2 research outputs found
Regenerative Astaxanthin Extraction from a Single Microalgal (<i>Haematococcus pluvialis</i>) Cell Using a Gold Nano-Scalpel
Milking
of microalgae, the process of reusing the biomass for continuous production
of target compounds, can strikingly overcome the time and cost constraints
associated with biorefinery. This process can significantly improve
production efficiency of highly valuable chemicals, for example, astaxanthin
(AXT) from Haematococcus pluvialis.
Detailed understanding of the biological process of cell survival
and AXT reaccumulation after extraction would be of great help for
successful milking. Here we report extraction of AXT from a single
cell of H. pluvialis through incision
of the cell wall by a gold nanoscalpel (Au-NS), which allows single-cell
analysis of wound healing and reaccumulation of AXT. Interestingly,
upon the Au-NS incision, the cell could reaccumulate AXT at a rate
two times faster than the control cells. Efficient extraction as well
as minimal cellular damage, keeping cells alive, could be achieved
with the optimized shape and dimensions of Au-NS: a well-defined sharp
tip, thickness under 300 nm, and 1–3 μm of width. The
demonstration of regenerative extraction of AXT at a single cell level
hints toward the potential of a milking process for continuous recovery
of target compounds from microalgae while keeping the cells alive
Magnetic-Nanoflocculant-Assisted Water–Nonpolar Solvent Interface Sieve for Microalgae Harvesting
Exploitation of magnetic flocculants
is regarded as a very promising energy-saving approach to microalgae
harvesting. However, its practical applicability remains limited,
mainly because of the problem of the postharvest separation of magnetic
flocculants from microalgal flocs, which is crucial both for magnetic-flocculant
recycling and high-purity microalgal biomasses, but which is also
a very challenging and energy-consuming step. In the present study,
we designed magnetic nanoflocculants dually functionalizable by two
different organosilane compounds, (3-aminopropyl)Âtriethoxysilane (APTES)
and octyltriethoxysilane (OTES), which flocculate negatively charged
microalgae and are readily detachable at the water-nonpolar organic
solvent (NOS) interface only by application of an external magnetic
field. APTES functionalization imparts a positive zeta potential charge
(29.6 mV) to magnetic nanoflocculants, thereby enabling microalgae
flocculation with 98.5% harvesting efficiency (with a dosage of 1.6
g of dMNF/g of cells). OTES functionalization imparts lipophilicity
to magnetic nanoflocculants to make them compatible with NOS, thus
effecting efficient separation of magnetic flocculants passing through
the water-NOS interface sieve from hydrophilic microalgae. Our new
energy-saving approach to microalgae harvesting concentrates microalgal
cultures (∼1.5 g/L) up to 60 g/L, which can be directly connected
to the following process of NOS-assisted wet lipid extraction or biodiesel
production, and therefore provides, by simplifying multiple downstream
processes, a great potential cost reduction in microalgae-based biorefinement