Keywords
Abstract
Expanding the planting of grape varieties with complex resistance requires the problem of reducing the content of
pectin substances in grape must to be solved. One of the ways to solve this problem is the use of pectolytic enzyme preparations obtained from mold fungi Aspergillus spp. and Trichoderma spp. If purification is insufficient, by-product enzymes can have a negative effect on base wines and cause the appearance of off-tones in the aroma and/or a tendency to form cloudiness. An alternative for obtaining pectinases from mold fungi can be yeast-producers of the species Kluyveromyces marxianus, with no side enzymes secreting. This paper presents the selection results by the method of improving selection of K. marxianus strain for the ability to produce endopolygalacturonase in grape must. It was shown that depending on the cultivation conditions, the activity of produced enzyme changes significantly. Regardless of the strain, when cultivated on grape must, the activity of the resulting enzyme was decreasing by 4.0–28.5 % compared to the synthetic YPD medium. The strain K. marxianus III-358 was elected, as secreted the largest amount of enzyme when cultivated on grape must, and was subjected to improving selection. As a result of selection work, 10 isolates with enzymatic activity from 1495.6 to 1521.5 units were chosen, which exceeded the activity of original strain by 19–21 %. The decrease in the activity of endopolygalacturonases of selected isolates on substrates with pH 3.0 and 3.5 (compared to pH 5.0) was 72.4–75.8 % and 58.6–62.0 %, respectively. Based on the research results, the yeast isolate K. marxianus III-358-60 was selected, which was recognized as promising and was deposited in the Сollection Microorganisms of Winemaking “Magarach”
with the number III-407.