Occurrence of aliphatic biopolymer in chlorophyceae algae and cyanobacteria-rich phytoplankton.

• Non-hydrolyzable organic matter (NHOM) was isolated from algae and cyanobacteria-rich phytoplankton. • The aliphatic structure of NHOM (algaenan-like) was observed through advanced NMR techniques. • Cyanobacteria-rich NHOM consisted of long, saturated and unbranched hydrocarbon chains. • Cyanobacteria-rich NHOM showed a high oil-prone potential. Two cultured chlorophyceae algae and two cyanobacteria-rich phytoplankton were separated into five fractions and characterized by 13C cross polarization/total sideband suppression (CP/TOSS) nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), Rock-Eval and closed pyrolysis analyses. The structures of the acid nonhydrolyzable organic matter (NHOM) fractions were similar to those of poly(methylene)-rich aliphatic algaenan. We found that the cyanobacteria-rich phytoplankton contained aliphatic nonhydrolyzable biopolymers. The NMR and Rock-Eval analyses showed that the isolated NHOM exhibited high oil-prone potentials. Pyrolysis analysis of the field-collected NHOM from Liuhuahu Park in Guangzhou (GP_NHOM) indicated that it exhibited high oil-prone potential and comprised a long, saturated and unbranched hydrocarbon chain (up to C 33) structural unit. The maximum oil and gaseous hydrocarbon generation potentials reached 55.9% and 7.2%, respectively and were very close to those derived from 13C CP/TOSS NMR, suggesting that 13C NMR is an effective approach for evaluation of oil and gas production potentials. This investigation is helpful for improving understanding of kerogen formation mechanisms through selective preservation and the generation mechanisms of biocrude oil. [ABSTRACT FROM AUTHOR]