Open AccessPolysaccharide from coccoliths (CaCO 3 biomineral)
Author(s) -
KOK Dik J.,
BLOMEN Leo J. M. J.,
WESTBROEK Peter,
BIJVOET Olav L. M.
Publication year - 1986
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1986.tb09734.x
Subject(s) - crystallization , polysaccharide , crystal growth , supersaturation , solubility , chemistry , chemical engineering , adsorption , crystal (programming language) , calcite , economies of agglomeration , monolayer , seed crystal , crystallography , mineralogy , organic chemistry , biochemistry , single crystal , programming language , computer science , engineering
A polysaccharide associated with coccoliths of the marine alga Emiliania huxleyi (coccoliths are elaborately shaped calcite biominerals) was isolated and its influence on the crystallization of calcium oxalate monohydrate crystals was studied. Crystallization was monitored in a carefully controlled system by measuring the incorporation of 45 Ca tracer from a supersaturated solution into seed crystals of calcium oxalate monohydrate in the absence and in the presence of polysaccharide. The method allowed differentiation between effects on solubility, growth and agglomeration of crystals. At the very low concentrations used in this study, the polysaccharide had no significant effect on the solubility product; it strongly inhibited the growth and strongly stimulated the agglomeration of the crystals. Thus, the two processes of growth and agglomeration, being both crystal‐surface‐related processes, may react in opposite directions upon surface adhesion of the additive. This finding opens new insights on how a mineralization process may be controlled. The inhibitory effect on growth is shown to proceed through a monolayer type of adsorption of the polysaccharide onto the crystal surface. The portion of the polysaccharide used for the stimulatory effect on agglomeration shows a different type of adsorption, whereby less crystal surface is covered per molecule of polysaccharide. This strongly suggests, that the mechanism whereby agglomeration is stimulated operates through ‘viscous binding’, with the polysaccharide bridging the gap between two crystal surfaces. In the discussion these findings are related to some possible biological functions of the polysaccharide.