Hydrogen production from glucose by inhibiting hydrogenotrophic methanogens carbon-18 long-chain fatty acids.

Dark fermentation is an attractive process for hydrogen (H2) production from organic substrates. Rapid conversion of H2 to other products, particularly methane, is a major hindrance to H2 accumulation and recovery from the process. Long chain fatty acids (LCFAs) namely oleic (C18:0) acid (OA) and linoleic (C18:1) acid are inhibitors of aceticlastic methanogens and are suspected inhibitors of hydrogenotrophic methanogens. However, the effect of such inhibition on increasing H2 recovery from organic substrates has not been examined. Hence, in this study, C18 LCFAs were used to increase the quantity of H2 from glucose degradation. Batch experiments were conducted at 23 +/- 2°C to examine the effect of LCFA concentration (0 to 2,000 mg 1-1) and the initial pH (pH 5, 6 and 7.8) on the fermentative H2 production. Glucose was re-injected on day 4 or day 5 to examine the combined effect of LCFA, volatile fatty acids (VFAs) and intermittent sparging on H2 production. H2 production was a function of LCFA concentration and the initial pH. The maximum H2 yield recorded was approximately 2.7 mol H2·mol-1 glucose in cultures receiving LA at an initial pH of 6. Glucose degradation was inhibited in cultures receiving LCFA. Inhibition of glucose degradation was enhanced at lower initial pH values. Overall, the data demonstrated that LA and OA can be used to enhance H 2 accumulation and recovery from organic substrates.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .G87. Source: Masters Abstracts International, Volume: 44-03, page: 1472. Thesis (M.A.Sc.)--University of Windsor (Canada), 2005

Rhoeo discolor leaf extract as a novel immobilizing matrix for the fabrication of an electrochemical glucose and hydrogen peroxide biosensor

A novel natural immobilizing matrix for the immobilization of glucose oxidase (GOx) and horseradish peroxidase (HRP) is presented in this article. The electrochemical biosensor was constructed by immobilizing the enzymes on Rhoeo discolor (Rd) leaf extract with 2.5% glutaraldehyde (GLD) on functionalized multiwalled carbon nanotubes (f-MWCNTs) modified graphite (Gr) electrode. The Gr/f-MWCNTs/(Rd-GLD)/GOx and Gr/f-MWCNTs/(Rd-GLD)/HRP biosensors showed excellent electrocatalytic activity concerning the detection of glucose and hydrogen peroxide. The physical morphology of the biosensors was studied using SEM and EDX. The electrochemical performance of the proposed biosensors was evaluated using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The effects of experimental variables such as pH, temperature, and applied potential on the current response of the biosensors were studied and optimized. The Gr/f-MWCNTs/(Rd-GLD)/GOx biosensor exhibited a rapid response time of less than 5 s, displayed a wide linear range of 0.5 to 28.5 mM, showed a low detection limit of 0.16 μM and revealed a high sensitivity of 15 μA mM-1 cm-2 for glucose. Similarly the Gr/f-MWCNTs/(Rd-GLD)/HRP biosensor showed a fast response time of 3 s, a good linear range of 0.2 to 6.8 mM with a 0.01 μM detection limit and an exceptional sensitivity of 2.1 mA mM-1 cm-2 for hydrogen peroxide. Subsequently, the practical applicability of the glucose biosensor for the analysis of glucose in Eleusine coracana wine and tender coconut water was examined while the Gr/f-MWCNTs/(Rd-GLD)/HRP modified electrode was tested for the determination of H2O2 in herbal bleach. In addition, the biosensors displayed long term stability, anti-interference ability and good reproducibility. © 2014 The Royal Society of Chemistry.

Development of a simple bioelectrode for the electrochemical detection of hydrogen peroxide using Pichia pastoris catalase immobilized on gold nanoparticle nanotubes and polythiophene hybrid

