VIABILITY OF MASS ALGAL CULTURES PRESERVED BY FREEZING AND FREEZE-DRYING

The microalgae Chaetoceros sp. and Phaeodactylum tricornutum were grow n in semicontinuous 151 cultures, a volume commonly used for mid-scale inocula in aquacultural practices. The daily yields were concentrated and stored by freezing and freeze-drying for up to 1 month. After slo w or fast freezing without the protective agents glycerol or Me2SO, ne ither of the microalgae was capable of active growth, while with the c ryoprotectants slow freezing gave good results after 7 days of storage at -20 degrees C. After 15 and 30 days, however, microalgae growth wa s poor, probably due to bacterial contamination. Freeze-drying gave ev en worse results, which we attribute to severe losses of storage produ cts after this treatment. (C) 1997 Elsevier Science B.V.