Ultrasound Driven Biofilm Removal for Stable Power Generation in Microbial Fuel Cell

Anodic biofilm plays a crucial role in bioelectrochemical system to make it sustainable for long-term performance. However, the accumulation of dead cells over time within the anode biofilm can be particularly detrimental for current generation. In this study, the effect of ultrasound on anode biofilm thickness was investigated in microbial fuel cells (MFCs). Ultrasonic treatment was employed for different durations to evaluate its ability to control the thickness of the biofilm to maintain stable power generation. Cell viability count and field emission scanning electron microscopy (FESEM) analysis of the biofilms over time showed that the number of dead cells increased with the increase of biofilm thickness, and eventually exceeded the number of live cells by many-fold. Electrochemical impedance spectroscopy (EIS) analysis indicated that the high polarization resistance appeared due to the dead layer formation, and thus the catalytic efficiency was reduced in MFCs. The stable power generation was achieved by employing ultrasonic treatment for 30 min every 6 days with some initial exception. The low frequency ultrasound treatment successfully dislodged the ineffective biofilm from the surface of the anode. Moreover, the ultrasound could increase the mass transfer rate of the nutrients and cellular waste through the biofilm leading to the increase in cell growth. Therefore, ultrasonic treatment is verified as an efficient method to control the thickness of the biofilm as well as enhance the cell viability in biofilm thereby maintaining the stable power generation in the MFC

Augmentation of Air Cathode Microbial Fuel Cell Performance using Wild Type Klebsiella Variicola

In the present work, simultaneous power generation and wastewater treatment in the single chamber air cathode microbial fuel cell (MFC) have been enhanced by introducing wild-type Klebsiella variicola (K. variicola) as an efficient inoculum for the anode operated with palm oil mill effluent (POME). K. variicola was isolated from municipal wastewater (MWW) and identified using BIOLOG gene III analysis, PCR and sequencing. The performance of K. variicola in MFC was evaluated by polarization curve measurement, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analysis. The MFC with K. variicola achieved a maximum power density of about 1.7 W m−3 which is comparatively higher than most widely used anaerobic sludge (215 mW m−3) as an inoculum whereas COD removal efficiency is (43%) lower than anaerobic sludge (74%). Moreover, K. variicola has the ability to produce electron shuttles and to form biofilms on the electrode surface which helps to significantly reduce the anode charge transfer (Rct) resistance compared to the anaerobic sludge. These results revealed the potential of K. variicola to be used in MFC

Carbon Nanotube-Modified MnO2: An Efficient Electrocatalyst for Oxygen Reduction Reaction

In this work, manganese dioxide/carbon nanotube (MnO2/CNT) have been synthesized by sonochemical-coprecipitation method and demonstrated that it could be an effective electrocatalyst for oxygen reduction reaction (ORR). Moreover, the effect of CNT inclusion with MnO2 was also investigated for ORR. The physical and electrochemical properties of the MnO2/CNT were examined by powder X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy/Energy Dispersive X-ray (FESEM/EDX), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky and Rotating Disk Electrode (RDE) analysis. CV showed higher currents for the ORR in MnO2/CNT than CNT; however, ORR current dropped when the MnO2 loading was increased from 20–40 %. The EIS analysis showed that charge-transfer resistance for MnO2/CNT was significantly lower compared to the MnO2 indicating that MnO2 has good contact with CNT and the composite possess high electrical conductivity. Mott-Schottky results demonstrated that incorporation of CNT into MnO2 resulted in producing larger electron density in n-type MnO2/CNT compared to MnO2 which is liable for efficient electron donation from the Mn3+ to adsorbed oxygen in the rate determining step. RDE results showed that MnO2/CNT follows 4e− transfer pathway, indicating its ability to act as an effective ORR electrocatalyst

Malaysian Healthy Diet Online Survey (MHDOS): Study rationale and methodology

Introduction: Access to accurate and timely dietary information is of paramount importance in evaluating and developing well-targeted public health nutrition interventions. However, nationwide nutrition surveys are conducted infrequently because they are very costly to design, conduct and analyse. Dietary assessment tools, which are quick and cost- effective, are needed for population research and regular monitoring of Malaysians’ dietary habits. This paper describes the rationale and methodology of the Malaysian Healthy Diet Online Survey (MHDOS) project, which aims to bridge this knowledge gap on dietary intake of Malaysian adults. The main objective of the two-year project is to develop MHDOS as a valid tool to measure compliance with the Malaysian Dietary Guidelines 2020. Methods: The MHDOS project has three study phases, namely (i) adaptation of an online survey and established diet quality scoring system for Malaysia, (ii) usability, validity and reliability testing of the online survey; and (iii) online survey administration in a nationwide study. The survey will be administered to approximately 10,000 Malaysian adults aged 18-59 years. Discussion: MHDOS consists of 38 questions that measures the quantity, quality and variety of foods consumed. Individuals will receive a diet quality score that reflects their overall compliance with the Malaysian Dietary Guidelines and feedback on how to improve their scores. The findings of the online survey, which serve to complement information between larger surveys, will be useful to measure compliance of Malaysians to national dietary guidelines and inform public health interventions

