• Journal of Life Science
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• v.33 no.4
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• pp.357-362
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• 2023

This report looks at an agar-degrading marine bacterium and characterization of its agarase. Agar-degrading marine bacterium JS-1 was isolated with Marine agar 2216 media from seawater from the seashore of Sojuk-do, Changwon in Gyeongnam Province, Korea. The agar-degrading bacterium was named as Agarivorans sp. JS-1 by phylogenetic analysis based on 16S rRNA gene sequencing. The extracellular agarase was prepared from the culture media of Agarivorans sp. JS-1 and used for characterization. Relative activities at 20℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, and 60℃ were 70%, 74%, 78%, 83%, 87%, 100%, 74%, and 66%, respectively. Relative activities at pH 5, 6, 7, and 8 were 91%, 100%, 90%, and 89%, respectively. Its extracellular agarase showed maximum activity (207 units/l) at pH 6.0 and 50℃ in 20 mM Tris-HCl buffer. The residual activity after heat treatment at 20℃, 30℃, and 50℃ for 30 minutes was 90%, 70%, and 50% or more, respectively. After a 2-hour heat treatment at 20℃, 30℃, 35℃, 40℃, and 45℃, the residual activity was 80%, 68%, 65%, 63%, and 57%, respectively. At 50℃ and above, after heat treatment for 30 minutes, the residual activity was below 60%. Thin layer chromatography analysis suggested that Agarivorans sp. JS-1 produces extracellular β-agarases as they hydrolyze agarose to produce neoagarooligosaccharides such as neoagarohexaose (20.6%), neoagarotetraose (58.5%), and neoagarobiose (20.9%). Agarivorans sp. JS-1 and its thermotolerant β-agarase would be useful in the production of neoagarooligosaccharides, showing functional activity such as inhibition of bacterial growth and delay of starch degradation.

• Applied Biological Chemistry
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• v.13 no.2
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• pp.153-170
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• 1970

1. Isolation and identification of amylase-producing bacteria. The powerful strain A-12 and S-8 were respectively isolated from air and soil after screening a large number of amylase-producing bacteria. Their bacterial characteristics have been investigated and it has been found that all characteristics of strain A-12 and S-8 are similar to Bac. subtilis of Bergey's manual except for the acid formation from a few carbohydrates and the citrate utilization, i.e., the strain A-12 shows negative in the citrate utilization, and the acid formation from arabinose and xylose, S-8 shows negative in the acid formation from xylose. 2. Amylase production by Liquid cultures with solid materials. Several conditions for amylase production by strain A-12 in stationary cultures have been studied. The results obtained are as follows. (1) The optimum conditions are:temperature $35^{\circ}C$, initial pH 6.5 to 7.0 and incubation time 3 to 4 days. (2) The amylase production is not affected by the preservation period of the stock cultures. (3) Among the various solid material, the defatted soy bean is found to be the best for t1e amylase production. However, the alkali treatment of the defatted soy bean gives no effect contrary to the cage of defatted rape seed. The addition of soluble starch to the alkali extract of defatted soy bean shows the increased amylase production. (4) Up to 1% addition of ethanol to carbon dificient media gives the improved amylase production, whereas the above effect is not found in the case of carbon rich media. (5) The amylase production can be increased 2.5 times when 10% of defatted soy bean is admixed to cheaply available wheat bran. (6) The excellent effect is found for amylase production when 20% of wheat bran is admixed to defatted dry milk which is a poor medium. The activity is found to be $D^{40^{\circ}}_{30'}$ 7,000(L.S.V. 1,800) in 10% medium. (7) No significant effect is observed due to the addition of various inorganic salts. 3. Amylase production by solid cultures. Several conditions for amylase production by strain A-12 in wheat bran cultures have been studied and the results obtained are as follows. (1) The optimum conditions: are temperature $33^{\circ}C$, incubation lime 2 days, water content added 150 to 175% and the thickness of the medium 1.5cm, The activity is found to be $D^{40^{\circ}}_{30'}$ 36,000(L.S.V. 15,000) (2) No significant effect is found in the case of the additions of various organic and inorganic substances.