Inhibition of Aspergillus oryzae Mycelium Growth and Conidium Production by Irradiation with Light at Different
Shangfei Lin1,2, Haokuan Qin1, Xiaolin Zhang3
1Institute of Future Lighting, Academy for Engineering and Technology, Fudan Universitygrid.8547.e, Shanghai, China.
Abstract:
Aspergillus oryzae is a safe filamentous fungus widely used in the food, medicine, and feed industries, but there is currently not enough research on the light response of A. oryzae. In this study, 12 different light conditions were set and A. oryzae GDMCC 3.31 was continuously irradiated for 72 h to investigate the effect of light on mycelial growth and conidium production. Specifically, each light condition was the combination of one light wavelength (475, 520, or 630 nm) and one light intensity (20, 40, 60, or 80 μmol photon m-2 s-1). The results show that mycelium growth was inhibited significantly by green light (wavelength of 520 nm and intensities of 20 and 60 μmol photon m-2 s-1) and blue light (wavelength of 475 nm and intensity of 80 μmol photon m-2 s-1). The production of conidia was suppressed only by blue light (wavelength of 475 nm and intensities of 40, 60, and 80 μmol photon m-2 s-1), and those levels of inhibition increased when the intensity of blue light increased. When the strain was irradiated by blue light (80 μmol photon m-2 s-1), the number of conidia was 57.4% less than that of the darkness group. However, within our set range of light intensities, A. oryzae GDMCC 3.31 was insensitive to red light (wavelength of 630 nm) in terms of mycelium growth and conidium production. Moreover, interaction effects between light wavelength and intensity were found to exist in terms of colony diameter and the number of conidia. This research investigated the light response of A. oryzae, which may provide a new method to regulate mixed strains in fermented foods by light. IMPORTANCE Studies on the monochromatic light response of Aspergillus nidulans and Neurospora crassa have gone deep into the molecular mechanism. However, research methods for the light response of A. oryzae remain in the use of white light sources. In this study, we first demonstrated that A. oryzae GDMCC 3.31 was sensitive to light wavelength and intensity. We have observed that blue light inhibited its growth and sporulation and the inhibitory effect increased with intensity. This research not only adds new content to the study of the photoreaction of Aspergillus but also brings new possibilities for the use of light to regulate mixed strains and ultimately improve the flavor quality of fermented foods.
Insights
Blue light inhibits Aspergillus oryzae growth and conidia production, with effects intensifying at higher levels. Red light showed no significant impact on this fungus within tested parameters.
Area of Science:
- Microbiology
- Mycology
- Food Science
Background:
- Aspergillus oryzae is a fungus vital to food, medicine, and feed industries.
- Limited research exists on the specific light responses of A. oryzae.
- Existing studies on light response in related fungi like Aspergillus nidulans and Neurospora crassa lack detailed molecular insights for A. oryzae.
Purpose of the Study:
- To investigate the effect of different light wavelengths and intensities on the mycelial growth and conidium production of Aspergillus oryzae GDMCC 3.31.
- To determine the sensitivity of A. oryzae to specific light conditions, including blue, green, and red light at varying intensities.
- To explore potential applications of light in regulating fungal growth for industrial purposes, such as in fermented foods.
Main Methods:
- Culturing A. oryzae GDMCC 3.31 under 12 distinct light conditions for 72 hours.
- Each condition involved specific combinations of light wavelengths (475 nm, 520 nm, 630 nm) and intensities (20, 40, 60, 80 μmol photon m⁻² s⁻¹).
- Assessing mycelial growth and conidium production under each light condition compared to a dark control group.
Main Results:
- Green light (520 nm) at 20 and 60 μmol photon m⁻² s⁻¹ significantly inhibited mycelial growth.
- Blue light (475 nm) at 80 μmol photon m⁻² s⁻¹ significantly inhibited mycelial growth.
- Blue light (475 nm) at intensities of 40, 60, and 80 μmol photon m⁻² s⁻¹ suppressed conidia production, with greater suppression at higher intensities (up to 57.4% reduction at 80 μmol photon m⁻² s⁻¹).
- A. oryzae showed insensitivity to red light (630 nm) within the tested intensity range for both growth and conidia production.
- Significant interaction effects between light wavelength and intensity were observed for colony diameter and conidia count.
Conclusions:
- Aspergillus oryzae GDMCC 3.31 exhibits sensitivity to light wavelength and intensity, particularly blue light.
- Blue light can be used to inhibit fungal growth and sporulation, offering a potential method for regulating mixed strains in fermentation.
- This study provides foundational data on A. oryzae's photobiology, opening avenues for light-based control in food fermentation to enhance flavor quality.
