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Electrochemical biosensors have become very important tools in analytical chemistry because of their advantages like accuracy, high sensitivity and easy handling, This article describes electrochemical detection of acetic acid based on the fungus Fusarium solani. The biosensor employed for the study of assimilation of substrates was fabricated by coupling the immobilized membrane with the DO probe using dialysis tubing, A microbial dispersion containing 0.2 g of wet weight of the organisms per mL was used for immobilization upon cellulose nitrate membrane. The membrane retaining the fungus was placed on the Teflon membrane of the oxygen electrode so that the fungus was trapped between the two membranes. The linear range was found to be between 2 and 70 ppm (v/v) of acetic acid. A polypropylene net increases the lifetime of the sensor due to its retention of humidity in the net. By dipping the electrochemical probe onto buffer (pH 7.2), the sensor was found to have an extended lifetime of 120 days with about 800 determinations.

Electrochemical biosensors have become very important tools in analytical chemistry because of their advantages like accuracy, great sensitivity and easy handling. This article reports on the electrochemical detection of ethanol based on the fungus Aspergillus niger. The fungus was isolated from polyurethane waste, at a factory in India. The fungal assimilation of ethanol came to light, when detailed biochemical characterization of the fungus for alcohols, organic acids, and amino acids was studied using cyclic voltammetry. The fungus was cultured in Czepek-Dox media. A dissolved oxygen (DO) probe was fabricated using a gold cathode, a platinum counter electrode and Ag/AgCl reference electrode. The biosensor employed for the assimilation characterization was fabricated by coupling the immobilized membrane with the DO probe using dialysis tubing. A microbial dispersion containing 0.2 g (wet weight) of the organisms/mL was used for immobilization upon cellulose nitrate membrane. The membrane retaining the fungus was placed on the Teflon membrane of the oxygen electrode so that the fungus was trapped between the two membranes. The maximum detectable concentration was 35.3 ppm (v/v) and the linear range was between 1 and 32 ppm (v/v) of ethyl alcohol. By dipping the assembly with the microbe in phosphate buffer, the sensor was found to have an extended lifetime of 90 days with about 1000 determinations.

A universal biochemical oxygen demand (BOD) sensor that can be used for the analysis of all types of organic pollutants is the objective of current researchers working in the area of biosensors. Development of such type of sensor involves the proper choice of a microorganism that can assimilate a wide spectrum of organic compounds. This study has led to the screening of many microorganisms and in this process we were able to identify Torulopsis candida as an attractive alternate for Trichosporon cutaneum. The BOD sensor employing T. candida was fabricated and evaluated in the batch mode as well as under flow conditions. The response time, linear range of estimation of BOD and storage life of the immobilized microbe and the assimilation spectrum have been studied.

Large number of biochemical activities and electron behavior have a very close relationship with life forms and living cells [1], which makes the study of physiological and biochemical characteristics an important area in analytical chemistry. In recent years, researchers have developed rapid methods of assessment of cell proliferation [2–3], including reports on methods involving ATP bioluminescence [4], antibody-direct epifluorescent filter technique [5], enzyme immunoassays [6, 7], polymerase chain reaction [8], resonant mirror biosensor [9], quartz crystal microbalance biosensor [10], dielectric measurement [11], electron transfer in protein [12], and the electric impedance sensing systems [13]. The applications of direct voltammetry of cell cultures in the detection of viable microbes in biological samples have been reported [14–16]. Recent research has demonstrated that the live microbes, Tetrahymena shanghaiensis [17] and the Saccharomyces cerevisiae [18], could be monitored using cyclic voltammetry (CV). An attempt has been made here to extend this for fungal strains. The conventional method of the studies on the growth phases of fungi is cumbersome and time consuming because the time period required for the growth of the fungi is in terms of days, while for bacterial strains, all the phases of growth are completed in a few hours. This manuscript discusses the voltammeric behavior of the fungus, Aspergillus niger that was isolated from polyurethane waste scraps.