Genetic Breeding of <i>Aspergillus oryzae</i> for Brazilian Soy Sauce Production: A Classical Approach for Contemporary Food Industry Challenges

Aspergillus oryzae, which is widely used in the food industry, is recognized as a multi-enzyme producing microorganism.Employing the mutagenesis-inducing agent ethyl-methane sulfonate (EMS), followed by classical recurrent mutation-selection cycles, this study produced mutants with enhanced amylolytic and proteolytic activities, both desirable traits for traditional soy sauce production.Thus, the selected mutant strains, called MT and H180, were grown on different substrates often used in the Brazilian industry for soy sauce production, and their performance was evaluated by quantitative assays.On a blend of cooked soybean and roasted corn grains, MT presented approximately a 21% and 27% increase in amylolytic and proteolytic enzyme activity, respectively, compared to the wild strain.Whereas, in the substrate comprised of extruded soybean and corn, the H180 strain stood out, presenting higher proteolytic activity, around 47%, than the wild strain.The performances of the strains for soy sauce production were accessed in a scaledown process.The strains produced higher protein content and other important aspects for improved product formulation, such as increased intensity in the dark color, which may lessen the need to add expensive coloring during the product formulation.Thus, the classical EMS-induced mutation technique is a valuable biotechnology tool in the food industry, yielding two strains with potential use in soy sauce production, for process and product formulation.