Jae-Hyuk Yu

Application of Food-Grade Fungi to Safeguard Global Food Safety

The filamentous fungus Aspergillus oryzae is a GRAS (Generally Recognized as Safe) organism that has been used for thousands of years to produce various foods, including Doen-Jang, Korean traditional liquors, miso, and sake. Growing this food-grade A. oryzae fungus in different proprietary culture media made of various food ingredients led to the development of two types of novel bioproducts, termed D-Tox™ and Natural Preservative™ (NP™). D-Tox™ is an edible culture fermentate that can effectively degrade aflatoxins (AFs; the most potent carcinogen found in nature) within various foods, herbal medicines, and oil. AF detoxification involves opening the AF lactone ring followed by decarboxylation and further fragmentation of the toxin into nontoxic substances. NP™ products are also edible food fermentates that can effectively control a broad range of food-borne pathogenic bacteria, at least 10 different MRSA strains, and the human pathogenic fungi Aspergillus fumigatus and Candida species. Due to the significant potential of these bioproducts to safeguard global food safety and serve as novel antimicrobials, various US, Korean, and international patent applications have been filed, and several industry partners are working with us. We are currently investigating the chemical and molecular nature of D-Tox™ and NP™, and are developing various application processes and commercial products.

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Food Flaw Fighters

Molecular genetics/genomics of fungal biology

The genus Aspergillus encompasses the most common fungi in our environment. Many Aspergillus species are beneficial to humans, but they also include serious animal and plant pathogens. Moreover, most (if not all) Aspergillus species have the ability to produce one or more toxic secondary metabolites called mycotoxins. All Aspergilli produce asexual spores as the main means of dispersion and biosynthesis of certain mycotoxins is intimately related with fungal sporulation. The primary interest of my research program is to understand how fungi coordinate growth, sporulation and toxin biosynthesis employing the model fungus Aspergillus nidulans. We showed that two antagonistic regulatory pathways govern vegetative growth and sporulation in A. nidulans. Vegetative growth is primarily mediated by a heterotrimeric G protein, which stimulates fungal growth while inhibiting asexual/sexual sporulation as well as production of the carcinogenic mycotoxin sterigmatocystin. We found that the initiation, progression and completion of sporulation are directed by the balanced activities of multiple positive and negative regulators. We are further investigating the detailed molecular mechanisms regulating these fundamental biological processes via forward/reverse genetics, genomics and biochemical analyses.