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PubMed1987

The effect of pH and concentration on the rates of kill of benzoic acid solutions against E. coli.

Mathematical models were developed which related benzoic acid concentrations to their D-values at room temperature. Linear regression was used to determine D-values (i.e. the time required for a particular concentration of preservative at specified pH, temperature and medium to cause a 90% reduction in the number of viable organisms, e.g. Escherichia coli. A number of concentrations of benzoic acid at either pH 3 or pH 4 were used. Linear regression of the log D-values versus the log of the concentration was used to derive power curves (a minimum of four points per pH were examined). Concentration exponents, eta-values (the logarithmic values relating changes in rates of kill to specified changes in concentrations) and A-values (extrapolated D-values at 1% concentration), were determined. The effect of pH on the eta and A-values of benzoic acid on E. coli was investigated. Benzoic acid was found to be more sensitive to pH changes than was anticipated from the Henderson-Hasselbalch equation which relates dissociated and undissociated fractions at the two pH levels investigated. However, the sensitivity of preservative activity to dilution at both pH values (3 and 4), as given by the eta-value, remained similar.

Anti-Infective Agents, Local↗
PubMed1988

Effect of benzoic Acid on growth yield of yeasts differing in their resistance to preservatives.

Yeasts grown in the presence of benzoic acid tolerated 40 to 100% higher benzoic acid concentrations than did those grown in the absence of weak-acid-type preservatives. They also accumulated less benzoate in the presence of glucose. In chemostat cultures, benzoic acid reduced growth yield and the rate of cell production but increased specific fermentation rates. Benzoate contents were lower than those required for equilibrium when cells were impermeable to benzoate anion. Intracellular pHs were maintained near neutrality. Between species, stimulation of fermentation was inversely related to preservation resistance but was unrelated to the maximum rate of fermentation. The results show that a major effect of benzoic acid on yeasts in the presence of an energy source is the energy requirement for the reduction in cytoplasmic benzoate concentration and maintenance of pH. This energy source is unavailable for growth, resulting in lower growth yields and rates. Resistant species may be less permeable to undissociated benzoic acid.

Journal Article↗
PubMed1982

Biotransformation of tribenoside into benzoic acid in man.

In an experiment on three healthy volunteers, plasma levels of tribenoside and the elimination of benzoic acid in plasma and urine were followed up during a 7-day period of daily oral medication with tribenoside. Plasma levels of tribenoside, and plasma and urine concentrations of free and total benzoic acid were determined quantitatively. The concentrations of alpha- and beta-tribenosides found in the plasma were very low and did not increase during treatment. Total benzoic acid in the plasma remained at almost the same level during treatment as that observed before treatment. Biotransformation of tribenoside therefore does not appear to result in any significant change in the plasma concentrations of free or total benzoic acid. The average daily excretion of total benzoic acid in the urine of the 3 subjects was greater during treatment than before. The average increases in total benzoic excretion in the 3 subjects correspond to 23.5, 11.9, and 23.7% of the theoretical amount that would be produced by the metabolic oxidation of the 3 benzyl groups. This study demonstrates that tribenoside does not accumulate in plasma. Around 20% of the administered dose is metabolized to benzoic acid, which is almost entirely present in the body as hippuric acid. Hippuric acid is excreted at such a rate that it does not accumulate in plasma and does not exceed the normal concentration range.

Adult↗
PubMed1980

The metabolic fate of [14C] benzoic acid in protein-energy deficient rats.

The metabolic fate of [14C] benzoic acid administered i.p. to marasmic-kwashiorkor rats has been investigated. Rats fed a normal diet with benzoic acid administered i.p. at 200 mg/kg, excreted the benzoic acid mainly as hippuric acid (99% of 24 h excretion), while marasmic-kwashiorkor rats excreted 62--85% as hippuric acid and 14--37% as the glucuronide conjugate. 2 weeks after repletion metabolism of benzoic acid by the marasmic-kwashiorkor rats on the stock diet had returned to normal; most of the benzoate was excreted as hippuric acid.

Animals↗