| The yeasts in a Riesling grape must from the Niagara grape-growing region of Ontario were identified and enumerated. Candida stellata was the most common yeast, making up 32% of the isolates. Hanseniaspora uvarum was the second most common yeast, 30% of isolates. Aureobasidium pullulans, Candida diversa, Pichia kluyveri and Rhodotorula glutinus made up most of the remainder of the isolates. Over the course of a natural fermentation, the population of H. uvarum reached approximately 10;The gene for pyruvate decarboxylase (PDC), a key enzyme in the biosynthetic pathway of higher alcohols, was isolated from S. cerevisiae and sequenced. This gene was used as a probe to screen wild wine yeasts for PDC genes. A gene was detected in H. uvarum and was isolated and sequenced. In addition, a PDC gene was isolated and sequenced from the yeast Kluyveromyces marxianus. The nucleotide sequences of these three genes were similar, approximately 80% identical between all three. The amino acid sequences encoded in these genes were also similar, greater than 70% of amino acids were identical and another 10% were conserved replacements. |
