Lipase and esterase formation by psychrophilic and mesophilic Acinetobacter species

Abstract

Acinetobacter O16, a psychrophilic species, produced extracelullar lipase (measured by hydrolysis of olive oil, tributyrin, or β-naphthyl laurate) when grown on a complex medium (peptone plus yeast extract). Most lipase was produced during the logarithmic phase of growth. Very little cell-bound lipase was formed. These cells also produced an esterase (measured by the hydrolysis of β-naphthyl acetate). At first, all esterase was cell bound; significant amounts appeared in the external medium late in growth.Breaking the cells did not increase cell-bound lipase activity. After breaking of the cells, most of the cell-bound lipase and esterase activity was solubilized, even after very high speed centrifugation. No appreciable amounts of these enzymes were released by osmotic shock.Lipase formation was greatly affected by nutrient conditions. Lowering either the yeast extract or the peptone content of the normal complex medium lowered or abolished lipase formation. Esterase activity was lowered to a lesser extent. Cells growing in synthetic amino acid plus vitamin medium or in acid-hydrolyzed casein produced substantial amounts of esterase but no cell-free or cell-bound lipase. However, if sodium taurocholate was added to these media, lipase was produced. Greatest production occurred if a mixture of di- and poly-peptides was also present. Taurocholate also stimulated lipase production in the normal complex medium. Adding Tween 80 or ethanol to the normal complex medium inhibited lipase production. Sodium acetate, oleic acid, olive oil, or Tween 20 added to synthetic media did not affect lipase production.The psychrophile grew more quickly at 30 °C than at 15 or 20 °C but produced more lipase at the lower temperatures. Esterase production was about the same at 20 and 30 °C. A mesophilic Acinetobacter species produced the same amount of lipase and esterase at 20 and 30 °C. The best production of lipase by the psychrophile occurred in standing cultures.