Arpita Nandy

Utilization of proteinaceous materials for power generation in a mediatorless microbial fuel cell by a new electrogenic bacteria Lysinibacillus sphaericus VA5.

In this study, a bacterial strain, Lysinibacillus sphaericus which is relatively new in the vast list of biocatalysts known to produce electricity has been tested for its potential in power production. It is cited from the literature that the organism is deficient in some sugar or polysaccharide processing enzymes and thus is tested for its ability to utilize substrates mainly rich in protein components like beef extract and with successive production of electricity. The particular species has been found to generate a maximum power density of 85mW/m(2) and current density of ≈270mA/m(2) using graphite felt as electrode. The maximum Open Circuit Voltage and current has been noted as 0.7Vand 0.8mA during these operational cycles. Cyclic voltammetry studies indicate the presence of some electroactive compounds which can facilitate electron transfer from bacteria to electrode. The number of electrogens able to generate electricity in mediator free conditions are few, and the study introduces more divergence to that population. Substrate specificity and electricity generation efficacy of the strain in treating wastewater, specially rich in protein content has been reported in the study. As the species has been found to be efficient in utilizing proteinaceous material, the technique can be useful to treat specific type of wastewaters like wastewater from slaughterhouses or from meat packaging industry. Treating them in a more economical way which generates electricity as a outcome must be preferred over the conventional aerobic treatments. Emphasizing on substrate specificity, the study introduces this novel Lysinibacillus strain as a potent biocatalyst and its sustainable role in MFC application for bioenergy generation.

A nanocomposite membrane composed of incorporated nano-alumina within sulfonated PVDF-co-HFP/Nafion blend as separating barrier in a single chambered microbial fuel cell

Nano-Al2O3 is incorporated within the blend of sulfonated PVDF-co-HFP/Nafion in varying molar ratios for the preparation of nanocomposite membranes. A series of tests namely, water uptake, swelling ratios, ion-exchange capacity (IEC), proton conductivity, oxygen diffusivity, etc. were conducted to analyze its capability in a microbial fuel cell (MFC). The enhanced water uptake, proton conductivity, and oxygen diffusivity results were observed with increasing nano-Al2O3 in the membrane. The sample A5, containing 5 wt% nano-Al2O3, exhibited superior proton conductivity over a naive SPVdF-co-HFP (∼88%) and Nafion 115 membrane (∼3.5%). In addition, this prospective membrane revealed comparable ion exchange capacity and reduced oxygen diffusivity than the corresponding Nafion 115. Furthermore, the electrical efficiency of this particular membrane was determined in single chambered MFCs as a constituent of a membrane electrode assembly. Employing mixed Firmicutes as biocatalysts, a maximum power and current density of 541.52 ± 27 mW m−2 and 1900 ± 95 mA m−2 were observed from MFC, which revealed an overall ∼48 and 11% increase over the naive SPVdF-co-HFP and Nafion 115 membrane. With a marked lowering in impedance, the results indicate the relevance of the Al2O3 filled nanocomposite as a separating barrier in single chambered MFCs for microbial bio-energy conversion.

Crosslinked inter penetrating network of sulfonated styrene and sulfonated PVdF-co-HFP as electrolytic membrane in a single chamber microbial fuel cell

In the present study, semi-IPN membranes of sulfonated styrene (SS) and sulfonated PVdF-co-HFP membranes have been analyzed as a polymer electrolyte membrane in single chamber microbial fuel cells (MFCs). 5%, 10%, 20% and 30% sulfonated styrene (SS) with varying concentrations of divinyl benzene (DVB) have been polymerized in the presence of sulfonated PVdF-co-HFP to prepare SPS-0 (0% SS), SPS-5 (5% SS), SPS-10 (10% SS), SPS-20 (20% SS) and SPS-30 (30% SS) membranes, respectively. Progressive improvements in membrane properties were observed with increasing SS and DVB concentrations, where excess DVB (<0.8 wt% of SS) resulted in increased crosslinks within the membrane structure. This eventually impeded the membrane properties and altered their rigidity. The membranes were characterized for their ion exchange capacity (IEC) and proton conductivity; IEC value of 0.39 meq g−1, 0.42 meq g−1, 0.47 meq g−1, 0.54 meq g−1 and 0.63 meq g−1 and proton conductivity of 3.23 × 10−3, 1.06 × 10−2, 1.87 × 10−2, 2.47 × 10−2 and 1.61 × 10−2 S cm−1 were observed for SPS-0 (0% SS), SPS-5 (5% SS), SPS-10 (10% SS), SPS-20 (20% SS) and SPS-30 (30% SS) membranes. The membranes were sandwiched as membrane electrode assemblies (MEA) and employed in single chamber MFCs with open air cathode to analyze their overall performance outputs. It was observed that amongst these membranes, the MFC with SPS-20 membrane showed the maximum power and current density of 447.42 ± 22 mW m−2 and 1729.63 ± 87 mA m−2 with an overall ∼91.27% COD removal in 28 days of operation, using electrogenic mixed firmicutes as biocatalysts. Overall, this study reveals the relevance of semi-IPN membranes of sulfonated styrene (SS) and sulfonated PVdF-co-HFP in MFC applications for harvesting bio-energy.

