RESISTANCE OF POTENTIAL AMYLASE PRODUCERS ALTERNARIA TENUISSIMA AND GEOMYCES PANNORUM TO LYOPHILIZATION

The purpose of the study is to test the possibility of lyophilization of Alternaria tenuissima and Geomyces pannorum strains isolated by the authors as potential amylase producers for the food industry. The conidia of the studied strains were suspended in protective media and lyophilized using a Bio-Rus-4SFD lyophilizer. Three protective media were used: standard gelatin-sucrose agar (sucrose 10 %, gelatin 1.5 %, agar 0.01 %) recommended by the All-Russian Collection of Microorganisms; gelatin-sucrose agar with the addition of 1 % ascorbic acid as an antioxidant; peptone-sucrose-glycerol mixture developed by the authors (distilled water 90 ml, glycerol 10 ml, sucrose 10 g, peptone 3.2 g). Conidia suspended in distilled water without lyoprotectors served as controls. The viability of lyophilized conidia was assessed by their ability to germinate on an agar culture medium. The survival rate of G. pannorum conidia during lyophilization in all variants, except for the control, was statistically significantly (p<0.001) higher than the survival rate of A. tenuissima conidia. The viability of lyophilized A. tenuissima conidia did not depend on the use of protective media and amounted to 75.9 % in the control variant, 76.4 % in the variant with gelatin-sucrose agar, and 77.1 % in the variant with peptone-sucrose-glycerol mixture. The viability of lyophilized G. pannorum conidia without the use of protective media was 82.0 %, in the variant with gelatin-sucrose agar 95.3 %, in the variant with peptone-sucrose-glycerol mixture 88.1 %. The addition of ascorbic acid as an antioxidant to the protective medium led to a statistically significant (p<0.001) decrease in the proportion of A. tenuissima conidia surviving during lyophilization to 7.2 %, and the proportion of G. pannorum conidia surviving to 44.4 %.