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

doi:10.1016/j.biortech.2012.07.090

Bioresource Technology

Volume 123, November 2012, Pages 713-716

https://doi.org/10.1016/j.biortech.2012.07.090 Get rights and content

Abstract

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 0.8 mmol l⁻¹ AQS, the Cr(VI) reduction efficiency was 98.5% in 7.5 h, 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 (R² = 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 13.249 mg Cr(VI) g⁻¹ dry cell weight h⁻¹,and the activation energy Ea was 28.01 kJ mol⁻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.

Highlights

► The relationship of reaction constant (k) and AQS concentration (CAQS) was k = 0.768CAQS + 1.553. ► The Arrhenius equation was used to describe the Cr(VI) reduction in the tested temperature range. ► The optimal carbon source and pH was glucose and pH 6.0, respectively.

Introduction

Chromium (Cr), commonly found as Cr(VI) and Cr(III), is one of the priority pollutants in surface water and ground water. Cr(VI) is approximately 100× more toxic and 1000× more mutagenic than Cr(III) because of its solubility across nearly the entire pH range and its greater mobility (Song et al., 2009). The US EPA requires Cr(VI) in drinking water and inland surface water to be at or below 0.05 and 0.1 mg l⁻¹, respectively (Kobya, 2004). Therefore, the reduction of Cr(VI)–Cr(III) is an attractive and useful process for remediation of Cr(VI) pollution.

Conventional treatment methods for Cr(VI) removal involve the reduction of Cr(VI)–Cr(III) using a strong reducing agent and precipitation of Cr(III). This process generates large quantities of hazardous sludge and may consume costly chemicals. An alternative treatment could be biotransformation of Cr(VI)–Cr(III) by various bacteria under both aerobic and anaerobic conditions (Liu et al., 2006, Liu et al., 2010), but this process can require several days or even weeks (Fredrickson et al., 2000, Lowe et al., 2003, Song et al., 2009). AQDS, AQS, lawsone and menadione have been shown to improve bacterial reduction of Cr(VI) (Fredrickson et al., 2000, Lowe et al., 2003, Liu et al., 2010). The biological Cr(VI) reduction with redox mediators is affected by temperature, pH and carbon source(Liu et al., 2006), and different redox mediators exhibited different accelerating effects(Liu et al., 2010).

Therefore, the present study investigated Cr(VI) reduction by E. coli BL21 in the presence of redox mediators at different temperatures and pHs as well as in the presence of various carbon sources. The relationship between the accelerating effects of redox mediators and their electrochemical characteristic (Ea values) of cyclic voltammetric analysis was also explored.

Section snippets

Chemicals, bacterial strains and culture conditions

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 analytical grade and supplied by Sigma–Aldrich. The chemical structures of these redox mediators are shown in Supporting Information (SI) Fig. S1. Other chemical reagents were of analytical grade and purchased from Xiandai Ltd. (Shijiazhuang, China).

E. coli BL21 was cultured in Luria–Bertani (LB)

Effect of redox mediators on Cr(VI) reduction

In sterile controls, only a 0.2% change in the Cr(VI) over 48 h was observed (data not shown). The reduction of Cr(VI) by E. coli BL21 in the absence and presence of redox mediators are shown in Fig. 1. At 0.8 mmol l⁻¹, AQS provided for the highest Cr(VI) reduction. The Cr(VI) reduction efficiency with AQS reached 98.5% after 7.5 h, whereas α-AQS, 1,5-AQDS, AQDS and 2,7-AQDS only allowed for reduction efficiencies of about 21–34%. The difference observed between AQS and AQDS is in agreement with

Conclusion

The biological Cr(VI) reduction efficiency was enhanced by different redox mediators, and the reaction constant k and the C_AQS was correlated by k = 0.768C_AQS + 1.5531 (R² = 0.9935). The biological Cr(VI) reduction with AQS was affected by different carbon source, pH and temperature. The study explored a great improvement of the redox mediator application for the Cr(VI) bioremediation, but this technology and mechanism needs to be studied in details.

Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant No. 50978082), the Hebei Natural Science Foundation for Distinguished Young Scholars (Grant No. E2012208012), the Program for New Century Excellent Talents in University (Grant No. NCET-10-0127), China Postdoctoral Science Fund Special Grant (Grant No. 201104152) and China Postdoctoral Science Foundation (Grant No. 20100480485).

