Preparation of extracts of culture liquids for gas-chromatographic determination of acidic fermentation products

An extraction method coupled with gas-chromatographic analysis has been devised for the determination of small amounts of C₁-C₇ branched and straight-chain saturated fatty acids as well as 18 mono-, di- and tricarboxylic acids and related compounds, the latter being analyzed either as their methylesters or as their trimethylsilyl-derivatives. Methods for extracting non-volatile acids or both volatile and non-volatile acids are described for large and small volumes of culture media. The proposed methods have been successfully applied to the determination of non-acidic fermentation products, known amounts of alcohols, and to volatile and non-volatile acids in bacterial fermentation solutions, namely a batch culture ofLactobacillus casei subsp.rhamnosus ATCC 7469. A carbon balance sheet of this organism's metabolic behaviour throughout growth is proposed.