Thirty-milliliter exponentially growing
culture (chlorophyll a content of 10 μg mL−1
) was concentrated
to 10 mL by centrifugation (2,500×g) and mixed thoroughly
with the sodium alginate solution at room temperature.
This solution was added drop-wise using a syringe canula into
100 mL of 0.1 M calcium chloride solution in a laminar flow
cabinet. The laminar flow cabinet was sterilized prior to use by
exposing the inner chamber to UV-C lamp for 10 min.
Calcium alginate beads thus formed were left in the same
solution for hardening at 4 °C for 1 h. The beads were
subsequently harvested and washed with sterile water followed
by medium. These were then left to air dry on Petri plates
inside a UV-sterilized laminar flow cabinet with HEPA filters.
The dried beads were stored in sterile vials at room temperature
and in dark. Cells were regenerated from alginate beads
every 3 months to study the performance of calcium alginate
as preserving material for cyanobacteria.