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A 43-fold increase in keratinase production by Kocuria rosea was achieved in batch fermentation using response surface methodology. Factorial designs were used to select the components of a culture medium that showed a significant effect on keratinase production. An orthogonal-central composite experimental design was performed, with only two (feathers and magnesium) from nine initial compounds being further analyzed by response surface methodology. An optimum keratinase production of 14 886.9 U/mg was obtained with the following medium composition (per litre): NH4Cl, 0.3 g; NaCl, 0.3 g; K2HPO4, 3.2 g; KH2PO4, 4.0 g; MgSO4.6H2O, 0.5 g; yeast extract, 0.1 g; and finely milled feathers, 30 g. The medium was shaken at 400 r/min with an incubation period of 14 h at 40 degrees C.

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The effect of nutritional limitations, such as phosphorus and carbon, on the production of L-lysine by Corynebacterium glutarnicum was studied in continuous culture. We observed that phosphate-limited cultures at low growth rates were favourable to L-lysine production. L-Lysine was produced when a culture at low dilution rate (0.03 h-~) was established. A dilution rate of about 0.04 h -1 should be maintained in order to assure good productivity and an L-lysine yield of 0.53 g/ g. Under carbon-limiting conditions the maintenance energy and growth yield of 0.03 g / g . g -1. h -1 and 0.41 g/g, respectively, have been obtained. Under these limiting conditions the L-lysine production was not favoured even at lower dilution rates.

Appfled MicrobiologyBiotechnology © Springer-Verlag 1992 Summary. Corynebacterium glutamicum was observed to undergo several morphological and ultrastructural changes during a shift in dilution rate when grown in phosphate-limiting continuous culture. At 0.1 h-1 the cell culture appeared homogeneous and the average diameter of cells and the cell length was approximately 0.7 gm and 1-1.5 gm respectively. At 0.04h -1 there was essentially no change in these readings, but at this dilution rate there was a significant proportion of cells that measured three times the original length. At six residence times the elongated cells were increasing in number, but these changes occurred without diminishing the system's performance. Some changes in cell ultrastructure were observed during the shift in dilution rate. Thus, the presence of polyphosphate granules and of glycogen appeared in the cytoplasm of producing cells (0.04 h -l ) . We have confirmed by.mass spectrometry the absence of poly-~-hydroxybutyrate (PHB) in C. glutamicum.