentration of 1200 mg/L, CC displayed specific growth rate of 0.04 h^?1, phenol degradation rate of 6.11 mg L^?1 h^?1 and biomass of 8.45 ± 0.35 (log₁₀ colony-forming units [CFU]/ml) at the end of incubation. Phenol was degraded via the ortho-cleavage pathway catalyzed by cathechol-1,2-dioxygenase with specific activity of 0.083 (µmol min^?1 mg^?1 protein). The different constituent bacterial isolates of CC preferentially grow on benzene, toluene, xylene, ethylbenzene, cresol, and catechol, suggesting a synergistic mechanism involved in the degradation process. Microtox assay showed that phenol degradation was achieved without producing toxic dead-end metabolites. Moreover, lead (Pb) and cadmium (Cd) at the highest tested concentration of 1.0 and 0.1 mg/L, respectively, did not inhibit phenol degradation by CC. Simultaneous metal removal during phenol degradation was achieved using CC. These findings confirmed the dual function of CC to degrade phenol and to remove heavy metals from a mixed-pollutant medium.     

Biodegradation of tributyl phosphate by novel bacteria isolated from enrichment cultures

Tributyl phosphate (TBP) is an organophosphorous compound, used extensively (3000–5000 tonnes/annum) as a solvent for nuclear fuel processing and as a base stock in the formulation of fire-resistant aircraft hydraulic fluids and other applications. Because of its wide applications and relative stability in the natural environment TBP poses the problem of pollution and health hazards. In the present study, fifteen potent bacterial strains capable of using tributyl phosphate (TBP) as sole carbon and phosphorus source were isolated from enrichment cultures. These isolates were identified on the basis of biochemical and morphological characteristics and 16S rRNA gene sequence analysis. Phylogenetic analysis of 16S rRNA gene sequences revealed that two isolates belonged to class Bacilli and thirteen to β and γ-Proteobacteria. All these isolates were found to be members of genera Alcaligenes, Providencia, Delftia, Ralstonia, and Bacillus. These isolates were able to tolerate and degrade up to 5 mM TBP, the highest concentration reported to date. The GC–MS method was developed to monitor TBP degradation. Two strains, Providencia sp. BGW4 and Delftia sp. BGW1 showed respectively, 61.0 ± 2.8% and 57.0 ± 2.0% TBP degradation within 4 days. The degradation rate constants, calculated by first order kinetic model were between 0.0024 and 0.0099 h⁻¹. These bacterial strains are novel for TBP degradation and could be used as an important bioresource for efficient decontamination of TBP polluted waste streams.     

Characterization of 2T engine oil degrading indigenous bacteria,isolated from high altitude (Mussoorie), India

The biodegradability of petroleum hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs) and n-branched alkanes etc. of 2T engine oil were studied in aqueous media using bacterial strain isolated from petroleum contaminated soil of high altitude. Out of five petroleum degrading bacterial strain one of the most growing bacteria was identified as Enterobacter strain by morphological, physiological, biochemical and partial sequencing of 16S rDNA. This strain was capable of degrading 75 ± 3% of n-alkanes, 32 ± 5% PAHs, and the abiotic loss was 24 ± 6% during 10 days incubation period. 85 ± 2% of n-alkanes and 51 ± 3% PAHs were biodegraded in 20 days. The abiotic loss during this period was 15 ± 3%. In 30 days of incubation period 98% ± 1% n-alkanes and 75 ± 3% PAHs were degraded. As expected abiotic losses were smaller with increasing long chain alkanes and PAH’s concentration. An increment in oil degradation was correlated to an increase in cell number indicating that the bacterial isolate was responsible for the oil degradation. The hydrocarbon contents were measured by Shimadzu QP-2000 Gas chromatography/mass spectrometry by ULBON HR-1 column.