MFC with vermicompost soil: power generation with additional importance of waste management

In the present study, vermicomposted soil has been analyzed as a substrate feed in a microbial fuel cell (MFC) for harvesting bioenergy. The results have shown that composting aided in providing a better environment with available organic matter and enriched microbial population. A maximum 66% COD removal with a highest power density of 4 mW m−2 has been observed from a MFC with vermicomposted soil. In comparison, a maximum power density of 134.44 μW m−2 with 31% COD removal has been observed for a MFC with non-vermicomposted (control) soil. The differences were mainly due to the predominant microbial species and organic matter additionally available in vermicomposted soil. In cyclic voltammetric analysis, the microbes present in the vermicomposted soil were found to be electrogenic. Electrochemical Impedence Spectroscopy (EIS) analysis allowed the evaluation of the internal resistance of the single chambered cell. Scanning electron microscopy (SEM) images revealed microbial association with the process, whilst energy-dispersive X-ray spectroscopy (EDS) analysis provided results for the elemental analysis of both kinds of soil.

Effect of electric impulse for improved energy generation in mediatorless dual chamber microbial fuel cell through electroevolution of Escherichia coli.

The main emphasis of this study is to understand the electroactive behavior of a microbe in microbial fuel cell (MFC) under specific selection pressure. This study explores potential of a non-electrogenic microbe for power production in a mediatorless MFC under the influence of a specific stress. Electric pulse of specific magnitude has been applied to Escherichia coli cells in a MFC and compared the results with unpulsed (control) MFC. Maximum power density of 187.77 mW/m(2) and 284.44 mW/m(2) for the control and experimental MFC has been observed at corresponding current density of 1444.44 mA/m(2) and 1777.77 mA/m(2). The results show improved performance for the pulsed (experimental) system, despite of initial downfall with respect to the control system. This suggests bacterial adaptation against electrical pulses which leads to evolution of an efficient electrogen. This observation is further confirmed by analyzing the results of Cyclic Voltammetry (CV), Scanning Electron Microscopy (SEM) Electrochemical Impedence Spectroscopy (EIS), enlightening different attributes like electrochemical property, bacterial morphology and impedance. The study is focused on development of a microbial fuel cell catalysed by E. coli, through triggering electroactive property in the microbe by exposing it to external stress. This study is unique in nature as it is mediatorless, economical and describes about a new method of natural bacterial evolution.

Assessment of in vivo chronic toxicity of chitosan and its derivates used as oral insulin carriers

Considering public health protection, the carrier system for oral insulin must be safe. Hence, in the present study, the chronic oral toxicity of chitosan derivates was investigated in a mouse model. Oral administration of polymers did not cause any significant change in the behavioural pattern, body weight, and clinical symptoms of the treated mice. There were also no significant alterations in the biochemical parameters of blood serum and urine. Further, histopathological examination revealed an almost normal architecture, suggesting no significant adverse effects on the liver, kidney and intestine of the treated animals. An in vitro haemolysis assay proved that chitosan and its derivatives were blood compatible. Finally, intestinal luminal bacteria were able to biodegrade the polymers completely. Overall, the results suggested that the oral administration of the derivatives of chitosan in mice did not produce any significant toxicity in chronic treatment. Hence, these polymers could be utilized as safe devices for oral delivery of insulin and also other drugs.

