Optimization of heat shock, acid shock and salt stress process and its mechanism of protection before spray drying of Baijiu yeast - Modified sporidiobolus Johnsonii A.

The low survival rate of high-quality baijiu yeast, Modified Sporidiobolus Johnsonii A (MSJA), during spray drying and the unclear mechanisms underlying its stress treatment processes (heat shock, acid shock, and salt stress) have significantly hindered its low cost and high effective application, thereby impacting the high-quality development of the liquor industry. To address this problem. A response surface experiment was first conducted to optimize the stress treatment process prior to spray drying. Subsequently, the mechanisms and efficacy of the stress treatments were analyzed using Field Emission Scanning Electron Microscopy (FESEM). The results demonstrated that the survival rate of spray-dried MSJA could be improved from 38.5 to 54.8% under the optimal conditions, with heat shock temperature (X) = 35.2 °C, acid stress pH (Y) = 3.2, and salt stress concentration (Z) = 4 g/L KH2PO4. The protective effects of the stress treatments on MSJA during spray drying were ranked as follows: comprehensive treatment > heat shock > acid stress > salt stress. Acid stress and heat shock protect MSJA by reducing cell shrinkage, collapse, and volume loss, while salt stress aids in maintaining osmotic pressure balance across MSJA cell membranes during drying. This study not only optimized the stress treatment scheme of MSJA before spray drying, but also laid a foundation for both high efficiency and high quality spray drying MSJA. It also revealed the mechanism of each stress treatment, and provided guidance for the protection of other microorganisms by spray drying stress treatment.