Tuning of Surface Characteristics of Anodes for Efficient and Sustained Power Generation in Microbial Fuel Cells.

The present study reports about the fabrication of a three-dimensional (3D) macroporous steel-based scaffold as an anode to promote specifically bacterial attachment and extracellular electron transfer to achieve power density as high as 1184 mW m-2, which is far greater than that of commonly used 3D anode materials. The unique 3D open macroporous configuration of the anode and the microstructure generated by the composite coating provide voids for the 3D bacterial colonization of electroactive biofilms. This is attributed to the sizeable interfacial area per unit volume provided by the 3D corrugated electrode that enhanced the electrochemical reaction rate compared to that of the flat electrode, which favors the enhanced mass transfer and substrate diffusion at the electrode/electrolyte interface and thereby increases the charge transfer by reducing the electrode overpotential or interfacial resistance. In addition, bacterial infiltration into the interior of the anode renders large reaction sites for substrate oxidation without the concern of clogging and biofouling and thereby improves direct electron transfer. A very low overpotential (-27 mV) with a very low internal resistance (7.104 Ω cm2) is achieved with the fabricated microbial fuel cell (MFC) that has a modified 3D corrugated electrode. Thus, easier and faster charge transfer at the electrode-electrolyte interface is confirmed. The study presents a revolutionary practical approach in the development of highly efficient anode materials that can ensure easy scale-up for MFC applications.

Synergistic action of Bacillus subtilis, Escherichia coli and Shewanella putrefaciens along with Pseudomonas putida on inhibiting mild steel against oxygen corrosion.

Microbial biofilm can effectively alter the electrochemical characteristics at metal/solution interface that can either accelerate or decelerate corrosion. The present paper reports about microbiologically induced corrosion inhibition (MICI) using Pseudomonas putida as a dominant bacterium under aerobic condition. Effective corrosion inhibition is achieved by the synergistic metabolic action of P. putida along with Escherichia coli, Bacillus subtilis or Shewanella putrefaciens. The synergistic metabolic actions of these bacteria in biopassivation are analysed with various aspects such as electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM) and confocal laser scanning microscopy (CLSM). Surface topography is quantitatively analysed using optical scanning profilometry (OSP). The binary culture system containing P. putida + E. coli and P. putida + S. putrefaciens achieves an inhibition efficiency of 90% and 85% respectively, despite S. putrefaciens being a corrosion causing bacteria. The P. putida + E. coli system could form a stable biofilm on mild steel surface, with a high corrosion potential (- 329 mV vs. Ag/AgCl/KCl sat'd) and a low corrosion rate (1.65 × 10-1 mmpy). The presence of B. subtilis in the culture promotes corrosion against normal predictions. In the present case, the metabolic activities of the bacterial system on the mild steel surface cause depletion of oxygen in the medium that leads to suppression of corrosion. In addition, the biofilm could form an effective protective barrier on the metal surface that can suppress diffusion of corrosion products resulting in enhanced corrosion inhibition efficiency.

Zn Wetted CeO2 Based Composite Galvanization: An Effective Route To Combat Biofouling.

The present paper reports for the first time the development and application of novel Zn wetted CeO2 (Zn/CeO2) composite galvanic zinc coating to combat microbial induced corrosion (MIC). Zinc metal-metal interaction causes the effective incorporation of composite into the galvanic coating and accordingly increases the active sites for antibiofouling activity. The developed coatings are explored for their anticorrosion/antibiofouling characteristics toward MIC induced by cultured seawater consortia. Enhanced antibiofouling activity of the composite galvanic coating is achieved due to the tuned content of 28 wt % Zn and 34 wt % of Ce. High charge transfer resistance as high as 4.0 × 1014 Ω cm2 and low double layer capacitance as low as 3.99 × 10-8 F are achieved by tuning the structure and composition of the coating. The synergistic effect of Zn and Ce ensures the stability and corrosion resistance of the coatings in a corrosive bacterial environment. Evident decreases in the bacterial attachment and biofilm formation are illustrated using antibiofouling assay. The antibiofouling activity is attributed to the effective reduction of Ce4+ to Ce3+ and the shuttling characteristics of oxidation state of CeO2. This impairs the cellular respiration and results in bacterial death. Thus, it can be used as an effective coating to protect the steel based equipment in corrosive marine environments to combat marine microorganisms and their interactions. The present study also paves the scope for exploration of similar effective protective systems.

Development of a High-Performance Mediatorless Microbial Fuel Cell Comprising a Catalytic Steel Anode.

