Liang Tan

Aerobic decolorization and degradation of azo dyes by growing cells of a newly isolated yeast Candida tropicalis TL-F1

The aim of this work was to investigate the decolorization and degradation of azo dyes by growing cells of a new yeast strain TL-F1 which was isolated from the sea mud. Strain TL-F1 was identified as Candida tropicalis on the basis of 28S rDNA analysis. Various azo dyes (20mg/L) were efficiently decolorized through aerobic degradation. Meantime, the effects of different parameters on both decolorization of Acid Brilliant Scarlet GR and growth of strain TL-F1 were investigated. Furthermore, possible degradation pathway of the dye GR was proposed through analysis of metabolic products using UV-Vis spectroscopy and HPLC-MS methods. As far as it is known, it is the first systematic research on a C. tropicalis strain which is capable of efficiently decolorizing various azo dyes under aerobic condition. This work provides a potentially useful microbial strain TL-F1 for treatment of azo dye contaminated wastewater.

Aerobic decolorization and degradation of Acid Red B by a newly isolated Pichia sp. TCL.

A yeast strain with strong abilities to decolorize various azo dyes aerobically was isolated from the sea mud. The strain designated as TCL was identified as Pichia sp. on the basis of 18S rDNA analysis. More than 90% of Acid Red B (100mg/L) was decolorized within 10h in the Martin Broth at 30°C and 150r/min, and strain TCL could tolerate up to 1000mg/L of the dye. Meantime, the effects of different physicochemical parameters (media, concentrations of glucose, NH(4)Cl, initial dye and NaCl) were investigated to improve the removal efficiency. The significant biodegradation process of Acid Red B rather than inactive surface adsorption was confirmed by UV-vis, HPLC analysis and colorless microbial cells. In addition, the metabolic products and partial degradation pathway were proposed with the help of HPLC-MS analysis. To the best of our knowledge, it is the first time that a yeast strain of Pichia sp. has been reported with the excellent decolorizing ability against azo dyes under shaking conditions. This work conferred the utilization possibility of strain TCL in the biological treatment of dyeing wastewater.

Aerobic decolorization, degradation and detoxification of azo dyes by a newly isolated salt-tolerant yeast Scheffersomyces spartinae TLHS-SF1

Isolation, identification and characterization of a salt-tolerant yeast capable of degrading and detoxifying azo dyes were investigated in this study. Possible degradation pathway of Acid Scarlet 3R was proposed through analyzing metabolic intermediates using UV-Vis and HPLC-MS methods. Furthermore, the Microtox test was performed to evaluate the acute toxicity of the dye before and after biodegradation. The results showed that a salt-tolerant yeast named TLHS-SF1 was isolated and identified as Scheffersomyces spartinae basing on 26S rDNA analysis. The optimal decolorization and growth parameters were: sucrose 2 g L(-1), (NH4)2SO4 0.6 g L(-1), yeast extract 0.08 g L(-1), NaCl ⩽ 30 g L(-1), 160 rmin(-1), 30 °C and pH 5.0-6.0. More than 90% of 80 mg L(-1) 3R could be decolorized within 16 h under the optimal conditions. 3R was possibly degraded successively through azo-reduction, deamination and desulfonation pathways, and its acute toxicity obviously decreased by strain TLHS-SF1.

Aerobic decolorization and degradation of azo dyes by suspended growing cells and immobilized cells of a newly isolated yeast Magnusiomyces ingens LH-F1.

Aerobic decolorization and degradation of azo dyes by both of suspended growing cells and immobilized cells of a newly isolated yeast strain LH-F1 were investigated in this study. A yeast strain LH-F1 capable of aerobically decolorizing various azo dyes (20mg/L) was identified as Magnusiomyces ingens basing on 26S rDNA analysis. Meanwhile, effects of different parameters on decolorization of Acid Red B by both of suspended growing cells and immobilized cells of strain LH-F1 were investigated. Furthermore, possible degradation pathway of the dye was proposed through analyzing metabolic intermediates using UV-Vis and HPLC-MS methods. As far as it is known, it is the first systematic research on a M. ingens strain which is capable of efficiently decolorizing azo dyes under aerobic condition. Additionally, this work would also provide a potentially useful microbial strain LH-F1 for treatment of industrial wastewaters containing azo dyes.

A novel integration system of magnetically immobilized cells and a pair of graphite plate-stainless iron mesh electrodes for the bioremediation of coking wastewater

Magnetically immobilized cells of Comamonas sp. JB coupling with electrode reaction was developed to enhance the treatment efficiency of coking wastewater containing phenol, carbazole (CA), dibenzofuran (DBF), and dibenzothiophene (DBT). The pair of graphite plate-stainless iron mesh electrodes was chosen as the most suitable electrodes. Magnetically immobilized cells coupling with graphite plate-stainless iron mesh electrodes (coupling system) exhibited high degradation activity for all the compounds, which were significantly higher than the sum by single magnetically immobilized cells and electrode reaction at the optimal voltage. Recycling experiments demonstrated that the degradation activity of coupling system increased gradually during eight recycles, indicating that there was a coupling effect between the biodegradation and electrode reaction. Phenol hydroxylase and qPCR assays confirmed that appropriate electrical stimulation could improve phenol hydroxylase activity and promote cells growth. Toxicity assessment suggested the treatment of the coking wastewater by coupling system led to less toxicity than untreated wastewater.

