Microbial decolorization of reactive azo dyes under aerobic conditions

Summary Kodam et al. reported a 100% decolorization of the sulfonated azo dyes Reactive Red 2, Reactive Red 141, Reactive Orange 4, Reactive Orange 7 and Reactive Violet 5 by an unidentified bacterium, KMK 48. High effectiveness was attained within 36 h of incubation at room temperature and neutral pH. Optimum decolorization took place strictly under aerobic conditions, which is contrary to other well-documented reports. Thus, this microorganism seems to be potentially effective for bioremediation of textile-dyeing industry effluents.     

Semicontinuous decolorization of azo dyes by rotating disc contactor immobilized with<Emphasis Type="Italic">Aspergillus sojae</Emphasis> B-10

Aspergillus sojae B-10 was immobilized and used to treat model dye compounds. The model wastewater, containing 10 ppm of azo dyes such as Amaranth, Sudan III, and Congo Red, was treated with cells attached to a rotating disc contactor (RDC). Amaranth was decolorized more easily than were Sudan III and Congo Red. Decolorization of Amaranth began within a day, and the dye was completely decolorized within 5 days of incubation. Both Sudan III and Congo Red were almost completely decolorized after 5 days of incubation. Semicontinuous decolorization of azo by reusing attached mycelia resulted in almost complete decolorization in 20 days. This experiment indicated that decolorization was successfully conducted by removing azo dyes withAspergillus sojae B-10.     

Decolorization kinetics of a recombinant Escherichia coli strain harboring azo-dye-decolorizing determinants from Rhodococcus sp.

A 6.3 kb DNA fragment containing genes responsible for azo-dye decolorization was cloned and expressed in Escherichia coli. The resulting recombinant strain E. coli CY1 decolorized 200 mg azo dye (C.I. Reactive Red 22) l^–1 at 28 °C at 8.2 mg g cell^–1 h^–1, while the host (E. coli DH5) had no color-removal activity. Addition of 0.5 mM isopropyl--d-thiogalacto-pyranoside (IPTG) increased the decolorization rate 3.4-fold. The dependence of the decolorization rate on initial dye concentration essentially followed Monod-type kinetics and the maximal rate occurred with the dye at 600 mg l^–1. The decolorization rate of E. coli CY1 was optimal at 40 °C and pH 11. Aeration (increased dissolved O₂ level) strongly inhibited the decolorization, but decolorization occurred effectively under static incubation conditions (no agitation was employed). The CY1 strain also exhibited excellent stability during repeated-batch operations.     

Capacity of Irpex lacteus and Pleurotus ostreatus for decolorization of chemically different dyes

The rate and efficiency of decolorization of poly R-478- or Remazol Brilliant Blue R (RBBR)-containing agar plates (200 μg g⁻¹) were tested to evaluate the dye degradation activity in a total of 103 wood-rotting fungal strains. Best strains were able to completely decolorize plates within 10 days at 28 °C. Irpex lacteus and Pleurotus ostreatus were selected and used for degradation of six different groups of dyes (azo, diazo, anthraquinone-based, heterocyclic, triphenylmethane, phthalocyanine) on agar plates. Both fungi efficiently degraded dyes from all groups. Removal of RBBR, Bromophenol blue, Cu-phthalocyanine, Methyl red and Congo red was studied with I. lacteus also in liquid medium. Within 14 days, the following color reductions were attained: RBBR 93%, Bromophenol blue 100%, Cu-phthalocyanine 98%, Methyl red 56%, Congo red 58%. The ability of I. lacteus to degrade RBBR spiked into sterile soil was checked, the removal being 77% of the dye added within 6 weeks. The capacity of selected white rot fungal species to remove efficiently diverse synthetic dyes from water and soil environments is documented.     

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.     

Triarylmethane Dye Decolorization by Pellets of Pycnoporus sanguineus: Statistical Optimization and Effects of Novel Impeller Geometry

A study was carried out to optimize selected parameters for decolorization of a triarylmethane dye, such as crystal violet by white rot fungus, Pycnoporus sanguineus, pellets. The parameters studied were initial dye concentration (ppm), agitation speed (rpm), and process time (days) and were optimized using response surface methodology (RSM). It is shown that process time, agitation speed, and their interactions have significant effects on the decolorization process. Following the optimization, the decolorization study was extended to a stirred tank reactor (STR) process. Effects of different geometry of impellers on the decolorization process and power consumption were studied. Novel impeller geometries, such as 180° curved blade and 60° angled blade impellers, were used in the STR. The application of 180° curved blade impeller resulted in higher percentage of decolorization at a relatively less power consumption as compared with 60° angled blade impeller.     

