• Korean Journal of Microbiology
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• v.26 no.3
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• pp.223-229
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• 1988

Bacillus subtilis K-4-3, which produces considerable amount of $\beta$-glucanase was selected among extracellular $\beta$-glucanase-producing bacteria isolated from soil. $\beta$-glucanase was purified by ammonium sulfate fractionation, Sephadex G-100 gel filtration and DEAE-sephacel ion exchange chromatography. The purified enzyme revealed a single band by polyacrylamide gel electrophoresis and SDS-polyacrylamide gel electrophoresis. Its molecular weight was estimated to be 17000 dalton by SDS-polyacrylamide gel electrophoresis. The optimum pH and temperature of the purified $\beta$-glucanase were 7.0 and $50^{\circ}C$, respectively. The enzyme was strongly inhibited by 1.0mM of $Fe^{3+}$, and activated by 1.0mm of $Li^{}47+$. The absence of glucose after thin layer chromatography of reaction products revealed that the purified enzyme contains no cellobiase or laminarinbiase activity. The loberation of ki, tri-and tetra-saccharide as reaction products can be explained by endoaction of the enzyme.

• Microbiology and Biotechnology Letters
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• v.35 no.3
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• pp.203-209
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• 2007

Soybean milk cake (SMC) was used for the solid-state fermentation by Bacillus subtilis PUL-A isolated from soybean milk cake. In the presence of 5% glutamate the maximum production of biopolymer (59.9 g/kg) was performed by fermentation at $42^{\circ}C$ for 24 hr. The recovered biopolymer was consisted of 87% $\gamma$-polyglutamic acid with molecular weight of $1.3{\times}10^6$ dalton and other biopolymer. The biopolymer solution showed the great decrease in consistency below pH 6.0, regardless of the molecular weight of PGA. Biopolymer solution has a typical pseudoplastic flow behavior and yield stress. The consistency of biopolymer solution was greatly decreased by increasing heating time and temperature in acidic condition compared to the alkaline condition. In kaolin clay suspension, the flocculating activity of biopolymer was the highest value with 15 mg/L biopolymer and 4.5 mM $CaCl_2$, but decreased greatly with $FeCl_3$. The flocculating activity of biopolymer was maximum at pH5, but decreased drastically by heating at $60{\sim}100^{\circ}C$. In particular, biopolymer with native PGA showed the efficient flocculating activity compared to that of modified biopolymer containing low molecular weight of PGA.