ENZYMATIC CHARACTERISTICS OF ALCOHOL ACETYLTRANSFERASE FROMHANSENIASPORA VALBYENSIS, A NON-SACCHAROMYCESYEAST

Abstract

Alcohol acetyltransferase (AAT) catalyzing 2‐phenylethyl alcohol and acetyl co‐enzyme A (acetyl‐CoA) to form phenylethyl acetate in Hanseniaspora valbyensis was studied. The enzyme was solubilized from lipid particles using 1% Triton X‐100 and then purified by three steps of chromatographic separations with diethylaminoethlyl (DEAE) Sepharose, Sephadex G‐75 and Octyl Sepharose, respectively. Its molecular weight was estimated to be about 37 kDa. It was discovered that AAT was most active at pH 7.0 and 30C and was stable between pH 7.0–8.0. But most activity was lost at temperatures above 10C. It was found that AAT was strongly inhibited by heavy metal ions such as Hg2+, Zn2+and Pb2+, slightly stimulated by Mg2+and slightly inhibited by ethylenediamine tetraacetic acid (EDTA) and Mn2+. The Km was 12.7 mM for 2‐phenylethyl alcohol and 23.2 mM for isoamyl alcohol. Finally, the enzyme was observed to catalyze the esterification of other alcohols with acetyl‐CoA, but have preference for 2‐phenylethyl alcohol. PRACTICAL APPLICATIONS Aroma and flavor are affected by the esters that exist in cider. Alcohol acetyltransferase (AAT) can catalyze the formation of esters. Moreover, Saccharomyces cerevisiae and non‐Saccharomyces yeast produce diverse esters with different concentration during fermentation. The influence of non‐Saccharomyces yeast on the sensory quality of wine and mixed fermentation using different yeasts have been discussed. So, the purification of AAT from Hanseniaspora valbyensis provides an understanding of the formation of esters in non‐Saccharomyces yeast.

Gene Mining and Flavour Metabolism Analyses of Wickerhamomyces anomalus Y-1 Isolated From a Chinese Liquor Fermentation Starter

“…Studies have shown that esters are synthesised by the lipase/esterase pathway ( Wang et al, 2008 ), alcohol transferase pathway ( Wolter et al, 1966 ) and alcohol dehydrogenase pathway ( Kusano et al, 1998 ). The lipase/esterase synthesis pathway, namely, the esterification reaction pathway, is the most common pathway used to generate esters in liquor ( Papamichael, 2013 ).…”