Comparative Analysis of the Effects of Different Substrates on Protease Production by Penicillium spp. Isolated from the Amazon

The genus Penicillium is widely recognized for its ability to produce a diverse range of enzymes, including proteases, which play crucial roles in various biotechnological applications. This study investigated the influence of three distinct inducers (skim milk, gelatin, and a combination of skim milk and gelatin) on protease production by different Penicillium species, using the cup-plate method—a qualitative technique that detects proteolytic activity in solid media. The proteolytic activity of Penicillium species was assessed by measuring degradation halos in culture media supplemented with these inducers. The results demonstrated that skim milk was the most effective inducer, yielding the highest Enzyme Index (EI) values. The highest EI was observed for P. citrinum 414 (3.6), followed by P. oxalicum and P. sumatraense, both with EIs of 3.3. The strains P. citrinum 409, P. paxilli, P. citrinum 457, and Penicillium spp. 5 and 546 exhibited EIs ranging from 3.0 to 3.2. The analysis of degradation halos highlighted that both substrate type and cultivation conditions significantly influence protease production. This study enhances our understanding of the enzymatic potential of Penicillium species and underscores the importance of optimizing cultivation parameters to maximize protease production, which has broad potential applications in industrial processes.