New insights on toluene biodegradation by Pseudomonas putida F1: influence of pollutant concentration and excreted metabolites

The influence of toluene concentration on the specific growth rate, cellular yield, specific CO₂, and metabolite production by Pseudomonas putida F1 (PpF1) was investigated. Both cellular yield and specific CO₂ production remained constant at 1.0 ± 0.1 g biomass dry weight (DW) g⁻¹ toluene and 1.91 ± 0.31 g CO₂ g⁻¹ biomass, respectively, under the tested range of concentrations (2–250 mg toluene l⁻¹). The specific growth rate increased up to 70 mg toluene l⁻¹. Further increases in toluene concentration inhibited PpF1 growth, although inhibitory concentrations were far from the application range of biological treatment processes. The specific ATP content increased with toluene concentration up to toluene concentrations of 170 mg l⁻¹. 3-Methyl catechol (3-MC) was never detected in the cultivation medium despite being an intermediary in the TOD pathway. This suggested that the transformation from toluene to 3-MC was the limiting step in the biodegradation process. On the other hand, benzyl alcohol (BA) was produced from toluene in a side chain reaction. This is, to the best of our knowledge, the first reported case of methyl monoxygenation of toluene by PpF1 not harboring the pWW0 TOL plasmid. In addition, the influence of 3-MC, BA, and o-cresol on toluene degradation was investigated respirometrically, showing that toluene-associated respiration was not significantly inhibited in the presence of 10–100 mg l⁻¹ of the above-mentioned compounds.     

Effect of volatile fatty acids on Shigella dysenteriae during anaerobic digestion of human night soil

Thein vitro toxic effect of different volatile fatty acids (VFA) on Shigella dysenteriae was studied in pure culture. Volatile fatty acids viz., acetate, propionate, butyrate, valerate, caproate and heptanoate, exerted pH dependent toxic effect on the pathogen, with minimum inhibitory concentration in the range of 10–3000 mg l⁻¹. The effect of high levels of VFA on S. dysenteriae was studied during anaerobic digestion of human night soil in an experimental digester with VFA level ≅ 9000 mg l⁻¹ and pH ≅ 6.5. Another digester, with VFA level ≅ 700 mg l⁻¹ and pH 7.4, served as the control. In the experimental digester, S. dysenteriae was completely eliminated within 18 days. In the control digester, a four-log reduction in pathogen count was achieved however the pathogen was not completely eliminated. T ₉₀ values for the experimental and control digesters were 2.2 and 3.7 days respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of Biochemical Pathway and Enzyme Involved in Metsulfuron-Methyl Degradation by <Emphasis Type="Italic">Ancylobacter</Emphasis> sp. XJ-412-1 Isolated from Soil

Ancylobacter sp. XJ-412-1, capable of degrading metsulfuron-methyl, was isolated from sulfonylurea-contaminated soil. When metsulfuron-methyl was provided as the sole carbon source, more than 90.5% of metsulfuron-methyl at concentration of 50 mg l⁻¹ was degraded by strain XJ-412-1 after incubation at 30°C for 7 days. The initial degradation products of metsulfuron-methyl (MSM), thifensulfuron-methyl (TSM), and bensulfuron-methyl (BSM) by XJ-412-1 were identified as corresponding deesterified derivatives by liquid chromatography-mass spectrometry, which indicated a primary pathway of the deesterification of these three sulfonylurea herbicides. The carboxyesterase activity of the cell-free extracts was assayed and strongly inhibited by 4-chloromercuribenzoic acid (PCMB), diethyl pyrocarbonate (DEPC), phenylmethylsulfonyl fluoride (PMSF), and malathion.     

Single-culture aerobic granules with <Emphasis Type="Italic">Acinetobacter calcoaceticus</Emphasis>

Aerobic granules are cultivated by a single bacterial strain, Acinetobacter calcoaceticus, in a sequencing batch reactor (SBR). This strain presents as a good phenol reducer and an efficient auto coagulator in the presence of phenol, mediated by heat-sensitive adhesins proteins. Stable 2.3-mm granules were formed in the SBR following a 7-week cultivation. These granules exhibit excellent settling attributes and degrade phenol efficiently at concentrations of 250–2,000 mg l⁻¹. The corresponding phenol degradation rate reached 993.6 mg phenol g⁻¹ volatile suspended solids (VSS) day⁻¹ at 250 mg l⁻¹ phenol and 519.3 mg phenol g⁻¹ VSS day⁻¹ at 2,000 mg l⁻¹ phenol concentration. Meanwhile, free A. calcoaceticus cells were fully inhibited at phenol >1,500 mg l⁻¹. Denaturing gradient gel electrophoresis fingerprint profile demonstrated no genetic modification in the strain during aerobic granulation. The present single-strain granules showed long-term structural stability and performed high phenol degrading capacity and high phenol tolerance. The confocal laser scanning microscopic test revealed that live A. calcoaceticus cells principally distributed at 200–250 μm beneath the outer surface, with an extracellular polymeric substance layer covering them to defend phenol toxicity. Autoaggregation assay tests demonstrated the possibly significant role of secreted proteins on the formation of single-culture A. calcoaceticus granules.     

