Biodegradation of Ochratoxin A by Aspergillus tubingensis Isolated from Meju

Introduction: Ochratoxin A (OTA), a mycotoxin, contaminates food commodities and poses a serious threat to public health worldwide. OTA is one of the most potent carcinogenic (IARC group 2B) mycotoxins. Microbiological methods are known to be an appropriate approach for biodegradation of OTA which is occasionally found in fermented soybean products.

Purpose: For microbiological reduction of OTA in fermented soybean products, fungi that have OTA-biodegradation activity were isolated from meju, a traditional starter for Korean soybean fermented products. The OTA-biodegradation activity of 7 fungi and their crude enzymes was investigated.

Methods: One hundred thirty fungal species were isolated from meju and their OTA-biodegradation activity was evaluated. Biodegradation of OTA was analyzed by thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC). Seven fungal isolates that show OTA-biodegradation activity were identified by sequencing β-tubulin gene and the Internal Transcribed Spacer (ITS) region of rDNA. 

Results: Seven Aspergilli were selected as OTA-biodegradable abilities and identified as A. tubingensis M013, M024, M036, M038, M069 and M074. They degraded more than 90% of OTA in 14 days in Soytone-Czapek broth and converted OTA to a much less toxic metabolite, ochratoxin α. Their crude enzymes degraded more than 85% and 75% of OTA at pH 5 and pH 7, respectively, for 24 h.

Significance: Our data suggests that A. tubingensis M013, M024, M036, M038, M069 and M074 isolated from meju samples and their OTA-biodegradable enzymes have potential for practical applications to reduce OTA levels in soybean fermented food and feed processing.