Mineralization of [14C]octacosane by Acinetobacter calcoaceticus S30

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Abstract
Acinetobacter calcoaceticus S30 could grow (doubling time, 7 h) on octacosane (C28) and degraded about 70% of the substrate during growth. Octacosanol, octacosanoic acid, and other lower carboxylic acids were identified during degradation of octacosane. Acinetobacter calcoaceticus S30 could also grow on intermediate metabolites, namely octacosanol and octacosanoic acid, although the doubling time was greater on octacosanoic acid (72 h on octacosanol and 120 h on octacosanoic acid). Whole cells of A. calcoaceticus S30 using [18-14C]octacosane mineralized 65% of the octacosane to 14CO2 and 30% of the radiolabel was retained in the cell biomass in 24 h. Acinetobacter calcoaceticus S30 converts octacosane to octacosanol through an oxidation step, which is then oxidized to octacosanoic acid and then β-oxidized to CO2. Among several metabolic inhibitors, those of the sulphydryl group greatly inhibited the uptake of octacosanol and octacosanoic acid at much lower concentrations. The electron transport inhibitors were potent inhibitors of octacosane, octacosanol, and octacosanoic acid uptake, suggesting that the oxidation of these substrates is an energy-dependent process.Key words: Acinetobacter calcoaceticus, mineralization, octacosane, octacosanol, octacosanoic acid.