Development of auditing in Malaysia: Legal, political and historical influences

This work investigates the role and contribution of external auditing as practised in the Malaysian society during the forty year period from independence in 1957 to just before the onset of the Asian Financial Crisis in 1997.It applies the political economic theory introduced by Tinker (1980) and refined by Cooper & Sherer (1984), which focuses on the social relations aspects of professional activity rather than economic forces alone.In a case study format where qualitative data was gathered mainly from primary and secondary source materials, the study found that the function of auditing in the Malaysian society in most cases is devoid of any essence of mission; instead it is created, shaped and transformed by the pressures which give rise to its development over time.The largely insignificant role that it serves is intertwined within the contexts in which it operates

Mutations of the Alpha-Subunit of G-Proteins: A Thesis

Signal transduction by G-proteins (a heterotrimer membrane protein composed of an α, β, and γ subunit) requires that the α-subunit undergoes a transition from a GDP-bound inactive state to an activated GTP-bound state. The exchange of GDP for GTP leads to a conformational change in the α-subunit that results in the loss of affinity for the βγ subunits. We predicted that appropriate genetic manipulation of key regions of the α-subunit could result in the induction of the active conformation that would mimic at least in part the activated GTP-bound state. We have demonstrated that the substitution of the 38 amino acid residue carboxyl termimus of Gαs with the last 36 amino acid residues of Gαi2 resulted in a chimeric Gα-subunit (C4) that exhibits a constitutively active Gαs-like activity. Similarly, the substitution of the amino terminal 61 amino acid residues of Gαs with the first 54 residues of Gαi2 also resulted in a chimeric Gα-subunit that is persistently active (Gs like). We have also generated point mutations in the Gαs subunit that are comparable to the activating mutations in the ras protein. Our results suggest that point mutations in the signature sequence of the A (Val 49) and C (Thr 225) homologous regions that are implicated in regulating the GTPase activity of the molecule also resulted in the activation of the subunit. The present study has identified four key regions of the α-subunit that are critical for the activity and regulation of the Gs protein

Tailoring manganese dioxide electrocatalyst by platinum and carbon nanotube for air-cathode microbial fuel cell

Air cathode microbial fuel cell (MFC) is a high potential green technology which could simultaneously generate bio-electricity and conducting wastewater treatment. However, the slow oxygen reduction reaction (ORR) is one of the limiting factors that bounds the power generation of the cell. Hence, ORR catalytic electrocatalysts are required to enhance the performance of the air-cathode MFC. Platinum (Pt) is the conventional electrocatalysts which have been used for various applications as it has the preeminent ORR catalytic activity with high stability. However, the precious metal electrocatalyst creates a big obstacle in the development and application of Pt electrocatalysts in MFCs. Therefore, alternative ORR electrocatalysts were developed to replace the Pt electrocatalyst. In recent years, manganese dioxide (MnO2) has been studied extensively and found that it has a great potential as an effective ORR electrocatalyst due to its unique properties, low cost, easy preparation and possesses ORR catalytic activity. However, the ORR activity of MnO2 is still low compared to that Pt electrocatalyst due to the intrinsic low electrical conductivity of MnO2. Therefore, modifications are needed to enhance the ORR activity of MnO2 to substitute the Pt electrocatalyst in air-cathode MFC application. In present work, MnO2 was developed via hydrothermal method and modified by incorporating trace amount of Pt nanoparticles, carbon nanotube (CNT) and both Pt and CNT to develop Pt/MnO2, MnO2/CNT and Pt-MnO2/CNT, respectively. The goal of this work is to develop an effective ORR electrocatalyst for improving the performance of the MFC for power generation and simultaneously treating palm oil mill effluent (POME). The as-prepared electrocatalysts were characterized comprehensively through Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray analysis (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction analysis (XRD), X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller analysis (BET), Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky analysis where the surface morphology, crystallinity, oxidation state and electrochemical activity of the as-prepared electrocatalysts were examined, respectively. The effectiveness of the electrocatalysts were tested in the air-cathode MFC with POME and anaerobic sludge as the anolyte and inoculum, respectively. The performance of the MFC was determined via polarization test. The stability, coulombic efficiency (CE) and chemical oxygen demand (COD) removal efficiency of the MFC with the respectively electrocatalysts were investigated. As the result, Pt-MnO2/CNT was found to be the best ORR electrocatalysts among the modified electrocatalysts which has the highest ORR activity with lowest total and charge transfer resistances which showed high stability and the highest maximum power density, open circuit potential (OCP), CE and COD removal efficiency of 100.63 mW/m2, 629.30 mV, 34.17% and 75.55%, respectively. From the study, it was found that the presence of the CNT increases the BET surface area and the conductivity of the electrocatalyst meanwhile the presence of Pt increases the ORR catalytic activity, conductivity and the stability of the electrocatalysts. By the combination of both Pt and CNT in the MnO2 electrocatalyst, a high ORR catalytic activity with high conductivity, stability and BET surface area electrocatalyst (Pt-MnO2/CNT) was developed which showed an improved MFC performance, operational stability and COD removal efficiency

