Anna Maria Pisanelli

Sensor array techniques for mimicking the mammalian olfactory system

Scales of human odour perception are subjective and there is much need for automated methods of odour measurement in a variety of industries. Organic conducting polymers have been developed as sensing devices, and many materials have been synthesised and characterised. The sensors show rapid adsorption and desorption characteristics and allow rapid measurements to be made. The responses are proportional to the concentration of the volatile chemical being sensed, and with calibration can be used to quantify single chemical species. Arrays of sensors produce patterns of responses that can be used as descriptors for discriminating complex odours. Examples of applications in food quality monitoring and agriculture malodours are given. The sensor array response may be correlated with olfactometric measurements in the case of pig slurry malodour.

Butanol production in S. cerevisiae via a synthetic ABE pathway is enhanced by specific metabolic engineering and butanol resistance

BackgroundThe fermentation of sugars to alcohols by microbial systems underpins many biofuel initiatives. Short chain alcohols, like n-butanol, isobutanol and isopropanol, offer significant advantages over ethanol in terms of fuel attributes. However, production of ethanol from resistant Saccharomyces cerevisiae strains is significantly less complicated than for these alternative alcohols.ResultsIn this study, we have transplanted an n-butanol synthesis pathway largely from Clostridial sp. to the genome of an S. cerevisiae strain. Production of n-butanol is only observed when additional genetic manipulations are made to restore any redox imbalance and to drive acetyl-CoA production. We have used this butanol production strain to address a key question regarding the sensitivity of cells to short chain alcohols. In the past, we have defined specific point mutations in the translation initiation factor eIF2B based upon phenotypic resistance/sensitivity to high concentrations of exogenously added n-butanol. Here, we show that even during endogenous butanol production, a butanol resistant strain generates more butanol than a butanol sensitive strain.ConclusionThese studies demonstrate that appreciable levels of n-butanol can be achieved in S. cerevisiae but that significant metabolic manipulation is required outside of the pathway converting acetyl-CoA to butanol. Furthermore, this work shows that the regulation of protein synthesis by short chain alcohols in yeast is a critical consideration if higher yields of these alcohols are to be attained.

Odor Evaluation of Foods Using Conducting Polymer Arrays and Neural Net Pattern Recognition

An increasing need exists for chemical sensing systems that mimic biological olfaction. Examples of potential applications of such systems are in quality control of foods and beverages and environmental monitoring.

Identification of wound infection by limited set of volatile products

Based on an array of combined metal oxide and conductive polymer gas sensors electronic an odor recognition system is being developed for detection of bacteria types at the early stages of wound infection. It is proved by GC-MS studies that living bacteria that are typical infectious agents in clinical practice can be distinguished from each other by means of a limited set of key volatile products. Using a set of these reference volatile compounds criteria for selection and calibration of gas sensors were defined. Aiming to increase reliability of bacteria identification SPME preconcentration was used for sampling of the headspace air and response to variable concentrations of volatiles emitted from the SPME fiber is processed for evaluation of the output parameters of the sensor module. Discrimination between classes of volatile products is obtained by a PCA analysis of the dynamic parameters of sensor responses to the headspace air of clinical samples collected by swabbing.

Odorant Binding Proteins as Sensing Layers for Novel Gas Biosensors: An Impedance Spectroscopy Characterization

In this work, an ab-initio study of the electrical response to odorants of a self-assembled monolayer of a pig OBP immobilized onto a miniaturized Si-substrate equipped with gold interdigitated electrodes (IDE), was started. Electrical Impedance Spectroscopy (EIS) was used as electrical characterization technique and a dedicated experimental set-up was arranged in order to carry out EIS measurements in controlled environment. The EIS data was fitted by using a fitting software based on Levenberg–Marquardt (LEVM) algorithm to determine the equivalent circuit of the system.

Electrical characterization of a pig odorant binding protein by Impedance Spectroscopy

In this work, an ab-initio study of the electrical response to odorants of a self-assembled monolayer of a pig OBP immobilized onto a miniaturized Si-substrate equipped with gold interdigitated electrodes (IDE), was started. Electrical Impedance Spectroscopy (EIS) was used as electrical characterization technique and a dedicated experimental set-up was arranged in order to carry out EIS measurements in controlled environment. The EIS data was fitted by using a fitting software based on Levenberg-Marquardt (LEVM) algorithm to determine the equivalent circuit of the system.

Development of a diagnostic aid for bacterial infection in wounds

Infection of wounds during hospitalisation often induces morbidity and sometimes mortality. The delay in patient recovery and subsequent increased length of hospital stay also has economic consequences. Standard techniques for microbiological detection are surface swabbing and wound biopsy culture. Surface swabbing is the most commonly used technique mainly because is quite inexpensive and is not invasive but can give only a representation of surface infection and analysis is also time consuming. Infected wounds are often characterised by an offensive odour that can be used as a diagnostic parameter. We report the results obtained by examining swabs and dressings taken from patients using a gas sensor array instrument developed as part of an EU funded project WOUNDMONITOR.

138 Electrical Impedance Spectroscopy of a Pig Odorant Binding Protein immobilized onto gold interdigited microelectrodes: an ab-initio study

In this work, an ab‐initio study of the electrical response to odorants of a self‐assembled monolayer of a pig OBP immobilized onto a miniaturized Si‐substrate equipped with gold interdigitated electrodes (IDE), was started. Electrical Impedance Spectroscopy (EIS) was used as electrical characterization technique and a dedicated experimental set‐up was arranged in order to carry out EIS measurements in controlled environment. The EIS data was fitted by using a fitting software based on Levenberg‐Marquardt (LEVM) algorithm to determine the equivalent circuit of the system.

Whole Tissue Voltage Clamp of Frog Olfactory Mucosa Using a Modified Ussing Chamber

In the olfactory receptor neuron, at least five membrane currents have been identified using patch-clamp techniques. These include two inward sodium currents, and three distinct outward potassium currents, some of which may be calcium modulated [1–4]. Odorant-induced currents in isolated cells may pass through nonselective monovalent cation channels, which may be blocked at high concentrations by amiloride, a drug whose action is normally to block sodium channels [5, 6]. The interaction of the various ion channels in the homeostasis of the intect olfactory mucosa is still only poorly understood. The understanding of what are now termed “perireceptor events” in olfaction [7], how they interact with olfactory transduction events, the feedback mechanisms, and the molecular interactions between different cell types in the olfactory mucosa, are open questions.