STUDY TO EVALUATE THE EFECTIVENESS OF FREEZE-DRYING PRESERVATION OF STRAINS STREPTOMYCES PARVULLUS HT19.1 AND STREPTOMYCES SP. HT17.8 CONTAINING THE ANTIBIOTIC ABILITY AGAINST PATHOGENIC FUNGI IN PLANTS BY DEEP FREEZING PRETREATMENT TECHNIQUE AND USE OF P

Abstract

To improve the efficiency of freeze-drying preservation of strains Streptomyces parvullus HT19.1 and Streptomyces sp. HT17.8, this study focused on evaluating the survival rate in freeze-drying using deep freezing pretreatment technique and protectants of two strains. The results showed that the survival rate of both strains in the sample pretreatment formula at -80°C was higher than at -20°C and higher than the control without deep freezing pretreatment, the survival rate reached 65% with HT19.1 strain and 69% with HT17.8 strain. When the two microorganism strains were deep freezing pretreatment combined with the use of protectants including lactose, sucrose, trehalose, and skim milk, their survival rates were 59 - 83%, which is significantly greater than the control (23 - 26%). Using a combination of protectants including trehalose 10%, skim milk 10%, sodium glutamate 1% and NaCl 0.9% and deep freezing pretreatment at -80°C provided the best protective effect, the survival rates were 92 - 95% and the density of microorganisms after freeze-drying reached ≥ 10¹⁰ CFU/mL. The quality of freeze-dried microbial strains after 12 months of preservation at room temperature.