MnO2/CNT as ORR Electrocatalyst in Air-Cathode Microbial Fuel Cells

Air-cathode microbial fuel cell (MFC) is a potential electrochemical device for green power generation simultaneously conducting wastewater treatment. In the present work, the MnO2 catalyst has been prepared and modified by inducing carbon nanotube (CNT) via sonochemical-coprecipitation method. The as-prepared catalyst (MnO2/CNT) was characterized by x-ray powder diffraction patterns (XRD), field emission scanning electron microscope (FESEM), energy-dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM) and cyclic voltammetry (CV) to examine its morphological surface, crystal structure, elemental analysis and oxygen reduction reaction (ORR) activity of the catalyst, respectively. The CV results revealed that MnO2/CNT catalyzed ORR at potential of -0.45 V. The effect of catalyst loading on the chemical oxygen demand (COD) removal efficiency of palm oil mill effluent (POME) and MFC performance were studied. The maximum power density and open circuit voltage (OCV) generated from with the as-prepared MnO2/CNT were measured to be 215.57 mW/m3 and 582 mV, respectively

Performance of Klebsiella oxytoca to Generate Electricity from POME in Microbial Fuel Cell

This study is aimed to evaluate the electricity generation from microbial fuel cell (MFC) and to analyze the microbial community structure of city wastewater and anaerobic sludge to enhance the MFC performance. MFCs, enriched with palm oil mill effluent (POME) were employed to harvest electricity by innoculating of Klebsiella oxytoca, collected from city wastewater and other microbes from anaerobic sludge (AS). The MFC showed maximum power density of 207.28 mW/m3 with continuous feeding of POME using microbes from AS. Subsequent replacement with Klebsiella oxytoca resulted maximum power density of 1236 mW/m3 by utilizing complex substrate POME which was six times higher as compared to MFC operated with AS. Based on Biolog gene III analysis, relatively higher abundance of Klebsiella oxytoca was detected in the city wastewater. Predominant microorganisms such as Gammaproteobacteria, Azospiraoryzae, Acetobacterperoxydans and Solimonasvariicoloris were isolated from palm oil anaerobic sludge as well as from biofilm of MFC. Enriched electrochemically active bacteria Klebsiella oxytoca showed better performance to generate electricity from complex POME substrates compare to AS. These results demonstrate that the power output of MFCs can be increased significantly using Klebsiella oxytoca

Electricity Generation form Pretreated Palm Oil Mill Effluent Using Klebsiella Variicola as an Inoculum in Microbial Fuel Cell

In this study, generation of electricity from pretreated palm oil mill effluent (POME) using Klebsiella variicola was investigated. POME wastewater with a COD value 68,360 mg/l was subjected to pretreatment with ultrasonication and used as a substrate. MFCs (Microbial Fuel Cell), enriched with pretreated palm oil mill effluent (POME) were subjected to generate electricity by using inoculation of K. variicola, collected from city wastewater. K. Variicola was isolated from city wastewater as well as from biofilm of MFC and identified using BIOLOG gene III analysis. The electrochemical activity and the performance of the MFC were evaluated by polarization curve measurement. The MFC showed average power density of 1648.70 mW/m3 and 1280.56 mW/m3 were obtained from ultrasonication pretrated POME and untreated POME respectively. The COD removal efficiency by K. variicola for POME with pretreatment was 74% and that for untreated was 48%. These results showed that the power output and COD removal efficiency can be raised in significant amount using pretreated POME in MFC