Structural analysis of resistant polymers in extant algae and ancient sediments

Abstract

Algaenans are non-hydrolysable insoluble aliphatic biopolymeric materials present in the cell walls of some green microalgae. In these cell walls it serves a protecting role against microbial attack and/or desiccation. In the cell wall, algaenan is probably present as an intricate part of a greater chemical structure most likely involving compounds like proteins and polysaccharides. Earlier studies have shown that, because of its resistant nature, algaenan is selectively preserved in sediments and suggested to constitute a significant part of the insoluble non-hydrolysable macromolecular part of sedimentary organic matter, termed kerogen. Here it can serve as a source material for the formation of oil and gas upon further catagenesis. The first part of this thesis mainly focuses on the distribution of algaenan-containing algae within the division Chlorophyta and the chemical composition of these algaenans. Most of the algae investigated in the first part of the thesis are reported from sediments and were likely candidates to fmd the resistant biopolymer algaenan. The second part of the thesis mainly focuses on the analysis of algal microfossils in order to determine if the specific chemistry of the algaenans as deduced from the extant species investigated in part I is preserved as such. Furthermore, upon comparison of these results with algaenans isolated from cultured algae it was possible to investigate if chemical changes have occurred during diagenesis. The final two Chapters involved the analysis of some very peculiar microfossils in order to determine if these consist of preserved algaenans. In this PhD study the techniques that have become available over the years to analyse these recalcitrant biopolymers were applied. Although each technique by itself only provided a small piece of the macromolecular puzzle, in combination the data provided new information about these resistant biopolymers, which are able to survive burial in sediments for millions of years.