The effects of acid hydrolysis on protein biosurfactant molecular, interfacial, and foam properties: pH responsive protein hydrolysates

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dc.contributor.authorDimitrijev-Dwyer, Men_AU
dc.contributor.authorHe, LZen_AU
dc.contributor.authorJames, Men_AU
dc.contributor.authorNelson, Aen_AU
dc.contributor.authorWang, LGen_AU
dc.contributor.authorMiddelberg, APJen_AU
dc.date.accessioned2012-06-18T02:09:17Zen_AU
dc.date.available2012-06-18T02:09:17Zen_AU
dc.date.issued2012-03-23en_AU
dc.date.statistics2012-06-18en_AU
dc.description.abstractThe success of hydrolysis in improving the functional foaming properties of surface-active proteins is usually attributed to three factors: decreased molecular size; increased hydrophobicity; and microchemical changes, specifically deamidation of glutamine and asparagine. Studying these individual factors is difficult using naturally-occurring proteins, as hydrolysate products are complex mixed systems, and the mechanisms of foam stabilization are likewise complex. To address this complexity we report studies of a recombinant protein (DAMP4) which comprises four peptide surfactant (DAMP1) molecules connected by acid-labile amino acid (Asp-Pro) linkers. Hydrolysis of DAMP4 under conditions of low pH and high temperature produced h-DAMP1, a mixture of deamidated variants of the chemically-synthesized DAMP1 peptide surfactant. By examining foaming performance of these molecules, we are able to isolate the effects of molecule size (DAMP1 vs. DAMP4) and deamidation (h-DAMP1 vs. DAMP1). Molecule size had little effect on foaming for the conditions studied. However, deamidation completely changed foaming behaviour, most likely due to alteration of interfacial charge structure (through deamidation of glutamine to glutamic acid) and consequent effects on thin-film stability. Good foaming was observed only at pH values away from the isoelectric points (pI) of the biomolecules where an electrostatic barrier to film rupture can occur. The addition of Zn2+ to DAMP4, h-DAMP1 and DAMP1 caused visible aggregation under all conditions, which assisted in stabilising foams only in situations where a net charge would be expected. © 2012, Royal Society of Chemistryen_AU
dc.identifier.citationDimitrijev-Dwyer, M., He, L. Z., James, M., Nelson, A., Wang, L. G., Middelberg, A. P. J. (2012). The effects of acid hydrolysis on protein biosurfactant molecular, interfacial, and foam properties: pH responsive protein hydrolysates. Soft Matter, 8(19), 5131-5139. doi:10.1039/c2sm25082aen_AU
dc.identifier.govdoc4305en_AU
dc.identifier.issn1744-683Xen_AU
dc.identifier.issue19en_AU
dc.identifier.journaltitleSoft Matteren_AU
dc.identifier.pagination5131-5139en_AU
dc.identifier.urihttp://dx.doi.org/10.1039/c2sm25082aen_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4338en_AU
dc.identifier.volume8en_AU
dc.language.isoenen_AU
dc.publisherRoyal Society of Chemistryen_AU
dc.subjectFilmsen_AU
dc.subjectAcid hydrolysisen_AU
dc.subjectProteinsen_AU
dc.subjectFoamsen_AU
dc.subjectSurface forcesen_AU
dc.subjectMoleculesen_AU
dc.titleThe effects of acid hydrolysis on protein biosurfactant molecular, interfacial, and foam properties: pH responsive protein hydrolysatesen_AU
dc.typeJournal Articleen_AU
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