In this paper, a simple and innovative electrochemical hydrogen peroxide biosensor has been proposed using catalase (CATpp) derived from Pichia pastoris as bioelectrocatalyst. The model biocomponent was immobilized on gold nanoparticle nanotubes (AuNPNTs) and polythiophene composite using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide (EDC-NHS) coupling reagent. In this present work, we have successfully synthesized gold nanoparticles (AuNPs) by ultrasonic irradiation. The tubular gold nanostructures containing coalesced AuNPs were obtained by sacrificial template synthesis. The assembly of AuNPNTs onto the graphite (Gr) electrode was achieved via S-Au chemisorption. The latter was pre-coated with electropolymerized thiophene (PTh) to enable S groups to bind AuNPNTs. The combination of AuNPNTs-PTh, i.e., an inorganic-organic hybrid, provides a stable enzyme immobilization platform. The physical morphology of the fabricated biosensor Gr/PTh/AuNPNTs/EDC-NHS/CATpp was investigated using scanning electron microscopy and energy-dispersive microscopy. The analytical performance of the bioelectrode was examined using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. Operational parameters such as working potential, pH, and thermal stability of the modified electrode were examined. The beneficial analytical characteristics of the proposed electrode were demonstrated. Our results indicate that the Gr/PTh/AuNPNTs/EDC-NHS/CATpp bioelectrode exhibits a wide linear range from 0.05 mM to 18.5 mM of H2O2, fast response time of 7 s, excellent sensitivity of 26.2 mA mM-1 cm-2, good detection limit of 0.12 μM and good Michaelis-Menten constant of 1.4 mM. In addition, the bioelectrode displayed good repeatability, high stability and acceptable reproducibility, which can be attributed to the AuNPNTs-PTh composite that provides a biocompatible micro-environment. © the Partner Organisations 2014.

An Electrochemical Perspective Assay for Anticancer Activity of Calotropis Procera Against Glioblastoma Cell Line (LN-18) using Carbon Nanotubes-Graphene Nano-Conglomerate as a Podium

In this article, we report the pre-screening of anti-cancer effect of Calotropis procera against glioblastoma cell lines (LN-18) by means of electrochemical methods. Soxhlet assisted extraction (SAE) has been employed to extract the polyphenol contents present in the leaf of Calotropis procera. The phytochemical analysis of the extract has been studied and the polyphenol contents were determined using Folin Ciocalteau method. To study the anticancer effects of the aqueous plant extract, a cytosensor (Gr/NT-G/LN-18) was fabricated and its possible mechanism for DNA binding was studied using graphite /poly(allylamine hydrochloride)/nanotube-graphene composite /polypyrrole /de-oxy ribonucleic acid (Gr/PAH/NT-G/PPy/DNA) modified electrode. The electrochemical characteristics of the proposed Gr/NT-G/LN-18 cytosensor towards the plant extract were evaluated using electrochemical techniques like cyclic voltammetry and differential pulse voltammetry. Scanning electron microscopy (SEM) and energy dispersive analysis of x-ray (EDAX) have been employed to study the physical characterization of the Gr/PAH/NT-G/PPy/DNA modified electrode. These results indicate that the plant extract has an ability to act as an antiglioblastoma against LN-18 cancer cells. Copyright © 2016 VBRI Press.

Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing

This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. © 2016 Elsevier B.V.

Amperometric hydrogen peroxide and cholesterol biosensors designed by using hierarchical curtailed silver flowers functionalized graphene and enzymes deposits

Novel flower-like silver particles with triangular plates as building block along with functionalized graphene (straggled sheets) and enzymes horseradish peroxidase (HRP) or cholesterol oxidase (ChOx), were obtained on graphite electrode by galvanostatic electrodeposition method. The morphology of the electrodeposits has been characterized using scanning electron microscopy and energy-dispersive analysis of X-ray. The resulting biosensors named Nf/(HRP-f-graphene-Ag)/Gr and Nf/(ChOx-f-graphene-Ag)/Gr were evaluated for electrochemical activity using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. Optimization of the interdependent experimental parameters such as pH and temperature were achieved and maintained constant throughout the experiments. An activation energy of 2.5 kJ mol -1 was obtained for Nf/(HRP-f-graphene-Ag)/Gr electrode while Nf/(ChOx-f-graphene-Ag)/Gr showed an activation energy of 2.06 and 3.12 kJ mol-1. Furthermore, the former electrode demonstrated a good linear range of 25 μM to 19.35 mM with rapid response time of 3 s and detection limit of 5 μM for hydrogen peroxide. Similarly, the Nf/(ChOx-f-graphene-Ag)/ Gr electrode revealed a linear range of 0.1-4.5 mM with rapid response time of 3 s and an excellent detection limit of 0.514 mM for cholesterol. Besides this, the Nf/(HRP-f-graphene-Ag)/Gr and Nf/(ChOx-f-graphene-Ag)/Gr electrodes displayed a Michaelis-Menten constant of 0.26 and 0.57 mM, respectively, suggesting high affinity and enzymatic activity. The enhanced performance of biosensors towards detection of substrate and rejection of interferents, provided an evidence for its high anti-interference ability. Additionally the biosensors exhibit long term storage stability and reproducibility with antifouling properties. © 2013 Springer-Verlag Berlin Heidelberg.