A volume of 400 L culture was inoculated into 100 mL of screening agar (0.67% yeast nitrogen base without amino acids and ammonium sulphate,2% D (+)-glucose anhydrate, 1 mLeach of 0.03 mg/mL of adenine (hemisulphate salt), 0.03 mg/mL of L-tryptophan, 0.03 mg/mL of L-leucine, 0.03 mg/mL of L-histidine and 1.5% bacteriological agar, pH 5.6