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A new process for the isolation of algaenans (insoluble non-hydrolysable, highly aliphatic biopolymers of microalga cell walls) which avoids their contamination with melanoidin-like polymer artifacts is presented and the algaenans of two species from the Chlorophyceae (Scenedesmus communis and Botryococcus braunii) are re-examined. Preliminary release of the polysaccharides from these microorganisms by trifluoroacetic acid hydrolysis affords a pure, or much less contaminated, algaenan for the two species. Re-examination of the pyrolysate of S. communis algaenan indicates that the long-chain n-alkylnitriles, previously detected when the algaenan was isolated by the usual process ( Berkaloff et al., 1983 ), do not actually originate from this biopolymer. We suggest that some nitrogen-containing molecules present in S. communis (or in other Chlorophyceae species) are incorporated into the structure of the melanoidin-like polymers generated when the algaenan is isolated by the usual process which lead, upon pyrolysis, to nitriles. Consideration of previous data, on the pyrolysates of numerous kerogens, suggests that a similar process occurs under natural conditions during early diagenesis. |
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