Lysine Production byS-(β-Aminoethyl)-l-cysteine Resistant Mutants ofCandida pellicutosa

S-(β-Aminoethyl)-l-cysteine (SAEC), a sulfur analog of l-lysine, significantly inhibited the growth of wild-type strains of Candida species. The growth inhibition of C. pelliculosa depended on SAEC concentrations, but l-Iysine and l-α-aminoadipate restored growth effectively. SAEC-resistant mutants were induced from the wild-type strain of C. pelliculosa by ultraviolet irradiation and N-methyl-N′-nitro-N-nitrosoguanidine treatment. Almost all resistant mutants excreted some l-lysine into the medium. Lysine excretion increased after repeated mutations. The mutant strain SR-V–1263 extracellularly produced about 2 mg/ml of l-lysine after shaking culture for 96 hr. The effect of various factors on lysine accumulation was investigated with strain SR-V–1263. The concentration of extracellular lysine reached a maximum (3.2 mg/ml) in medium containing 2% polypeptone under the experimental conditions.