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Modulation of water activity on fungicide effect on Aspergillus niger growth in Sabouraud dextrose agar medium *
Author(s) -
Ni X.,
Streett D.A.
Publication year - 2005
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.2005.01761.x
Subject(s) - aspergillus niger , fungicide , agar , potato dextrose agar , food science , itraconazole , biology , amphotericin b , spore , agar plate , horticulture , chemistry , botany , microbiology and biotechnology , antifungal , bacteria , genetics
Aims: To examine whether water activity ( a w ) in combination with low concentration of fungicides can be used to effectively control Aspergillus niger van Tieghem growth in cultural medium, the Sabouraud dextrose agar (SDA). The data would be used as baseline information for reducing A. niger contamination in insect artificial diets. Methods and Results: Aspergillus niger was isolated from an insect artificial diet. Four concentration levels (i.e. 0, 1, 10 and 20 μ mol) of two fungicides (i.e. amphotericin B and itraconazole) were tested against A. niger under four a w levels (i.e. 0·994, 0·961, 0·921 and 0·859) adjusted by including 0, 12·5, 25 and 38% of glycerol in the medium mixture. Aspergillus niger growth was significantly reduced at low fungicide concentration (1 μ mol), and at reduced a w . The spore germination was prevented with either higher fungicide concentration (>10 μ mol), or low a w in the medium ( a w < 0·921). The two ecological determinants (fungicides and a w ) showed a significant impact on A. niger survival in the medium ( P < 0·0001). Itraconazole is more effective than amphotericin B in controlling A. niger contamination in the agar medium. Conclusion: Adjustment of a w (with 12·5% of glycerol) in combination with 1 μ mol of itraconazole can effectively prevent A. niger growth in the SDA cultural medium. Significance and Impact of the Study: Aspergillus niger contaminations have frequently affected the quality of insects produced from mass rearing facilities. Low a w in combination with low fungicide concentration has the potential to become one of the most cost‐effective management strategies to prevent A. niger contamination in insect artificial diets. The effect of fungicides and low a w in artificial diets on insect biology needs to be further examined.