Degradation of p-nitrophenol and pentachlorophenol mixtures by Sphingomonas sp. UG30 in soil perfusion bioreactors

The degradation of mixtures of pentachlorophenol (PCP) and p-nitrophenol (PNP) were evaluated in pure cultures of Sphingomonas sp. UG30, statically incubated soils (60% water-holding capacity) and soil perfusion bioreactors where encapsulated cells of UG30 were used as a soil inoculant. In pure-culture studies, conditions were optimized for mineralization of PCP and PNP mixtures at concentrations of 30 mg l⁻¹ each. Optimum in vitro mineralization of PCP and PNP mixtures by UG30 was facilitated using ammonium phosphate as a nitrogen source, while inhibition was observed with ammonium nitrate. The bioreactor system used columns containing soil treated with mixtures of 100, 225 or 500 mg kg⁻¹ of PCP and PNP. Rapid dissipation of both substrates was observed at the 100 mg kg⁻¹ level. Inoculation with UG30 enhanced PCP degradation at the 100 mg kg⁻¹ level in bioreactors but not in static soil microcosms. At higher PCP and PNP concentrations (225 mg kg⁻¹), occasional complete degradation of PNP was observed, and PCP degradation was about 80% compared to about 25% in statically incubated soils after 20 days at 22°C. There was no additional degradation of the PCP and PNP mixtures attributable to inoculation with encapsulated cells of UG30 in either soil system at concentrations of 225 or 500 mg kg⁻¹. Journal of Industrial Microbiology & Biotechnology (2000) 25, 93–99. Received 25 February 2000/ Accepted in revised form 07 June 2000     

Agrobacterium tumefaciens-mediated transformation of Lesquerella fendleri L., a potential new oil crop with rich lesquerolic acid

A protocol was developed for regeneration and Agrobacterium-mediated genetic transformation of Lesquerella fendleri. Calli were first induced from hypocotyls and cotyledons on MS plus 0.5 mg l⁻¹ BA, 1 mg l⁻¹ NAA and 1 mg l⁻¹ 2,4-D, then co-cultivated for 2–3 days in darkness on MS supplemented with 0.5 mg l⁻¹ BA, 0.2 mg l⁻¹ NAA and 100 μmol l⁻¹As together with Agrobacterium tumefaciens strain EHA105/pCAMBIA1301 that harbored genes for uidA (GUS) and hygromycin resistance. Following co-cultivation, calli transfected by A. tumefaciens were transferred to MS with 0.5 mg l⁻¹ BA, 0.2 mg l⁻¹NAA, 500 mg l⁻¹ Cef and 10 mg l⁻¹ hygromycin and cultured for 10 days, then the hygromycin was increased to 20 mg l⁻¹ on the same medium. After 4 weeks the resistant regenerants were transferred to MS with 0.5 mg l⁻¹BA, 0.2 mg l⁻¹ NAA, 500 mg l⁻¹ Cef and 25 mg l⁻¹ hygromycin for further selections. Transgenic plants were confirmed by polymerase chain reaction analysis, GUS histochemical assay and genomic Southern blot hybridization. With this approach, the average regeneration frequency from transfected calli was 22.70%, and the number of regenerated shoots per callus was 6–13. Overall results described in this study demonstrate that Agrobacterium-mediated transformation is a promising approach for improvement of this Lesquerella species.     

