Study of cellulases from a newly isolated thermophilic and cellulolytic <Emphasis Type="Italic">Brevibacillus</Emphasis> sp. strain JXL |
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Authors: | Yanna Liang Jemil Yesuf Steve Schmitt Kelly Bender John Bozzola |
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Institution: | (1) Department of Civil and Environmental Engineering, Southern Illinois University Carbondale, 1230 Lincoln Dr., Carbondale, IL 62901, USA;(2) Integrated Microscopy and Graphics Expertise (IMAGE), Southern Illinois University Carbondale, 750 Communications Dr., Carbondale, IL 62901, USA;(3) Department of Microbiology, Southern Illinois University Carbondale, 1125 Lincoln Dr., Carbondale, IL 62901, USA |
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Abstract: | A potentially novel aerobic, thermophilic, and cellulolytic bacterium designated as Brevibacillus sp. strain JXL was isolated from swine waste. Strain JXL can utilize a broad range of carbohydrates including: cellulose,
carboxymethylcellulose (CMC), xylan, cellobiose, glucose, and xylose. In two different media supplemented with crystalline
cellulose and CMC at 57°C under aeration, strain JXL produced a basal level of cellulases as FPU of 0.02 IU/ml in the crude
culture supernatant. When glucose or cellobiose was used besides cellulose, cellulase activities were enhanced ten times during
the first 24 h, but with no significant difference between these two simple sugars. After that time, however, culture with
glucose demonstrated higher cellulase activities compared with that from cellobiose. Similar trend and effect on cellulase
activities were also obtained when glucose or cellobiose served as a single substrate. The optimal doses of cellobiose and
glucose for cellulase induction were 0.5 and 1%. These inducing effects were further confirmed by scanning electron microscopy
(SEM) images, which indicated the presence of extracellular protuberant structures. These cellulosome-resembling structures
were most abundant in culture with glucose, followed by cellobiose and without sugar addition. With respect to cellulase activity
assay, crude cellulases had an optimal temperature of 50°C and a broad optimal pH range of 6–8. These cellulases also had
high thermotolerance as evidenced by retaining more than 50% activity at 100°C after 1 h. In summary, this is the first study
to show that the genus Brevibacillus may have strains that can degrade cellulose. |
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Keywords: | Cellulase Brevibacillus Cellulose Cellulosome |
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