Liquid Hydrocarbon Production Potential of a Novel Strain of the Microalga Botryococcus braunii: Assessing the Reliability of in Situ Hydrocarbon Recovery by Wet Process Solvent Extraction

Abstract

Botryococcus braunii is considered a promising source of non-oxygenated liquid biofuels. Harvesting and pre-extraction processing of the algal biomass are among the major challenges for commercial sustainability of algae-based biofuel production. An energy-efficient and cost-effective method of in situ recovery of the hydrocarbon-rich oil from the harvest aqueous culture of B. braunii without pre-extraction processing is an attractive proposition. In this study, in situ recovery of lipid-hydrocarbons by wet process solvent extraction (WPSE) was assessed using the harvest aqueous culture of a novel strain B. braunii GUBIOTJTBB1. The strain yielded 56.3% (w/w) total lipids, 42.6% of which was Soxhlet n-hexane extractable. The recovery of lipid contents was found to vary significantly (P < 0.001) with the extraction solvent. Fractionation of the total lipids using silica gel column chromatography with n-hexane as eluent yielded lipids (24.9%), which revealed the presence of mostly aliphatic hydrocarbons by GC-MS analysis. In situ recovery rate of the hydrocarbon-rich oil by WPSE, which varies significantly (P < 0.05) with the method of pretreatments, was the maximum (88.99%) with autoclave-assisted WPSE followed by microwave-assisted WPSE (80%). Applications of multivariate chemometrics in FTIR fingerprint assessment confirmed the reliability of the method. Besides rapidity and minimizing the use of toxic solvents, the principal fate of the method was on the fact that the hydrocarbon-rich oil could be recovered from the harvest aqueous culture, which circumvents the energy intensive pre-extraction processing of the algal biomass.