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

Dimitrijev-Dwyer, Mirjana, He, Lizhong, James, Michael, Nelson, Andrew, Wang, Liguang and Middelberg, Anton 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/c2sm25082a


Author Dimitrijev-Dwyer, Mirjana
He, Lizhong
James, Michael
Nelson, Andrew
Wang, Liguang
Middelberg, Anton P. J.
Title The effects of acid hydrolysis on protein biosurfactant molecular, interfacial, and foam properties: pH responsive protein hydrolysates
Journal name Soft Matter   Check publisher's open access policy
ISSN 1744-683X
1744-6848
Publication date 2012
Sub-type Article (original research)
DOI 10.1039/c2sm25082a
Open Access Status Not Open Access
Volume 8
Issue 19
Start page 5131
End page 5139
Total pages 9
Place of publication Cambridge, United Kingdom
Publisher Royal Society of Chemistry
Collection year 2013
Language eng
Formatted abstract
The 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.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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Created: Thu, 26 Apr 2012, 00:07:29 EST by Dr Liguang Wang on behalf of School of Chemical Engineering