Molecular Techniques for Yeast Identification in Food Processing

Sonja Smole Možina, Peter Raspor

Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia

Article history:
Received September 30, 1996
Accepted December 18, 1996

Key words:
yeasts, identification, classification, molecular methods, food processing

Summary:
Yeasts are crucial agents in many important natural and industrial bioprocesses as well as in spoilage of foods and in some diseases in humans and animals. Quick and reliable methods for yeast identification and classification are highly appreciated. Classical methods include morphological and physiological-biochemical tests. They are time and material consuming; reliability and distinctive capacity of closely related isolates are low. Besides phenotypic characterization many molecular biology analyses of yeast nucleic acids have recently been developed. They can give stable and unique electrophoretic profiles independently of the microbial cultivation conditions. In this paper the application of nuclear and mitochondrial DNA analyses for identification of food-borne yeasts is reviewed - electrophoretic karyotyping, study of the restriction fragment length polymorphism (RFLP) of mtDNA, and two techniques based on PCR amplification of yeast DNA: the amplification with nonspecific primers (AP-PCR, arbitrarily primed PCR, RAPD, random amplified polymorphic DNA analysis) and PCR ribolyping - restriction analysis of amplified ribosomal RNA genes of tested yeasts. The advantages and limitations of the application of molecular methods based on DNA analysis for yeast characterization in research and routine industrial laboratories are discussed. Generally, nucleic acid-based assays offer sensitivity and specificity that could not be achieved by conventional identification methods. However, the described methods still rely on cultural enrichment and DNA isolation. In perspective, specific DNA probes/primers and direct sequencing of PCR amplified DNA fragments will likely replace the currently used techniques as a uniform method for identification of yeasts in general.