Morphological responses of two <i>Aspergillus oryzae</i> strains to various metal ions at different concentrations

<i>Aspergillus</i> species take up various metal ions from environment. The morphology of <i>Aspergillus oryzae</i> strains can vary under the influence of various metal ions. Here, the effects of Ti⁴⁺, V³⁺, Sr²⁺, Ba²⁺, Al³⁺, Fe²⁺, Zn²⁺, Mn²⁺, Ca²⁺, and Cu²⁺ on morphological parameters of <i>A. oryzae</i> strains RIB40 and RIB143 were estimated. Colony diameter, conidiation, vesicle head size, and stipe width in both strains varied with concentration. Ti⁴⁺, Sr²⁺, Ba²⁺, Al³⁺, Fe²⁺, and Ca²⁺ affected conidiation in similar tendency between two strains. The effects of Ti⁴⁺, V³⁺, Sr²⁺, and Ba²⁺ on the morphology of <i>A. oryzae</i> are reported here for the first time. Induction of growth of both strains by 0.0001% Ti⁴⁺ may help the fermentation industry. Induction of conidiation in RIB40 by 0.001% Cu²⁺ confirmed previous results that low concentrations of Cu²⁺ promote the growth of <i>Aspergillus</i>. The most novel finding is that 0.001% Zn²⁺ increased the vesicle head size in RIB40; possible reasons are discussed.