Isolation, Characterization and Phylogenetic Analysis of an Aerobic Bacterium Capable of Degrading Bensulfuronmethyl

Summary An aerobic bacterium named strain BH was isolated from soil samples based on its bensulfuronmethyl-degrading characteristics using continuous enrichment cultures. The cells of the strain were non-motile, gram-positive short rods. Colonies formed on agar medium were round, smooth, sticky, white-yellow in colour and of butyrous consistency. Analyses of nutritional utilization in Biolog microplates, conventional phenotypic characteristics and 16S rRNA gene sequencing were consistent with assigning strain BH to the genus Brevibacterium. Growth of the cells and their ability to degrade bensulfuronmethyl were simultaneously monitored under different liquid medium conditions during 7 days of incubation. They degraded bensulfuronmethyl from 100 to 70.6 mg l⁻¹ in mineral M9 medium and exhibited more effective degradation in the presence of yeast extract, completely removing an initial concentration of 100 mg l⁻¹ and at best 80% of an initial concentration of 200 mg l⁻¹. Further studies are required to determine the potential use of the isolate in the disposal of bensulfuronmethyl residues in agriculture and industry.     

Rapid multiplication of Polyscias filicifolia by secondary somatic embryogenesis

Efficient plant regeneration through somatic embryogenesis was achieved in Polyscias filicifolia. Embryogenic calluses were induced on Murashige and Skoog (MS) basal medium supplemented with 0.5 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg l⁻¹ benzylaminopurine (BAP; type I callus) and on MS medium with 2.0 mg l⁻¹ 2,4-D and 0.01 mg l⁻¹ kinetin (type II callus) from leaf explants of a 2-yr-old plant. Primary somatic embryos (PSEs) developed after four passages of suspension culture established from embryogenic callus when cultured in liquid half-strength MS medium (1/2 MS) without growth regulators. PSEs in the cotyledonary stage were multiplied by adventitious embryogenesis. Single secondary somatic embryos (SSEs) or their clusters developed at the base of PSE hypocotyls and regenerated into plantlets in a one-step process on plant growth regulator-free 1/2 MS medium. Low sucrose concentration of 15 g l⁻¹ promoted development of normal SSEs. All SSEs regenerated into single, well-rooted plantlets on a Nitsch and Nitsch medium supplemented with 0.5 mg l⁻¹ kinetin, 0.1 mg l⁻¹ indole-3-butyric acid, and 10 mg l⁻¹ adenine sulfate. Subsequent two subculture cycles on the same medium were necessary to obtain plantlets sufficiency developed to allow successful transfer to the soil. Rooted plantlets were established in a peat mixture with 90% survival, with the plants showing normal morphological characteristics.     

Tissue culture and plant regeneration of blue grama grass, Bouteloua gracilis (H.B.K.) Lag. Ex Steud

Summary As a first step towards applying biotechnology to blue grama, Bouteloua gracilis (H. B. K.) Lag. ex Steud., we have developed a regenerable tissue culture system for this grass. Shoot apices were isolated from 3-d-old seedlings and cultured in 15 different growth regulator formulations combining 2,4-dichlorophenoxyacetic acid (2,4-D), Picloram (4-amino-3, 5,6-trichloropicolinic acid), N⁶-benzyladenine (BA) or adenine (6-aminopurine). The highest induction of organogenic callus was obtained with formulations containing 1 mg l⁻¹ (4.52 μM) 2,4-D plus 0.5 mg l⁻¹ (2.22 μM) BA. and 2 mg l⁻¹ (8.88 μM) BA plus 1 mg l⁻¹ (4.14 μM) Picloram with or without 40 mg l⁻¹ (296.08 μM) adenine. Lower frequencies of induction were obtained for embryogenic as compared to organogenic callus. The most efficient treatments for induction of embryogenic callus contained 2 mg l⁻¹ (9.05 μM) 2,4-D combined with 0.25 (1.11 μM) or 0.50 mg l⁻¹ (2.22 μM) BA, or 1 mg l⁻¹ (4.52 μM) 2,4-D with 0.50 mg l⁻¹ (2.22 μM) BA. Regeneration was achieved in hormonefree Murashige anmd Skoog (MS) medium, half-strength MS medium or MS medium plus 1 mg l⁻¹ (1.44 μM) gibberellic acid. The number of plantlets regenerated per 500 mg callus fresh weight on MS medium ranged from 9 for 2 mg l⁻¹ (9.05 μM) 2,4-D to 62.2 for induction medium containing 2 mg l⁻¹ (8,28 μM) Picloram, 1 mg l⁻¹ (4.44 μM) BA and 40 mg l⁻¹ (296.08 μM) adenine. Regnerated plants grown in soil under greenhouse conditions reached maturity and produced seeds.     

