BIOTECHNOLOGY LETTERS Volmne 18 No.6 (June 1996) p.701-706 Received as revised 15th April. CEPHALOSPORIN-C PRODUCTION, MORPHOLOGY AND ALTERNATIVE RESPIRATION OF ACREMONIUM CHR YSOGENUM IN GLUCOSE-LIMITED CHEMOSTAT Levente Karaffa*, Erzs6bet S~indor, J6zsef Kozma and Attila Szentirmai Dept. Microbiology and Biotechnology, Kossuth University of Sciences, P.O.Box. 63, Debrecen, H-4010, Hungary Summary: In this paper, the connection between morphology, cephalosporin-C production and alternative respiration ofAcremonmm chlysogemtm is examined. As demonstrated by chemostat experiments, the ratio of the filamentous and the yeast-like forms depended on the growth rate. The yeast-like form, but not the filamentous tbrm exhibited cyanide-resistant alternative respiration. As a consequence, the yeast-like form was regarded to be more suitable for antibiotic overproduction. Introduction: The filamentous mould Acremonmm chrysogemml is the main producer of the cephalosporin-C antibiotic. The fungus shows different morphological forms in submerged cultures: hyphae, conidia, metabolically inactive arthrospores and wide, swollen hyphae fragments named yeast-like forms (Bartoshevich et al, 1990). While the wild strains form conidia predominantly, the strains with high and medium cephalosporin-C productivity tend to differentiate into yeast-like form (Bartoshevich et al, 1985). That the maximum rate of cephalosporin-C production coincides with the conversion of slender hyphal filaments to swollen hyphal fragments (Huber and Nash, 1971). Furthermore, it has also been demonstrated, that the antibiotic-producing potential of the yeast-like form is considerably higher than that of any other cell types with different morphology and they are appearing at the second half of fermentation (Bartoshevich et al, 1990). Previous data indicate, that growth rate might be a crucial factor in the changes of morphology and antibiotic production. In the case of another 13-1actam producer mould, Penic'illium chlysogenmn, it was shown, that the steady-state penicillin concentration (unit m1-1) rose as the reciprocal of the specific growth rate (Pirt and Righelato, 1967), while the specific penicillin production rate (unit mgl,h l) was independent of it. 701