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A novel enzyme-based antimicrobial system comprising iodide and a multicopper oxidase isolated from Alphaproteobacterium strain Q-1.

Applied microbiology and biotechnology (2015-08-10)
Tri Yuliana, Kyota Ebihara, Mio Suzuki, Chie Shimonaka, Seigo Amachi
ABSTRACT

Alphaproteobacterium strain Q-1 produces an extracellular multicopper oxidase (IOX), which catalyzes iodide (I-) oxidation to form molecular iodine (I2). In this study, the antimicrobial activity of the IOX/iodide system was determined. Both Gram-positive and Gram-negative bacteria tested were killed completely within 5 min by 50 mU mL(-1) of IOX and 10 mM iodide. The sporicidal activity of the system was also tested and compared with a common iodophor, povidone-iodine (PVP-I). IOX (300 mU mL(-1)) killed Bacillus cereus, B. subtilis, and Geobacillus stearothermophilus spores with decimal reduction times of 2.58, 7.62, and 40.9 min, respectively. However, 0.1% PVP-I killed these spores with much longer decimal reduction times of 5.46, 38.0, and 260 min, respectively. To evaluate the more superior sporicidal activity of the IOX system over PVP-I, the amount of free iodine (non-complexed I2) was determined by an equilibrium dialysis technique. The IOX system included more than 40 mg L(-1) of free iodine, while PVP-I included at most 25 mg L(-1) free iodine. Our results suggest that the new enzyme-based antimicrobial system is effective against a wide variety of microorganisms and bacterial spores, and that its strong biocidal activity is due to its high free iodine content, which is probably maintained by re-oxidation of iodide released after oxidation of cell components by I2.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Iodine, ACS reagent, ≥99.8%, solid
Sigma-Aldrich
Iodine, ≥99.99% trace metals basis
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Iodine, flakes, ReagentPlus®, ≥99%
Supelco
Iodine, ReagentPlus®, ≥99.8% (titration)
Sigma-Aldrich
Iodine, puriss., meets analytical specification of Ph. Eur., BP, USP, 99.8-100.5%
Sigma-Aldrich
Iodine, 99.999% trace metals basis
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Iodine, anhydrous, beads, −10 mesh, 99.999% trace metals basis
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Iodine, ReagentPlus®, 99.7% trace metals basis, beads, 1-3 mm
Sigma-Aldrich
Iodine, puriss., ≥99.5% (RT), particles (round)