Lyophilized microorganisms as a basis for biosensitive element of a BOD-biosensor

Previously created laboratory models and commercially available BOD biosensors are usually formed using the biomass of microorganisms obtained by centrifugation of the culture fluid. In this work we developed and tested BOD biosensors based on lyophilized bacteria Paracoccus yeei VKM V-3302 and yeast Debaryomyces hansenii VKM Y-2482. The use of a lyophilized form of microorganisms makes it possible to switch to a new analysis format – the use of easily replaceable biosensitive elements with a short service life. It will simplify the introduction of BOD biosensors in environmental laboratories, enterprises and organizations involved in the routine determination of BOD using a methodology based on a 5-day sample incubation. The long shelf life (up to 2 years), low cost and easy applying of a dry preparation to the electrode will greatly facilitate the transportation of biosensitive elements to the end user, allow analysis in the field and at any time and will not require constant calibration of a sensor. It has been shown that the lyophilization process does not lead to significant changes in the metabolic activity of microorganisms. The biosensors are characterized by high sensitivity (the lower limit of BOD5 determination is 0.5 mgO2/dm3), convergence of results (4.5%) and are not inferior to existing analogs in terms of basic characteristics. They make it possible to analyze water samples classified as “pure” (BOD5 range 0.05–0.5 mg/dm3) and obtain results with a high correlation (R=0.9951) to the standard method. Thus, the use of bacteria P. yeei and yeast D. hansenii in a lyophilized form as part of the sensitive elements of BOD biosensors makes it possible to use them in prototypes of biosensors for mass production.