Abstract
Lipases are enzymes that hydrolyse lipids to produce free fatty acids and glycerol. Fungi were cultured on sabouraud dextrose agar (SDA) plates and identified using microscopic techniques. Screening for lipase producers was carried out on SDA media supplemented with 3 % olive oil at ambient temperature. M. pusillus, M. canis, A. fumigatus, Yeast and T. mentagrophytes were found to produce lipases in different amounts with Yeast and M. canis being the highest producers, they were further characterised for this reason. Lipase production was carried out using submerged fermentation. Both Yeast and M. canis produced lipases maximally at 72 h. Optimum pH and temperature of activity for the lipases from Yeast were determined to be 5 and 35 ℃ respectively whereas, those from M. canis were 6 and 40 ℃ correspondingly. Yeast and M. canis lipases had preference for olive oil than vegetable and palm oils and both enzymes were activated by K<sup>+</sup>, Mg<sup>2+</sup> and Ca<sup>2+</sup> and inhibited by Fe<sup>3+</sup>, Hg<sup>2+</sup> and Co<sup>2+</sup>. The lipase enzyme from Yeast had V<sub>max</sub> of 0.0006 U/mL/Sec, K<sub>m</sub> of 0.4242 mM and K<sub>cat</sub> of 0.0004 S<sup>-1</sup> while that from M. canis had corresponding V<sub>max</sub>, K<sub>m</sub> and K<sub>cat</sub> of 0.0001 U/mL/Sec, 3.2287 mM and 0.0001 S<sup>-1</sup>.
Highlights
Lipases (E.C. 3.1.1.3) are biological catalysts that break down fats and oils releasing free fatty acids and glycerol
The effect of different metal ions on lipase activities was studied by using K+, Co2+, Mg2+, Hg2+, Cu2+, Ca2+ and Fe3+. 0.2 μL of 1mM of each metal ion already prepared in 1M Tris-HCl buffer was added to the substrate mixture and treated as described in assay for lipase activity above
Out of the 9 fungi isolated from the vegetable oil contaminated soil following incubation on sabouraud dextrose agar (SDA), 5 isolates exhibited different magnitudes of zones of clearance when 3 % olive was used as a substrate (Table 2)
Summary
Lipases (E.C. 3.1.1.3) are biological catalysts that break down fats and oils releasing free fatty acids and glycerol They participate in esterification and transesterification reactions, lactonization, aminolysis [1], acidolysis [2], aminolysis, alcoholysis, hydrolysis [3], [4] and interesterification reactions in non-aqueous media [5]. The all-round properties of lipases make them to have many potential applications in diverse aspects including, food processing, detergent, pharmaceutical, cosmetics, textile, agrochemical [6], paper, dairy, oleo-chemicals and leather industries [2] They find usefulness in the management of waste water, fine chemicals synthesis [6] and the production of other important bioactive compounds such as polyunsaturated fatty acids and carotenoids [8].
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