Chemical structure of algaenans from the fresh water algae Tetraedron minimum, Scenedesmus communis and Pediastrum boryanum

The cell wails of the fresh water green microalgae Tetraedron minimum, Scen edesmus communis and Pediastrum boryanum are composed of highly resistant, non-hydrolyzable aliphatic biopolymers as revealed by C-13-NMR, FTIR and th ermal and chemical degradations. The biopolymers are composed of long-chain even-carbon-numbered omega(9)-unsarurated omega-hydroxy fatty acid monomer s varying in chain length from 30 to 34 carbon atoms. These monomers are in termolecularly ester linked to form linear chains in which the unsaturation s act as the starting position of ether cross-linking. S. communis biosynth esises a more densely cross-linked algaenan than T. minimum and P. boryanum . The monomers of T. minimum have, on average, larger chain lengths than th ose of P. boryanum and S. communis. The polyether nature of these algaenans makes them highly resistant against degradation, so that they are selectiv ely preserved in the sedimentary record. Therefore, these algaenans probabl y are important precursors for Type I kerogens. (C) 1998 Elsevier Science L td. All rights reserved.