Green biocatalysis: Box–Behnken-optimized cellulase from thermophilic Streptomyces griseorubens NBR14 for waste management and dye removal

Abstract

Thermotolerant actinobacteria are important because they thrive in harsh environments and efficiently degrade agricultural residues, producing valuable enzymes for various applications. In this study, a thermophilic Streptomyces griseorubens NBR14 strain was used to produce cellulase from wheat straw via submerged fermentation. The production was optimized using a Box–Behnken Design (BBD). The enzyme was partially purified with acetone, followed by an analysis of its properties and potential use in dye removal. The results indicated that the enzyme yield increased 2.48-fold using this design under the optimized parameters 30 °C, pH 7.0 and 3% wheat straw after 5 days of incubation. The partially purified cellulase was characterized by 3.48-fold purification, with a specific activity of 158.22 U/mg. The optimal temperature and pH for cellulase activity were 50 °C and 7.0, respectively. It remained 96% at pH 9.0 and 73% active at 80 °C, respectively. The enzyme exhibited high activity (125%) and stability at 7% NaCl. Its activity was enhanced by 5% of tween 20 and 5 mM of sodium dodecyl sulfate (SDS) and sodium lauryl sulfate (SLS). The kinetic analysis of the partially purified cellulase showed that Km and Vmax were 0.74 mmol and 20.92 U/mL, respectively. The partially purified enzyme removed 83.6% of 50 mg/L of crystal violet in a quiescent state after 24 h of incubation. The Cellulase was immobilized in calcium alginate beads, resulting in an immobilization yield of 75.07 ± 1.35%, which suggested a considerable potential for reuse. Therefore, cellulase from the thermophilic NBR14 enzyme is a promising biotechnological candidate for cellulosic waste management and a valuable tool for industrial monitoring under extreme conditions.

Graphical abstract

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