The conditions of thermal acid hydrolysis of lactobacillus mass were studied within the framework of the development of a new preparation possessing immunomodulating properties. The parameters for optimization were the process temperature and duration and pH of the medium. The optimization criteria were the contents of total and amine nitrogen, proteins, peptides, and amino sugars. The coefficients of hydrolysis and proteolysis were determined. Based on the analysis of data, hydrolysates containing 2% peptides and 0.02–0.03% amino sugars were selected for subsequent investigations.