Lysine production by S-(.BETA.-aminoethyl)-L-cysteine resistant mutants of Candida pelliculosa.

Abstract

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 de-pended on SAEC concentrations, but L-lysine 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 2mg/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.