Isolation, screening and optimization of cellulase production by a novel bacterial isolate of Enterococcus durans

Abstract

Cellulose is an abundant plant biomass and a renewable source of energy in the ecosphere. The breakdown of cellulose occurs via the cellulase enzyme, which is commonly produced by microbes. This study aimed to optimize the fermentation parameters for enhanced cellulase production. Standardized parameters include isolation and screening of cellulase-producing bacteria (CPB), production of an enzyme, biochemical and molecular identification of bacterial isolate, optimization of cultural parameters, and application in wash performance. A total of 581 bacterial strains were isolated from soil samples, of which 16 isolates formed zones of hydrolysis on carboxymethylcellulose (CMC) agar media and were categorized as CPB. Based on maximum hydrolysis zone formation, three isolates, Krishi Vigyan Kendra-5 (KVK-5), Greenhouse-4 (GA-4), and Medicinal Garden-5 (MG- 5) were chosen for bacterial cellulase production (BCP), with the isolate MG-5 proving to be the best cellulase producer (1.75 ± 0.01 U ml-1). Based on 16S rRNA gene sequencing the isolate MG-5 was identified as Enterococcus durans. The optimized parameters for the production of the cellulolytic enzyme were an incubation period of 48 h, CMC (carbon source), and yeast extract (nitrogen source) at a concentration of 1.5% w/v, pH 7, 45 °C, 1.5% v/v inoculum size and 100 rpm. Optimum conditions resulted in a 1.92-fold increase (3.36 U ml-1) in cellulase activity. Cellulase enzyme when used with detergent (Surf Excel), resulted in more efficient removal of chocolate stains on cotton fabric. This is the first report of Enterococcus durans producing cellulolytic enzymes. The analysis of cellulase in stain removal provides valuable evidence regarding the application of this enzyme in laundry cleaning.