Optimal substrate composition (C, N, and trace metals) for liquid culture of Akanthomyces attenuatus JEF 147 isolate

Akanthomyces attenuatus JEF 147 is a promising entomopathogenic fungus with notable acaricidal activity against spider mites. Controlled submerged cultivation with defined nutritional sources enables efficient mycelial and blastospore production while revealing vital features of fungal metabolism and adaptability. This study aimed to optimize liquid culture conditions for the production of A. attenuatus JEF 147, focusing on various carbon sources (fructose, glucose, maltose, sucrose, and potato starch), nitrogen sources (peptone, tryptone and yeast extract), and trace metals, (copper(II) sulfate, iron(II) sulfate, magnesium sulfate, manganese(II) sulfate, and zinc sulfate). Among the carbon sources tested, potato starch yielded the blastospores count 32 × 10⁷ after 7 days of culture. The nitrogen source, tryptone, produced the highest number of blastospores, up to 42 × 10⁷, representing a 31.3% increase over potato starch. Meanwhile, optimizing the carbon-to-nitrogen (C:N) ratio to 0.5:1 further increased blastospores production to 67 × 10⁷, a 109.4% increase compared with potato starch and a 59.5% over tryptone alone. Zinc sulfate (ZnSO₄) as a trace metal resulted in a blastospores count of 37 × 10⁷, indicating a 11.9% decrease compared with tryptone and a 44.8% decrease compared with the 0.5:1 C:N condition. These results suggest that a C:N ratio of 0.5:1 maximizes blastospore production; furthermore, the addition of trace metals enhances the size and morphology of A. attenuatus blastospores but reduces total blastospore production. This study highlights the importance of optimizing culture conditions for the production of A. attenuatus JEF 147 spores, benefiting both research and industrial applications.