Performance of a newly isolated salt-tolerant yeast strain Pichia occidentalis G1 for degrading and detoxifying azo dyes

A salt-tolerant yeast named G1 which could decolorize various azo dyes was recently isolated and identified as Pichia occidentalis. Systematic researches on characterization, degradation pathway, detoxification effects and enzymes analysis of this yeast were done. The results showed that the optimal metabolism and growth parameters for strain G1 were: 2.0gL-1 glucose, 0.6gL-1 ammonium sulfate, 0.08gL-1 yeast extract, 30gL-1 NaCl, 160rmin-1, 30°C and pH 5.0. More than 98% of 50mgL-1 Acid Red B (ARB) could be decolorized within 16h under the optimal conditions. Additionally, strain G1 degraded and obviously detoxified ARB through a possible pathway successively consisting of decolorization, deamination/desulfonation and TCA cycle processes. Moreover, NADH-DCIP reductase was estimated as the key reductase for decolorization and ligninases including lignin peroxidase, manganese peroxidase and laccase were important oxidoreductases for further degradation of decolorization intermediates.

Efficient treatment of phenolic wastewater with high salinity using a novel integrated system of magnetically immobilized cells coupling with electrodes

A novel integrated system in which magnetically immobilized cells coupled with a pair of stainless iron meshes-graphite plate electrodes has been designed and operated to enhance the treatment performance of phenolic wastewater under high salinity. With NaCl concentration increased, phenol, o-cresol, m-cresol, p-cresol and COD removal rates by integrated system increased significantly, which were obviously higher than the sum of removal rates by single magnetically immobilized cells and electrode reaction. This integrated system exhibited higher removal rates for all the compounds than that by single magnetically immobilized cells during six cycles for reuse, and it still performed better, even when the voltage was cut off. These results indicated that there was a coupling effect between biodegradation and electrode reaction. The investigation of phenol hydroxylase activity and cells concentration confirmed that electrode reaction played an important role in this coupling effect.

Enhanced treatment performance of coking wastewater and reduced membrane fouling using a novel EMBR

A novel EMBR (electric field applied in MBR) by placing stainless steel mesh cathode inside a flat membrane module and stainless steel mesh anode outside the module was built and operated to enhance the treatment performance of coking wastewater containing phenol, pyridine and quinoline and reduce the membrane fouling. The degradation rates of COD, phenol, pyridine and quinoline in EMBR with electric field (reactor A) were significantly higher than the sum of EMBR without electric field (reactor B) and only electro-catalytic degradation during the long-term treatment, confirming that a coupling effect was existed between biodegradation and electro-catalytic degradation process. Illumina sequencing data revealed that bacterial community was richer and more diverse in reactor A. Comamonas strain JB as the inoculums was the most dominant genus in each reactor and electric field applied in reactor A further improved the abundance of strain JB. The membrane fouling in reactor A was reduced.

Biosynthesis of 1,2-dihydroxydibenzofuran by magnetically immobilized cells of Escherichia coli expressing phenol hydroxylase in liquid-liquid biphasic systems.

Escherichia coli cells expressing phenol hydroxylase (designated as PHIND) were used to biosynthesize 1,2-dihydroxydibenzofuran (1,2-dihydroxyDBF) from dibenzofuran (DBF). The pathway of DBF biotransformation by strain PHIND was proposed, in which DBF was initially monohydroxylated at C-1 and C-4 positions to produce 1- and 4-hydroxyDBF, then underwent successive hydroxylation to yield 1,2- and 3,4-dihydroxyDBF, of which 1,2-dihydroxyDBF was identified for the first time. Magnetically immobilized cells of strain PHIND in biphasic systems with dodecane as the solvent presented highest biosynthesis activity for 1,2-dihydroxyDBF, which was a 6.5-fold improvement compared to biosynthesis in aqueous system. The recycling experiments demonstrated that magnetically immobilized cells exhibited higher biosynthesis activity for 1,2-dihydroxyDBF than that by nonmagnetically immobilized cells during five cycles in biphasic systems. These works support the development of an efficient biosynthesis process using magnetically immobilized cells in biphasic systems and provide a promising technique for improving the productivity in 1,2-dihydroxyDBF biosynthesis.

Performance of the biological aerated filter bioaugmented by a yeast Magnusiomyces ingens LH-F1 for treatment of Acid Red B and microbial community dynamics

Biological aerated filters (BAFs) were constructed and operated for assessing the effectiveness of bacterial community bioaugmented by a yeast Magnusiomyces ingens LH-F1 for treatment of azo dye Acid Red B (ARB). Dynamics of both bacterial and fungal communities were analyzed through MiSeq sequencing method. The results showed that the bioaugmented BAF displayed obviously better performance for decolorization, COD removal and detoxification of ARB wastewater than the other two which were inoculated with activated sludge (AS) and single M. ingens LH-F1, respectively. Moreover, the bioaugmented BAF also exhibited higher tolerance and stability to shock loading. MiSeq sequencing results demonstrated that both of bacterial and fungal communities remarkably shifted with operation conditions, and the increasing fungal diversity in the bioaugmented BAF was probably related to the relatively high biodegradation and detoxification efficiency. Furthermore, M. ingens LH-F1 survived in the bioaugmented BAF and became one of the dominant fungal species. Therefore, bioaugmentation with yeast M. ingens LH-F1 was successful for improving traditional biological processes aiming at treatment of azo compounds. This method was also potentially useful and meaningful for treating other recalcitrant organic pollutants in practical applications.