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Title: SEXUALLY COMPATIBLE, NATURALLY OCCURRING STRAINS OF TRICHODERMA REESEI CAPABLE OF ASSIMILATING SUCROSE AND NITRATE

Author
item LIECKFELDT, ELKE - BERLIN, GERMANY
item KULLNIG, CORNELIA - WIEN AUSTRIA
item Samuels, Gary
item KUBICEK, CHRISTIAN - WIEN AUSTRIA

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fungi are useful in the production of industrial enzymes because they grow rapidly and can be screened for strains that produce high levels of the desired enzyme. Such a fungus, Trichoderma reesei, produces cellulase that breaks down cellulose into simple sugars so that waste products such as sugarcane bagasse and pulp paper residues can be fed to animals. The commonly used fungal strain reproduces itself without undergoing sex but has been found to be the same as strains that do reproduce sexually. In addition the most commonly used strain will not grow on certain common chemical substrates that are used to grow fungi in large quantities. Additional strains of this fungus have been identified and characterized for cellulase production, sexual production, and substrate utilization. Although no producing cellulase in such large quantities, these new strains have been found to undergo sexual reproduction and are able to grow on the common chemical substrates. By modifying and manipulating these newly characterized strains, it may be possible to develop a better cellulase producing strain of this fungus.

Technical Abstract: The hyphomycete Trichoderma reesei, well known for its commercial production of cellulases and hemicellulases, is unique among industrial fungi because it is known only from a single, sucrose-and nitrate non-utilizing isolate. Here we report for the first time the isolation of three further isolates of T. reesei from soil in French Guiana and Brazil. The identification of the strains with T. reesei was confirmed by analaysis of the internal transcribed spacer regions 1 and 2 of the nuclear rDNA cluster and by their ability to produce the teleomorph of T. reesei, Hypocrea jecorina, when mated with appropriate strains. All three isolates exhibited cellulolytic activities in shake flasks, albeit final titers were somewhat lower than that of the original, QM6a. In contrast to othe original isolate, however, they grew on sucrose as sole carbon source and on nitrate as sole nitrogen source. Comparison of the original isolate QM 6a and the three new isolates in a more detailed analysis showed that the lack of utilization of sucrose and nitrate is due to a lack of the uptake system for sucrose and of nitrite reductase activity, respectively, in isolate AM 6a. All T. reesei isolates contain intracellular but not extracellular invertase.The possibility to use these findings in the biotechnological improvement of T. reesei is discussed.