Decolorization of the azo dye Acid Red 18 by crude manganese peroxidase: Effect of system parameters and kinetic study

Abstract

To optimize operating conditions for the decolorization of the azo dye Acid Red 18 (AR18) by crude manganese peroxidase (MnP), some important factors affecting enzymatic decolorization were systematically investigated. Under the optimal enzyme reaction conditions, a decolorization efficiency of more than 82.3% was achieved after 60 min treatment. Furthermore, the manganese chelators, malate, tartrate, and lactate were found to be more favorable for the decolorization of AR18 than malonate, acetate, succinate, maleate, oxalate, and citrate. However, the presence of NaCl or Na₂SO₄ had a negative impact on the decolorization of AR18. The K_m and V_max values of MnP for AR18 were 169.66 μmol L^{? 1} and 20.63 μmol L^{? 1} min^{? 1}, respectively. The decolorization of AR18 by MnP followed second-order reaction kinetics with respect to the dye concentration. The decolorization rate constant increased with increasing temperature from 20°C to 35°C, which indicated an activation energy (E_a) of 15.87 kcal mol^{? 1} and frequency factor (k₀) of 1.36 × 10⁸ mg^{? 1} L min^{? 1} according to the Arrhenius equation. The results obtained provide experimental data for the application of crude MnP for the decolorization of AR18, and help to elucidate the biochemical mechanism of dye decolorization by the enzyme.     

Biochemical insights into a novel thermo/organo tolerant bilirubin oxidase from Thermosediminibacter oceani and its application in dye decolorization

Higher activity and stability at neutral pH and tolerance toward anions have made bilirubin oxidases (BODs) proper candidates for industrial utilizations. A putative BOD from Thermosediminibacter oceani (ToBOD) exhibited high stability over a pH range of 3.5–10.0 after heterologous expression and purification. The optimal temperature for the enzyme activity was 75 °C. ToBOD displayed a high thermostability with a half-life of 180 min at 70 °C and 120 min at 80 °C, respectively. K_m and K_cat values were 126.5 μM and 130.9 S⁻¹ for ABTS, 19.6 μM and 72.5 S⁻¹ for SGZ, and 31.2 μM and 76.2 S⁻¹ for unconjugated bilirubin, respectively. ToBOD showed tolerance to 10% and 50% (v/v) of water-miscible organic solvents and Triton X-100 as a non-ionic surfactant. In the presence of ABTS as the mediator, ToBOD decolorized malachite green (MG) and Congo red (CR) dyes at a rate of about 63% and 71%, respectively in 2 h. Decolorization was improved within 4 h at a rate of 86% and 89% for MG and CR, respectively. Structural analyses of ToBOD showed that lower folding heat capacity, folding enthalpy, folding free energy, and side-chain hydrogen bonds have a correlation with in vitro biochemical properties.     

Aggregation and Fragmentation of Phaseolus vulgaris Lectin

The effects of temperature on 6-O-α-maltosyl cyclodextrins (G₂-CDs) production from α- maltosylfluoride (α-G₂F) and cyclodextrins (CDs) by the transfer action of debranching enzymes such as pullulanase and isoamylase were studied.

The amounts of 6-O-α-maltosyl α-cyclodextrin (G₂-α-CD) production by purified pullulanase from Aerobacter aerogenes (A-pullulanase) and from Bacillus acidopullulyticus (B-pullulanase) increased with a rise in temperature, e.g., the amounts at 60°C were about 1.5 times higher than those at 30°C. Initial transfer ratios (G₂-α-CD formed/α-G₂F consumed) of A-pullulanase and B- pullulanase were about 62% and 25% (at 40°C), and about 50% and 15% (at 20°C), respectively. The transfer ratios of both A-pullulanase and B-pullulanase in the reaction using β-CD or γ-CD as acceptor also increased with a rise in temperature.

The transfer ratios were little affected by any change in temperature or any kind of acceptor CDs, in the case of isoamylase, and were about 60%.     

毛木耳对孔雀石绿染料降解条件的优化

随着我国印染工业的发展,废水对生态环境的危害日趋严重,亟需开发一种脱色明显且成本低廉的降解方法。本研究发现毛木耳Auricularia cornea菌株AC5对不同结构的染料均具有一定的降解作用,尤其是三苯甲烷类染料。利用26℃、160r/min振荡培养7d的粗酶液对染料（75.0mg/L）进行12h降解,结果显示三苯甲烷染料孔雀石绿、结晶紫,蒽醌染料活性蓝19和偶氮染料活性蓝222的降解效率分别为83.27%、71.77%、67.81%和63.92%。染料降解实验和酶活力测定结果表明,毛木耳对孔雀石绿的降解率达到最高时漆酶活性最高,为321.0U/mL,木质素过氧化物酶和锰过氧化物酶活性较低。因此,推测在降解过程中漆酶起到主要作用。研究表明利用毛木耳菌丝发酵液降解染料废水成本低且操作方便,为染料废水的降解研究提供了前期基础。