Mixed Bacterial Consortium Research Articles

Isolation, characterization and decolorization of textile dyes by a mixed bacterial consortium JW-2

Soil samples collected from dye contaminated sites of Jetpur, Gujarat were exploited for isolation of dye decolorizing organism. A microbial consortium JW-2 was selected based on its efficiency, showing maximum and faster decolorization of textile dyes. The consortium consisted of three isolates. Identification of isolates by 16SrRNA technique revealed that the organisms were Paenibacillus polymyxa, Micrococcus luteus and Micrococcus sp. The concerted metabolic activity of these isolates led to complete decolorization of Reactive Violet 5R (100 ppm) within 36 h whereas individual isolates could not show decolorization even on extended incubation. The culture exhibited good decolorization ability in the pH range from 6.5 to 8.5 and temperature from 25 to 37 °C. The consortium showed complete decolorization utilizing low amount of co-substrates like glucose (0.1% w/v) and yeast extract (0.05% w/v) and could also utilize a cheaper carbon source like starch in place of glucose as an alternative co-substrate. The consortium had the ability to decolorize nine different dyes amongst 10 tested. Potential of this consortium JW-2 to decolorize textile effluent containing a mixture of textile dyes is to be carried out using appropriate bioreactors.

Biotreatment of groundwater contaminated with MTBE: interaction of common environmental co-contaminants

Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by many aromatic components such as benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX). In this study, a laboratory-scale biotrickling filter for groundwater treatment inoculated with a microbial consortium degrading MTBE was studied. Individual or mixtures of BTEX compounds were transiently loaded in combination with MTBE. The results indicated that single BTEX compound or BTEX mixtures inhibited MTBE degradation to varying degrees, but none of them completely repressed the metabolic degradation in the biotrickling filter. Tert-butyl alcohol (TBA), a frequent co-contaminant of MTBE had no inhibitory effect on MTBE degradation. The bacterial consortium was stable and showed promising capabilities to remove TBA, ethylbenzene and toluene, and partially degraded benzene and xylenes without significant lag time. The study suggests that it is feasible to deploy a mixed bacterial consortia to degrade MTBE, BTEX and TBA at the same time.

Toluene removal in membrane bioreactors under recirculating and non-recirculating liquid conditions

A single-, dual- and multiple-tube dense phase silicone rubber membrane bioreactor were investigated for control of toluene-contaminated air under circulating and non-recirculating liquid conditions. A mathematical model was developed to describe the system. The reactors were seeded with a mixed bacterial consortium isolated from activated sludge and capable of aromatic biodegradation. After operating with recirculating liquid nutrient solution, the reactors were operated with no recirculation of the liquid, for 50 days or more in each instance. Average toluene removal measured in the single-tube reactor was 93 ppm with recirculating liquid and 102 ppm without recirculation of the liquid. Average removal measured in the dual-tube reactor was 396 ppm with recirculating liquid and 319 ppm without recirculation of the liquid. Operation under stagnant liquid conditions had no significant detrimental impact on bioreactor performance. Biokinetic parameters were measured for both the suspension and biofilm with values of the maximum specific utilization rate values (k) ranging from 0.01 to 0.42 h−1 and half saturation constant values (K S) ranging from 1.5 to 14.3 mg L−1. Results suggest that membrane bioreactors might be operated under non-recirculating liquid conditions without performance detriment, reducing or eliminating the energy requirements and costs associated with pump operation.

Anaerobic PAH degradation in soil by a mixed bacterial consortium under denitrifying conditions

Polycyclic aromatic hydrocarbons (PAHs) are one of the main classes of contaminants in the terrestrial environment. Concentrations of biphenyl, fluorene, phenanthrene and pyrene were added to soil samples in order to investigate the anaerobic degradation potential of PAHs under denitrifying conditions. A mixed population of microorganisms obtained from a paddy soil was incubated for 20 days in anaerobic conditions in the presence of soil alone or with nitrate, adding, as electron donors, PAHs and, in some samples, glucose or acetate. At regular time intervals oxidation–reduction potential, PAHs concentration, microbial ATP and nitrate concentration into the solution were measured. Degradation trends for each hydrocarbon are similar under all conditions, indicating that the molecular conformation prevails over other parameters in controlling the degradation. Poor degradation results were obtained when PAHs were the only organic matter available for the inoculum, thus confirming the recalcitrance to degradation of these compounds. Biodegradation was influenced by the addition of other carbon sources. As better degradation results were generally obtained when acetate or glucose were added, the hypothesis of a co-metabolic enhancement of PAH biodegradation seems likely. Thus, anaerobic biodegradation of PAHs studied, biphenyl, fluorene, phenanthrene and pyrene, seems to be possible both through fermentative and respiratory metabolism, provided that low molecular weight co-metabolites and suitable electron acceptors (nitrate) are present.

