PRODUCTION OF TRANS - l -EPOXYSUCCINIC ACID BY FUNGI AND ITS MICROBIOLOGICAL CONVERSION TO MESO -TARTARTIC ACID

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Abstract
A soil isolate of Aspergillus fumigatus was found to produce appreciable quantities of trans-l-epoxysuccinic acid from glucose or ethanol as substrates. The acid was isolated in crystalline form and characterized by several criteria. Several fungi, bacteria and a yeast capable of using trans-l-epoxysuccinate as the sole C source were isolated from soil. One bacterium, identified as Flavobacterium sp., was found to oxidize trans-J-epoxysuccinate and the synthetic racemic trans-dlepoxysuccinate acid, but not the geometric isomer cis-epoxysuccinate acid. Cell-free enzymatic extracts converted trans-l -epoxysuccinate to meso-tartrate. This is the first reported natural occurrence of meso-tartrate. The free acid was isolated in crystalline form and characterized chemically. It was also identified by the X-ray diffraction pattern on the Ca salt. The enzyme was named trans-succinic epoxide hydrolase and apparently required no dialyzable cofactor. The reaction it catalyzes is: K ?00H OH OH HC-CH HOH H00C CH CH____C00H HOOC trans-Uepoxysuccinic acid meso-tartaric acid Whole cells of Flavobacterium sp. harvested from trans-_l-epoxy-succinate medium were simultaneously adapted to oxidize meso-tartrate but not d- or _l-tartrates. Whole cells harvested from meso-tartrate medium did not oxidize d- or_l-tartrate but did oxidize trans-l-epoxysuccinate only after a short lag period. Extracts of meso-tartrate cells contained no trans-succinic epoxide hydrolase activity, hence these cells were not back-adapted to trans-I-epoxysuccinate. These data are taken to indicate that the 1st stage in the utilization of epoxysuccinate by these bacteria is via meso-tartrate. Proof that meso-tartrate is formed from trans-l- epoxysuccinate by whole cells was obtained by the addition of Ca to the medium. The intermediate meso-tartrate was trapped as the insoluble Ca salt which crystallized in the medium. All the several fungi, bacteria and the yeast formed calcium meso-tartrate in this way.

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