EFFECT OF WATER ACTIVITY ON PRODUCTION OF BETA-LACTAM ANTIBIOTICS BY STREPTOMYCES-CLAVULIGERUS IN SUBMERGED CULTURE

The amount of available water in the environment of micro-organisms, d efined as water activity (a(w)), has been shown to affect growth, resp iration, enzyme synthesis, sporulation and other physiological functio ns. The aim of this study was to examine the impact of a(w) on product ion/excretion of a secondary metabolite. For this purpose, the product ion of beta-lactam antibiotics and biomass of Streptomyces clavuligeru s was studied in relation to the a(w)-depressing agents glucose, sorbi tol and NaCl. These were chosen because NaCl and sorbitol are often us ed to depress a(w) and glucose was not thought to be taken up by S. cl avuligerus. The filamentous bacterium S. clavuligerus NRRL, 3585 (ATCC 27064) is a prokaryotic producer of penicillin N, cephalosporins incl uding cephamycin C and clavulanic acid. Under water stress conditions, a greater effect upon antibiotic biosynthesis than upon growth was co nsistently observed. When a(w) was decreased to below 0.997, antibioti c production began to decrease. For growth, inhibition was much more g radual and did not become intensive until an a(w) of 0.990 was reached .