Biodegradation of c5+ hydrocarbons by a mixed bacterial consortium from a c5+‐contaminated site

C5+, a mixture of benzene, toluene, xylene, styrene, dicyclopentadiene (DCPD), naphthalene and other compounds, is a byproduct of polyethylene production and has been introduced into the environment via accidental release. The degradation of C5+ was studied using a defined consortium of 11 distinct bacterial strains isolated from C5+‐contaminated soil. Vigorous growth of individual strains on C5+ was no prediction of dominance in the consortium, when the latter was grown under the same conditions. The defined consortium was able to degrade benzene, toluene, styrene and naphthalene, and to codegrade m‐xylene in the presence of toluene or naphthalene. It was unable to degrade DCPD, which was inhibitory when degradation of pairs of C5+ components was examined. The complete C5+ mixture appeared to be the best substrate for the consortium.

The Potential of Bacterial Isolates for Emulsification with a Range of Hydrocarbons

AbstractA study was undertaken to investigate the distribution of biosurfactant producing and crude oil degrading bacteria in the oil contaminated environment. This research revealed that hydrocarbon contaminated sites are the potent sources for oil degraders. Among 32 oil degrading bacteria isolated from ten different oil contaminated sites of gasoline and diesel fuel stations, 80% exhibited biosurfactant production. The quantity and emulsification activity of the biosurfactants varied. Pseudomonas sp. DS10‐129 produced a maximum of 7.5 ± 0.4 g/l of biosurfactant with a corresponding reduction in surface tension from 68 mN/m to 29.4 ± 0.7 mN/m at 84 h incubation. The isolates Micrococcus sp. GS2‐22, Bacillus sp. DS6‐86, Corynebacterium sp. GS5‐66, Flavobacterium sp. DS5‐73, Pseudomonas sp. DS10‐129, Pseudomonas sp. DS9‐119 and Acinetobacter sp. DS5‐74 emulsified xylene, benzene, n‐hexane, Bombay High crude oil, kerosene, gasoline, diesel fuel and olive oil. The first five of the above isolates had the highest emulsification activity and crude oil degradation ability and were selected for the preparation of a mixed bacterial consortium, which was also an efficient biosurfactant producing oil emulsifying and degrading culture. During this study, biosurfactant production and emulsification activity were detected in Moraxella sp., Flavobacterium sp. and in a mixed bacterial consortium, which have not been reported before.

1-Butanol Removal from a Contaminated Airstream under Continuous and Diurnal Loading Conditions

A polysulfone microporous membrane module was investigated for control of 1-butanol-contaminated gas streams. A diurnal loading condition, using two different butanol concentrations, was used to simulate startup and stop conditions associated with shift work. The membrane module was also used to remove 1-butanol from air under continuous loading conditions in a bioreactor. The reactors were seeded with a mixed bacterial consortium capable of butanol biodegradation. Biokinetic parameters for butanol utilization were determined for the culture to be a maximum specific utilization rate (k) equal to 4.3 d−1 and a half saturation constant (Ks) equal to 8.9 mg L−1. A biofilter running only with diurnal loading conditions giving a “40-hr workweek” had an average 1-butanol removal rate of 29% (111 ppm, 74 gm−3 hr−1) from a 350-ppm influent at the end of an 8-hr operational day. End-of-day removal varied between 4 and 67% during the operational period. With continuous steady-state operation followed by placement on a diurnal loading schedule and influent butanol concentrations increased to 700 ppm, butanol removal averaged 38% (269 ppm, 145 gm−3 hr−1). Under continuous loading, steady-state conditions, 1-butanol removal from the airstream was greater than 99% (200 ppm, 73 gm−3 hr−1). These results suggest that the bioreactor can be operated on a diurnal schedule or 40-hr week operational schedule without any decline in performance.

Occurrence of crude oil degrading bacteria in gasoline and diesel station soils.

Microbial enumeration and identification were carried out on several oil contaminated soil samples collected from gasoline and diesel stations. Bacteria were the most dominant microbiota and were therefore classified to generic level. Eleven main genera were detected and Corynebacterium was the predominant genus in all the samples. Biochemical characterisation and substrate utilisation showed high percentage of lipolytic ability combined with high inorganic nitrogen utilisers. The ability of these cultures to degrade crude oil was tested individually and in mixed bacterial consortium at different temperatures and pH values. Maximum crude oil biodegradation of 78% was achieved using a bacterial consortium containing five cultures (Micrococcus sp. GS2-22, Corynebacterium sp. GS5-66, Flavobacterium sp. DS5-73, Bacillus sp. DS6-86 and Pseudomonas sp. DS10-129) with 1% crude oil at 30 degrees C and pH 7.5. Such a consortium may be useful for bioaugmentation of oil contaminated environments.

