Effect of Temperature and Preservation Period on the Viability of Lyophilized Bacillus subtilis
Keywords:Bacillus subtilis, Temperature, Preservation period, Viability, Lyophilized
Objective: We sought to study the effect of temperature and preservation period on the viability of lyophilized Bacillus subtilis. Methods: Forty-five test tubes that contained suspension of B. subtilis ATCC 6633 were incubated for 4 hours at 37°C and washed twice before freeze-drying. Next, the lyophilized bacteria were exposed to different temperatures (-20°C, 2-8°C, and 25°C) and storage periods (30 days, 120 days, and 240 days). Further, the lyophilized bacteria were evaluated for their viability using the Miles and Misra method. Finally, the colony count of B. subtilis in each group was compared and analyzed using the two-way ANOVA and the Tukey-test (post-hoc test). Results: The lyophilized B. subtilis showed the viability of 93.3% (42/45) of test tubes. All of the lyophilized B. subtilis stored at -20°C for 30, 120, and 240 days remained viable while the bacteria stored at 2-8°C and 25°C showed the viability of 93.3% (14/15) and 86.6%, respectively. The lyophilized B. subtilis stored at three group temperatures and kept for 120 and 240 days showed a significant decline in their number over the control group (p <0.05). Conclusion: In conclusion, the temperature and preservation period significantly affect the viability of the lyophilized B. subtilis. © 2022 iGlobal Research and Publishing Foundation. All rights reserved.