Analysis of the MAT1-1 and MAT1-2 Gene Ratio in Black Koji Molds Isolated from Meju

Aspergillus luchuensis is known as an industrially important fungal species used for making fermented foods such as awamori and shochu in Japan, makgeolli and Meju in Korea, and Pu-erh tea in China. Nonetheless, this species has not yet been widely studied regarding mating-type genes. In this study, we examined the MAT1-1 and MAT1-2 gene ratio in black koji molds (A. luchuensis, Aspergillus niger, and Aspergillus tubingensis) and in Aspergillus welwitschiae isolated from Meju, a fermented soybean starting material for traditional soy sauce and soybean paste in Korea. The number of strains with the MAT1-1 locus was 2 of 23 (A. luchuensis), 6 of 13 (A. tubingensis), 21 of 28 (A. niger), and 5 of 10 (A. welwitschiae). Fungal species A. tubingensis and A. welwitschiae showed a 1 : 1 ratio of MAT1-1 and MAT1-2 mating-type loci. In contrast, A. luchuensis revealed predominance of MAT1-2 (91.3%) and A. niger of MAT1-1 (75%). We isolated and identified 2 A. luchuensis MAT1-1 strains from Meju, although all strains for making shochu in Japan are of the MAT1-2 type. These strains may be a good resource for breeding of A. luchuensis to be used in the Asian fermented-food industry.

Aspergillus Associated with Meju, a Fermented Soybean Starting Material for Traditional Soy Sauce and Soybean Paste in Korea

Aspergillus is an important fungal genus used for the fermentation of Asian foods; this genus is referred to as koji mold in Japan and China. A. oryzae, A. sojae, and A. tamari are used in the production of miso and shoyu in Japan, but a comprehensive taxonomic study of Aspergillus isolated from Meju, a fermented soybean starting material for traditional soy sauce and soybean paste in Korea, has not been conducted. In this study, various Aspergillus species were isolated during a study of the mycobiota of Meju, and the aspergilli were identified based on phenotypic characteristics and sequencing of the beta-tubulin gene. Most strains of Aspergillus were found to belong to the following sections: Aspergillus (n = 220), Flavi (n = 213), and Nigri (n = 54). The most commonly identified species were A. oryzae (n = 183), A. pseudoglaucus (Eurotium repens) (n = 81), A. chevalieri (E. chevalieri) (n = 62), A. montevidensis (E. amstelodami) (n = 34), A. niger (n = 21), A. tamari (n = 15), A. ruber (E. rubrum) (n = 15), A. proliferans (n = 14), and A. luchuensis (n = 14); 25 species were identified from 533 Aspergillus strains. Aspergillus strains were mainly found during the high temperature fermentation period in the later steps of Meju fermentation.

The Mycobiota of Air Inside and Outside the Meju Fermentation Room and the Origin of Meju Fungi

The fungi on Meju are known to play an important role as degrader of macromolecule of soybeans. In order to elucidate the origin of fungi on traditional Meju, mycobiota of the air both inside and outside traditional Meju fermentation rooms was examined. From 11 samples of air collected from inside and outside of 7 Meju fermentation rooms, 37 genera and 90 species of fungi were identified. In outside air of the fermentation room, Cladosporium sp. and Cladosporium cladosporioides were the dominant species, followed by Cladosporium tenuissimum, Eurotium sp., Phoma sp., Sistotrema brinkmannii, Alternaria sp., Aspergillus fumigatus, Schizophyllum commune, and Penicillium glabrum. In inside air of the fermentation room, Cladosporium sp., Aspergillus oryzae, Penicillium chrysogenum, Asp. nidulans, Aspergillus sp., Cla. cladosporioides, Eurotium sp., Penicillium sp., Cla. tenuissimum, Asp. niger, Eur. herbariorum, Asp. sydowii, and Eur. repens were collected with high frequency. The concentrations of the genera Aspergillus, Eurotium, and Penicillium were significantly higher in inside air than outside air. From this result and those of previous reports, the origin of fungi present on Meju was inferred. Of the dominant fungal species present on Meju, Lichtheimia ramosa, Mucor circinelloides, Mucor racemosus, and Scopulariopsis brevicaulis are thought to be originated from outside air, because these species are not or are rarely isolated from rice straw and soybean; however, they were detected outside air of fermentation room and are species commonly found in indoor environments. However, Asp. oryzae, Pen. polonicum, Eur. repens, Pen. solitum, and Eur. chevalieri, which are frequently found on Meju, are common in rice straw and could be transferred from rice straw to Meju. The fungi grow and produce abundant spores during Meju fermentation, and after the spores accumulate in the air of fermentation room, they could influence mycobiota of Meju fermentation in the following year. This could explain why concentrations of the genera Aspergillus, Eurotium, and Penicillium are much higher inside than outside of the fermentation rooms.

