Introduction
Microalgae are considered as one of the most promising feedstocks
for biofuels [1,2]. Botryococcus braunii is rich in a variety
of hydrocarbons which are regarded as a potential algal oil source
for renewable biofuel production [3,4]. In order to achieve efficient
algal oil recovery, the wet algal cells need to be harvested and pretreated
by a cost-effective dewatering process [5,6]. The algal oil in
B. braunii accumulates externally in successive outer walls and can
be easily recovered from dry algal biomass with non-polar solvents,
but it still remains a big challenge to extract the algal oil
from wet algal biomass because water around algal cell forms hydrated
shell which acts as a barrier and severely decreases the algal
oil recovery [7]. Recently, several extraction methods have been
developed to recover the algal oil from wet biomass, including
thermal pre-treatment disruption process, switchable-polarity solvent
extraction and DME-mediated extraction method [8–10]. In
these methods, the extraction solvent played a key role to disrupt
the hydrated shell barrier and algal cell walls in order to achieve
satisfactory algal oil recovery from wet biomass [9,10]. Up to date,
there still is a great interest to develop an efficient extraction technique
to disrupt the algal cell walls and recover the algal oil from
the wet biomass without dewatering process for low-cost renewable
energyapeney