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Effect of ultraviolet (UV) radiation on the abundance and respiration rates of probiotic bacteria

Authors

  • M. Angélica Garrido-Pereira,

    1. Post-graduation Course on Aquaculture, Oceanography Institute, Federal University of Rio Grande, Rio Grande, Brazil
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  • André Luiz Braga,

    1. Post-graduation Course on Biological Oceanography, Oceanography Institute, Federal University of Rio Grande, Rio Grande, Brazil
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  • Andréa Ferretto da Rocha,

    1. Post-graduation Course on Aquaculture, Oceanography Institute, Federal University of Rio Grande, Rio Grande, Brazil
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  • Luís André Sampaio,

    1. Institute of Oceanography, Federal University of Rio Grande, Rio Grande (RS), Brazil
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  • Paulo César Abreu

    Corresponding author
    1. Institute of Oceanography, Federal University of Rio Grande, Rio Grande (RS), Brazil
    • Post-graduation Course on Aquaculture, Oceanography Institute, Federal University of Rio Grande, Rio Grande, Brazil
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Correspondence: P. C. Abreu, Institute of Oceanography, Federal University of Rio Grande, C.P. 474, 96201-900, Rio Grande (RS), Brazil. E-mail: docpca@furg.br

Abstract

Effects of ultraviolet radiation (UV) on probiotic bacteria (Bacillus subtilis and B. licheniformis) were tested in two experiments, with the following treatments: (i) UV treatment – using fluorescent and UV-lamps and (ii) Control – CTRL, using fluorescent lamps. Bacterial abundance and respiration were evaluated every 24 h for 3 days for Experiment 1, and at 0, 6 and 24 h for Experiment 2. In the Experiment 1, total UV dose was 4 336.41 mW cm−2. UV treatment presented small respiration rates only on day 3, while in the CTRL oxygen consumption was always high. On all days, the abundance of the Bacilli exposed to UV was significantly smaller than that of the CTRL. The second experiment, with total UV dose of 1 445.47 mW cm−2, presented oxygen consumption in the UV treatment only during the first 6 h. In the CTRL, oxygen consumption increased from the beginning due to the bigger abundance Bacilli cells. Small coccus-shaped bacteria ocurred in the UV treatment of both experiments. It may be concluded that exposure to UV, normally used for water disinfection, can inactivate probiotic bacteria.

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