Factors increasing poly-γ-glutamic acid content of cheongguk-jang fermented by Bacillus subtilis 168
2019
Pov Ratha, Chonnam National University, Gwangju, Republic of Korea | Jhon, D.Y., Chonnam National University, Gwangju, Republic of Korea
Cheongguk-jang is a Korean traditional food produced by natural fermentation of boiled soybean. In cheongguk-jang, bacilli are dominant bacteria and produce highly viscous poly-γ-glutamic acid (γ-PGA), which improves human health functions. The purpose of this experiment was to find maximum production condition for the γ-PGA content during fermentation of cheongguk-jang with Bacillus subtilis 168. The most viscous cheonggukjang was produced when soybean was cooked at 121℃ for 60 min in the presence of 50%(w/w) added water, followed by fermentation at 40℃ for 2 days. Additional conditions for maximum production of γ-PGA were the addition of 0.1%(w/w) FeCl₃ · 6H₂O, 3.0%(w/w) lactose and 3.0%(w/w) yeast extract as nutrients of inorganic salts, carbon source and nitrogen source, respectively. The three conditions did not show cumulative effect on the γ-PGA production and the addition of iron salt induced the most γ- PGA (0.97 ± 0.05%(w/w)), which corresponded to 2.7 times of the content in control cheongguk-jang.
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