Biodegradation kinetics of the benzimidazole fungicide thiophanate-methyl by bacteria isolated from loamy sand soil

Degradation of the fungicide thiophanate-methyl (TM) by Enterobacter sp. TDS-1 and Bacillus sp. TDS-2 isolated from sandy soil previously treated with TM was studied in mineral salt medium (MSM) and soil. Both strains were able to grow in MSM supplemented with TM (50 mg l⁻¹) as the sole carbon source. Over a 16 days incubation period, 60 and 77% of the initial dose of TM were degraded by strains TDS-1 and TDS-2, respectively, and disappearance of TM was described by first-order kinetics. Medium supplementation with glucose markedly stimulated bacterial growth; while the final rate of TM degradation was reduced by 21 and 27% for strains TDS-1 and TDS-2, respectively as compared to medium with TM only. Moreover, this additional carbon source changed the TM degradation kinetics, which proceeded according to a zero-order model. This effect was linked to substrate competition and/or a strong decrease of medium pH. Isolates degraded TM (100 mg kg⁻¹) in soil with rate constants of 0.186 and 0.210 day⁻¹, following first-order rate kinetics, and the time in which the initial TM concentration was reduced by 50% (DT50) in soils inoculated with strains TDS-1 and TDS-2 were 6.3 and 5.1 days, respectively. Analysis of TM degradation products in soil showed that the tested strains may have the potential to transform carbendazim (MBC) to 2-aminobenzimidazole (2-AB), and may be useful for a bioremediation of MBC-polluted soils.     

Enrichment, isolation, and characterization of 4-chlorophenol-degrading bacterium Rhizobium sp. 4-CP-20

The objectives of this research were to monitor the variations of species in mixed cultures during the enrichment period, isolate species and identify and characterize the pure 4-chlorophenol (4-CP) degrading strains from enriched mixed cultures. Strain Rhizobium sp. 4-CP-20 was isolated from the acclimated mixed culture. The DGGE result indicated that strain Rhizobium sp. 4-CP-20 was undetectable at the beginning but detectable after 2 weeks of enrichment. The optimum growth temperatures for Rhizobium sp. 4-CP-20 were both 36°C using 350 mg l⁻¹ glucose or sodium acetate as the substrate. The optimum pH range for degrading 100 mg l⁻¹ 4-CP was between 6.89 and 8.20. Strain Rhizobium sp. 4-CP-20 could degrade 4-CP completely within 3.95 days, as the initial 4-CP concentration was 100 mg l⁻¹. If the initial 4-CP concentration was higher than 240 mg l⁻¹, the growth of bacterial cells and the activity of degrading 4-CP were both inhibited.     

Uptake by corn and chemical extractability of heavy metals from a four year compost treated soil

This paper gives the results from four-year field experiments on compost application, added at the maximum rate allowed by Italian legislation (30 t/ha/y). The purpose of the experiment was to evaluate any eventual heavy metal accumulation in soil and corn plants. Cadmium in corn plants increased particularly in the roots from 0.22 mg kg⁻¹ to 1.31 mg kg⁻¹, concentration of Zn and Cu increased in grains, from 26.8 to 35.8 and from 2.4 to 4.2 mg kg⁻¹ respectively. Relevant increase in the roots was detected for Zn from 34.6 to 146.8 mg kg⁻¹. Only in the 4th year Ni concentration increases in the root portion while the content of Pb and Cr in corn was generally unaffected by the compost application. Heavy metals in the soil determined by a sequential chemical extraction, indicated that extractability changed with time. A certain increase was found from the beginning to the end of the experiment particularly for Zn, from 23.3 mg kg⁻¹ to 45.1 mg kg⁻¹ in extractable forms. Nevertheless the extractable amounts are rather small in respect to the total heavy metal content of compost.     

Mineralization of diuron [3-(3,4-dichlorophenyl)-1, 1-dimethylurea] by co-immobilized <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. and <Emphasis Type="Italic">Delftia acidovorans</Emphasis>

Mineralization of diuron has not been previously demonstrated despite the availability of some bacteria to degrade diuron into 3,4-dichloroaniline (3,4-DCA) and others that can mineralize 3,4-DCA. A bacterial co-culture of Arthrobacter sp. N4 and Delftia acidovorans W34, which respectively degraded diuron (20 mg l⁻¹) to 3,4-DCA and mineralized 3,4-DCA, were able to mineralize diuron. Total diuron mineralization (20 mg l⁻¹) was achieved with free cells in co-culture. When the bacteria were immobilized (either one bacteria or both), the degradation rate was higher. Best results were obtained with free Arthrobacter sp. N4 cells co-cultivated with immobilized cells of D. acidovorans W34 (mineralization of diuron in 96 h, i.e., 0.21 mg l⁻¹ h⁻¹ vs. 0.06 mg l⁻¹ h⁻¹ with free cells in co-culture).     

