with fixed concentration of glucose resulting in a decreasing C/N ratio from 200 to 2, and (ii) varying the glucose concentration from 4.5 to 35 g/l with a concentration of (NH4)2SO4 fixed at 0.1 g/l to yield a C/N molar ratio varying from 100 to 800. The flasks cultures were then incubated in an incubator shaker at 200 rpm and 30°C.