Wastewater treatment systems harbor specific and diverse yeast communities

Yeasts, as a group of single-celled fungi, are widely distributed in nature and play important roles in biotechnological applications. However, how the types of wastewater and the treatment processes influence yeast populations is not clear. In this study, both cultivation and culture-independent methods were used to investigate the distribution and diversity of yeasts in three typical full-scale plants processing biopharmaceutical, papermaking and municipal wastewater. Cultivable yeasts were very abundant ranging from 10(2) to 10(5) cfu g(-1) sludge, and highly diverse with 48 taxons belonging to 21 different genera, thus exceeding the yeast richness reported for marine and sugar-rich soil habitats. Genera Rhodotorula, Candida, Trichosporon, Pichia and some unidentified Ascomycetes were the most frequent populations cultivated. However, the compositions of yeast community structures in the plants were dissimilar and were shaped primarily by the type of wastewater treated but also by processing conditions. Culturing yeasts is a powerful way to complement culture-independent approaches to study their diversity, since significant more yeast species, especially quite a few possible novel species were recorded and isolated by cultivation method. (C) 2011 Elsevier B.V. All rights reserved.