Biodegradation of lipid-rich wastewater by a mixed bacterial consortium

A mixed bacterial culture comprising Pseudomonas aeruginosa LP 602, Bacillus sp. B 304 and Acinetobacter calcoaceticus LP 009 for use in treatment of lipid-rich wastewater was formulated. In our tests, 1 l of wastewater was treated with a mixed inoculum of 6.1×10 8 CFU of LP 602, 4.8×10 8 CFU B 304 and 8.9×10 7 CFU of LP 009 in 20 ml of basal salt solution ( 1.5 mg/ ml Na 2 HPO 4, 0.6 mg/ ml KH 2 PO 4, 40 μg/ ml MgSO 4 and 4 μg/ ml FeSO 4 ) supplemented with 1% (w/v) CaCl 2. The intended role of B 304 was that of a protease and amylase producer while those of LP 602 and LP 009 were those of lipase producers. The BOD value and lipid content were reduced from ∼3500 and 20,000 mg/ l , respectively, to <20 mg/ l within 12 days under aerobic conditions.

Bioremediation of gasoline contaminated soil by a bacterial consortium amended with poultry litter, coir pith and rhamnolipid biosurfactant

The aim of the present study was to find methods for enhancing rates of hydrocarbon biodegradation in gasoline contaminated soil by ex situ bioremediation. Red soil (RS) was treated with gasoline-spilled soil (GS) from a gasoline station and different combinations of amendments were prepared using (i) mixed bacterial consortium (MC), (ii) poultry litter (PL), (iii) coir pith (CP) and (iv) rhamnolipid biosurfactant (BS) produced by Pseudomonas sp. DS10-129. The study was conducted for a period of 90 days during which bacterial growth, hydrocarbon degradation and growth parameters of Phaseolus aureus RoxB including seed germination, chlorophyll content, shoot and root length were measured. Approximately 67% and 78% of the hydrocarbons were effectively degraded within 60 days in soil samples amended with RS + GS + MC + PL + CP + BS at 0.1% and 1%. Maximum percentage of seed germination, shoot length, root length and chlorophyll content in P. aureus were recorded after 60 days in the above amendments. Further incubation to 90 days did not exhibit significant improvements. Statistical analysis using analysis of variance (ANOVA) and Duncan's multiple range test (DMRT) revealed that the level of amendments, incubation time and combination of amendments significantly influenced bacterial growth, hydrocarbon degradation, seed germination and chlorophyll content at a 1% probability level. All tested additives MC, PL, CP and rhamnolipid BS had significant positive effects on the bioremediation of GS.

Decolorization of textile dyestuffs by a mixed bacterial consortium

A mixed anaerobic bacterial culture decolorized Drimaren Orange K-GL, Everzol Red RBN and Everdirect Supra Yellow PG dyestuffs at 200 mg dyestuff l−1 over 24 h. Improved performance with complete decolorization within 24 h was achieved by incubation with 5 g yeast extract l−1 compared to glucose, lactose and sucrose though 50 mg yeast extract l−1 supplemented with 5 g lactose l−1 or 5 g sucrose l−1 also resulted in complete decolorization within 24 h.

Influence of Soil Organic Matter and Soil Surfaces on a Bacterial Consortium that Mineralizes Fenamiphos

AbstractMicroorganisms are often responsible for enhanced degradation of pesticides in soil. This study was conducted to isolate microorganisms capable of mineralizing fenamiphos [ethyl‐3‐methyl‐4‐(methylthio)‐phenyl(1‐methylethyl)phosphoramidate] from soil collected at a turfgrass site that showed an enhanced degradation rate of the chemical. Batch‐culture enrichment techniques were employed to isolate microor‐ganisms from the soil capable of mineralizing 14C‐fenamiphos, and the evolved 14CO2 was quantified by liquid scintillation counting. No axenic bacterial cultures capable of mineralizing fenamiphos could be isolated. A mixed bacterial consortium enriched with glucose‐basal mineral medium mineralized fenamiphos only in the presence of a small amount of the nonsterile soil, autoclaved soil, or H2O2‐treated soil. The mixed culture consisted of at least 6 gram‐negative rod‐shaped bacteria, with none of the individual isolates having any capacity to mineralize fenamiphos. The mixed culture grew well in soil extract and, at the same time, mineralized fenamiphos. This suggests that soluble organic components serve as inducers for the production of enzymes necessary for the mineralization of fenamiphos or that soil surfaces might play a role in induction of the enzymes.