Authors: Manuel J Díaz Encarnación Ruiz Inmaculada Romero Cristóbal Cara Manuel Moya Eulogio Castro
Publish Date: 2009/01/29
Volume: 25, Issue: 5, Pages: 891-899
Abstract
The ethanolic fermentation of liquid fractions hydrolysates issued from dilute acid pretreatment 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 pretreatment of olive tree biomass at 190°C 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 035 to 042 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 hydrolysatesThis work was partially financed by Agencia Española de Cooperación Internacional para el Desarrollo AECID under Project ref D/9619/07 Ministerio de Educación y Ciencia Project ENE200508822 and FEDER funds Financial support from Azucareras Reunidas de Jaén S A is also gratefully acknowledged
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