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Novel Aflatoxin-Degrading Enzyme from Bacillus shackletonii L7.

ABSTRACT: Food and feed contamination by aflatoxin (AF)B? has adverse economic and health consequences. AFB? degradation by microorganisms or microbial enzymes provides a promising preventive measure. To this end, the present study tested 43 bacterial isolates collected from maize, rice, and soil samples for AFB?-reducing activity. The higher activity was detected in isolate L7, which was identified as Bacillus shackletonii. L7 reduced AFB?, AFB?, and AFM? levels by 92.1%, 84.1%, and 90.4%, respectively, after 72 h at 37 °C. The L7 culture supernatant degraded more AFB? than viable cells and cell extracts; and the degradation activity was reduced from 77.9% to 15.3% in the presence of proteinase K and sodium dodecyl sulphate. A thermostable enzyme purified from the boiled supernatant was designated as Bacillus aflatoxin-degrading enzyme (BADE). An overall 9.55-fold purification of BADE with a recovery of 39.92% and an activity of 3.85 × 10³ U·mg-1 was obtained using chromatography on DEAE-Sepharose. BADE had an estimated molecular mass of 22 kDa and exhibited the highest activity at 70 °C and pH 8.0, which was enhanced by Cu2+ and inhibited by Zn2+, Mn2+, Mg2+, and Li?. BADE is the major protein involved in AFB? detoxification. This is the first report of a BADE isolated from B. shackletonii, which has potential applications in the detoxification of aflatoxins during food and feed processing.

SUBMITTER: Xu L

PROVIDER: S-EPMC5308268 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Novel Aflatoxin-Degrading Enzyme from Bacillus shackletonii L7.

Xu Liang L Eisa Ahmed Mohamed Farah MF Sangare Lancine L Zhao Yueju Y Selvaraj Jonathan Nimal JN Xing Fuguo F Wang Yan Y Yang Hongping H Liu Yang Y

Toxins 20170114 1

Food and feed contamination by aflatoxin (AF)B₁ has adverse economic and health consequences. AFB₁ degradation by microorganisms or microbial enzymes provides a promising preventive measure. To this end, the present study tested 43 bacterial isolates collected from maize, rice, and soil samples for AFB₁-reducing activity. The higher activity was detected in isolate L7, which was identified as <i>Bacillus shackletonii</i>. L7 reduced AFB₁, AFB₂, and AFM₁ levels by 92.1%, 84.1%, and 90.4%, respect ...[more]

PMID: 28098812

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Project description:Aflatoxin B1 is a carcinogenic and mutagenic mycotoxin mainly produced by Aspergillus flavus and A. parasiticus, and prevalent in food and feed. Microbial degradation is a promising strategy which can be performed in mild and environmental friendly condition. This work is a step towards identifying the enzyme responsible for biodegradation of AFB1 by P. putida. Experiments were performed with P. putida lysate and compared with commercial lipase to see the degradation efficiency and the temperature stability. The cell free lysate of P. putida efficiently degraded AFB1 in a range of temperature from 20 to 90 °C. The lysate is thermostable and could retain its activity on pre-incubation up to 90 °C. Highest rate of degradation was observed at 70 °C. These observations show that the P. putida lysate is not only stable at higher temperatures but its enzymatic activity increases after incubation. Similarly, the commercial lipase degraded AFB1 efficiently. However, both, the P. putida lysate and lipase ceased degradation in presence of a lipase inhibitor, HgCl2. The Hill function accurately predicted enzyme activity at various times and temperatures. Like lipase, the lysate also hydrolyses the p-nitrophenyl palmitate to p-nitrophenol. Kinetic parameters such as Vmax, Km and n values are good measures to characterize the lysate response with respect to changing paranitro phenyl palmitate levels. The substrate specificity test of lipase showed linear correlation between the absorbance at 410 nm vs amount of product paranitro phenol. The value of Km, Vmax and n are 0.62 mM, 355.7 μmol min-1 and 1.29, respectively. The lipase gene presence in P. putida was confirmed using PCR technique. These observations indicate that the main enzyme responsible for AFB1 degradation by P. putida is lipase. Thus, lipase as a multifunctional biocatalyst provides a promising future for a variety of industries and may also help to ensure the food safety by degrading the mycotoxins.

Dataset Information

Novel Aflatoxin-Degrading Enzyme from Bacillus shackletonii L7.

Publications

Novel Aflatoxin-Degrading Enzyme from Bacillus shackletonii L7.

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