In a survey of the microbial quality of raw materials used in fruit juice processing, yeast counts in fruit concentrates and pulps were found to range from 51to 2?9610 3 cfu g 71. Ascomycetous yeasts were represented by 76% of the isolates while 24% were basidiomycetes.The identi¢cation of strains isolated by the simpli¢ed identi¢cation system (SIM) revealed19 yeast species representing12 genera.The most frequently isolated yeasts belonged to the genera Saccharomyces, Pichia, Cryptococcus, Kluyveromyces and Candida. Fatty acid yeast composition allowed the separation of contaminating yeasts into one of three major groups. Group I included yeasts without linoleic (C 18:2) and linolenic (C 18:3) fatty acids such as Saccharomyces cerevisiae. Group II comprised yeasts without C 18:3 fatty acid like Zygosaccharomyces rouxii and Torulaspora delbrueckii, and group III included yeasts with C 18:2 and C 18:3 acids that belong, among others, to one of the following yeast genera: Pichia, Candida, Kluyveromyces or Cryptococcus. Species-speci¢c PCR primers were used for the rapid detection and identi¢cation of the most dangerous species a¡ecting fruit concentrate stability. The simpli¢ed protocol used consisted of PCR-ampli¢cation of conserved tracts in the ITS region of the rDNA unit, thus enabling the detection of potentially dangerous £ora such as Zygosaccharomyces species andT. delbrueckii in contaminated fruit concentrates. Results from PCR-typing were in full agreement with the fatty acid compositions of these species. The grouping of contaminant yeasts into three main groups showed that fatty acid composition may be used to di¡erentiate yeasts according to their technological signi¢cance.Yeasts isolated in this work as being most dangerous to product stability belong to either group II (Z. rouxii and T. delbrueckii) or group I (Saccharomyces spp.). Group III was comprised of several species regarded as indicators of de¢ciencies in 'good manufacturing practices'. Thus, each of the groups delineated may be considered to be a zymological indicator of technological signi¢cance. The conjugation of fatty acid pro¢les with PCR-typing methods may be used as a rapid detection system for contaminant yeasts. The fatty acid pro¢les provide a preliminary identi¢cation of yeasts potentially dangerous to product stability present

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Two new species of the ascosporic yeast genus Metschnikowia were isolated from nectaries and associated muscoid flies of flowers from the common milkweed (Asclepias syriaca) in North America, and are described as Metschnikowia vanudenii [type strain=PYCC 4650. As with the previously described Metschnikowia gruessii, M. vanudenii has vegetative cells with an 'aeroplane' or cross-like configuration, produces ovoid chlamydospores and forms ellipsoidopedunculate asci with two acicular ascospores. Metschnikowia lachancei is distinguished from other Metschnikowia species by formation of club-shaped asci with 1-2 thick clavate ascospores. The phylogenetic positions of the proposed new species within Metschnikowia were determined from sequence analysis of the D1/D2 domain of 26S rDNA. The new species show low nuclear DNA relatedness with neighbouring taxa.

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The taxonomy of the yeast genus Metschnikowia has undergone profound changes over the past century. Major developments, from the capacity to obtain pure cultures of parasitic species to progress associated with the extensive use of molecular biology tools in yeast systematics, are briefly reviewed. Results from past work and new data are combined to evaluate evolutionary relationships and clarify the classification of both terrestrial and aquatic species. Recent physiological studies, including the utilization of non-conventional carbon and nitrogen sources, and characteristics like lipolytic activity and maximum temperatures for growth, are presented. The assessment of the genetic diversity within the genus by restriction analysis of the mitochondrial DNA and by the production of specific DNA probes has been explored. The results indicate the potential application of the latter in rapid identification procedures.

To test whether DNA probes derived from ribosomal DNA spacer sequences are suitable for rapid and species-specific yeast identification, a pilot study was undertaken. A 7.7 kb entire ribosomal DNA unit of the type strain of Metschnikowia reukaufii was isolated, cloned and mapped. A 0.65 kb BamHI-HpaI fragment containing non-transcribed spacer sequences was amplified and selected for testing as a 32P hybridization probe with total DNA from the type strains of M. reukaufii, M. pulcherrima, M. lunata, M. bicuspidata, M. australis, M. zobellii, M. krissii, five other strains identified as M. reukaufii and strains of Schizosaccharomyces pombe, Hansenula canadensis, Saccharomyces cerevisiae and Yarrowia lipolytica. The probe hybridized exclusively with DNA from the type strain and four other strains of M. reukaufii. DNA from one strain labelled M. reukaufii did not hybridize with the probe. Subsequent % G + C comparison and DNA-DNA reassociation with the type strain revealed that the non-hybridizing strain does not belong to the species M. reukaufii.

A new yeast species of basidiomycetous affinity Kurtzmanomyces tardus was isolated from contaminated demineralized water. It differs from K. nectairii, the only other Kurtzmanomyces species so far described, in its carbon assimilation pattern and low DNA-DNA homology (2.3% +/- 2.1).

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