A comparative study of macromolecular substances of a Coorongite and cell walls of the extant alga Botryococcus braunii

A Coorongite sample of Lake Balkash (Kazakhstan, CIS) was analyzed in detail by 13C-NMR, FTIR, Curie point pyrolysisgas chromatographymass spectrometry, and by fractionation and derivatization with dimethyldisulphide of an off-line pyrolysate. Both the spectroscopic and the pyrolysis data indicate that the Coorongite was derived almost entirely of organic matter of the green microalga Botryococcus braunii race A. Homologous series of n-alkanes and n-alk-1-en-9 in all pyrolysates indicated the presence of algaenan, a highly aliphatic and resistant cell wall biomacromolecule of B. Braunii race A. Highly specific pyrolysis products, in particular n-alkadienes, n-alkatrienes, alk-1-en-9-ones, and alk-1-en-10-ones with C27, C29, and C31 carbon atoms clearly indicated that C27, C29, and C31 alkadienes and alkatrienes, originally present in B. braunii race A as such, were cross-linked by oxygen during the very early stages of diagenesis under oxic conditions. Furthermore, several types of dialkenylethers, also present as soluble lipids in B. braunii race A, had undergone cross-linking by oxygen as well. These cross-linked lipids contribute significantly to the Coorongite and clearly demonstrate that under specific conditions kerogen consists of both preserved biomacromolecules and insoluble, cross-linked, low-molecular-weight lipids

Resistant biomacromolecules as major contributors to kerogen

Current research concerning the chemical characterization of organic macromolecules present in well-preserved fossilized materials with known morphologies revealed by (electron) microscopic studies results in the recognition of unknown, resistant biomacromolecules in a variety of organisms. It is shown that highly aliphatic, non-saponifiable biomacromolecules in cell walls of algae (algaenans) have unique structures, probably as a result of different biosynthetic pathways and that they consist of n-alkyl-, isoprenoid and tricyclic alkyl units. It is also becoming clear that algaenans are structurally different from the highly aliphatic, non-saponifiable biomacromolecules occurring in plant cuticles (cutans), periderm tissue (suberans), some sporopollenins and in tegmens of seeds of water plants. All these types of aliphatic biomacromolecules are highly resistant and therefore selectively preserved in the geosphere. In particular, Type I and II kerogens consist mainly, in some cases exclusively, of these aliphatic biomacromolecules. Polysesquiterpenoids and polyditerpenoids occur in fresh and fossil angiosperm and gymnosperm resins respectively and also show resistant behaviour in the geosphere. Some waxy crude oils contain large amounts of compounds derived from these substances after thermal cracking. A completely new polyphenol type of biomacromolecule was encountered in several fossilized outer walls of seeds (testae) of water plants. Preliminary results indicate that this phenolic biomacromolecule is an alternative source of phenolic moieties in lignites and coals. The significance of lignin as a source of phenolic moieties in subsurface organic matter (e.g. vitrinites) is probably overestimated

Mechanisms of flash pyrolysis of ether lipids isolated from the green microalga Botryococcus braunii race

Two types of ether lipids isolated from the microalga Botryococcus braunii have been subjected to flash pyrolysis. The pyrolysis products were separated and analyzed by GC/MS. The nature and distribution of the pyrolysis compounds gave clues to the different mechanisms involved in the pyrolysis of ether-linked alkyl chains. The relatively abundant presence of alkenes, alkadienes, alken-9-ones and alken-10-ones with chain lengths corresponding to those of the ether-bound alkyl chains indicated that the cleavage of the C---O bond is an important first step in the pyrolysis process