A collagen-hydrolyzing halotolerant protease for enhanced dye decolorization and toxicity reduction in high-salinity textile tannery wastewater

Abstract

In this study, PersiProtease1, a halotolerant alkaline protease, was derived from tannery metagenome and used to hydrolyze collagen in textile tannery wastewater. Beyond its primary role, PersiProtease1 also demonstrated significant potential for the decolorization of azo, anthraquinone, and triphenylmethane dyes. PersiProtease1 was tested under various environmental conditions, showing a superior dye removal efficiency of 52–89 % under 200 g/L salinity within 60 min, following second-order kinetics, is significantly higher than that of other reported proteases that typically achieve below 60 % efficiency under similar conditions. Additionally, compared to other proteases reported in high-salinity environments, PersiProtease1 exhibited a degree of hydrolysis (DH) of 43.08 %, surpassing the typical DH values of <30 % reported in previous studies for similar conditions, for collagen degradation in a 5 mg/mL solution of textile tannery wastewater after 120 min. In addition to its collagen-degrading capabilities, protease achieved 80 % decolorization in textile tannery wastewater containing a mixture of dyes at 250 ppm, outperforming enzymes such as laccases, which typically achieve approximately 60 % decolorization under similar conditions. The enzyme was also capable of decolorizing high concentrations (500 ppm) of azo, anthraquinone, and triphenylmethane dyes, achieving > 85 % efficiency within 60 min. Phytotoxicity and microbial toxicity tests were also conducted to evaluate the detoxification efficacy of PersiProtease1. These findings demonstrated reduced dye toxicity through increased plant germination rates and enhanced bacterial growth rates, indicating the potential of the enzyme to mitigate the harmful effects of dyes by promoting both plant and microbial growth. These results demonstrate PersiProtease1′s versatility as a biocatalyst for the treatment of high-salinity textile and tannery wastewater, making it an effective tool for pollution control and sustainable waste management.