Jingliang Yang

Biological catalyzed denitrification by a functional electropolymerization biocarrier modified by redox mediator

Electropolymerization biocarriers were prepared by the electropolymerization of polypyrrole (PPy) on an active carbon felt (ACF) electrode using doping anions anthraquinone-2-sulfonate (AQS) or Na(2)SO(4). The functional electropolymerization biocarrier (ACF/PPy/AQS) with AQS was used as an immobilized redox mediator for the denitrification process. The characteristics of the electropolymerization biocarriers were analyzed by scanning electron microscope, elemental analyses, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The results suggested that the denitrification efficiency increased nearly 1.5-fold with ACF/PPy/AQS (0.04 mmol L(-1) AQS) compared to the control. A linear correlation was found for the k value and the AQS concentration (C(AQS)), which was k=624.71C(AQS)+83.87 (R(2)=0.9893). The ORP value stabilized around -200 mV for the denitrification process with ACF/PPy/AQS, which was -25 mV lower than that with ACF/PPy/Na(2)SO(4). Repeated-batch operations indicated that the denitrification efficiency with ACF/PPy/AQS maintained over 90% of the original value and exhibited better catalytic activity and durability.

Study on a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology

There are little literatures about the accelerating effect of redox mediators on the denitrification processes. In this paper, a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology was first explored, and the accelerating effect of redox mediator on the denitrification processes was conducted with immobilized anthraquinone. Anthraquinone as a redox mediator was able to increase the denitrification rate, and was immobilized by entrapment in calcium alginate (CA). The results suggested that the artificial redox mediator anthraquinone was found to be capable of raising about 2-fold denitrification rate, and the stabilized oxidation-reduction potential (ORP) values with anthraquinone immobilization beads were lower around 20mV than the control without anthraquinone immobilization beads. The results of repeated-batch operations shown that anthraquinone immobilization beads appeared to exhibit good reusability. The study explored a great improvement of the redox mediator application and the new bio-treatment concept for the denitrification processes.

The new incorporation bio-treatment technology of bromoamine acid and azo dyes wastewaters under high-salt conditions

The accelerating effect of quinones has been studied in the bio-decolorization processes, but there are no literatures about the incorporation bio-treatment technology of the bromoamine acid (BA) wastewater and azo dyes wastewaters under high-salt conditions (NaCl, 15%, w/w). Here we described the BA wastewater as a redox mediator in the bio-decolorization of azo dye wastewaters. Decolorization of azo dyes was carried out experimentally using the salt-tolerant bacteria under the BA wastewater and high-salt conditions. The BA wastewater used as a redox mediator was able to increase the decolorization rate of wastewater containing azo dyes. The effects of various operating conditions such as dissolved oxygen, temperature, and pH on microbial decolorization were investigated experimentally. At the same time, BA was tested to assess the effects on the change of the Oxidation–Reduction Potential (ORP) values during the decolorization processes. The experiments explored a great improvement of the redox mediator application and the new bio-treatment concept.

Reduction of Cr(VI) by Escherichia coli BL21 in the presence of redox mediators

Anthraquinone-2,7-disulfonate (2,7-AQDS), anthraquinone-1-sulfonate (α-AQS), anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate (AQDS) and anthraquinone-1,5-disulfonate (1,5-AQDS) were selected as redox mediators for Cr(VI) reduction by Escherichia coli BL21. In the presence of 0.8mmoll(-1) AQS, the Cr(VI) reduction efficiency was 98.5% in 7.5h, whereas it was only 21-34% in the absence of a mediator or in the presence of α-AQS, 1,5-AQDS, AQDS, 2,7-AQDS. A linear correlation, k=0.768C(AQS)+1.5531 (R(2)=0.9935), was found for the reaction constant, k (mg Cr(VI) g(-1) dry cell weight h(-1)) and the AQS concentration (C(AQS)). The Arrhenius equation described the Cr(VI) reduction in the tested temperature range, and the pre-exponential factor A was 13.249mg Cr(VI) g(-1) dry cell weight h(-1),and the activation energy Ea was 28.01kJmol(-1). Glucose was the best carbon sources, and the optimum pH was 6.0. The Cr(VI) reduction rate obtained with AQS is a significant improvement over low conventional anaerobic reduction rates.

Effect of thermal–alkaline pretreatment on the anaerobic digestion of streptomycin bacterial residues for methane production

The anaerobic digestion of streptomycin bacterial residues, solutions with hazardous waste treatments and bioenergy recovery, was tested in laboratory-scale digesters at 35°C at various organic loading rates (OLRs). The methane production and biomass digestion were efficient at OLRs below 2.33 gVS L(-1) d(-1) but were deteriorated as OLR increased because of the increased total ammonia nitrogen (TAN) concentration from cell protein decay. The thermal-alkaline pretreatment with 0.10 NaOH/TS at 70°C for 2 h significantly improved the digestion performance. With the thermal-alkaline pretreatment, the volumetric reactor productivity and specific methane yield of the pretreated streptomycin bacterial residue increased by 22.08-27.08% compared with those of the unpretreated streptomycin bacterial residue at an OLR of 2.33 gVS L(-1) d(-1). The volatile solid removal was 64.09%, with less accumulation of TAN and total volatile fatty acid.

