Concomitant extracellular accumulation of alpha-keto acids and higher alcohols by Zygosaccharomyces rouxii.
Alpha-keto acids are key intermediates in the formation of higher alcohols, important flavor components in soy sauce, and produced by the salt-tolerant yeast Zygosaccharomyces rouxii. Unlike most of the higher alcohols, the alpha-keto acids are usually not extracellularly accumulated by Z. rouxii when it is cultivated with ammonium as the sole nitrogen source. To facilitate extracellular accumulation of the alpha-keto acids from aspartate-derived amino acid metabolism, the amino acids valine, leucine, threonine and methionine were exogenously supplied during batch and A-star cultivations of (routants of) Z. rouxii. It was shown that all alpha-keto acids from the aspartate-derived amino acid metabolism, except alpha-ketobutyrate, could be extracellularly accumulated. In addition, it appeared from the concomitant extracellular accumulation of alpha-keto acids and higher alcohols that in Z. rouxii, valine, leucine and methionine were converted via Ehrlich pathways similar to those in Saccharomyces cerevisiae. Unlike these amino acids, threonine was converted via both the Ehrlich and amino acid biosynthetic pathways in Z. rouxii.
Van Der Sluis
Catrinus
C
Wageningen University, Department of Agrotechnology and Food Sciences, Food and Bioprocess Engineering Group, P.O. Box 8129, 6700 EV Wageningen, The Netherlands. Catrinus.vanderSluis@algemeen.pk.wau.nl
Rahardjo
Yovita S P
YS
Smit
Bart A
BA
Kroon
Pieter J
PJ
Hartmans
Sybe
S
Ter Schure
Eelko G
EG
Tramper
Johannes
J
Wijffels
Renéh
R