ABSTRACT
BACKGROUND: The mycotoxin zearalenone (ZEA) produced by toxigenic fungi is widely present in cereals and its downstream products. The danger of ZEA linked to various human health issues has attracted increasing attention. Thus, powerful ZEA-degrading or detoxifying strategies are urgently needed. Biology-based detoxification methods are specific, efficient, and environmentally friendly and do not lead to negative effects during cereal decontamination. Among these, ZEA detoxification using degrading enzymes was documented to be a promising strategy in broad research. Here, two efficient ZEA-degrading lactonases from the genus Gliocladium, ZHDR52 and ZHDP83, were identified for the first time. This work studied the degradation capacity and properties of ZEA using purified recombinant ZHDR52 and ZHDP83. RESULTS: According to the ZEA degradation study, transformed Escherichia coli BL21(DE3) PLySs cells harboring the zhdr52 or zhdp83 gene could transform 20 µg/mL ZEA within 2 h and degrade > 90% of ZEA toxic derivatives, α/ß-zearalanol and α/ß-zearalenol, within 6 h. Biochemical analysis demonstrated that the optimal pH was 9.0 for ZHDR52 and ZHDP83, and the optimum temperature was 45 °C. The purified recombinant ZHDR52 and ZHDP83 retained > 90% activity over a wide range of pH values and temperatures (pH 7.0-10.0 and 35-50 °C). In addition, the specific activities of purified ZHDR52 and ZHDP83 against ZEA were 196.11 and 229.64 U/mg, respectively. The results of these two novel lactonases suggested that, compared with ZHD101, these two novel lactonases transformed ZEA into different products. The slight position variations in E126 and H242 in ZDHR52/ZEA and ZHDP83/ZEA obtained via structural modelling may explain the difference in degradation products. Moreover, the MCF-7 cell proliferation assay indicated that the products of ZEA degradation using ZHDR52 and ZHDP83 did not exhibit estrogenic activity. CONCLUSIONS: ZHDR52 and ZHDP83 are alkali ZEA-degrading enzymes that can efficiently and irreversibly degrade ZEA into non-estrogenic products, indicating that they are potential candidates for commercial application. This study identified two excellent lactonases for industrial ZEA detoxification.
