Isolation and identification of cellulase producing Bacillus subtilis EG7 and its potential in composting of agricultural wastes

Abstract

In the current study, some bacterial isolates capable of utilizing Rice straw as an agricultural waste were obtained. Among them, the cellulolytic activity of the isolate EG7, detected both qualitatively and quantitatively, was promising. This isolate degraded the different cellulosic substrates used; Carboxymethylcellulose, Avicel, Cotton seed linters and Rice straw. The isolate was identified by classical bacteriological examination, metabolic fingerprinting using Biolog MicroPlate and phylogenetic analysis of 16S ribosomal Ribo-Nucleic Acid (16SrRNA) gene nucleotide sequence as Bacillus subtilis, GenBank accession number (KX817281). Cellulase enzyme of the isolate EG7 was produced under the determined optimum conditions. Among these conditions, static incubation for three days at initial pH 7.00 and incubation temperature 40 o C with cellulose concentration 10 % (w/v) were favorable. Under these conditions, the enzyme activity recorded 45.00 UmL -1 . Purification of the produced enzyme was performed and the results revealed that the enzyme activity recorded 64.50UmL -1 . Molecular weight determination revealed the presence of two distinct bands of about 43 and 37 KDa. The use of the isolate EG7 in composting of Rice straw and Banana peels waste resulted in enhancing the process and reducing time of composting into five to seven days. Our results indicated the potential of using the isolate EG7 in enhancing composting of agricultural wastes, besides, the use of its cellulase in the different industrial applications.