The Ancient Koji Mold: A Modern Biotechnological Tool

Supriyo Mukherjee, Kalyani Mahavidyalaya

The word “mold” is well known in the culinary vocabulary which sounds like the opposite of delicious. However, for fermented food-lovers, mold worship is a novel character quirk. Aspergillus oryzae – or koji is been called for centuries in Japan that enjoys one of the most storied and versatile relationships with humans. In this article, we’ll explore koji in detail.

What is Koji?

Koji (A. oryzae) is a multicellular, filamentous mold that much like the type generally might find growing on bread or oranges. Molds are micro-fungus that is used in the fermentation of different foods in many countries for centuries. This beneficial mold is a rich source of many bioactive secondary metabolites. It has a secretory system that secretes high concentrations of proteins into its culturing medium that supports its use as a biotechnological tool in veterinary, food, industrial, and pharmaceutical fields. Neoculin, an important taste-modifying hetero-oligomeric protein, is produced by A. oryzae. Human lysozyme and recombinant antibodies like adalimumab are also produced by A. oryzae, to reduce their production costs. 

The various aspects are discussed below:

1. In Industrial Enzymes Production: In industrial applications, enzymes from the microbial origin are preferred over enzymes produced by conventional methods due to economic feasibility, eco-friendliness, low toxicity, better quality products, better efficiency, and also low energy demand. It is commonly directed by either submerged fermentation (SmF) or solid-state fermentation (SSF). Scientific studies suggest high quantities of hydrolytic enzymes in soybean inoculated with mold including neutral and alkaline protease, amylase, glutaminase, and metallopeptidase. 
2. Strategies for A. oryzae functional genomics: Different strategies are employed to investigate functional genomics including genetic manipulations, conducting transformations, and the use of selection markers. The most commonly employed selection markers are auxotrophic and drug resistance markers. PyrG is the most commonly employed marker for A. oryzae. The second strategy to investigate functional genomics is the transformation of A. oryzae. The key obstacle is the low A. oryzae transformation efficiency. Therefore, protoplast-mediated transformation, Agrobacterium-mediated transformation, and electroporation techniques are employed to overcome this problem. 
3. Production of human pharmaceutical proteins using A. oryzae: A. oryzae is a promising host for the production of heterologous proteins due to its ability to secrete high protein concentration into the culture medium. Researchers suggest the production of active human lysozyme through the expression of the HLY gene. In scientific studies, it is employed for the production of adalimumab, an IgG antibody that binds to the inflammatory cytokine, TNFα. Adalimumab is used to treat some chronic inflammatory diseases such as rheumatoid arthritis.

Conclusion and future prospects:

A. oryzae is considered a modern biotechnological tool due to its various applications in the food, pharmaceutical, and veterinary industries. In the recent days of research, the research on the function of genomics is improved due to the recent advances in techniques such as next-gen sequencing. It is helpful for the enhancement of the fermentative strains of A. oryzae. Transformation strategies such as protoplast-mediated and Agrobacterium-mediated transformations will contribute to enhancing the transformation process. The functional genomics of A. oryzae will be helpful for getting maximum benefits in industrial production by discovering new strategies, and optimization of current strategies.  

Also read: A special chloroplast protein to combat environmental stress

Reference:

1. Daba, G.M., Mostafa, F.A. & Elkhateeb, W.A. The ancient koji mold (Aspergillus oryzae) as a modern biotechnological tool.  Bioresour. Bioprocess. 8, 52 (2021). https://doi.org/10.1186/s40643-021-00408-z
2. Yoon, J., Maruyama, Ji. & Kitamoto, K. Disruption of ten protease genes in the filamentous fungus Aspergillus oryzae highly improves production of heterologous proteins. Appl Microbiol Biotechnol89, 747–759 (2011). https://doi.org/10.1007/s00253-010-2937-0

About author:

Supriyo Mukherjee is an undergraduate student in Microbiology. His areas of interest are Spectroscopy, Immunology, Microbiology and Bioinformatics.

His previous publication at BioXone is:

1. A Viral DNA-packaging Motor Mechanism: https://bioxone.in/news/worldnews/a-viral-dna-packaging-motor-mechanism/

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