Investigation of Graphite Electrodes Modified with Cellobiose Dehydrogenase from the Ascomycete Myriococcum thermophilum

Abstract

The catalytic properties of cellobiose dehydrogenase (CDH) from the ascomycete fungus Myriococcum thermophilum adsorbed on a graphite electrode were investigated for a large variety of carbohydrate substrates. The effects of applied potential, pH and buffer composition were tested and optimized, and the most suitable conditions were used to evaluate the detection limit, linear range, and sensitivity of the sensor for different carbohydrates in the flow injection mode. Subsequently, the long term stability of the modified electrodes was determined. Additionally, the direct and mediated electron transfer between the active site of the enzyme and the electrode has been investigated by amperometric flow injection measurements in the absence and presence of the mediator 1,4-benzoquinone in the presence of cellobiose or lactose.

A Direct Electron Transfer‐Based Glucose/Oxygen Biofuel Cell Operating in Human Serum

“…The redox potential of the heme group, the electrochemically active domain of CtCDH acting as the electron donor to the bioanode, is not yet known. However, based on the starting potentials of glucose bioelectrooxidation, on the steady-state potentials of CtCDH-modified SPGEs in the absence and presence of glucose (Table 3), as well as on previous studies of other CtCDHs from different fungi [11,12,14,17,28,32,33], one can assume that the redox potential of the heme group is close to 150 mV versus NHE. The differences between the steady-state potentials of the MvBOx-and CtCDH-SPGEs determine the maximal open circuit potential of the BFC operating in glucose-containing PBS and human serum, i.e.…”

“…One of the most attractive electrode elements for a potentially implantable BFC is a carbon material, which is cheap, abundant and biocompatible. To design this BFC, SPGE were chosen, as such electrodes are well-characterised [30] and widely used for bioelectrochemical studies of variety of enzymes including different CDH [17,28,31,32] and BOx [20,29], on which both bioelements showed excellent DET-based bioelectrocatalysis (Figures 2 and 3).…”

“…CtCDH was purified from the culture supernatant of the ascomycete C. thermophilus, CBS 405.69 obtained from the Centralbureau voor Schimmelcultures (Baarn, The Netherlands). Cultivation and purification of the enzyme were similar to previously reported protocols for Myriococcum thermophilum CDH [17]. The homogeneous preparation of the enzyme was stored in a 50 mM acetate buffer, pH 5.5 at -80°C.…”

“…CDH oxidises cellodextrins and lactose at the FAD domain and may, depending on its origin, also oxidise monosaccharides such as glucose [16]. The reduced FAD domain can be reoxidised directly by various electron acceptors or the electrons can be sequentially transferred to the heme domain, which in turn donates the electrons directly to the electrode acting like a 1 e -acceptor [17].…”

Substrate Specificity and Interferences of a Direct-Electron-Transfer-Based Glucose Biosensor

“…Cellobiose dehydrogenase has been tested in combination with various electrode materials to utilize and enhance DET and increase the current density of CDH bioelectrodes. [26][27][28][29][30] Previous studies applying CDH as the biorecognition element showed promising results, including high current densities (6.84 µA cm -2 ), a good linear range (0.1-30 mM), and a low detection limit (0.05 mM). 31,32 However, until now, no study has investigated the effects of known interfering compounds possibly encountered in vivo.…”