Study the catalyzing mechanism of dissolved redox mediators on bio-denitrification by metabolic inhibitors

The effect of dissolved redox mediators on denitrification by Paracoccus versutus sp. GW1 were studied with α-AQS, AQS, 1,5-AQDS, AQDS and 2,7-AQDS. AQDS presented the best catalytic effect which increased denitrification rate by 1.5-fold with 0.17 mmol L(-1). Denitrification rate was found to be pseudo-zero order with 0-0.32 mmol L(-1) AQDS (k=19.874C AQDS+10.301 (R(2)=0.9984)). The accelerating mechanism for respiratory chain was also explored by using metabolic inhibitors. Addition of AQDS eased the inhibitions of rotenone, dicumarol, sodium azide on respiratory chain, and enhanced the nitrite accumulation during bio-denitrification process. AQDS exhibited slight catalytic effect on nitrite denitrification. These results allowed us to deduce the accelerating site of AQDS on the denitrification respiratory chain. Increased nitrate denitrification by AQDS might mainly attribute to the accelerated electrons transfer from NADH to nitrate reductase via complex I and ubiquinone/ubiqunol. This study provided further understanding of the mechanism of redox mediators on denitrification.

The structure activity relationship of non-dissolved redox mediators during azo dye bio-decolorization processes

Structure activity relationships were elucidated by applying chemical structure, electrochemistry and quantum chemical calculations for non-dissolved redox mediators (RM, quinones) with similar chemical structure. The decolorization efficiencies of acid red B by a Halomonas sp. GYW were enhanced 2.68, 2.58, 1.91 and 1.49 times with 1,5-dichloroanthraquinone, 1,8-dichloroanthraquinone, anthraquinone, and 1,4,5,8-tetrachloroanthraquinone, respectively. The order of oxidation reduction potential (ORP) during the decolorization process with four redox mediators agreed with their order of reduction potential (Ea) from cyclic voltammetry. The decolorization rate (k) with four redox mediators has a linear relation with their Ea values (k=269.05Ea+85.782, R(2)=0.9226). The calculated ρ(r(c)) at the Ring Critical Point (RCP) based on Atoms in Molecules (AIM) and the inductive/resonance effects of the four redox mediators were also consistent with the accelerating effects on the decolorization. These established relationships might to be predictive models and mechanistic explanations for the accelerating decolorization with redox mediator.

Effective and characteristics of anthraquinone-2,6-disulfonate (AQDS) on denitrification by Paracoccus versutus sp.GW1

The effects of anthraquinone-2,6-disulfonate (AQDS) on microbial populations and the biocatalysing characteristics of AQDS on denitrifying strain GW1 are discussed. The results showed that microbial population abundances were 30, 6, 12 and 18% during the different periods (1st, 5th, 10th and 20th days). Strain GW1 utilized AQDS as an electron acceptor in the respiration chain and reduced AQDS to hydroquinone (QH2). The nitrate removal efficiency of strain GW1 was increased 1.14–1.63 fold with 0.04–0.32 mmol/L AQDS. A linear correlation was found between the nitrate removal reaction constant (where VSS is volatile suspended solids) and AQDS concentration (CAQDS), which was k=19.332 CAQDS+11.115(R2=0.9749). The stabilized oxidation–reduction potential (ORP) values with AQDS were lower 22–92 mv than the control during the denitrification process. The concentration of nitrite sequentially accumulated up to around 250 mg/L when nitrate have removed completely. The results suggested that AQDS as redox mediator was capable of biocatalysing the nitrate and nitrite removal rate.

Development of bioreactor systems with functional bio-carrier modified by disperse turquoise blue S-GL for disperse scarlet S-BWFL decolorization

The effect of redox mediator has been studied in details in the bio-decolorization processes, but there are little literatures about bioreactor systems with functional bio-carrier modified by redox mediator. Two different bioreactor configurations (bioreactor R1 with functional bio-carrier modified by disperse turquoise blue S-GL (as redox mediator) and bioreactor R2 with non-modified bio-carrier) were designed and tested for disperse scarlet S-BWFL decolorization by Halomonas sp. GYW (EF188281) in this study. Influencing factors such as co-substrate, temperature and pH were optimized through batch experiments. Compared to bioreactor R2, bioreactor R1 exhibited good decolorization efficiency and performance ability for the disperse scarlet S-BWFL decolorization, which showed higher decolorization efficiency (over 96% color removal with 0.8 g L(-1) dye concentration) and less hydraulic retention time to attain the same decolorization efficiency. The combinational technology of redox mediator and bio-carrier was a new bio-treatment concept and a great improvement for the application of redox mediator.

Decolorization and Degradation of Azo Dyes by Redox Mediator System with Bacteria

Azo dyes are the largest and the most diverse group of synthetic dyes widely used in many industries, which are generally recalcitrant to biodegradation due to their xenobiotic nature. The effective treatment of azo dye wastewaters has been a big challenge, and up to now there is no single and economically attractive treatment that can effectively decolorize dyes. However, notable achievements have been conducted to explore the accelerating effects of different redox mediators during the anaerobic decolorization and degradation of azo dyes over the last two decades. The accumulated evidence suggest that redox mediators play a major role of electron shuttles in the reductive decolorization of azo dyes, both by chemical and biological mechanisms. This review is focused on the bacterial decolorization and degradation of azo dyes catalyzed by redox mediators and the further investigation to enhance the applicability of redox mediators on the bio-transformation of azo dyes.