A new screening method for pectin-depolymerizing microorganisms is des
cribed. The method is based on precipitation of non-hydrolyzed citrus
pectin with hexadecyltrimethylammonium bromide in a medium solidified
with a bacterial gelling gum. A substrate depolymerized by the secrete
d enzymes does not precipitate, and the positive strains thus show tra
nsparent areas around the colonies. The method was used to screen 300
yeast and yeast-like microorganisms belonging to 52 different genera.
The secretion of pectin-depolymerizing enzymes occurred with different
frequencies in 13 genera (69 positive strains of 207 tested), the low
est frequency being found in the genus Candida (13 positive out of 125
strains tested) and the highest frequency in the genera Aureobasidium
(4 of 6) Cryptococcus (29 of 38), Geonichum (4 of 9), Kluyveromyces (
5 of 5), Rhodosporidium (2 of 2), Leucosporidium (2 of 2), Trichosporo
n (3 of 6) and Ustilago (2 of 2). Strains giving the highest number of
harvested cells after growth on pectin in a liquid medium have been i
dentified.