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KMID : 0525720210260010022
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Journal of Chitin and Chitosan
2021 Volume.26 No. 1 p.22 ~ p.28
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Screening of Cellulolytic Microorganism from Doenjang, Korean Fermented Food and Characterization of Cellulase from Bacillus subtilis DJ3
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Kim Sang-Jin
Choi Min-Su
Park Chang-Su
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Abstract
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Six kinds of cellulolytic strains were selected as cellulose production microorganisms from the Korean fermented food, Doenjang. The selected strains formed active zone on LB-Agar plate containing carboxymethylcellulose (CM-cellulose) with trypan blue by their cellulase. Among the strains, one strain, Bacillus subtilis identified by the analysis of 16S rRNA gene, was selected because of the highest cellulase activity for CM-cellulose. We named this strain as Bacillus subtilis DJ3 from the result of strain identification. The B. subtilis DJ3 produced its cellulase maximally after cultivation of 48 h and the cellulase exhibited the highest enzyme activity at pH 5.0 and 40 ℃. In the effects of pH and temperature on the enzyme stability, the enzyme was stable up to 40℃ and pH 4.0-6.0 range after treatment for 30 min at each condition. In the investigation of substrate specificities, the cellulase from B. subtilis DJ3 has the highest activity for CM-cellulose for several substrates such as CM-cellulose, Alkali swollen cellulose, a-cellulose, Sigmacell Cellulose, and Avicel. In the efficient of substrate concentration for enzyme activity, the cellulase from B. subtilis DJ3 showed maximum activity on the 2% of CM-cellulose. When the 2% of CM-cellulose was used, the cellulase showed the highest degradation activity for CM-cellulose after 80 min. From the characterization of cellulosic substrates, the cellulase from B. subtilis DJ3 showed the highest enzyme activity for CM-cellulose, a typical substrate for endo-type cellulase. From this result, it was suggested that the cellulase from B. subtilis DJ3 is an endo-type cellulase.
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KEYWORD
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Bacillus subtilis, Cellulase, Characterization, Doenjang, Screening
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