Preparation and optimization of lyophilized powder of Aspergillus nidulans

Abstract:

[Background] At present, the bacterial agents used to degrade lignin in landscaping waste are mostly liquid or solid bacterial agents, and there is few research on powdered bacterial agents. [Objective] To develop the lyophilized powder with high activity and high lyophilized survival rate and optimize the process, thus solving the existing problems in transportation, storage, and application of the liquid or solid bacterial agents. [Methods] Aspergillus nidulans, a lignin-degrading strain, was taken as the research object, and the lyophilized powder was prepared by vacuum lyophilization. The lyophilized survival rate of the strain was used as the evaluation index. The types and concentration gradients of protective agents suitable for the lyophilizing process of the strain were screened out through the single factor test, and the compound formula of protective agents of lyophilized bacterial powder was optimized through the orthogonal test. The rehydration and storage conditions of lyophilized powder were further explored after obtaining the formula. [Results] The influencing order of the four protective agents with a superior protective effect on the lyophilized survival rate after compounding was sucrose>glucose>skimmed milk powder>α-lactose. The optimum formula for protective agents was 15% sucrose, 1% glucose, 10% α-lactose, and 1% skimmed milk powder. The optimum rehydration condition was 30 min rehydration with normal saline as the solvent. The lyophilized survival rate of the strain of lyophilized powder prepared and applied under the above conditions reached 83.33% with 1.2×10¹⁰ CFU/g effective live bacteria. There was no significant decrease of the activity of lyophilized powder storing at the optimum temperature (-20 ℃) for 28 days. [Conclusion] The preparation and storage conditions of the lyophilized powder of A. nidulans obtained in this study have low strain loss rate and can be stored for a long term time, which plays a positive role in promoting the application of lignin-degrading bacteria in practical production.