title: Optimised purification and characterisation of lipid transfer protein 1 (LTP1) and its lipid-bound isoform LTP1b from barley malt.
abstract: In beer brewing, brewers worldwide strive to obtain product consistency in terms of flavour, colour and foam. Important proteins contributing to beer foam are lipid transfer proteins (LTPs), in particular LTP1 and its lipid-bound isoform LTP1b, which are known to transport lipids in vivo and prevent lipids from destabilising the beer foam. LTP1 and LTP1b were successfully purified using only five purification steps with a high purified protein yield (160 mg LTP1 and LTP1b from 200 g barley). Circular dichroism of LTP1 and LTP1b confirmed that both proteins are highly tolerant to high temperatures (>90 °C) and are pH stable, particularly at a neutral to a more basic pH. Only LTP1 exhibited antiyeast and thermo-stable lytic activity, while LTP1b was inactive, indicating that the fatty acid moiety compromised the antimicrobial activity of LTP1. This lack in antiyeast activity and the positive foam properties of LTP1b would benefit beer fermentation and quality.
authors.affiliation: BIOPEP Peptide Group, Department of Biochemistry, Science Faculty, University of Stellenbosch, South Africa; Department of Food Science, Faculty of AgriScience, University of Stellenbosch, South Africa.
authors.forename: Melanie
authors.initials: M
authors.lastname: Nieuwoudt
authors.affiliation: BIOPEP Peptide Group, Department of Biochemistry, Science Faculty, University of Stellenbosch, South Africa.
authors.forename: Nicolaas
authors.initials: N
authors.lastname: Lombard
authors.affiliation: BIOPEP Peptide Group, Department of Biochemistry, Science Faculty, University of Stellenbosch, South Africa. Electronic address: mra@sun.ac.za.
authors.forename: Marina
authors.initials: M
authors.lastname: Rautenbach
mesh_terms: D001515:Beer / Q000032:analysis; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification*; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D050556:Fatty Acid-Binding Proteins; D001467:Hordeum / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008055:Lipids / Q000737:chemistry; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification; D055550:Protein Stability; D012441:Saccharomyces cerevisiae
chemical_list: D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D008055:Lipids; C422456:Ltp1 protein, barley; D020033:Protein Isoforms
keywords: Antiyeast activity; LTP1; Lipid transfer protein; Purification; Secondary structure; Stability