References (12)

J. Guo et al.
Study on a novel non-dissolved redox mediator catalyzed biological denitrification (RMBDN) technology
Bioresour. Technol.
(2010)
J. Guo et al.
The structure activity relationship of non-dissolved redox mediators during azo dye bio-decolorization processes
Bioresour. Technol.
(2012)
J. Guo et al.
Biocatalyst effects of immobilized anthraquinone on the anaerobic reduction of azo dyes by the salt-tolerant bacteria
Water Res.
(2007)
Y. Liu et al.
Cr(VI) reduction by Bacillus sp. isolated from chromium landfill
Process Biochem.
(2006)
G. Liu et al.
Enhanced chromate reduction by resting Escherichia coli cells in the presence of quinone redox mediators
Bioresour. Technol.
(2010)
H. Song et al.
Simultaneous Cr(VI) reduction and phenol degradation in pure cultures of Pseudomonas aeruginosa CCTCC AB91095
Bioresour. Technol.
(2009)

There are more references available in the full text version of this article.

Cited by (33)

Recent advances in enhanced technology of Cr(VI) bioreduction in aqueous condition: A review
2024, Chemosphere
Due to the extensive application of chromate in industry, chromium-contaminated water has emerged as a significant hidden danger that threatens human health and the safety of the ecological environment. The reduction of Cr(VI) to Cr(III) through microbial processes has become one of the most notable methods for remediating water polluted by chromium due to its economic efficiency and environmentally friendly nature. However, several issues persist in its practical application, such as low reduction rates, the need for additional nutrients, and challenges in solid-liquid separation. Therefore, there is a growing focus on seeking enhanced methods for Cr(VI) microbial reduction, which has become a key area of research. This review represents the initial effort to systematically classify and summarize the means of enhancing Cr(VI) microbial reduction. It categorizes the enhancement methods into two main approaches: microbial-based and multi-method combined enhancement, offering detailed explanations for their mechanisms. This research provides both inspiration and theoretical support for the practical implementation of the Cr(VI) microbial reduction method.
Metabolic mechanism of Cr(VI) pollution remediation by Alicycliphilus denitrificans Ylb10
2024, Science of the Total Environment
Cr(VI) is a well-known toxic pollutant and its remediation has attracted great attention. It is important to continuously discover and explore new high-efficiency Cr(VI) reducing bacteria to further improve the efficiency of Cr(VI) pollution remediation. In this paper, metabolic mechanism of Cr(VI) reduction in a new highly efficient Cr(VI) reducing bacterium, Alicycliphilus denitrificans Ylb10, was investigated. The results showed that Ylb10 could tolerate and completely reduce 450 mg/L Cr(VI). Cr(VI) can be reduced in the intracellular compartment, membrane and the extracellular compartment, with the plasma membrane being the main active site for Cr(VI) reduction. With the addition of NADH, the reduction efficiency of cell membrane components for Cr(VI) increased 2.3-fold. The omics data analysis showed that sulfite reductase CysJ, thiosulfate dehydrogenase TsdA, nitrite reductase NrfA, nitric oxide reductase NorB, and quinone oxidoreductase ChrR play important roles in the reduction of Cr(VI), in the intracellular, and the extracellular compartment, and the membrane of Ylb10, and therefore Cr(VI) was reduced by the combined action of several reductases at these three locations.
Thermodynamic considerations on the combined effect of electron shuttles and iron(III)-bearing clay mineral on Cr(VI) reduction by Shewanella oneidensis MR-1
2023, Journal of Hazardous Materials
Electron shuttles (ESs) and Fe-bearing clay minerals are commonly found in subsurface environments and have shown potential in enhancing the bioreduction of Cr(VI). However, the synergistic effect of ESs at different redox potentials and Fe-bearing clay minerals on Cr(VI) bioreduction, as well as the fundamental principles governing this process, remain unclear. In our study, we investigated the role of ESs and Fe(III) in Cr(VI) bioreduction. We found that the acceleration of ESs and Fe(III) are crucial factors in this process. Interestingly, the promotion of ESs on Cr(VI) and Fe(III) showed opposite trends. Electrochemical methods confirmed the limited steps are the extent of reduced ESs and the redox potential difference between ESs and Fe(III), separately. Furthermore, we investigated the combined effect of ESs and NAu-2 on Cr(VI) bioreduction. Our results revealed two segments: in the first segment, the ES (5-HNQ) and NAu-2 did not synergistically enhance Cr(VI) reduction. However, in the second segment, ESs and NAu-2 demonstrated a synergistic effect, significantly increasing Cr(VI) reduction by MR-1. These bioreduction processes all follow linear free energy relationships (LFERs). Overall, our study highlights the fundamental principles governing multivariate systems and presents a promising approach for the remediation of Cr(VI)-contaminated sites.
Enhanced microbial reduction of Cr(VI) in soil with biochar acting as an electron shuttle: Crucial role of redox-active moieties
2023, Chemosphere