Fabrication of laminated and coated Nafion 117 membranes for reduced mass transfer in microbial fuel cells

Sulfonation of polyvinylidinefluoride (PVdF) with chlorosulfonic acid for 2 hours revealed a respective 33% degree of sulfonation (DS) in a SPVdF membrane. The resulting sulfonated PVdF resins were used for Nafion 117 modification as coat and laminating materials, where the modified Nafion 117 membranes (laminated and coated with SPVdF) were used as polymer electrolyte membranes in microbial fuel cells (MFCs). Coating/lamination exhibited reduced oxygen diffusion across membranes by a magnitude of less than two orders over a pristine Nafion 117 membrane. This resulted in higher open circuit voltages (OCVs) with increased coulombic efficiency (CE) in MFCs. With SPVdF coated and laminated Nafion 117 membranes, respective IEC values of 0.57 and 0.46 meq g−1 and proton conductivities of 5.91 × 10−3 and 5.11 × 10−3 S cm−1 were observed, indicating maximum power and current densities of 446.45 ± 21 mW m−2 & 1721.78 ± 86 mA m−2 and 413.79 ± 20 mW m−2 & 1657.57 ± 82 mA m−2 in MFCs using mixed Firmicutes as biocatalysts. The obtained coulombic efficiencies were higher (approx. 1–2%) than those of pristine Nafion 117, indicative of its reduced oxygen diffusion at the anode. In effect, the study enumerates the efficiency of modified Nafion 117 with sulfonated PVdF coated and laminated membranes as a separating barrier in single-chambered MFCs for microbial bio-energy conversion.

Analysis of partially sulfonated low density polyethylene (LDPE) membranes as separators in microbial fuel cells

In the present study, sulfonated low density polyethylenes (LDPEs) in varied molar ratios have been analyzed as separating barriers in microbial fuel cells (MFCs) for bioelectricity production. LDPE sulfonation was performed with chlorosulfonic acid for 7, 15, 30, 45 and 60 minutes which revealed respective degree of sulfonation (DS) results of 9%, 12%, 15%, 10% and 7% in SPE-7, SPE-15, SPE-30, SPE-45 and SPE-60 membranes. Prolonged sulfonation (above 30 minutes) has shown additional sulfone crosslinking formation within the membrane structure, thereby reducing the respective DS in the SPE-45 and SPE-60 membranes. Enhanced membrane properties in terms of water uptake, ion-exchange capacity (IEC) and proton conductivity have been observed with an increasing DS as a result of the incorporated sulfonic acid in the membranes. In succession, respective IEC values of 0.0056, 0.015, 0.048, 0.0087 and 0.0012 meq g−1 and proton conductivities of 2.67 × 10−7, 3.12 × 10−6, 4.74 × 10−5, 2.76 × 10−7 and 2.13 × 10−8 S cm−1 have been observed with the SPE-7, SPE-15, SPE-30, SPE-45 and SPE-60 membranes, where reduced membrane properties in the SPE-45 and SPE-60 membranes were observed with additional sulfone crosslinks being formed in the structure. The casted membranes were assembled as a membrane electrode assembly (MEA) in single chambered MFCs, where a maximum power and current density of 85.73 ± 5 mW m−2 and 355.07 ± 18 mA m−2 were observed with the SPE-30(DS 15%) membrane with an overall ∼88.67% chemical oxygen demand (COD) removal in a 30 day run. The employed electrogenic firmicutes showed marked reductions in the overall systemic resistance, depicting the relevance of sulfonated LDPE membranes in MFCs as potent separators for bio-energy conversion.

Performances of Separator and Membraneless Microbial Fuel Cell

Microbial fuel cell (MFC) is a typical bio-electrochemical system (BES) that produces green electricity from organic wastes by mimicking bacterial interactions under anoxic conditions. This bacteria catalysed system cannot only provide a renewable alternative clean source of energy without the need for fossil fuels, but also become as a remote power source in the field of domestic wastewater treatment, breweries, hydrogen production, remote sensing, desalination plants, pollution remediation and so on (Pant et al. 2010). Though MFC technology belongs to its infancy stage in our modern day, but it has several advantages over other conventional systems. Firstly, it can eliminate pollution caused by burning fossil fuels in a mild reaction condition. Maintenance is quite simple and economically viable. It can also be operated without any noise and has no memory effect while getting refuelled. It can provide high quality DC power output and the power densities are very higher than expected. To set up the basis of an MFC, the bacteria are allowed to grow on the electrode (placed in anode), commonly known as biofilm in order to bio-catalyse the reaction. The anode is separated from the cathode compartment through the ion exchange membrane, salt bridge, sediment, etc. Another electrode without bio-film is placed in the cathode compartment. These two electrodes are connected by an external conductive wire. During the conversion of organic materials by the metabolic activity of bacteria, the generated electrons are transferred from anode to cathode compartment through the wire. The protons produced in this process also flow from anode to cathode through separator in order to maintain the charge difference. At the cathode side an oxidant (generally oxygen) is reduced. Thus, electrons and protons are consumed with oxygen to form water on the cathode side (Perez et al. 2012). This has been pictorially represented in Fig. 7.1.