Abstract
Ochratoxin A (OTA) is toxic to animals and threatens food safety through residues in animal tissues. A novel degrading strain Bacillus subtilis ANSB168 was isolated and further investigated. We cloned d-alanyl-d-alanine carboxypeptidase DacA and DacB from ANSB168 and over-expressed them in Escherichia coli Rosetta (DE3). Then, we characterized the OTA degradation mechanism of DacA and DacB, which was degrading OTA into OTα. A total of 45 laying hens were divided into three equal groups. The control group was fed basal feed, and other groups were administered with OTA (250 μg/kg of feed). A freeze-dried culture powder of ANSB168 (3 × 107 CFU/g, 2 kg/T of feed) was added to one of the OTA-fed groups for 28 days from day one of the experiment. We found that OTA significantly damaged the kidney and liver, inducing inflammation and activating the humoral immune system, causing oxidative stress in the layers. The ANSB168 bioproduct was able to alleviate OTA-induced kidney and liver damage, relieving OTA-induced inflammation and oxidative stress. Overall, DacA and DacB derived from ANSB168 degraded OTA into OTα, while the ANSB168 bioproduct was able to alleviate damages induced by OTA in laying hens.
Highlights
Ochratoxin A (OTA), produced by several strains of Aspergillus and Penicillium [1–6], is a naturally occurring mycotoxin that commonly contaminates foods and feeds, causing enormous harm to humans and animals
Strain ANSB168 was isolated by the enrichment method from the cecum of donkeys, and the strain showed efficient degradation activity of OTA
High-performance liquid chromatography (HPLC) analysis indicated that the DacA and DacB degradation products were eluted as a peak with a retention time of 6.7 min that had the same transition time of ochratoxin α (OTα) (Figure 5), suggesting that DacA and DacB break the amide bond of OTA
Summary
Ochratoxin A (OTA), produced by several strains of Aspergillus and Penicillium [1–6], is a naturally occurring mycotoxin that commonly contaminates foods and feeds, causing enormous harm to humans and animals. OTA is thermally stable up to 18 ◦C [16], which means most ochratoxins in agriculture products can pass through industrial processing programs This contributes to the prevalence of mycotoxin contamination, causing enormous economic losses and threatening human health. With 3 h of UV irradiation, 81–86% of OTA in feed can be degraded [18], but it requires extra equipment and is time-consuming Chemical agents, such as ozone, ammonium, bisulfites, and alkaline hydrolysis, are commonly applied in detoxification [15,19]. A number of articles have reported different kinds of carboxypeptidases derived from different OTA-degrading strains, the mechanism and purified enzyme of a novel screened strain Bacillus subtilis have yet to be researched. The results obtained from this study demonstrate that the strain ANSB168 and its specific enzyme could be applied in OTA degradation
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