Evaluation of extracellular alkaline proteases from Bacillus for environmentally friendly detergent additives

Abstract

Growing demand for environmentally friendly and sustainable enzyme solutions drives markets for alkaline proteases across various industries. Alkaline proteases produced by different Bacillus strains exhibit unique properties and versatility. Production of alkaline proteases from Bacillus amyloliquefaciens TBRC 2902, B. siamensis TBRC 1180, B. subtilis TBRC 6663, and B. velezensis TBRC 7773 was optimized by adjusting production media, considering carbon and nitrogen sources to enhance extracellular enzyme activities. Optimized extracellular protease activity was achieved using tapioca starch for TBRC 2902 and TBRC 1180, and soluble starch for TBRC 7773, while both carbon sources were optimal for TBRC 6663. Skim milk was an equally effective nitrogen source for TBRC 2902, TBRC 1180, and TBRC 7773, whereas soytone was as effective as yeast extract for TBRC 6663. Inorganic nitrogen sources, such as diammonium hydrogen phosphate for TBRC 2902 and potassium nitrate for TBRC 1180, enhanced alkaline protease activity by 10-20%. The protease from B. siamensis TBRC 1180 exhibited optimal pH and temperature values of 9.0 and 60°C, respectively, while the others had optimal values of 8.0 and 50°C. All enzymes tolerated non-ionic surfactants, retaining over 40% activity after 24 hours exposure to Triton X-100, Tween-20, and Tween-80, indicating their potential as detergent additives.