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Novel polysaccharide–protein-based amphipathic formulations


Previous results showed that the cell-surface esterase from Acinetobacter venetianus RAG-1 enhances the emulsification properties of the polymeric bioemulsifier emulsan and its deproteinated derivative apoemulsan (Bach H, Berdichevsky Y, Gutnick D (2003) An exocellular protein from the oil-degrading microbe Acinetobacter venetianus RAG-1 enhances the emulsifying activity of the polymeric bioemulsifier emulsan. Appl Environ Microbiol 69:2608–2615). Here we show that in the presence of the his-tagged recombinant esterase from RAG-1, 18 different polysaccharides from microbial, plant, insect and synthetic sources formed hexadecane-in-water emulsions. Emulsifying activities were distributed over a 13-fold range from over 4800 U/mg protein/mg polysaccharide in the case of apoemulsan to 370 U/mg protein/mg polysaccharide in the case of alginic acid. The stability of the emulsions ranged between 95 and 58%. Emulsions formed in the presence of seven of the polysaccharides exhibited stabilities of over 80%. The esterase from A. calcoaceticus BD4, which shows sequence homology to the RAG-1 esterase, was inactive in emulsification enhancement. The sequence of the RAG-1 esterase was shown to contain two conserved peptide sequences previously shown to be implicated in carbohydrate/polysaccharide binding. A hypothetical model illustrating a possible mode of interaction between the esterase, the apoemulsan and the oil droplet is presented. The complex is presumed to generate a series of “coated” oil droplets which are restricted in their ability to coalesce resulting in a relatively stable emulsion.

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This work was supported in part by a grant from the CDR project of the US A.I.D. We thank Rina Avigad for excellent technical assistance. Thanks also to David Nakar for ideas and useful suggestions. HB was a predoctoral fellow in the Department of Molecular Microbiology and Biotechnology at Tel-Aviv University.

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Correspondence to David L. Gutnick.

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Bach, H., Gutnick, D.L. Novel polysaccharide–protein-based amphipathic formulations. Appl Microbiol Biotechnol 71, 34–38 (2006). https://doi.org/10.1007/s00253-005-0149-9

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  • Polysaccharide
  • Alginic Acid
  • Emulsan
  • Hexadecane
  • Acinetobacter