• Korean Journal of Microbiology
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• v.48 no.1
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• pp.48-51
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• 2012

A novel Chryseobacterium sp. JK1 strain producing extracellular protease had been isolated from soil. The largest clear zones were observed on nutrient agar plates supplemented with 1% skim milk at $30-35^{\circ}C$ along with the growth of Chryseobacterium sp. JK1. The cell growth of JK1 strain was maximal at 24 h and maximum protease activity was reached up to 560 unit/ml at the stationary phase in liquid culture. In the presence of maltose, glucose or mannitol in Nutrient broth, cells grew well, but protease were produced poorly with lower production yields of 64-77% than in NB broth only. Similarly, the addition of skim milk, beef extract, yeast extract, malt extract or tryptone showed good growth and poor enzyme production. On the contrary, the addition of $(NH_4)_2HPO_4$ or $(NH_4)_2SO_4$ gave poor growth and good enzyme production of 121-146%.

• Korean Journal of Microbiology
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• v.49 no.1
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• pp.78-82
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• 2013

A novel Chryseobacterium sp. JK1 strain isolated from soil had been reported that this isolate produced large amount of extracellular protease at mesophilic temperature in previous study. The optimal temperature and pH of extracellular protease were $40^{\circ}C$ and 7.0, respectively, showing narrow range of optimal temperature and relatively broad activity from pH 6.0 to 9.0. In addition, the protease showed greatest activity against skim milk and lowest against bovine serum albumin (BSA). The protease strongly inhibited by ethylenediaminetetraacetic acid (EDTA), ethylene glycol tetraacetic acid (EGTA) or phenylmethylsulfonyl fluoride (PMSF), and addition of cation $Ag^+$ or $Cu^{2+}$, and slightly inhibited by $Al^{3+}$. No significant inhibition was found with pepstatin, and addition of cation, $K^+$, $Ca^{2+}$, $Na^+$, $Fe^{2+}$ or $Mg^{2+}$. On the contrary, protease was enhanced by addition of divalent cation $Mn^{2+}$ (5 mM). Zymography analysis of concentrated culture supernatant revealed two major bands at 67 and 145 kDa. These results suggest that Chryseobacterium sp. JK1 strain produced extracellular neutral serine proteases which could apply in food industry.