Identification and potential biotechnological application of yeast isolates in the UNESCO-MIRCEN biotechnological yeast culture collection of the University of the Free State

[摘要] English: As the initiative for establishing a yeast culture collection began in the early 1980's in the department of Microbial, Biochemical and Food Biotechnology, research pertaining to the identification of isolates became the main focus. Yeasts such as Candida shehatae and Pichia stipitis claimed potential applications in the fermentation industry and received the most research attention. This research area and others reflected the potential of the culture collection as one of the sources of microbial diversity. As a result, this granted this culture collection a Microbial Resources Centre by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1996. Isolation, preservation, identification and determination of taxanomic affinities of yeasts are some of the important aspects of this culture collection in addition to others such as bioprospecting and elucidation of biotechnological applications of strains. As a general practice, these isolates must be identified reliably and rapidly using techniques such as polymerase chain reaction (PCR) and sequencing of the ribosomal DNA. Polymerase chain reaction (PCR) and sequencing of the ribosomal DNA was mainly used in this study to identify isolates present in the UNESCO-MIRCEN Biotechnological Yeast Culture Collection. Ribosomal DNA was amplified and sequenced, followed by analysis of sequence data that was searched against available sequences on National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). In the case of new species, verification of novelty was performed by sequencing the internal transcribed spacers and doing phylogenetic analysis based on multigenic approach. New species were assigned to their phylogenetic groups and described using standardized traditional techniques. It was apparent from this study that using molecular identification methods, the number of identified ascomycetes and basidiomycetes as well as yeast-like taxa, with possible applications in the industrial, clinical, pharmaceutical, environmental and agricultural settings can be rapidly identified in great numbers. In this study, three basidiomycete strains representing new species in the genus Cryptococcus, with potential applications in cyanide bioremediation, were identified and described. These strains represent a new species which form part of a small group of yeasts (including Cryptococcus humicolus strain) with the ability to utilize inorganic cyanide as sole carbon and nitrogen source. Some of the applications and importance of strains representing known ascomycetes, basidiomycetes and yeast-like taxa are also highlighted here. Not only was the identification of isolates achieved in this study, but also full description of new yeasts present in the UNESCO-MIRCEN Biotechnological Yeast Culture Collection with possible applications in bioremediation. However, the applications of species such as Trichosporon africanensis sp. nov. will be elucidated elsewhere.

[发布机构] University of the Free State