Aflatoxin B 1 (AFB 1 ) is one of the most harmful mycotoxins in animal production and food industry. A safe, effective and environmentally sound detoxification method is needed for controlling this toxin. In this study, 65 samples were screened from various sources with vast microbial populations using a newly developed medium containing coumarin as the sole carbon source. Twenty five single-colony bacterial isolates showing AFB 1 reduction activity in a liquid culture medium were selected from the screen. Isolate 35-3, obtained from tapir feces and identified to be Stenotrophomonas maltophilia, reduced AFB 1 by 82.5% after incubation in the liquid medium at 37 °C for 72 h. The culture supernatant of isolate 35-3 was able to degrade AFB 1 effectively, whereas the viable cells and cell extracts were far less effective. Factors influencing AFB 1 degradation by the culture supernatant were investigated. Activity was reduced to 60.8% and 63.5% at 20 °C and 30 °C, respectively, from 78.7% at 37 °C. The highest degradation rate was 84.8% at pH 8 and the lowest was only 14.3% at pH 4.
The exposure of intact broccoli to 6 mL/kg ethanol for 5 h was effective in inhibiting the senescence of fresh‐cut broccoli florets. During the 8 d of storage at 10 °C, the weight loss, protein, and chlorophyll degradation of the treated broccoli florets were significantly retarded. The ethanol content of the ethanol‐treated broccoli rose sharply and then descended rapidly to a level close to that of the control broccoli stored at 10 °C after 8 d. The acetaldehyde level of the treated broccoli was higher than that of the control broccoli over the whole storage period. The alcohol dehydrogenase activity of the treated broccoli was significantly higher than that of the control after 6 d. There had been higher activities of peroxidase, superoxide dismutase, and catalase in ethanol‐treated broccoli. Our study showed that the fresh‐cut broccoli treated with ethanol maintained better quality during the storage. Ethanol vapor would be commercially a good candidate for extending the shelf‐life of fresh‐cut broccoli florets and reducing the loss in postharvest.
A new ribonuclease (RNase) with tobacco mosaic virus inhibition was isolated and purified from Bacillus cereus ZH14 through ammonium sulfate precipitation, ultrafiltration, ion-exchange chromatography of DEAE-Sephadex A-50 column, and gel chromatography of Sephacryl S-200HR column. The enzyme was purified approximately 134-fold with a recovery of 9.2%. The RNase had an MW of 75.6 kDa in SDS-PAGE, which differed from RNases reported previously. The inhibitory activity of the RNase in the purification process against tobacco mosaic virus was tested, and the percentage inhibition of the purified RNase (48 U/ml) reached 90%. The protein could tolerate 90 degrees C and pH 4.0.
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