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Influence of glucose on xylose metabolization by Spathaspora passalidarum

2021; Academic Press; Volume: 157; Linguagem: Inglês

10.1016/j.fgb.2021.103624

1096-0937

Lílian Emídio Ribeiro, Fernanda Matias Albuini, Alex Gazolla de Castro, Valquíria Júnia Campos, Gilza Barcelos de Souza, João Guilherme Pereira Mendonça, Carlos A. Rosa, Tiago Antônio Oliveira Mendes, Mateus Ferreira Santana, Wendel Batista da Silveira, Luciano Gomes Fietto,

Microbial Metabolic Engineering and Bioproduction

The yeast Spathaspora passalidarum is able to produce ethanol from D-xylose and D-glucose. However, it is not clear how xylose metabolism is affected by D-glucose when both sugars are available in the culture medium. The aims of this work were to evaluate the influence of D-glucose on D-xylose consumption, ethanol production, gene expression, and the activity of key xylose-metabolism enzymes under both aerobic and oxygen-limited conditions. Ethanol yields and productivities were increased in culture media containing D-xylose as the sole carbon source or a mixture of D-xylose and D-glucose. S. passalidarum preferentially consumed D-glucose in the co-fermentations, which is consistent with the reduction in expression of genes encoding the key xylose-metabolism enzymes. In the presence of D-glucose, the specific activities of xylose reductase (XR), xylitol dehydrogenase (XDH), and xylulokinase (XK) were lower. Interestingly, in accordance with other studies, the presence of 2-deoxyglucose (2DG) did not inhibit the growth of S. passalidarum in culture medium containing D-xylose as the sole carbon source. This indicates that a non-canonical repression pathway is acting in S. passalidarum. In conclusion, the results suggest that D-glucose inhibits D-xylose consumption and prevents the D-xylose-mediated induction of the genes encoding XR, XDH, and XK.