Mycoflora and Enzymatic Characterization of Fungal Isolates in Commercial Meju, Starter for a Korean Traditional Fermented Soybean Product

Mycoflora was assessed in the commercial meju from four well-separated geographic origins. A total of 112 fungal isolates were identified by phenotypic characteristics and molecular taxonomy using sequencing the internal transcribed spacer of the rDNA and revealed 19 species from 13 genera. Enzymatic characteristics of protease and amylase, and mycotoxin production were analyzed.

Effect of fermented soybean curd residue (FSCR; SCR-meju) by aspergillus oryzae on the anti-obesity and lipids improvement / 한국영양학회지

In this study, we designed to confirm the dietary effect of anti-obesity of fermented soybean curd residue (FSCR; SCR-Meju; Biji-meju) by A. oryzae, which is well known as a Korean traditional meju microbe. We observed that body weight gain, serum and hepatic lipid profile, as well as the activity of ROS generating enzyme and ROS scavenging enzyme in high-fat diet induced obese mice fed experimental diet (SCR and SCR-meju). Body weight gain and epididymal fat weight of HC (high-fat diet control) was markedly higher than that of NC (Normal control). Conversely, body weight gain and epididymal fat weight of the SCR (Biji) and SCR-meju (Biji-meju) group was significantly lower than that of HC; these of the SCR-meju group was lower than that of the SCR group. Furthermore, serum TG and total-cholesterol and LDL-cholesterol contents of SCR and SCR-meju groups were lower than that of HC, and HDL-cholesterol level of the SCR-meju group was significantly higher than that of HC. In conclusion, although precise mechanisms of the antiobese effects of SCR-meju in this study are unknown, the present study provides an experimental evidence that SCR-meju may prevent obesity and obesity related metabolic syndromes, such as hyperlipidemia, hypertension and diabetes, and liver disease by high-fat diet. Nevertheless, further study in this filed will be needed.

Identification and Characterization of Eurotium rubrum Isolated from Meju in Korea

We isolated and identified a strain of Eurotium rubrum from Meju that has not been reported in Korea. This fungus is yellowish brown; reverse dark brown on CYA and PDA while yellow on 2% MEA at 25degrees C. Cleistothecia are first bright yellow and gradually turned brown. Mycerial growth on CYA attained a diameter of 30 mm at 20degrees C, 37 mm at 25degrees C and 32 mm at 30degrees C after 15 days. The isolate grew slower on 2% MEA (< 20 mm 15 days at 25degrees C) compared to CYA and PDA (< 40 mm 15 days at 25degrees C). Cleistothecia are superficial, yellow to light brown, globose to subglobose, 40~75 microm in diameter. Asci are 8-spored and globose to subglobose 8~11 microm. Ascospores are disciform, 4.0~5.0 microm in length and 4.2~4.5 microm in width. Conidia are ovate or bacillar, finely roughened to densely spinulose, 4.6~6.0 microm in length and 3.0~4.3 microm in width. Compared to known Eurotium rubrum, the Korean isolate showed 99% sequence similarity in ITS rDNA (554 bp) and calmodulin (750 bp) gene and 100% in beta-tubulin (1016 bp) gene. The E. rubrum isolate also had weak beta-glucosidase and protease activities.

Mutagenic and Anti-Mutagenic Properties of Meju and Other Korean Food Products from Fermented Soybeans

ln order to investigate the mutagenic activity of Meju, an important component of the Korean diet, both chemical techniques and the Ames test were used. To determine if antimutagenic activity is present in Meju and other soybean based foods, the Ames Test was done in the presence of aflatoxin B1, benzo(a)pyrene, and other mutagens. Although aflatoxin contamination was found in 6 of 43 samples of Meju tested, the amounts were less than 1 ppb in all but one. Meju had a protective effect against mutations produced by both aflatoxins and benzo(a)pyrene, both of which act via an epoxide, but not against other mutagens tested.