Optimization and enhancement of soil bioremediation by composting using the experimental design technique

The objective of this study was the application of the experimental design technique to optimize the conditions for the bioremediation of contaminated soil by means of composting. A low-cost material such as compost from the Organic Fraction of Municipal Solid Waste as amendment and pyrene as model pollutant were used. The effect of three factors was considered: pollutant concentration (0.1–2 g/kg), soil:compost mixing ratio (1:0.5–1:2 w/w) and compost stability measured as respiration index (0.78, 2.69 and 4.52 mg O₂ g⁻¹ Organic Matter h⁻¹). Stable compost permitted to achieve an almost complete degradation of pyrene in a short time (10 days). Results indicated that compost stability is a key parameter to optimize PAHs biodegradation. A factor analysis indicated that the optimal conditions for bioremediation after 10, 20 and 30 days of process were (1.4, 0.78, 1:1.4), (1.4, 2.18. 1:1.3) and (1.3, 2.18, 1:1.3) for concentration (g/kg), compost stability (mg O₂ g⁻¹ Organic Matter h⁻¹) and soil:compost mixing ratio, respectively.     

In vitro micropropagation of Gymnema sylvestre – A multipurpose medicinal plant

The nature of the explant, seedling age, medium type, plant growth regulators, complex extracts (casein hydrolysate, coconut milk, malt extract and yeast extract) and antioxidants (activated charcoal, ascorbic acid, citric acid and polyvinylpyrrolidone) markedly influenced in vitro propagation of Gymnema sylvestre. A maximum number of shoots (57.2) were induced from 30 day old seedling axillary node explants on Murashige and Skoog (MS) medium containing 6-benzyladenine (1 mg l⁻¹), kinetin (0.5 mg l⁻¹), 1-napthalene acetic acid (0.1 mg l⁻¹), malt extract (100 mg l⁻¹) and citric acid (100 mg l⁻¹). High frequency of rooting was obtained in axillary node explant derived shoots (50%) on half strength MS medium supplemented with IBA (3 mg l⁻¹). The plantlets, thus developed, were hardened and successfully established in natural soil. This revised version was published online in June 2006 with corrections to the Cover Date.     

Biodegradation of hexazinone by two isolated bacterial strains (WFX-1 and WFX-2)

Two hexazinone-degrading bacterial strains were isolated from soil by enrichment culture technique, and identified as Pseudomonas sp. and Enterobacter cloacap, respectively. The two purified isolates, designated as WFX-1 and WFX-2, could rapidly degrade hexazinone with half-lives of 3.08 and 2.95 days in mineral salts medium (hereafter referred to as MSM). In contrast, their mixed bacterial culture (herein abbreviated as MBC) was found to degrade hexazinone, at an initial concentration of 50 mg l⁻¹, by enhancing 2.3-fold over that when the isolates were used alone. The degradation of hexazinone by MBC in MSM clearly decreased concomitant with the increase of initial concentration, and the level of hexazinone that was toxic enough to totally inhibit degradation was in the range of 150–200 mg l⁻¹. The appropriately combined conditions for hexazinone degradation by MBC in MSM were studied, and found to be pH 5.5, 30 °C and at agitation of 120 rpm. The addition of MBC to soil had a greater impact on disappearance of hexazinone, which nearly increased fivefold over that of the control set. As a result, findings in the present investigation provide useful information for soil and water decontamination of hexazinone.     

Isolation and characterization of phenol-degrading yeasts from an oil refinery wastewater in Brazil

