A multifactorial design for studying factors influencing the growth and tyramine production of the lactic acid bacteria Lactobacillus brevis CECT 4669 and Enterococcus faecium BIFI-58

摘要

A central composite face design was used to study growth and tyramine production of two strains of lactic acid bacteria, Lactobacillus brevis\udCECT 4669 and Enterococcus faecium BIFI-58. The effects of five physicochemical factors (incubation temperature and time, environmental pH,\udadded tyrosine concentration, and pyridoxal-5-phosphate (PLP) supplementation) on cell growth and tyramine production were analyzed under\udaerobic and anaerobic conditions. The parameters of the quadratic model for each response variable were estimated by multiple linear regression\ud(MLR), and statistical analysis of the results led to the elucidation of mathematical models capable of predicting the behavior of the responses\udas a function of the main variables involved in the process. Incubation time was found to be the most important variable influencing growth in\udL. brevis, while pH showed the highest contribution in E. faecium. The production of tyramine was dependent on the added tyrosine concentration\udand incubation time. The proposed MLR model predicted the optimum conditions that gave maximum responses for L. brevis and E. faecium\udgrowth and tyramine production. In both strains, this model predicted that the anaerobic condition at acidic pH (4.4) in the presence of a high\udtyrosine concentration favors tyramine production