Evaluation of de-lipidated egg yolk and yeast autolysate as growth supplements for lactic acid bacteria culture

Abstract

Four strains of lactic acid bacteria (LAB) were cultivated on deproteinated whey supplemented with yeast autolysate (YA) and/or de-lipidated egg yolk (DEY). Growth was compared to that recorded on the widely used MRS medium. The feasibility of the use of YA in place of yeast extract was confirmed. In the presence of YA in the medium, cell numeration gained nearly 1 log for only 0.4% DEY added in the culture medium, namely 0.1 g/L additional nitrogen, showing that DEY also supplies LAB growth in trace elements and growth factors like vitamins. If compared to the MRS medium, final cell numerations were about 1 log lower on deproteinated whey supplemented with YA and DEY, while the protein nitrogen ratio of both media was 2.7, showing the high potential of the tested supplements, and especially DEY. Subsequent works with higher and hydrolysed DEY may be therefore useful. © 2007 Society of Dairy Technology.