Effect of aeration on production of biofungicide using Streptomyces hygroscopicus

Apple fruit diseases caused by phytopathogenic species of the genus Alternaria have become current in recent years in Serbia as well as in other parts of the world. Due to the fact that pesticides have a number of side effects on the environment and human health, scientists around the world are concerned with finding alternative ways to control this important food. Usage of microorganisms, optimization of the medium and process conditions for their cultivation and production of biofungicides are the actual research direction. The effect of aeration on biofungicide production by Streptomyces hygroscopicus was studied in a 3 l stirred tank bioreactor using a previously optimized cultivation medium with glycerol as a carbon source. Aeration rates of 0.5, 1.0, and 1.5 vvm with constant agita­tion speed of 100 rpm were studied. It was found that the greatest production of antifungal metabolites effective against two Alternaria alternata isolates occurred with an aeration of 1.5 vvm and an agitation speed of 100 rpm. Statistical analysis showed that the largest inhi­bition zone diameters of A. alternata KA10 (78 mm) and T1Jg3 (78.67 mm) mycelial growth were achieved under the indicated conditions in 96 h of cultivation.