J. Biotechnol.

The medium composition for bacteriocin production by Lactococcus lactis ATCC 11454 was optimized using response surface methodology. The selected six factors based on CM medium were sucrose, soybean peptone, yeast extract, KH2PO4, NaCl, and MgSO4.7H(2)O. Fractional factorial designs (FFD) and the path of steepest ascent were effective in searching for the main factors and approaching the optimum region of the response. By a 2(6-2) FFD, sucrose, soybean peptone, yeast extract, KH2PO4 were found to be significant factors and had positive effects on cell growth, however, only soybean peptone and KH2PO4 were shown to be the two significant factors for bacteriocin production and had negative and positive effects, respectively. The effects of the two main factors on bacteriocin production were further investigated by a central composite design and the optimum composition was found to be 1% sucrose, 0.45% soybean peptone, 1% yeast extract, 2.84% KH2PO4, 0.2% NaCl, and 0.02% MgSO4.7H(2)O. The optimal medium allowed bacteriocin yield to be doubled compared to CM medium. (C) 2002 Elsevier Science B.V. All rights reserved.The medium composition for bacteriocin production by Lactococcus lactis ATCC 11454 was optimized using response surface methodology. The selected six factors based on CM medium were sucrose, soybean peptone, yeast extract, KH2PO4, NaCl, and MgSO4.7H(2)O. Fractional factorial designs (FFD) and the path of steepest ascent were effective in searching for the main factors and approaching the optimum region of the response. By a 2(6-2) FFD, sucrose, soybean peptone, yeast extract, KH2PO4 were found to be significant factors and had positive effects on cell growth, however, only soybean peptone and KH2PO4 were shown to be the two significant factors for bacteriocin production and had negative and positive effects, respectively. The effects of the two main factors on bacteriocin production were further investigated by a central composite design and the optimum composition was found to be 1% sucrose, 0.45% soybean peptone, 1% yeast extract, 2.84% KH2PO4, 0.2% NaCl, and 0.02% MgSO4.7H(2)O. The optimal medium allowed bacteriocin yield to be doubled compared to CM medium. (C) 2002 Elsevier Science B.V. All rights reserved