Abstract

Aspergillus niger isolated from some common medicinal and herbal plants used in Egypt, was found to be producer for ochratoxin A. This research investigate the biological control of ochratoxin A production by A. niger, using some bacterial isolates belonging to true bacteria (Bacillus pumilus), Lactic acid bacteria (Lactobacillus acidophilus, Lactobacillus bulgaricus and Lactobacillus plantarum) and Actinomycete isolates numbered 1, 2, 3, 4, 5, 6 and 7, that proved variable antagonistic activity against A. niger. The Actinomycete isolate number 3 was the most effective and identified as Streptomyces noursei. The optimal conditions for antifungal production by S. noursei were performed on starch nitrate medium at pH 7 after 7 days of growth at 30°C. The active antifungal substance(s) were separated, semi purified and characterized as a protein substance. The semi purified substance inhibited spores formation, thinned the conidiophores and deformed both strigmata and conidial heads.

Key words: Aspergillus niger, Streptomyces noursei, ochratoxin A.