Long-term storage of a number of microorganism species using different cryoprotectants

Abstract

This study aims to generate a microalgae culture collection, and ensure the long-term survival of this collection by prolonging the period when the isolated microalgae and other microorganism cultures can be preserved. The microalgae cultures included four microalgae species (Chlorella vulgaris Beyerinck [Beijerinck], Klebsormidium subtile (Kützing) Mikhailyuk, Glaser, Holzinger & Karsten, Microcoleus autumnalis (Gomont) Strunecky, Komárek & J.R. Johansen and Synechococcus bigranulatus Skuja), two bacteria species (Staphylococcus aureus and Escherichia coli) and two fungi species (Aspergillus Niger and Pénicillium sp.). The study applied a cryopreservation protocol at -80°C directly to each of the species. The cryoprotective agents used in the study were dimethyl sulfoxide (DMSO), glycerol and skimmed milk at a final concentration of 5% for the microalgae in addition to an application without any cryoprotectant at all. The cryoprotectant agents used for this procedure were 15% final glycerol concentration for the bacteria and 10% skimmed milk for the fungi. After six months, the strains of C. vulgaris (93%), S. bigranulatus (83%) and M autumnalis (80%) showed higher viability rates in glycerol, while the strain of K. subtile (93%) showed higher viability rates in skimmed milk. The recovery ratio of E. coli, S. aureus, A. Niger and Pénicillium sp. were found to be 5.10, 3.23, 1.98 and 2.67 log CFU/ml, respectively. © by PSP