The lipid contents in the microalgal cells were recovered after cell
disruption measurements using the various sequences described
above. The lipid recovery yields for the various treatments is shown in
Fig. 3
A, which looks remarkably similar to the cell disruption efficiency
presented in
Fig. 1
. As lipid yield is expected to be directly related to cell
disruption efficiency, lipid yield was increased in the presence of the
copolymers relative to the pure enzyme treatment. The highest lipid
yield of 59% was achieved with pNcAA-10 addition prior to enzyme
addition, which had the corresponding highest cell disruption efficiency
of 68%. Furthermore, enzymatic lipid yield is correlated with amine con-
tent in the polymers, in a similar fashion as cell disruption efficiency.
The correlation between lipid yield and cell disruption is shown in
Fig. 3
B, and the linear fit to the data is indicated by the dotted red line.
The recovered lipid was not always directly proportional to the extent
of cell disruption because the intracellular contents are not entirely
released into bulk suspension for lipid extraction by hexane, which
has been observed previously with the enzymatic cell wall disruption
method
[5]
. Another reason could be that the released lipid was trapped
by microalgal cells which formed clusters of cell aggregates during the
extraction process