Evaluation of Detoxifying Effect of Bacillus licheniformis CK1 on Zearalenone
Date Issued
2012
Date
2012
Author(s)
Wang, Yue-Chun
Abstract
Zearalenone (ZEN), one kind of mycotoxins, is a phenolic resorcylic acid lactone produced by certain species of Fusarium that infects cereals and grains, such as corn, oats, wheat and hey. ZEN can induce infertility, abortion or other breeding problems in livestock. Furthermore, it is carcinogenic, genotoxic, hepatotoxic and immunotoxic in both livestock and humans. Bacillus licheniformis CK1 was found to be capable to decrease ZEN residue in vitro, and the mechanisms might be both adsorption and degradation. This study is aimed at investigation of the binding interaction between B. licheniformis CK1 and ZEN and evaluating the efficacy of detoxification of ZEN by B. licheniformis CK1 in BALB/c mice.
First, the extent of ZEN binding over the range of 5-50 ppm (37℃, 30 min) was studied for viable, heat- and acid-killed B. licheniformis CK1. Both heat- and acid-killed bacteria showed greater ZEN-binding ability than viable bacteria; the absorption of ZEN by viable and heat-killed bacteria seemed to be saturated at higher initial ZEN concentration. To identify the type of chemical moieties and interactions involved in binding with ZEN, B. licheniformis CK1 was subjected to different chemical and enzymatical treatments prior to the binding experiments. Pre-treating acid-killed B. licheniformis CK1 with pronase E significantly decreased ZEN bound concentration, and pre-treating viable and heat-killed bacteria with 8 M urea significantly decreased ZEN bound concentration, suggesting that ZEN binds predominantly to protein components. Besides, ionic strength (125-1000 mM of Ca2+ or Na+) and pH value (pH 1.5-8.5) did not affect the concentration of ZEN bound with B. licheniformis CK1, suggesting that electrostatic interactions and hydrogen bonding do have minor effects on binding and that bacterial binding of ZEN might occur at any point along the gastrointestinal tract.
In animal trial, fifty 7-week old BALB/c mice were divided into five groups (10 mice/group) and orally administered 1) PBS; 2) olive oil; 3) 109 CFU/kg BW of B. licheniformis CK1 in PBS; 4) 40 mg/kg BW of ZEN in olive oil; 5) 40 mg/kg BW of ZEN in olive oil + 109 CFU/kg BW of B. licheniformis CK1 in PBS each day for 28 days. The mice were sacrificed at the end of experiment and the blood and organ samples were collected and analyzed. The results showed that, compared with control groups, liver relative weight tended to decrease in ZEN group but not in ZEN + B. licheniformis CK1 group. ZEN treatment resulted in a significant increase of alanine aminotransferase (ALT) level in plasma and a decrease of blood urea nitrogen (BUN) level. Moreover, ZEN treatment also caused a slight decrease of liver catalase (CAT) activity, indicating that the liver might be injured. Treatment with ZEN and B. licheniformis CK1 simultaneously seemed to restore these changes. However, treatment with ZEN and B. licheniformis CK1 simultaneously did not decrease the elevated level of plasma interleukin-1β (IL-1β) and increase the decreased level of total immunoglobulin G (IgG) induced by ZEN.
In conclusion, the ZEN binding ability of B. licheniformis CK1 is stable in various conditions. The exact binding sites on the surface of B. licheniformis CK1 might be protein components. Oral administration of B. licheniformis CK1 could partially ameliorate the harmful effect of ZEN in mice. More studies needs to be investigated to confirm the protective effects of B. licheniformis CK1 on ZEN toxicity in vivo.
Subjects
myxotoxin
zearalenone
Bacillus licheniformis CK1
Type
thesis
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