%0 Journal Article 
%A Díaz Villanueva, Manuel Jesús
%A Ruiz-Ramos, Encarnación
%A Romero-Pulido, Inmaculada
%A Cara-Corpas, Cristobal
%A Moya, Manuel
%A Castro, Eulogio
%T Inhibition of Pichia stipitis fermentation of hydrolysates from olive tree cuttings
%D 2009
%@ 0959-3993
%U http://hdl.handle.net/10498/33306
%X The ethanolic fermentation of liquid fractions (hydrolysates) issued from dilute acid pre-treatment of
olive tree biomass by Pichia stipitis is reported for the first time. On the one side, P. stipitis has been
reported as the most promising naturally occurring C5 fermenting microorganism; on the other side,
olive tree biomass is a renewable, low cost, and lacking of alternatives agricultural residue especially
abundant in Mediterranean countries. The study was performed in two steps. First, the fermentation
performance of P. stipitis was evaluated on a fermentation medium also containing the main inhibitors
found in these hydrolysates (acetic acid, formic acid, and furfural), as well as glucose and xylose as
carbon sources. The effect of inhibitors, individually or in a mixture, on kinetic and yield parameters
was calculated. In a second step, hydrolysates obtained from 1% (w/w) sulfuric acid pre-treatment of
olive tree biomass at 190ºC for 10 min were used as a real fermentation medium with the same
microorganism. Due to inhibition, effective fermentation required dilution of the hydrolysate and
either overliming or activated charcoal treatment. Results show that ethanol yields obtained from
hydrolysates, ranging from 0.35 to 0.42 g/g, are similar to those from synthetic medium, although the
process proceeds at lower rates. Inhibiting compounds affect the fermentation performance in a
synergistic way. Furfural is rapidly assimilated by the yeast; acetic acid and formic acid
concentrations decrease slowly during the process. Activated charcoal or overliming detoxification
improve the fermentability of diluted hydrolysates.
%K detoxification
%K ethanol
%K fermentation inhibition
%K olive tree biomass
%K Pichia stipitis
%~ Universidad de Cádiz