The thermotolerant yeast K. marxianus CECT 10875 was able
to ferment the whole slurry obtained by steam explosion pre-
treatment of wheat straw at 220 ◦C for 2.5 min in a SSF process
at low substrate loading (5% w/v), reaching an ethanol concentra-
tion of 9.6 g/L. However, presaccharification prior to SSF inhibited
totally the yeast. A better yeast performance was observed on the
slurry obtained at softer conditions (200 ◦C for 2.5 min). Its lower
inhibitors content allowed the use of the yeast in both SSF and PSSF
processes at higher consistency (10% w/v), obtaining an ethanol
concentration of 12.3 g/L.
The specific removal of phenols by laccase reduced the
inhibitory effects of slurry samples. It led to enhance the yeast fer-
mentation performance and to increase the substrate loadings of
broths during SSF and PSSF processes, increasing consequently the
ethanol production. In spite ofthe boosted laccase action by presac-
charification, even at higher substrate loadings,the highest ethanol
concentration (16.7 g/L) was achieved when the laccase treatment
was carried out without presaccharification on the slurry produced
at lower severity conditions (200 ◦C for 2.5 min) and higher con-
sistency (12% w/v). Nevertheless, this ethanol concentration is not
enough for a cost-effective bioethanol production (ethanol con-
centrations over 4% v/v). Therefore, further researches with new
operation modes such as fed batch processes, are necessaries in