Acidity/alkalinity Aqueous solutions are neutral to litmus.
Antimicrobial activity Benzyl alcohol is bacteriostatic and is used
as an antimicrobial preservative against Gram-positive bacteria,
molds, fungi, and yeasts, although it possesses only modest
bactericidal properties. Optimum activity occurs at pH below 5;
little activity is shown above pH 8. Antimicrobial activity is
reduced in the presence of nonionic surfactants, such as
polysorbate 80. However, the reduction in activity is less than
is the case with either hydroxybenzoate esters or quaternary
ammonium compounds. The activity of benzyl alcohol may also
be reduced by incompatibilities with some packaging materials,
particularly polyethylene; see Section 12.
See Table II for reported minimum inhibitory concentrations
(MICs).
Table II: Minimum inhibitory concentrations (MICs) of benzyl
alcohol.(4)
Microorganism MIC (mg/mL)
Aspergillus niger 5000
Candida albicans 2500
Escherichia coli 2000
Pseudomonas aeruginosa 2000
Staphylococcus aureus 25
Bacteria Benzyl alcohol is moderately active against most
Gram-positive organisms (typical MICs are 3–5 mg/mL),
although some Gram-positive bacteria are very sensitive
(MICs 0.025–0.05 mg/mL). In general, benzyl alcohol is less
active against Gram-negative organisms.
Fungi Benzyl alcohol is effective against molds and yeasts;
typical MICs are 3–5 mg/mL.
Spores Benzyl alcohol is inactive against spores, but activity
may be enhanced by heating. Benzyl alcohol 1% v/v, at pH
5–6, has been claimed to be as effective as phenylmercuric
nitrate 0.002% w/v against Bacillus stearothermophilus at
1008C for 30 min.
B
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