On-line determination of the total lipolytic activity in a four-phase system using a lipase adsorption law

Lipases have a very well known affinity for organic-aqueous interfaces. A previously developed on-line turbidimetric analyser can only analyse the lipase activity present in the aqueous phase of a culture broth. An adsorption law of Langmuir type has been derived to determine the lipolytic activity remaining in the organic-aqueous interface formed between oleic acid and culture broth in Candida rugosa lipase production fermentation. In the concentration range of oleic acid (0-8 g.l(-1)) and lipolytic activity (0-35 U.ml(-1)) tested, lipases were not adsorbed in a multilayer form and the Brunauer-Emmet-Teller (B.E.T.) law was not applicable. The Langmuir adsorption law has been shown to be the most suitable to describe the adsorption process involved. The methodology employed enables on-line determination of the total lipolytic activity produced by the microorganism, using the adsorption law determined. This finding, in combination with the on-line measurement of variables such as biomass, aqueous lipolytic activity, oleic acid concentration and specific growth rate, permits the development of control systems for ensuring improved throughput, quality and repeatability of the process.