Kulnaree Phetrong, Aran H-Kittikul and Suppasil Maneerat

pp. 297 - 305

Abstract

Marine bacterium strain SM7 was isolated as a bioemulsifier-producing bacterium from oil-spilled seawater in Songkhla lagoon, Thailand. It was identified as Acinetobacter calcoaceticus subsp. anitratus based on morphology, biochemical characteristics and 16S rRNA sequence. A. calcoaceticus subsp. anitratus SM7 produced an extracellular emulsifying agent when grown in a minimal salt medium (pH 7.0) containing 0.3% (v/v) n-heptadecane and 0.1% (w/v) ammonium hydrogen carbonate as carbon source and nitrogen source, respectively, at 30°C with agitation rate of 200 rpm. Crude bioemulsifier was recovered from the culture supernatant by ethanol precipitation with a yield of 2.94 g/l and had a critical emulsifier concentration of 0.04 g/ml. The crude bioemulsifier was capable of emulsifying n-hexadecane in a broad pH range (6-12), temperatures (30-121°C) and in the presence of NaCl up to 12% (w/v). The bioemulsifier was stable in salt solution ranging from 0 to 0.1% (w/v) of MgCl₂ and CaCl₂. The broad range of pH stability, thermostability and salt
tolerance suggested that the bioemulsifier from A. calcoaceticus subsp. anitratus SM7 could be useful in environmental application, especially bioremediation of oil-polluted seawater.

Keywords

• bioemulsifier
• marine bacteria
• Acinetobacter sp.
• production
• characterization