Viability of Basidiomycete fungal strains under different conservation methods: cryopreservation vs. freeze-drying processes

Four basidiomycete fungi, Agaricus blazei Murrill (Agaricomycetideae), Ganoderma lucidum (W.Curt.: Fr.) P. Karst., Grifola frondosa (Dicks.: Fr.) S.F. Gray (Higher Basidiomycetes), and Pleurotus pulmonarius (Fr.) Quél. (Agaricomycetideae) were evaluated using three conservation methods for 12 months, recording their viability in order to establish the best conservation method. Growth kinetics, biomass, and polysaccharide production were studied. The conservation methods implemented included: distilled water at 24 °C; sawdust and rice bran with 10% glycerol at -20 °C; sawdust and rice bran with 10% glycerol at -80 °C; and freeze-drying of biomass with trehalose or skimmed milk. After conducting the analysis of the results after 12 months of conservation, we determined that the distilled water treatment at 24 °C was the best conservation method with the highest percentage of recoverability, at 83.3% during the 12th month, followed by the cryoconservation treatment at 80 °C, where 75% were recovered with no negative effects on biomass and polysaccharide production. The -20 °C and freeze-drying treatments were not effective; with cryoconservation at -20 °C treatment, strain recovery only occurred during the first month and with freeze-drying it was not possible to recover any strains during the entire 12-month period evaluated.