Biochar has been proven to participate in the biotic reduction of hexavalent chromium (Cr(VI)) in environment since its involvement may accelerate the extracellular electron transfer (EET). However, roles of the redox-active moieties and the conjugated carbon structure of biochar in this EET process remain unclear. In this study, 350 °C and 700 °C were selected to produce biochar with more O-containing moieties (BC350) or more developed conjugated structures (BC700), and their performances in the microbial reduction of soil Cr(VI) were investigated. Our results showed that BC350 presented a 241% increase of Cr(VI) microbial reduction after 7-day incubation, much higher than that of BC700 (39%), suggesting that O-containing moieties might play more important roles in accelerating the EET process. Biochar, especially BC350 could serve as an electron donor for microbial anaerobic respiration, but its contribution (73.2%) as an electron shuttle for EET was dominant to the enhanced Cr(VI) reduction. The positive correlation between electron exchange capacities (EECs) of pristine and modified biochars and the corresponding maximum reduction rates of Cr(VI) evidenced the crucial role of redox-active moieties in electron shuttling. Moreover, EPR analysis suggested the nonnegligible contribution of semiquinone radicals in biochars to the accelerated EET process. This study demonstrates the crucial role of redox-active moieties, i.e., O-containing moieties in mediating the EET process during the microbial reduction of Cr(VI) in soil. Findings obtained will advance the current understanding of biochar as an electron shuttle participating in the biogeochemical processes of Cr(VI).
Riboflavin as a non-quinone redox mediator for enhanced Cr(VI) removal by Shewanella putrefaciens
2022, Journal of Molecular Liquids
Bioreduction of Cr(VI) has proven to be cost-effective and environmentally friendly, and has attracted widespread interest. However, the slow bioreduction rate of Cr(VI) has been a bottleneck for practical applications. Riboflavin (RF) is a widely distributed micronutrient in the aquatic environment and can function as an endogenous redox mediator to enhance the extracellular electron transfer (EET) rate, thereby promoting the bioreduction rate of Cr(VI). However, research on the role of RF during Cr(VI) removal by dissimilatory iron-reducing bacteria (DIRB) remains scarce. In this study, we investigated the use of RF as a redox mediator to facilitate the bioreduction of Cr(VI) by DIRB. The results showed that RF can serve as a redox mediator for Shewanella putrefaciens (SP) to significantly enhance EET efficiency and accelerate Cr(VI) reduction. Under optimal conditions, 40 mg/L Cr(VI) could be completely removed by SP/RF within 7 d, whereas only 24.10% of Cr(VI) was removed by the SP strain alone. Cu²⁺, Mn²⁺, and Cd²⁺ significantly inhibited Cr(VI) removal; Zn²⁺, Fe³⁺, and Pb²⁺ demonstrated negligible inhibitory effects on Cr(VI) removal, whereas different concentrations of NO₃^– exhibited different inhibitory effects on Cr(VI) removal. In the method herein, the electron transfer process between the DIRB, RF, and electrodes during the EET process was confirmed. Mechanistic studies indicated that Cr(VI) was partially reduced to Cr(III); subsequently, Cr(III) was immobilized by secretion of the SP strain. Meanwhile, the surface functional groups of SP cell participated in Cr adsorption, reduction and complexation. These findings provide valuable insights into the role of RF in the remediation of Cr(VI)-contaminated water in natural aquatic environments.
Application of different redox mediators induced bio-promoters to accelerate the recovery of denitrification and denitrifying functional microorganisms inhibited by transient Cr(VI) shock
2021, Journal of Hazardous Materials
Citation Excerpt :
Furthermore, the redox mediators were added into R-R2 to R-R5 biofilm reactor, which could transfer electrons through continuous oxidation and reduction. Redox mediators were proved to increase the transfer rate of electrons (Li et al., 2013), thereby weaken the chromium toxicity by promoting the Cr(VI) reduction process (Guo et al., 2012). At the end of Phase III, the concentration of adsorbed Cr(VI) and intercellular Cr(VI) in R-R5 decreased by 28.13 mg/L, while the concentration of Cr(III) increased by 30.23 mg/L (Fig. 4c and d).
The transient hexavalent chromium (Cr(VI)) shock may directly inhibit the denitrification process of municipal wastewater treatment plants (WWTPs), which is difficult to recover in a short time. This study developed four nontoxic bio-promoters (combination of L-cysteine, flavin adenine dinucleotide (FAD), biotin, cytokinin and different redox mediators) to quickly restore the denitrification performance after high-loading Cr(VI) suppressing. After feeding with 100 mg/L of Cr(VI) for 42 cycles (T, 4 h), the removal efficiency of nitrate was reduced by 85.00%, and nitrite was accumulated simultaneously. The denitrification performance was recovered quickly with the addition of bio-promoters, introducing redox mediators showed noticeable superiority on the bio-inhibition release. Compared with sodium humate and riboflavin, the AQDS induced bio-promoter achieved the best nitrate removal recovery performance within only 28 T, and the recovery rate was 2.16 times faster than the natural recovery. Microbial analysis showed that Cr(VI) specially inhibited napA-type denitrifiers, and the OTU numbers sharply dropped by 48.74%. Redox mediators induced bio-promoters could effectively recover the abundance of napA-type and nirS-type denitrifying microorganisms, which was consistent with the change of nitrate removal efficiency. This study offers a cost-effective approach to deal with Cr(VI) shock problem, which may promote the development of bio-promoters for WWTPs.

