Abstract
The cell walls of the fresh water green microalgae
Tetraedron minimum,
Scenedesmus communis and
Pediastrum boryanum are composed of highly resistant, non-hydrolyzable aliphatic biopolymers as revealed by
13C-NMR, FTIR and thermal and chemical degradations. The biopolymers are composed of long-chain even-carbon-numbered
ω
9-unsaturated
ω-hydroxy fatty acid monomers varying in chain length from 30 to 34 carbon atoms. These monomers are intermolecularly ester linked to form linear chains in which the unsaturations act as the starting position of ether cross-linking.
S. communis biosynthesises a more densely cross-linked algaenan than
T. minimum and
P. boryanum. The monomers of
T. minimum have, on average, larger chain lengths than those of
P. boryanum and
S. communis. The polyether nature of these algaenans makes them highly resistant against degradation, so that they are selectively preserved in the sedimentary record. Therefore, these algaenans probably are important precursors for Type I kerogens.