HYBRID BIOSENSORS TO ESTIMATE LACTOSE IN MILK

Hybrid biosensors for the determination of lactose were developed. Sac charomyces cerevisiae was entrapped in agar. Lactases (Lactozym and be ta-galactosidase of Enterobacter agglomerans) were adsorbed onto dieth ylaminoethyl cellulose (DE-52). Catalytic components were confined bet ween the surface of a gas-permeable membrane of a CO2 electrode and a dialysis membrane. Lactases hydrolysed lactose and Saccharomyces cerev isiae fermented glucose and galactose producing CO2. This gas was meas ured by a CO2 electrode. These biosensors showed Nernstian characteris tics. The semilogarithmic concentration range was between 0.5% and 10% . The lifetime of these biosensors was two weeks and two months, respe ctively. The results were applied to lactose analysis in milk samples. Validation of the assays was made on milk of several dairy brands by comparison with a spectrophotometric method.