Fermentation of lignocellulose hydrolysates with yeasts and xylose isomerase (original) (raw)

1989, Enzyme and Microbial Technology

Untreated spent sulfite liquor (SSL) was fermented with five yeasts, Candida tropicalis, Pichia stipitis, Pachysolen tannophilus, Schizosaccharomyces pombe, Saccharomyces cerevisiae, and a co-culture of P. tannophilus and S. cerevisiae, in the presence of commercial xylose (glucose) isomerases and 4.6 mM azide. The highest yield of ethanol, 0.41 g g ~ total sugar, was obtained with S. cerevisiae. The yield based on consumed sugars and per gram cell dry weight was also highest with this yeast. C. tropicalis and P. tannophilus produced considerable amounts of polyoles, mainly xylitol. With P. stipitis sugar uptake was rapidly inhibited in untreated SSL. The presence of azide contributed to the yield by about 0.04, mainly due to the fermentation of stored carbohydrates. The fermentation of hydrogen fluoride-pretreated and acid-hydrolysed wheat straw with S. cerevisiae, xylose isomerase, and azide gave a yield of O.40 g ethanol g-Z total sugar. In this substrate the xylose utilization was 84% compared with 51% in SSL, which is discussed in relation to the salt sensitivity of xylose isomerases.