The present paper reports for the first time the construction of a sugar cane bagasse-mediated double-chambered microbial fuel cell (MFC), consisting of a novel bioanode of an iron/titanium Ni-P composite. This anode could facilitate uninterrupted extracellular electron transfer (EET) from bacteria (mixed culture). The Ni-P composite anode had a significant corrosion resistance and enhanced electrocatalytic activity. The corrosion rate was reduced to 0.187 mmpy, which was 3 times less than that of the noncomposite anode. A steady decrease in internal resistance from 3.84 × 103 Ω to 2.94 × 102 Ω was achieved with the incorporation of the iron/titanium-based composite on the anode surface. The presence of Fe (III) ion centers in the composite surface favored electroactive biofilm formation and enhanced the capacitive nature of the anode, thereby accelerating EET. The constructed MFC showed an internal resistance as low as 1.12 × 10-2 Ω in comparison with the control MFC. This led to a very high power density of ∼2.1 W/m2, which was 20% higher than that of the control MFC, while a stacked MFC obtained a maximum open-circuit potential of 3.2 V with power density and current density outputs of 6.3 W/m2 and 2.7 mA/m2, respectively. Even though an extensive amount of literature is available in this field, this report is the first of its kind because it includes such a simple reproducible system that can be extended to other similar systems.

Effect of W-TiO2 composite to control microbiologically influenced corrosion on galvanized steel.

Microorganisms tend to colonize on solid metal/alloy surface in natural environment leading to loss of utility. Microbiologically influenced corrosion or biocorrosion usually increases the corrosion rate of steel articles due to the presence of bacteria that accelerates the anodic and/or cathodic corrosion reaction rate without any significant change in the corrosion mechanism. An attempt was made in the present study to protect hot-dip galvanized steel from such attack of biocorrosion by means of chemically modifying the zinc coating. W-TiO2 composite was synthesized and incorporated into the zinc bath during the hot-dipping process. The surface morphology and elemental composition of the hot-dip galvanized coupons were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The antifouling characteristics of the coatings were analyzed in three different solutions including distilled water, seawater, and seawater containing biofilm scrapings under immersed conditions. Apart from electrochemical studies, the biocidal effect of the composite was evaluated by analyzing the extent of bacterial growth due to the presence and absence of the composite based on the analysis of total extracellular polymeric substance and total biomass using microtiter plate assay. The biofilm-forming bacteria formed on the surface of the coatings was cultured on Zobell Marine Agar plates and studied. The composite was found to be effective in controlling the growth of bacteria and formation of biofilm thereafter.

Serum bilirubin and antioxidant levels in first degree relatives of patients with ischemic heart disease and normal subjects.

BACKGROUND: Coronary diseases appear to result from an overbalance between radical-generating, compared with radical-scavenging systems, a condition called as oxidative stress. Total antioxidant status (TAS) in human plasma reflects the balance between oxidants and antioxidants in each system. Bilirubin has been considered an antioxidant, with capacity to remove reactive species of oxygen. Present study tried to measure the total antioxidant status of first degree relatives of patients with IHD. Study also tried to evaluate the prognostic role of serum bilirubin in disease prevention or progression. METHODS: Seventy five apparently healthy subjects in age group 20-50 years, comprising equal number of males and females, who were first degree relatives of ischemic heart disease patients, were included in the study. Family members were divided on the bases of their numbers, i.e., one family member (Group-A), 2 family members (Group-B) and more than 3 family members (Group-C). Study was cross sectional and carried out in a period of 6 months (Jun 2008-Jan 2009). Subjects with letter of consent were taken from general population. Seventy five healthy age matched people with no history of ischemic heart disease in family were taken as control. An overnight fasting blood sample was taken. Total antioxidant status was determined using a commercially available kit. Serum bilirubin was estimated by auto analyzer. RESULTS: Family history of ischemic heart disease with serum bilirubin showed a significant negative correlation (p<0.05). But the values of TAS failed to show any significant correlation with the family history. It was observed that the value of serum bilirubin was decreased significantly (p<0.05) with an increased number of family members. Total antioxidant status failed to show any significant difference among all the three groups. CONCLUSION: Our data demonstrated that reduced serum levels of bilirubin were seen in people with a higher prevalence of coronary artery disease in the family. The levels of serum bilirubin showed a downward trend with an increase in number of family members affected with ischemic heart disease. Present study failed to show a definite association of total antioxidant status with family history of ischemic heart disease. Additional studies are still necessary on large number of first degree relatives to confirm and demonstrate the association of these findings with clinical outcomes.