Identification of a yeast isolated from glutinous rice tapai via morphological and molecular analysis

Abstract

Yeasts are facultative unicellular fungi of the phylum Ascomycota and Basidiomycota that are classified in the Kingdom Fungi. This group of microorganisms is quantitatively and economically important for human consumption, and indeed has many advantages as hosts for recombinant protein expression. The purpose of this research is to identify a yeast species, Yeast UKM-B, isolated from a local traditional food, the glutinous rice tapaifros Bangi. The purpose of this research is achieved via two approaches; morphological and molecular analyses. In the morphological analysis, characterization of the yeast was done through macroscopic observation on growth media, and observation under light microscope and Scanning Electron Microscope (SEM). The yeast UKM-B formed smoot cream coloured colonies on Yeast Extract Peptone Dextrose agar after 16 hours of incubation at 3(fC. Observation under light microscope and SEM showed that UKM-B cells are apiculate-shaped with bipolar budding structures. The diameter of the yeast cells are between 2-3 um and the cells are 3-6 pm long. The molecular analysis was done PCR, amplifying two specific regions ofrDNA, the DUD2 domain of26S rDNA (614bpi size) and 18S rDNA region (1785bp in size). These PCR products were then cloned sequenced and analysed. Phylogenetic analysis was used to analyze the nucleotide data sequence for identification of the isolated yeast strain. Neighbour-Joining (NJ) trees built based on the D11D2 domain of26S and 18S rDNA region showed that the UKM-B yeast isolate is similar to Hanseniaspora guilliermondii, supported by the bootstrap probabilility of 99%. Sequence analysis based on Internal Transcribe Spacer (ITS) rDNA also showed 99% bootstrap probability to H. guilliermondii, thus indicating that the UKM-B yeast isolate is H. guilliermondii.