Acid protease is an enzyme derived from the fermentation and refined extraction of Aspergillus niger, a type of black mold. This enzyme exhibits activity within a specific range of conditions. Its effective temperature range typically falls between 30°C and 65°C, with the optimum working temperature generally between 40°C and 50°C. Moreover, this enzyme demonstrates enhanced activity under acidic conditions, with an effective pH range typically ranging from 2.0 to 6.0, and the most favorable pH range typically between 2.5 and 3.5. The activity of acid protease is influenced by the presence of certain metal ions. Some metal ions like Ca²⁺, Mg²⁺, and K⁺ can activate its activity, while others like Cu²⁺, Hg²⁺, and Al²⁺ may inhibit it. Therefore, it is essential to consider the presence and concentration of metal ions in industrial applications to maintain the enzyme's optimal activity. Acid protease is a protease with an active site containing aspartic acid. It exhibits a preference for cleaving peptide bonds involving aromatic or hydrophobic amino acids, particularly those between aromatic amino acids and other amino acids. These characteristics make acidic protease highly valuable in various industrial applications, including alcohol production, leather processing, feed preparation, food fermentation, and other fields, facilitating protein hydrolysis and product preparation needs.