Biomass production enriched in intracellular methionine by a mutant of Saccharomyces cerevisiae
Albornoz, I.J.; Sánchez Crispin, J.A.; Moreno, R.
Acta Cientifica Venezolana 44(5): 307-311
1993
ISSN/ISBN: 0001-5504 PMID: 7483968 Document Number: 1317
According with FAO reported data-15 the methionine intracellular content in Saccharomyces cerevisiae is higher than another yeast. For increasing the yeast methionine internal concentration three S. cerevisiae mutant strains were chosen (M2, M4 y M9), obtained by ethionine (0.1 mg/ml) and norleucine (0.33 mg/ml) resistance by Gonzalez Miliani (personal communication). The resistance levels in culture were modified until selection of a mutant LF-M9 et-r, nor-r, which shows resistance to ethionine (6 mg/ml). Optimal conditions for growth were fixed on shaked flasks and later mutationally experiments were conducted with nitrosoguanidine (0.5 mg/ml) and U.V. light (240 nm in 9 minutes d = 32 cm). Mutants obtained were selected on plate replicates and microbiological test, using Escherichia coli 303 (Wollman, met-b-1-str-r) as the indicating strain. The mutant LF-M9 treo-et-rnor-r, shows an intracellular methionine content 3 times higher that the control strain DSM D273-10B and 1.8 times higher than parental strain M9. The mutant was cultivated on different agroindustrial wastes and the optimal growth was reached in acid hydrolysates of cassava foliage. Fermentations in 1 litre stirred fermenter were accomplished using these medium and the biomass obtained was 6.3 g of the yeast (dry weight) enriched in methionine per litre of extract.
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