View all citing articles on Scopus

View full text

Article preview

Bioresource Technology

Abstract

Highlights

Introduction

Section snippets

Chemicals, bacterial strains and culture conditions

Effect of redox mediators on Cr(VI) reduction

Conclusion

Acknowledgements

References (12)

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

Bioresour. Technol.

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

Bioresour. Technol.

Biocatalyst effects of immobilized anthraquinone on the anaerobic reduction of azo dyes by the salt-tolerant bacteria

Water Res.

Cr(VI) reduction by Bacillus sp. isolated from chromium landfill

Process Biochem.

Enhanced chromate reduction by resting Escherichia coli cells in the presence of quinone redox mediators

Bioresour. Technol.

Simultaneous Cr(VI) reduction and phenol degradation in pure cultures of Pseudomonas aeruginosa CCTCC AB91095

Bioresour. Technol.

Cited by (33)

Recent advances in enhanced technology of Cr(VI) bioreduction in aqueous condition: A review

Metabolic mechanism of Cr(VI) pollution remediation by Alicycliphilus denitrificans Ylb10

Thermodynamic considerations on the combined effect of electron shuttles and iron(III)-bearing clay mineral on Cr(VI) reduction by Shewanella oneidensis MR-1

Enhanced microbial reduction of Cr(VI) in soil with biochar acting as an electron shuttle: Crucial role of redox-active moieties

Riboflavin as a non-quinone redox mediator for enhanced Cr(VI) removal by Shewanella putrefaciens

Application of different redox mediators induced bio-promoters to accelerate the recovery of denitrification and denitrifying functional microorganisms inhibited by transient Cr(VI) shock

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

Abstract

Highlights

Introduction

Section snippets

Chemicals, bacterial strains and culture conditions

Effect of redox mediators on Cr(VI) reduction

Conclusion

Acknowledgements

Bioresour. Technol.

Bioresour. Technol.

Water Res.

Process Biochem.

Bioresour. Technol.

Bioresour. Technol.

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