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

El-Sayed, Ahmed F.; Abo-Sereih, Nivien A.; Mahmoud, Abeer E.; El-Kawokgy, Tahany M.; El-Ghamery, Abbas A.

doi:10.4103/epj.epj_51_19

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

Authors

Abstract

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 , 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. 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 (1.9 cm) and 1.0 cm). A promising Lysinibacillus sp. completely identified as QS6 (GenBank MN493725.1) is an efficient source of β-glucosidase production.

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