This study investigated the aerobic degradation of phenol by yeast strains isolated from an oil refinery wastewater from the Northeast of Brazil. The samples displayed low fungal diversity, as only yeast colonies were detected on Sabouraud dextrose agar containing chloramphenicol 0.05% (w/v). Among the isolates, three yeast strains were selected to be evaluated for their potential for degrading high phenol concentrations. These species were identified through morphological and biochemical characteristics as Candida tropicalis, C. rugosa, and Pichia membranaefaciens. Although the strains were able to degrade the phenol concentration present in the wastewater, which was 7 mg l⁻¹, only C. tropicalis was capable of growing at high concentrations of phenol such as 500 mg l⁻¹ and 1,000 mg l⁻¹ in a mineral medium containing this pollutant as the only carbon source. C. rugosa and P. membranaefaciens were inhibited in the presence of 500 mg l⁻¹ of phenol. However, a longer incubation time was needed for C. tropicalis strain to degrade 1,000 mg l⁻¹ of phenol compared to the time required to degrade 500 mg l⁻¹. Moreover, the strain released a significant amount of polysaccharide biosurfactant in the medium probably to minimize the toxic effect of the high phenol concentration. When challenged with 1,500 and 2,000 mg l⁻¹ of phenol, C. tropicalis was unable to grow at the tested conditions. The results indicate that this strain of C. tropicalis can be considered both a good phenol-degrader and biosurfactant-producer. Application of this strain might be useful in bioremediation activities or treatment of phenol-polluted wastewater.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of the chinese medicinal plant, <Emphasis Type="Italic">Dendrobium candidum</Emphasis> wall. ex lindl., from axenic nodal segments

Summary Dendrobium candidum Wall. Ex Lindl. is an important species used in the formulation of Shih-hu, a Chinese traditional medicine. An efficient protocol for in vitro propagation of D. candidum using the axenic nodal segments of the shoots, originated from the in vitro germinated seedlings, was developed. The seeds from 120-d-old capsules after pollination were first germinated on half-strength Murashige and Skoog (MS) basal medium supplemented with 30 g l⁻¹ sucrose. After 4 mo., the seedlings were subcultured on a similar medium supplemented with 1 ml l⁻¹ HYPONeX, 80 g l⁻¹ potato homogenate and 2 g l⁻¹ activated charcoal for further growth. Axenic nodal segments excised from 9-mo.-old seedlings were cultured on the medium in the presence of 2 mg l⁻¹ benzyladenine (BA) and 0.1 mg l⁻¹ naphthaleneacetic acid (NAA). After 75 d, 73.2% of the explants gave rise to buds/shoots. The elongated shoots were rooted on the medium containing 0.2 mg l⁻¹ NAA and the plantlets were successfully acclimatized in soil.     

Biodegradation of phenol and 4-chlorophenol by the yeast <Emphasis Type="Italic">Candida tropicalis</Emphasis>

Biodegradation of phenol and 4-chlorophenol (4-cp) using a pure culture of Candida tropicalis was studied. The results showed that C. tropicalis could degrade 2,000 mg l⁻¹ phenol alone and 350 mg l⁻¹ 4-cp alone within 66 and 55 h, respectively. The capacity of the strain to degrade phenol was obviously higher than that to degrade 4-cp. In the dual-substrate system, 4-cp intensely inhibited phenol biodegradation. Phenol beyond 800 mg l⁻¹ could not be degraded in the presence of 350 mg l⁻¹ 4-cp. Comparatively, low-concentration phenol from 100 to 600 mg l⁻¹ supplied a sole carbon and energy source for C. tropicalis in the initial phase of biodegradation and accelerated the assimilation of 4-cp, which resulted in the fact that 4-cp biodegradation velocity was higher than that without phenol. And the capacity of C. tropicalis to degrade 4-cp was increased up to 420 mg l⁻¹ with the presence of 100–160 mg l⁻¹ phenol. In addition, the intrinsic kinetics of cell growth and substrate degradation were investigated with phenol and 4-cp as single and mixed substrates in batch cultures. The results illustrated that the models proposed adequately described the dynamic behaviors of biodegradation by C. tropicalis.     

Decolorization of 1:2 metal complex dye Acid blue 193 by a newly isolated fungus, Cladosporium cladosporioides

Summary A fungus Cladosporium cladosporioides isolated from coal sample as a decolorizing microorganism. It decolorized five different azo and triphenylmethane dyes like acid blue 193, acid black 210, crystal violet, reactive black B(S) and reactive black BL/LPR both on solid and in liquid broth medium. Culture broth of this fungus decolorized completely 100 mg of acid blue 193 l⁻¹ in 8 days. The extracellular enzyme of Cladosporium cladosporioides decolorized acid blue 193 on repeated addition to a total (out of 700 mg l⁻¹) concentration of 564 mg l⁻¹ within 168 h without significant decline in the activity, showing the resistant property of Cladosporium cladosporioides to a high concentration of the dye. The optimal temperature 40 °C, pH 5.6 and sugar concentration of 4% required for decolorization of acid blue 193. Cladosporium cladosporioides showed manganese peroxidase activity with 41 U l⁻¹, laccase activity with 1413 U l⁻¹ and lignin peroxidase activity was negligible after day 8 of incubation.