摘要
为了获得高产活性共轭亚油酸(conjugated linoleic acid,CLA)的嗜热链球菌并开发功能性发酵乳,研究甘氨酸浓度、菌体生物量、电极缓冲液、电压、质粒浓度对电转化效率的影响。结果表明,嗜热链球菌菌体生长与甘氨酸质量浓度呈现负相关,质量浓度为10 g/L时电转化效率最高。电转化效率的影响呈现先上升后下降的趋势;随着菌体生物量、转化电压和质粒浓度的增加,OD600=0. 8、电压1. 8 k V、质粒质量浓度为1. 0 g/L时电转化效率最高;电转缓冲液bufferⅡ(0.5 mol/L蔗糖,1 mmol/L柠檬酸铵; p H 6.0)表现出较好的转化效率。优化嗜热链球菌的电转化条件,提高其转化率,为乳酸菌的高效转化提供一定的理论基础,并为生产具有CLA生理功能的发酵乳提供新的思路。
In order to obtain Streptococcus thermophilus with high yield of conjugated linoleic acid( CLA) to develop functional fermented milk,effects of glycine concentration,bacterial density,buffer solution,voltage and plasmid concentration on electroporation efficiency of S. thermophilus were investigated. The growth of S. thermophiles was negatively correlated with glycine concentration,and its electroporation efficiency was the highest when the cells grew with 10 g/L glycine. The efficiency increased and then decreased with increasing cell density,transformation voltage,and plasmid concentration. The optimal conditions for electroporation were: cell density of 0. 8( OD600),voltage of 1. 8 kV,and plasmid concentration of 1. 0 g/L. Moreover,buffer II( pH = 6. 0) composed of 0. 5 mol/L sucrose and 1 mmol/L ammonium citrate showed good transformation efficiency. By optimizing electrotransformation conditions,the transformation rate of S. thermophiles increased,which provides a theoretical basis for transforming lactic acid bacteria efficiently and also gives a new idea for producing fermented milk with CLA.
引文
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