The optimization of the culture medium to design Streptomyces sp.M7 based impedimetric biosensors

MARIA LORENA LÓPEZ RODRIGUEZ; MADRID, R.E.; CARLA E. GIACOMELLI

SENSORS AND ACTUATORS B-CHEMICAL

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2014 vol. 193 p. 230 - 237

0925-4005

tElectrochemical impedance has been widely used in microbiology in detection, quantifying and identify-ing microorganisms. Streptomyces strain M7 (SM7) is capable to grow in the presence of organochlorinepesticides (OCPs) as carbon source, using the amino acid asparagine as nitrogen source. This bacte-rial growth can be valuable and hence used in an impedimetric biosensor to detect and, eventually,quantify these pesticides. Since amino acids frequently used in culture media interfere in impedancedeterminations, this work presents an optimized design regarding the culture medium capabilities onthe impedance response of SM7 activity, as a first stage toward the development of an impedimetricbiosensor to detect OCPs. With such a purpose, SM7 growth in liquid or adhered to a solid media wasmeasured by impedance in the presence of asparagine or (NH4)2SO4as nitrogen source and glucose asa model carbon source. Impedimetric SM7 measurements were performed in the Quantibac instrumentthat can be employed to evaluate the metabolic behavior of microorganisms in different culture mediausing two fixed frequencies. We found that SM7 used asparagine as carbon source in the absence of glu-cose. Since this consumption strongly contributed to the impedance signal, this is not a suitable mediumto be used with an impedimetric biosensor. On the other hand, (NH4)2SO4appears as an ideal mediumbecause it supports SM7 growth in liquid and solid media without interfering the impedimetric detection.This simple and cost-effective technique combined with a spore-based platform is a promising strategyto design OCPs bacteria-based biosensors.