REUSABLE SOLID-PHASE IMMUNOASSAY FOR THE DETECTION OF CITRATE LYASE

An enzymatic immunoassay on a solid phase was developed to detect citr ate lyase, an intracellular enzyme of Lactococcus lactis subsp. lactis biovar. diacetylactis. A monoclonal antibody to citrate lyase was imm obilized on a nylon membrane. The capture of the antigen was proved by measurement of citrate lyase activity. The immunologic support could capture citrate lyase either in a purified solution or in bacterial ly sates. Citrate lyase activity on the support increased with the time o f incubation of the antigen: within 60 min, 60% of the initial soluble activity was retained (i.e., about 5 x 10(-12) mole of citrate lyase per cm(2) of membrane). The support was stored for at least six months . The antibody bound to the solid phase was regenerated by immersion o f the support in one of the two chaotropic solutions: phosphoric acid (10 mM) or potassium thiocyanate (3 M). The immunologic solid phase wa s reused for 50 consecutive assays losing at most 45% of its capture c apacity when phosphoric acid was the regenerant.