Produce bacteriocin from L. lactis using alternative culture media.

Bacteriocins from lactic acid bacteria have potential use as biopreservatives to control spoilage and pathogenic bacteria. Bacteriocins are active against key pathogenic organisms, such as clostridia, staphylococci, bacilli and Listeria, in processed meats, dairy products and similar products.

High bacteriocin production usually occurs in complex media, but the high cost of this operation makes the process unsuitable for a large-scale production. There has been increased interest in using by-products from food processing as the basis of such culture media as dairy whey. Studies on complex and alternative media have demonstrated that bacteriocin production depends on the composition of the medium. Mexican scientists wanted to identify the major factors that affect bacteriocin production by L. lactis UQ2, using supplemented whey as an alternative medium. They found that bacteriocin production was significantly determined by the medium.

Bacteriocin activity was assayed using M. luteus NCBI8166 as the indicator organism. The researchers studied the effects of sweet whey, yeast extract, MnS[O.sub.4], MgS[O.sub.4] and Tween 80 on bacteriocin production. They performed their experiments in a 3-L commercial fermenter at 30 C and 200 rpm, with and without air flow of 248 mL per minute for 24 hours.

Results showed that the composition of the culture media had an important effect on the titer amounts of the produced bacteriocin. Sweet whey and yeast extract were the only significant factors with predicted concentrations that led to the highest bacteriocin production of 20 g per L. The titers of bacteriocin were higher than those obtained using MRS broth, and for this reason the scientists were able to confirm the feasibility of producing bacteriocin using a highly abundant, low-cost raw material. The kinetics of bacteriocin activity helped to clarify the effect of the nutrients used in this research.

Further information. G. Pena-Gomar, Department of Food Research, Biotechnology Group, Universidad Autonoma de Quer,taro, C.U., Cerro de las Campanas S/N, 76010 Quer,taro, Quer,taro, Mexico; phone: [phone]; fax: [phone]; URL: <http://www.uaq.mx/>.