Comparing Bioalcohols Production from Olive Pruning Biomass by Biotechnological Pathway with Candida guilliermondii and Pichia stipitis

After acid hydrolysis with H 2 SO 4 from olive pruning, subsequent fermentations were carried out in order to compare two non-traditional yeasts: Candida guilliermondii and Pichia stipitis . During the fermentations, sugar uptake as well as ethanol and xylitol production were determined. However, both yeast employed for the biotransformations showed different behaviours; C. guilliermondii produced ethanol from D -glucose and xylitol from D -xylose but, in contrast, P. stipitis only was able to produce ethanol from hexoses and pentoses although, due to the inhibitors amount (acetic acid and polyphenols mainly), it required a detoxification step. To solve this problem, activated charcoal treatment as well as a vacuum evaporation process (concentration ratio 2.7) were performed as physical detoxification methods with positive results. The maximum ethanol and xylitol yields ( Y P / S ) (calculated on consumed sugars) obtained with C. guilliermondii were 0.38 and 0.31 kg kg - 1 respectively; while P. stipitis was able to produce 0.33 kg of ethanol per kg of fermentable sugar.