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Appl Environ Microbiol. 1981 May; 41(5): 1088-1096

Derivation of Aromatic Amino Acid Mutants from a Methanol-Utilizing Yeast, Hansenula polymorpha

Emmanuel O. Denenu and Arnold L. Demain

¹ Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 0213

ABSTRACT

Three classes of mutants, deregulated to enhance the flow of aromatic intermediates through the tryptophan biosynthetic branch, were obtained. 5-Fluorotryptophan, an antimetabolite of tryptophan, was employed to obtain one class of deregulated mutants. By sequential resistance development, three resistant mutants were isolated. Hansenula polymorpha strains showed greater sensitivity to 5-fluorotryptophan when growing on methanol than when growing on glucose. Yeast extract stimulated the production of total indole metabolites (indoles) by wild-type and mutant strains, with each 5-fluorotryptophan mutant producing higher amounts of these metabolites than its predecessor. Two other mutant classes were isolated: (i) a mutant resistant to anthranilate (an inhibitory intermediate in the tryptophan biosynthetic branch) and (ii) a phenylalanine-plus-tyrosine bradytroph. Each of these produced a higher extracellular titer of total indoles than its immediate parent. With respect to the overproduction of indoles, resistance to 5-fluorotryptophan was a more useful selection method than were anthranilate resistance and phenylalanine-plus-tyrosine bradytrophy.

Present address: Medical Research Division, Lederle Laboratories, Pearl River, NY 10965.