No abstract

An improved analytical method compared with conventional ones was developed for simultaneous determination of 13 mycotoxins (deoxynivalenol, nivalenol, 3-acetylnivalenol, aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, fumonisin B1, fumonisin B2, T-2, HT-2, zearalenone, and ochratoxin A) in cereal grains by liquid chromatography-tandem mass spectrometry (LC/MS/MS) after a single immunoaffinity column clean-up. The method showed a good linearity, sensitivity, specificity, and accuracy in mycotoxin determination by LC/MS/MS. The levels of 13 mycotoxins in 5 types of commercial grains (brown rice, maize, millet, sorghum, and mixed cereal) from South Korea were determined in a total of 507 cereal grains. Mycotoxins produced from Fusarium sp. (fumonisins, deoxynivalenol, nivalenol, and zearalenone) were more frequently (more than 5%) and concurrently detected in all cereal grains along with higher mean levels (4.3–161.0 ng/g) in positive samples than other toxins such as aflatoxins and ochratoxin A (less than 9% and below 5.2 ng/g in positive samples) from other fungal species.

Ochratoxin A (OTA), a mycotoxin, contaminates agricultural products and poses a serious threat to public health worldwide. Microbiological methods are known to be a promising approach for OTA biodegradation because physical and chemical methods have practical limitations. In the present study, a total of 130 fungal isolates obtained from 65 traditional Korean meju (a fermented starter for fermentation of soybeans) samples were examined for OTA-biodegradation activity using thin-layer chromatography. Two fungal isolates were selected for OTA-biodegradation activity and were identified as M036 and M074 through sequence analysis of the beta-tubulin gene. After culturing both isolates in Soytone-Czapek medium containing OTA (40 ng/ml), OTA-biodegradation activity was analyzed using high-performance liquid chromatography (HPLC). Both strains degraded OTA by more than 95.0% after 14 days, and the HPLC analysis showed that the OTA biodegradation by the strains led to the production of ochratoxin α, which is much less toxic than OTA. Moreover, crude enzymes from the cultures of A. tubingensis M036 and M074 led to OTA biodegradation of 97.5% and 91.3% at pH 5, and 80.3% and 75.3% at pH 7, respectively, in a buffer solution containing OTA (40 ng/ml) after 24 h. In addition, the OTA-biodegrading fungi did not exhibit OTA production activity. Our data suggest that isolates and their enzymes have the potential for practical application to reduce levels of OTA in food and feed.

Kombucha is a fermented beverage containing organic acids by yeast and acetic acid bacteria. In this study, microbial community analysis of kombucha produced in Korea was performed, and changes in components during kombucha fermentation were analyzed using commercial kombucha pellicle and culture broth as starter. The major phylum-level strains of commercial kom-1 and kom-2 showed differences in proteobacteria of 35.60% and 78.1%, and Firmicutes of 64.06% and 15.57%, respectively. During fermentation with pellicle (Kom-P) and broth (Kom-F), the level of reducing sugar during fermentation tended to decrease rapidly. The production of acetic acid and D-saccharic acid-1,4-lactone (DSL) in Kom-P and -F tended to increase with increasing fermentation time. In Kom-P, lactic acid and glucuronic acid production increased until 7 days of fermentation and then decreased, whereas in Kom-F, it continued to increase with fermentation time. ABTS radical scavenging activity tended to decrease with increasing fermentation time. However, DPPH radical scavenging activity increased within 7 days of fermentation and then decreased slightly (Kom-P) or remained constant (Kom-F). It has been found that the use of culture broth rather than the use of pellicle as a starter is advantageous to increase the active compound content and DPPH radical scavenging ability.

Aflatoxins are classified as Group 1 (carcinogenic to humans) by the International Agency for Research on Cancer. In this study, a total of 134 fungal strains were isolated from 65 meju samples, and two fungal isolates were selected as potential aflatoxin B (AFB)-biodetoxification fungi. These fungi were identified as MAO103 and MAO104 by sequencing the beta-tubulin gene. The two strains were able to degrade more than 90% of AFB (initial concentration: 40 μg/l) in a culture broth in 14 days. The mutagenic effects of AFB treated with MAO103 and MAO104 significantly decreased to 5.7% and 6.4%, respectively, in the frame-shift mutation of Ames tests using TA98. The base-substituting mutagenicity of AFB was also decreased by the two fungi. Moreover, AFB production by was significantly decreased by the two strains on soybean-based agar plates. Our data suggest that the two AFB-detoxifying strains have potential application to control AFB in foods and feeds.