Production of pectic enzymes in yeasts

When grown in the appropriate medium, several yeast species produce pectina ses able to degrade pectic substances. It is mainly exocellular endopolygal acturonases that break pectins or pectate down by hydrolysis of alpha-1,4-g lycosidic linkages in a random way. Biochemical characterisation of these e nzymes has shown that they have an optimal pH in the acidic region and an o ptimal temperature between 40 and 55 degrees C. Their production by yeasts is a constitutive feature and is repressed by the glucose concentration and aeration. Pectic substances and their hydrolysis products are used as carb on sources by a limited number of yeasts and hence these enzymes must be in volved in the colonisation of different parts of plants, including fruits. The first yeast pectic enzyme (encoded by the PSE3 gene) was cloned from Ti chosporon penicillatum. Recently, a polygalacturonase-encoding gene from Sa ccharomyces cerevisiae has been cloned and overexpressed in several strains and the gene for an extracellualar endopolygalacturonase from Kluyveromyce s marxianus has also been described. Taking all the results together, the i dea is now emerging that this type of yeast enzyme could offer an alternati ve to fungal enzymes for industrial applications. (C) 1999 Federation of Eu ropean Microbiological Societies. published by Elsevier Science B.V. All ri ghts reserved.