초록
<P><B>Background</B></P><P>Efficient xylose alcoholic fermentation is one of the key to a successful lignocellulosic ethanol production. However, regulation of this process in the native xylose-fermenting yeasts is poorly understood. In this work, we paid attention to the transcriptional factor Cat8 and its possible role in xylose alcoholic fermentation in <I>Ogataea (Hansenula) polymorpha.</I> In <I>Saccharomyces cerevisiae,</I> organism, which does not metabolize xylose, gene <I>CAT8</I> encodes a Zn-cluster transcriptional activator necessary for expression of genes involved in gluconeogenesis, respiration, glyoxylic cycle and ethanol utilization. Xylose is a carbon source that could be fermented to ethanol and simultaneously could be used in gluconeogenesis for hexose synthesis. This potentially suggests involvement of <I>CAT8</I> in xylose metabolism.</P><P><B>Results</B></P><P>Here, the role of <I>CAT8</I> homolog in the natural xylose-fermenting thermotolerant yeast <I>O. polymorpha</I> was characterized. The <I>CAT8</I> ortholog was identified in <I>O. polymorpha</I> genome and deleted both in the wild-type strain and in advanced ethanol producer from xylose. Constructed <I>cat8</I>Δ strain isolated from wild strain showed diminished growth on glycerol, ethanol and xylose as well as diminished respiration on the last substrate. At the same time,<I> cat8</I>Δ mutant isolated from the best available <I>O. polymorpha</I> ethanol producer showed only visible defect in growth on ethanol. <I>CAT8</I> deletant was characterized by activated transcription of genes <I>XYL3, DAS1</I> and <I>RPE1</I> and slight increase in the activity of several enzymes involved in xylose metabolism and alcoholic fermentation. Ethanol production from xylose in <I>cat8</I>Δ mutants in the background of wild-type strain and the best available ethanol producer from xylose increased for 50 and 30%, respectively. The maximal titer of ethanol during xylose fermentation was 12.5 g ethanol/L at 45 °C. Deletion of <I>CAT8</I> did not change ethanol production from glucose. Gene <I>CAT8</I> was also overexpressed under control of the strong constitutive promoter <I>GAP</I> of glyceraldehyde-3-phosphate dehydrogenase. Corresponding strains showed drop in ethanol production in xylose medium whereas glucose alcoholic fermentation remained unchanged. Available data suggest on specific role of Cat8 in xylose alcoholic fermentation.</P><P><B>Conclusions</B></P><P>The <I>CAT8</I> gene is one of the first identified genes specifically involved in regulation of xylose alcoholic fermentation in the natural xylose-fermenting yeast <I>O. polymorpha</I>.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-017-0652-6) contains supplementary material, which is available to authorized users.</P>