RESISTANT BIOMACROMOLECULES IN MARINE MICROALGAE OF THE CLASSES EUSTIGMATOPHYCEAE AND CHLOROPHYCEAE - GEOCHEMICAL IMPLICATIONS

Non-hydrolysable macromolecular constituents (i.e. algaenans) were iso lated from two out of seven marine microalgae investigated. Nannochlor opsis salina and Nannochloropsis sp. from the class of Eustigmatophyce ae produce highly aliphatic algaenans. Flash pyrolysis and chemical de gradations with HI and RuO4 allowed for the identification of their ch emical structure, which is mainly composed of polyether-linked long-ch ain (up to C-36) n-alkyl units. The building blocks of this polymer we re also recognized in lipid fractions. The green microalgae (Chlorophy ceae) Chlorella spaerckii, Chlorococcum sp. and Nannochloris sp. were earlier thought to biosynthesize algaenans comprising aliphatic and/or aromatic moieties. However, a new isolation method utilizing trifluor oacetic acid (TFA) prior to the other hydrolyses revealed that the mac romolecular material isolated from these three chlorophytes was either hydrolysable with TFA or artefacts from the former method. Similar to algaenans from fresh water green microalgae, the aliphatic eustigmato phyte algaenans are likely to be selectively preserved in depositional environments and might ultimately serve as source rock organic matter of marine crude oils. Furthermore, they may play an important role in the cycling of carbon. (C) 1997 Elsevier Science Ltd.