Characterization of the squalene-rich Botryococcus braunii Abt02 strain

Abstract

Botryococcus braunii is widely studied due to its high hydrocarbon content. In this study, B. braunii Abt02 was subjected to several analyses, including cytological observation, hydrocarbon composition analysis by gas chromatography mass spectrometry (GC-MS), phylogenetic identification using known races (A, B and L) of B. braunii strains based on their 18S rDNA sequences, and qPCR-based investigation of transcript accumulation levels of hydrocarbon biosynthesis-related enzymes (DXS, MCS, DLS, SQS) during different growth phases (lag phase, log phase, early stationary growth phase, late stationary growth phase) under nitrogen-replete and nitrogen-depleted growth conditions, respectively. Based on cytological observation and on the 18S rDNA phylogenetic analysis, strain Abt02 was assigned to race B. Analysis of the strain’s chemical composition showed that the B. braunii Abt02 contained high levels of hydrocarbons, which accounted for 43.75% of the cell’s dry weight. Of these hydrocarbons, squalene and its derivatives accounted for up to 87.54%. In addition, all four enzymes investigated were expressed at higher levels during the log growth phase under nitrogen depleted conditions than under nitrogen replete conditions.