The effects of high initial D-glucose and ammonium sulfate concentrations on the production of cephalosporin C by Cephalosporium acremonium (ATCC 14615)

The production of cephalosporin C (CPC) was achieved at high initial D- glucose and ammonium sulfate concentrations in growth medium by means of whole free cells of Cephalosporium acremonium (ATCC 14615) in cotton plugged shaker flasks. D-glucose and ammonium sulfate levels in fermentation broth were adjusted to 10-150 gL^-1 and 7.5-100 gL^-1, respectively, and CPC, microorganism, dissolved oxygen, D-glucose concentrations and pH were determined in the liquid samples. Maximum antibiotic concentration and specific product yield constantly increased with increasing glucose concentration although maximum microorganism yield and specific growth rate started to decrease after experiencing a maximum due to the inhibition effect of higher glucose concentrations. Nevertheless, specific growth rate started to increase again denoting the capability of microorganisms to alter cell metabolism against substrate inhibition which was impossible to explain by any inhibition model existing in the literature. Maximum product yield and specific production rate showed identical oscillatory trends against inhibiting glucose levels. With increasing ammonium sulfate concentration, specific growth rate, maximum CPC concentration and specific product yield showed similar trends as those of glucose case while specific production rate and antibiotic yield did not present an oscillatory behavior.