Screening of yeast and fungal strains for lipolytic potential and determination of some biochemical properties of microbial lipases

Abstract

For the screening of yeast and fungal strains with lipolytic potential from Chem. Pharm. Res. Institute Culture Collection, we employed a sensitive agar plate method, using a suitable medium supplemented with CaCl 2 and Tween 80. By determination of the opacity areas developed around the colonies of lipolytic microorganisms consisting of calcium soaps, the good lipase producing strains were selected. Candida lipolytica CPhI-50 and Hansenula anomala CPhI-23 from the yeast strains and Rhizopus nigricans CPhI-Rn-8, Aspergillus oryzae CPhI-20-9 and Aspergillus niger CPhI-8- N-9 from the fungal strains were good lipase producers. When these strains were submerged cultivated on modified GYP medium, Candida lipolytica CPhI-50 and Aspergillus oryzae CPhI-20-9 had the highest yield of lipase in the medium at the end of the bioprocess. Also, we determined the pH dependence of lipase activities from the good producing strains, and we found that these enzymes exhibited various pH sensitivities, dividing them into three groups: I. lipase active at pH 5.0–6.5 produced by Candida lipolytica CPhI-50. II. lipase active at pH 6.5–7.5 produced by Hansenula anomala CPhI-23 and Rhizopus nigricans CPhI-Rn-8. III. lipase active at pH 7.5–8.5 produced by Aspergillus oryzae CPhI-20-9 and Aspergillus niger CPM-8- N-9. By screening at 50 °C and pH 8.5 we identified a thermostable semialkali-tolerant lipase produced by Aspergillus niger CPhI-8- N-9).