Fabrication of the macro and micro-scale microbial fuel cells to monitor oxalate biodegradation in human urine

Efficient enrichment of free target sequences in an integrated microfluidic device for point-of-care detection systems

Nucleic acid biomarker detection has great importance in the diagnosis of disease, the monitoring of disease progression and the classification of patients according to treatment decision making. Nucleic acid biomarkers found in the blood of patients have generated a lot of interest due to the possibility of being detected non-invasively which makes them ideal for monitoring and screening tests and particularly amenable to point-of-care (POC) or self-testing. A major challenge to POC molecular diagnostics is the need to enrich the target to optimise detection. In this work, we describe a microfabricated device for the enrichment of short dsDNA target sequences, which is especially valuable for potential detection methods, as it improves the probability of effectively detecting the target in downstream analyses. The device integrated a heating element and a temperature sensor with a microfluidic chamber to carry out the denaturation of the dsDNA combined with blocking-probes to enrich the target. This procedure was validated by fluorescence resonance energy transfer (FRET) technique, labelling DNA with a fluorophore and a quencher. As proof of concept, a 23-mer long dsDNA sequence corresponding to the L858R mutation of the EGFR gene was used. The qualitative results obtained determined that the most optimal blocking rate was obtained with the incorporation of 11/12-mer blocking-probes at a total concentration of 6 μM. This device is a powerful DNA preparation tool, which is an indispensable initial step for subsequent detection of sequences via nucleic acid hybridisation methods.

Electrochemical process for petroleum refinery wastewater treatment to produce power and hydrogen using microbial electrolysis cell

This research aims to assess the microbial electrolysis cell (MEC) fed with petroleum refinery wastewater (PRW) to produce power density and bio-electrochemical hydrogen. The MEC produces a maximum bio-electricity of 21.4 mA and a power density of 1200123.90 W/m2 with a loading of chemical oxygen demand (COD) of 17000 mg/L. Due to catalyzed oxidation of complex compounds in PRW with a maintained microbial biofilm growth was observed after 90 d of operation of MEC. Results showed that the oxidation of organic substances in PRW enhanced the size in the growth of microbial film which further increased the generation of electrons leading to current density of 5890 mA/m2. The COD removal efficiency of MEC was found to be 89.9%. The bio-electricity and hydrogen production of the MEC was estimated to be 24.5 mA and 19.2 L respectively when loaded with PRW having a COD of 17500 mg/L after 130 d. Present experiments demonstrate the efficiency of MEC technology efficiency in treating petroleum wastewater with the help of microbial biofilm.

Biodegradation of petroleum wastewater for the production of bioelectricity using activated sludge biomass

Objective

This research is based on the treatment of petroleum wastewater (PWW) with pretreated activated sludge for the production of electricity and removal of chemical oxygen demand (COD) using microbial fuel cell (MFC).

Methods

The application of the MFC system which uses activated sludge biomass (ASB) as a substrate resulted in the reduction of COD by 89.5% of the original value. It generated electricity equivalent to 8.18 mA/m2 which can be reused again. This would solve the majority of environmental crises which we are facing today.

Results

This study discusses the application of ASB to enhance the degradation of PWW for the production of a power density of 1012.95 mW/m2 when a voltage of 0.75 V (voltage) is applied at 30:70% of ASB when MFC is operated in a continuous mode. Microbial biomass growth was catalyzed using activated sludge biomass. The growth of microbes was observed by scanning through an electron microscope. Through oxidation in the MFC system, bioelectricity is generated which is used in the cathode chamber. Furthermore, the MFC operated using ASB in a ratio of 35 with the current density, which decreased to 494.76 mW/m2 at 10% ASB.

Application

Our experiments demonstrate that the efficiency of the MFC system can generate bioelectricity and treat petroleum wastewater by using activated sludge biomass.

Over-expressing NadA quinolinate synthase in Escherichia coli enhances the bioelectrochemistry in microbial fuel cells

The microbial fuel cell (MFC), which converts biomass energy into electricity through microbial metabolism, is one of the important devices for generating new bioenergy. However, low power production efficiency limits the development of MFCs. One possible method to solve this problem is to genetically modify the microbial metabolism pathways to enhance the efficiency of MFCs. In this study, we over-expressed the nicotinamide adenine dinucleotide A quinolinate synthase gene (nadA) in order to increase the NADH/+ level in Escherichia coli and obtain a new electrochemically active bacteria strain. The following experiments showed an enhanced performance of the MFC, including increased peak voltage output (70.81 mV) and power density (0.29 μW/cm2), which increased by 361% and 20.83% compared to the control group, respectively. These data suggest that genetic modification of electricity producing microbes could be a potential way to improve MFC performance.