Abstract:

Two kinds of yeast extracts including 1 brewer＇s yeast extract produced by a Chinese company and 4 baker＇s yeast extracts produced by the Chinese company, a UK company, two French companies were selected to compare their characteristics and the effects on the growth of typical engineering bacteria such as E.coli BL21, DH5 αand DH10B. The results showed that the clarity of brewer＇s yeast extract from the Chinese domestic producer was lower than those of the 3 baker＇s yeast extracts from overseas producers while no differences in the contents of total nitrogen and amino nitrogen were observed between the bakers＇yeast extract from the domestic producer and from the overseas producers. E.coli DH5 α showed better growth in the domestic yeast extracts while E.coli DH10B in the yeast extracts from the overseas producers. No significant effect, however, was observed on the growth of E.coli BL21 between the domestic and overseas products. Therefore, a suitable yeast extract is one of the key factors affecting the microbial fermentation according to the growth and metabolism of different strains.

Key words: yeast extract, characteristics, typical engineering strains, growth curve