Abstract:
Objective Bacteria with a high cellulase-producing capacity were isolated from different varieties of tobacco for the potential of upgrading the economic value of tobacco raw materials.
Methods Candidate bacterial strains were isolated and purified from 37 flue-cured tobacco strip samples using dilution coating method. They were screened by the Congo red staining combined with shaking flask culture and cellulase activity determination. Phylogenetic property of a strain identified by morphological observation was confirmed with 16S rRNA sequencing. The cellulase activities were investigated.
Results FX-1 was preliminarily identified as a strain that produced high cellulase activity of 56.261 U·mL−1 after 48h fermentation at 37 ℃. It was a gram-positive, rod-shape, spore-producing bacterium that showed a perfectly matching 16S rRNA sequence in a branch of Bacillus subtilis phylogenetic tree. The cellulase from FX-1 displayed a peak activity at 60 ℃ and pH 5.0. Greater than 90% of its relative activity was retained after being held at 30-55 ℃ or pH 3.0-7.0 for 30 min.
Conclusion A high cellulase-producing bacterium screened from 37 flue-cured tobacco strip samples was preliminarily identified as a strain of B. subtilis. The cellulase produced by the strain FX-1 exhibited a wide-range temperature and pH stability, and thus, had a considerable potential to be developed for new commercial use in tobacco manufact.
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