Poly-${gamma}$-glutamic Acid(${gamma}$-PGA)를 다량 생산하는 균주를 우리나라의 전통발효식품인 청국장으로부터 Bacillus subtilis GS-2를 분리하였다. 이 균은 glutamic acid 의존형 균으로, 이 균에 의한 ${gamma}$-PGA 생산 최적 조건을 검토한 바, 단순배지(L-glutamic acid 2.0%, glucose 1.0%, $NH_4Cl$ 0.5%, $KH_2PO_4$ 0.05%, $MgSO_4$ $7H_2O$ 0.01%, pH 7.0)로 진탕배양(220 rpm) 하였을 때, 배양시간 48시간, 최적온도 $33^{circ}C$, 그리고 초기 pH 6.5로 나타났다. 영양원으로 glutamic acid 3%, sucrose 3%, $NH_4Cl$ 0.25%, $KH_2PO_4$ 0.15%, $MgSO_4$ $7H_2O$ 0.015%에서 ${gamma}$-PGA 최대 생산량이 31.0 $g/{ell}$이었다.
A bacterium strain GS-2 isolated from the Korean traditional seasoning food, Chungkookjang and was determined to produce large amounts of ${gamma}$-PGA with high productivity when provided with simple nutrients (L-glutamic acid 2.0%, glucose 1.0%, $NH_4Cl$ 0.5%, $KH_2PO_4$ 0.05%, $MgSO_4{cdot}7H_2O$ 0.01%, pH 7.0). In this study, the culture medium for this strain was optimized for the production of ${gamma}$-PGA. The Bacillus subtilis GS-2 required supplementation with L-glutamic acid and other nutrients for maximal production of ${gamma}$-PGA. The optimal culture conditions for ${gamma}$-PGA production were a 48 hr culture time, a temperature of $33^{circ}C$ and initial pH of 6.5 by rotary shaking (220 rpm). A maximum ${gamma}$-PGA production of 31.0 $g/{ell}$ was obtained with L-glutamic acid (30 $g/{ell}$), sucrose (the main carbon source, 30 $g/{ell}$), $NH_4Cl$ (the main nitrogen source, 2.5 $g/{ell}$), $KH_2PO_4$ (1.5 $g/{ell}$) and $MgSO_4{cdot}7H_2O$ (0.15 $g/{ell}$) in the culture medium.
