Lipase production by lactic acid bacteria and activity on butter oil

Over 100 different lactic acid bacteria representing the genera, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Streptococcus, were screened for lipase production using an agar medium containing rhodamine b and three different lipid substrates, triolein (C18:1), tributyrin (C4:0), and butter oil. A total of 29 lipase-producing strains were identified. Assays using extracellular material (supernatant) and intracellular extracts (prepared by sonication) showed that lipases were produced as intracellular enzymes in the strains studied. Several different lipase assays were employed to measure lipase activities of lipases produced by selected lactic acid bacteria. The best lipase assay was the pH stat titrator, which gave quick, quantitative results of lipase activity toward a number of synthetic triacylglyceride substrates, as well as natural substrates, such as butter oil. Activities for cell free extracts ranged from <1.0-55 μmol free fatty acid released per minute per milligram of protein. However, lipase activities of extracts obtained from lactic acid bacteria were substantially lower than those reported for other micro-organisms, such as Pseudomonas spp. and Candida spp. Studies on the substrate specificity of selected lipases indicated the lipases were generally operating in a random fashion with regard to fatty acid type, although there was a slight preference for oleic acid.