Use of sorghum seed tissue as a biocatalyst in a stirred reactor for oxalic acid determination

The enzyme oxalate oxidase, E.C. 1.2.3.4 from Sorghum vulgare seeds (variety BR303) was used to develop a new sensor for oxalate determination without any purification. The sorghum seeds were conditioned in a 0.10 mol l(-1) KCl solution. Then, these seeds were put in a stirring bar type enzymic reactor and coupled with an electrode for CO2. This device vas introduced into a cell containing 10.0 ml of a 0.10 mol l(-1) KCl solution saturated with oxygen. This sensor showed a linear response between 1.0 and 4.0 x 10(-3) mol l(-1) with a slope of 30 mV per decade of oxalate concentration at 25.0 degrees C. The sensor was stable for one month or 200 determinations. The response time was about 60 s. The Michaelis-Menten constant determined for this enzyme was 1.5 x 10(-3) mol l(-1).