Abstract
Proteases that are detergent stable are of great industrial value, because they are used in many laundry detergents and biotechnological processes. This research aimed to effectively create a protease enzyme that is compatible with detergents by Aspergillus niger by solid state fermentation (SSF) and optimize the production condition by Response Surface Methodology (RSM) to overcome the problem of high cost of producing the enzyme from agro-industrial residues. Substrate screening, optimization of five physico-chemical parameters (pH, temperature, inoculum size, incubation period, moisture content) by a Central Composite Design(CCD), extraction and partial purification of enzymes, biochemical characterization and compatibility testing of enzymes with commercial detergents were followed. The following parameters were used for the evaluation: protease activity (U/g), protein content, specific activity (U/mg) and statistical validation (ANOVA and regression modelling). Wheat bran was determined to be the most appropriate substrate leading to the highest protease activity (168.4 ± 4.2 U/g) and the RSM optimization increased the protease activity to ~305 U/g. The purified protease showed optimal activity at pH 4.0-4.5 and 40 °C and showed good stability of detergents and good shelf life performance of 30 days. This work is relevant for sustainable enzyme biotechnology by demonstrating the feasibility of the production of the protease in low-cost substrates that is not affected by the presence of detergent. Scale-up strategies and genetic engineering to further increase yield and stability may be explored in the future.