title: Superior biolubricant from a species of red microalga.
abstract: The rheological properties of the sulfated polysaccharide of the red microalga Porphyridium sp., a heteropolymer with a molecular weight of 3-5 x 10(6) Da, indicated that this material might be an excellent candidate for lubrication applications: the viscosity of the polysaccharide is stable over a range of temperatures, pH values, and salinities. In this study, various rheological and lubricant properties of the polysaccharide were evaluated in comparison with those of a widely used biolubricant, hyaluronic acid. The viscosity of the Porphyridium sp. polysaccharide remained essentially unchanged in a temperature range of 25-70 degrees C. In tribology tests on a ball-on-flat ceramic pair, the values for the friction coefficient and wear rate for the pair lubricated with polysaccharide were remarkably lower than those for hyaluronic acid, especially at high loads. In a test on a steel ring/ultrahigh-molecular-weight polyethylene (UHMWPE) block pair, the wear tracks on the surface of the UHMWPE were more pronounced for hyaluronic acid than for the polysaccharide. Atomic force microscopy showed that the polysaccharide was effectively adsorbed onto mica surfaces, forming ultrathin coating layers in the nanometer range. As is required for biolubricant applications, the polysaccharide was not degraded by hyaluronidase. The stability of the Porphyridium sp. polysaccharide to heat and to hyaluronidase combined with its ability to reduce friction and wear indicate its potential as an advantageous biolubricant.
authors.affiliation: Department of Biotechnology Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel. arad@ bgu.ac.il
authors.forename: Shoshana Malis
authors.initials: SM
authors.lastname: Arad
authors.forename: Lev
authors.initials: L
authors.lastname: Rapoport
authors.forename: Alex
authors.initials: A
authors.lastname: Moshkovich
authors.forename: Dorit
authors.initials: D
authors.lastname: van Moppes
authors.forename: Mark
authors.initials: M
authors.lastname: Karpasas
authors.forename: Roxana
authors.initials: R
authors.lastname: Golan
authors.forename: Yuval
authors.initials: Y
authors.lastname: Golan
mesh_terms: D006820:Hyaluronic Acid / Q000737:chemistry; D006821:Hyaluronoglucosaminidase / Q000737:chemistry; D008153:Lubrication; D018625:Microscopy, Atomic Force; D011134:Polysaccharides / Q000737:chemistry*; D044665:Porphyridium / Q000737:chemistry*; D012212:Rheology
chemical_list: D011134:Polysaccharides; D006820:Hyaluronic Acid; D006821:Hyaluronoglucosaminidase