Investigation of stress tolerance of Pichia kudriavzevii for high gravity bioethanol production from steam-exploded wheat straw hydrolysate

This study investigated a newly isolated thermotolerant strain of Pichia kudriavzevii with respect to its stress tolerance and fermentation performance. Response surface methodology was applied to evaluate the combined effects of furfural, osmotic and thermal stress on ethanol yield. The proposed model shows that P. kudriavzevii has a natural resistance against multiple stress factors. Further evolutionary adaptation of the isolated strain in lignocellulosic hydrolysates improved the ethanol yield by ≥ 24 %. The adapted strain HYPK213_ELA was able to produce ethanol from wheat straw hydrolysates at a high solid loading of 37 %ww^-1 at 40 °C and anaerobic conditions. The highest ethanol concentration of 56.8 ± 1.0 gL^-1 was reached at 40°C with an inoculum size of 2.5 × 10⁶cellsmL^-1. The results show that Pichia kudriavzevii has the potential to enable high gravity bioethanol production under conditions where most yeast strains are unable to grow.