Strawberry Protease as a Laundry Detergent Additive Candidate: Immobilization, Compatibility Study with Detergent Ingredients, and Washing Performance Test

Abstract

The potential of strawberry-derived protease as a component of laundry detergent is investigated. The compatibility of the enzyme with various surfactants, oxidizing agents, and commercial detergents is tested. The immobilized enzyme prepared by immobilizing Co²⁺ ions together with the enzyme is also tested. Strawberry crude protease shows high stability in the presence of surfactants frequently used in detergents. The enzyme is found to be relatively stable to oxidizing agents. In addition, it is determined that strawberry protease works in excellent compatibility with different commercial solid and liquid detergents in the Turkish market and also maintains its stability very well. Washing tests based on visual examination also reveal that the enzyme improves the washing performance of the tested detergent. All these properties and high activity at alkaline pH make this enzyme a very strong candidate for use in laundry detergent formulations.

Keywords: detergents; fragaria ananassa; immobilization; protease; strawberry.

Figure 1

Thermal and pH profile of immobilized and free strawberry protease enzyme. Error bars represent the standard deviation of triple measurements. One‐way ANOVA test was used for statistical evaluation. A) Optimum pH graph of immobilized and free protease. n: 14; after immobilization, the change in activity was significant (p < 0.05) compared to free enzyme at acidic and basic pH values. B) pH stability graph of immobilized and free protease. n: 14; after immobilization, the increase in stability was not statistically significant (p > 0.05) compared to free enzyme. C) Optimum temperature graph of immobilized and free protease. n: 18; after immobilization, the change in activity was found to be significant (p < 0.05) when the temperature value was 60 °C and above compared to free enzyme. D) Thermal stability graph of immobilized protease. n: 32; a significant increase was observed in the thermal stability, above 40 °C (p < 0.03).

Figure 2

Storage stability graph of immobilized and free protease. Error bars represent the standard deviation of triple measurements. A one‐way ANOVA test followed by the Bonferroni post hoc test was used for statistical evaluation. n: 32, p < 0.01. The immobilization process significantly increased the stability of the enzyme, and the increase in stability was significant compared to the free enzyme at 4 °C.

Figure 3

Effect of commercial solid and liquid detergents on strawberry protease activity. Error bars represent the standard deviation of triple measurements. One‐way ANOVA test followed by the Bonferroni post hoc test was used for statistical evaluation. A) Effect of commercial solid detergents on protease activity. n: 12, p < 0.01. The stability of the enzyme immobilized with Co²⁺ ions in the presence of solid detergents was significantly different compared to the free enzyme. B) Effect of commercial liquid detergents on protease activity. n: 12, p < 0.03. The stability of the enzyme immobilized with Co²⁺ ions in the presence of liquid detergents was significantly different compared to the free enzyme.

Figure 4

A) Cotton fabric pieces (5 cm × 5 cm) stained with barbecue sauce (BS), ketchup (K), and chocolate sauce (CS). B) Results after washing (in all wash water samples) and drying of cotton fabric pieces stained with barbecue sauce, ketchup, and chocolate sauce. TW, tap water; TW+D, tap water with detergent; TW+D+E, tap water with detergent and enzyme; C.E., crude enzyme; I.E., immobilized enzyme; Co²⁺‐I.E., immobilized enzyme with Co²⁺ ions; BS, barbecue sauce; K, ketchup; CS, chocolate sauce.