Effects of Potassium Sorbate and Natamycin on Growth and Penicillic Acid Production by Aspergillus ochraceus

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Potassium sorbate at 500, 1000 and 1500 μg/ml delayed initiation of growth and sporulation by Aspergillus ochraceus 0L24 in yeast extract-sucrose (YES) broth at 15°C, 25°C and 35°C. At 25°C, sporulation and growth were more rapid. Potassium sorbate at 500 μg/ml resulted in an increase in mycelial weight, but at 1000 and 1500 μg/ml the mycelial mass was decreased. Potassium sorbate also reduced or prevented production of penicillic acid, especially at 15 and 35°C. Natamycin at 1, 10 and 20 μg/ml delayed initiation of growth and sporulation in YES broth. At 20 μg of natamycin/ml, mycelial growth was inhibited by 80 to 100% and penicillic acid production was completely inhibited. Growth and penicillic acid production on olive paste by A. ochraceus in the presence of potassium sorbate and natamycin showed that sorbate at 1500, 3000, and 6000 μg/g delayed growth and sporulation. Also, the extent of growth was greatly reduced by 3000 and 6000 μg of potassium sorbate/g. Penicillic acid production was reduced over the control at all the potassium sorbate levels. At 6000 μg of sorbate/g, no penicillic acid was detected after 21 d of incubation. Natamycin at 85, 175, and 350 μg/g delayed growth and sporulation by A. ochraceus on olive paste. Increasing levels of natamycin resulted in decreased growth. Production of penicillic acid was also decreased by natamycin, 350 μg of natamycin/g decreased penicillic acid production by 96%.