Reusable solid phase immunoassay for the detection of citrate lyase

An enzymatic immunoassay on a solid phase was developed to detect citrate lyase, an intracellular enzyme of Lactococcus lactis subsp. lactis biovar. diacetylactis. A monoclonal antibody to citrate lyase was immobilized on a nylon membrane. The capture of the antigen was proved by measurement of citrate lyase activity. The immunologie support could capture citrate lyase either in a purified solution or in bacterial lysates. Citrate lyase activity on the support increased with the time of incubation of the antigen: within 60 min, 60% of the initial soluble activity was retained (i.e., about 5 × 10−12 mole of citrate lyase per cm2 of membrane). The support was stored for at least six months. The antibody bound to the solid phase was regenerated by immersion of the support in one of the two chaotropic solutions: phosphoric acid (10 mM) or potassium thiocyanate (3 M). The immunologie solid phase was reused for 50 consecutive assays losing at most 45% of its capture capacity when phosphoric acid was the regenerant.