Chemical structure and hydrocarbon generation potentials of cyanobacteria Schizothrix calcicole and its resistant biopolymer

Microalgae have attracted much attention because of their great potential in the development of sustainable biofuel. In this study, cyanobacteria Schizothrix calcicole was fractionated into different fractions and characterized by elemental analyses, Rock-Eval pyrolysis, and ¹³C NMR. Closed pyrolysis experiments were carried out on the bulk (BL) sample of S. calcicole and its nonhydrolyzable organic matter (NHOM) fraction. The results suggested the NHOM fraction was composed of a saturated and unbranched or weakly branched hydrocarbon chain with a chain length up to 32, which was highly aliphatic resistant biopolymer similar to algaenan in structure, and exhibited higher oil yield (58.1 %) and oil and gas production potentials (OGPs, 63.9 %) than the BL sample did. Moreover, the n-alkanes for the NHOM fraction showed bimodal distribution and were dominated by long chains higher than C₁₅. On the contrary, the BL sample exhibited unimodal distribution of n-alkanes, in which middle- and short-chain n-alkanes with chain length <17 were more abundant. In addition, the results indicated ¹³C NMR is an effective approach to evaluate hydrocarbon generation potentials. Our investigation identifies aliphatic biopolymers in cyanobacteria S. calcicole and improves the understanding of hydrocarbon generation of its different fractions.