Isolation, Characterization, and Lipase Production of Lipolytic Yeasts Isolated from Mt. Makiling Forest Reserve, Philippines

Abstract

Mt. Makiling Forest Reserve (MMFR) is an untapped source of microorganisms that have great potential for the production of industrially important enzymes like lipases. In this study, yeasts were isolated from various forest materials by serial dilution and plating methods. Out of the 185 isolated putative yeasts, 54 showed lipolytic activity in the plate assay using a lipase production medium. These yeasts were secondarily screened by a liquid assay using basal mineral medium (BMM) with 2.0% (v/v) olive oil. Top putative yeasts based on measured cell density after incubation in BMM were molecularly identified as Candida duobushaemulonis, C. jaroonii, C. quercuum, Vanrija humicola, and Wickerhamomyces sp. by ITS-5.8S sequencing. Further screening of the identified lipolytic yeasts using non-enriched (with 0.5% peptone) and enriched (with 5.0% peptone) medium revealed that Wickerhamomyces sp. SS-2 was the top lipase-producing yeast, with the highest measured lipolytic activity of 0.62 U/mL after 48 h of enriched media fermentation. The performance of the select yeast was then tested on different fermentation mediums with different compositions. Medium composed of 0.2% yeast extract, 0.05% KH2PO4, 0.05% K2HPO4, 0.05% MgSO4.H2O, 0.01% CaCl2, 0.01% NaCl, and 1.0% (v/v) olive oil, at pH 6.0, was found best for the select yeast's lipase productivity. Furthermore, olive oil as the main plant oil and the use of a 48h-old slant seed culture were found best for the lipase production of the select yeast Wickerhamomyces sp. SS-2.