Resistant biopolymer in the outer walls of Botryococcus braunii, B race
A biopolymer highly resistant to non-oxidative treatments (PRBB) occurs in the outer walls of theB race of Botryococcus braunii. PRBB accounts forca 10% of the total algal biomass and fulfils the usual requirements to be regarded as a sporopollenin; however, the structural information obtained indicate it does not derive from carotenoids. A complete lack of relationship was also noted between PRBB and the isoprenoid hydrocarbons produced in large amount by theB race. The PRBB structure is based upon saturated, normal, hydrocarbon chains up to C31; these chains are probably linked by ether bridges. PRBB also comprises ester and hydroxyl groups protected from external attacks by the polymeric network. PRBB and PRBA (the resistant biopolymer isolated from the outer walls of theA race of B. braunii, which produces non-isoprenoid hydrocarbons) are not identical. Nevertheless they show the same major structural features and belong to the samegroup of resistant biopolymers (probably derived from the polymerisation of very long chain fatty acid derivatives). Analogies between PRBA and PRBB would have resulted in the formation, via fossilization of A andB races, of kerogens with a similar structure and a high oil potential.