Isolation and identification of phytase-active yeasts from sourdoughs

Abstract

Identification of high phytase-active yeasts is necessary in order to find prominent candidates for the production of wholemeal bread with high content of bioavailable minerals. Tested yeasts were isolated from Danish and Lithuanian sourdoughs, since high phytase-active yeasts adapted to grow in sourdough matrix would be a good choice for bread industry. Isolated species were; Saccharomyces cerevisiae, Pichia kudriavzevii, Pichia occidentalis, Candida humilis and Kazachstania exigua. Studies of phytase-positive isolates were carried out at conditions optimal for leavening of bread dough (pH 5.5 and 30 °C). All the tested yeasts isolated from sourdoughs exhibited phytase activities. The most prominent isolates for extracellular phytase production were found to be S. cerevisiae L1.12 with a specific extracellular activity of 10.6 U/1010 CFU, followed by S. cerevisiae L6.06 with a specific extracellular activity of 8.2 U/1010 CFU. Some other isolates of S. cerevisiae, one of C. humilis, and one of P. kudriavzevii also had high specific extracellular activities of c. 4–7 U/1010 CFU. These isolates may be potential candidates for improving mineral bioavailability in whole grain bread.