ORIGINAL ARTICLE
Year : 2019  |  Volume : 18  |  Issue : 4  |  Page : 341-355

Genetic identification and optimization of novel β-glucosidase-producing Lysinibacillus sphaericus QS6 strain isolated from the Egyptian environment


1 Department of Microbial Genetic, Genetic Engineering and Biotechnology Division, National Research Center, Giza, Egypt
2 Department of Biochemistry, Genetic Engineering and Biotechnology Division, National Research Center, Giza, Egypt
3 Department of Botany and Microbiology, Faculty of Sciences, Al-Azhar University, Nasr city, Egypt

Correspondence Address:
Ahmed F El-Sayed
Master’s Degree in Microbial Genetics, Assistant Researcher at Department of Microbial Genetics, Genetic Engineering and Biotechnology Division, National Research Center, 12311 Dokki, Giza
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/epj.epj_51_19

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Background and objective β-Glucosidase-producing bacteria are potential sources for biotransformation of lignocellulose biomass and agricultural wastes into biofuels. The aim was the isolation, screening, molecular identification, and optimization of highly efficient β-glucosidase-producing bacteria under different growth conditions. Materials and methods Cellulose-degrading bacteria were isolated and screened for β-glucosidase enzymes. Then, they were identified by phenotypic and genotypic identification. Optimization for β-glucosidase production was studied under different culture conditions. Results and conclusion Highly efficient β-glucosidase-producing strain QS6 was selected and identified morphologically and biochemically as Lysinibacillus sp. using 16 s rDNA gene sequencing approach and bioinformatics analysis. Strain QS6 was most similar to Lysinibacillus sphaericus, with similarity of 98%. Phylogenetic analysis was done to determine the relationship of strain QS6 with different strains of genus Lysinibacillus sp. It indicated that the suitable culture conditions of producing β-glucosidase were the culture temperature of 35°C, the initial pH of 7.0, the incubation time of 24 h, and 1% inoculum size. While studying the effect of carbon sources on β-glucosidase production, it was found that cellobiose (1%w/v) was the best carbon source for inducing β-glucosidase production. Moreover, the nitrogen source peptone at 0.5% w/v was optimum for β-glucosidase production by this bacterium. L. sphaericus QS6 was found to be sensitive to antibiotics (amoxicillin, streptomycin, tetracycline, cefadroxil, kanamycin, chloramphenicol, ampicillin, erythromycin, and tobramycin). Moreover, in-vitro antibacterial bioassay of the most potent β-glucosidase-producing strain (QS6) showed high antimicrobial activity against Escherichia coli (1.9 cm) and Pseudomonas aeruginosa 1.0 cm). A promising Lysinibacillus sp. completely identified as L. sphaericus QS6 (GenBank MN493725.1) is an efficient source of β-glucosidase production.


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