Olive tree pruning as an agricultural residue for ethanol production. Fermentation of hydrolysates from dilute acid pretreatment

M. J. Díaz-Villanueva, C. Cara-Corpas, E. Ruiz-Ramos, I. Romero-Pulido, E. Castro-Galiano

Abstract


The use of agricultural residues for ethanol production constitutes one of the most promising alternatives from an environmental point of view for substituting fossil fuels in the transport sector. This work deals with the fermentability of hydrolysates obtained from olive tree pruning biomass and the influence of the pH of the culture medium. Hydrolysates of olive tree biomass were obtained by dilute acid pre-treatment of the raw material at 180ºC and 1% (w/v) sulfuric acid concentration. After pretreatment, solid residue and liquid were separated by filtration. The liquid fraction (hydrolysate) was then submitted to detoxification (overliming) before being used as fermentation medium. Pichia stipitis and Pachysolen tannophilus were compared as fermenting microorganisms. Different initial pH values were also tested. The best results in terms of ethanol yield were obtained by P. tannophilus with values as high as 0.44 g ethanol g-1 sugar, and all liquids were fermented, to a different extent. P. stipitis could not ferment hydrolysates with initial pH below 6.5. It was also determined that ethanol production did not improve once glucose in the medium was totally converted, even if other sugars (xylose) were also consumed.

Keywords


bioethanol; olive tree biomass; pentoses; Pichia stipitis; Pachysolen tannophilus

Full Text:

PDF

References


Agbogbo FK, Coward-Kelly G, 2008. Cellulosic ethanol production using the naturally occurring xylose-fermenting yeast, Pichia stipitis. Biotechnol Lett 30: 1515-1524.
http://dx.doi.org/10.1007/s10529-008-9728-z
PMid:18431677

Agbogbo FK, Haagensen FD, Milam D, Wenger KS, 2008. Fermentation of acid-pretreated corn stover to ethanol without detoxification using Pichia stipitis. Appl Biochem Biotechnol 145: 5358.
http://dx.doi.org/10.1007/s12010-007-8056-4
PMid:18425611

Cara C, Ruiz E, Oliva JM, Sez F, Castro E, 2008. Conversion of olive tree biomass into fermentable sugars by dilute acid pretreatment and enzymatic saccharification. Bioresour Technol 99: 1869-1876.
http://dx.doi.org/10.1016/j.biortech.2007.03.037
PMid:17498947

Daz M, Ruiz E, Romero I, Cara C, Moya M, Castro E, 2009. Inhibition of Pichia stipitis fermentation of hydrolysates from olive tree cuttings. World J Microb Biotechnol 25: 891-899.
http://dx.doi.org/10.1007/s11274-009-9966-9

Paraj JC, Domnguez H, Domnguez JM, 1998. Biotechnological production of xylitol. Part 3: Operation in culture media made from lignocellulose hydrolysates. Bioresour Technol 66: 25-40.
http://dx.doi.org/10.1016/S0960-8524(98)00037-6

Pienkos PK, Zhang M, 2009. Role of pretreatment and conditioning processes on toxicity of lignocellulosic biomass hydrolysates. Cellulose 16: 743-762.
http://dx.doi.org/10.1007/s10570-009-9309-x

Purwadi R, Niklasson C, Taherzadeh MJ, 2004. Kinetic study of detoxification of dilute-acid hydrolyzates by Ca(OH)2. J Biotechnol 114: 187-198.
http://dx.doi.org/10.1016/j.jbiotec.2004.07.006
PMid:15464612

Romero I, Moya M, Snchez S, Ruiz E, Castro E, Bravo V, 2007a. Ethanolic fermentation of phosphoric acid hydrolysates from olive tree pruning. Ind Crops Prod 25: 160-168.
http://dx.doi.org/10.1016/j.indcrop.2006.08.008

Romero I, Snchez S, Moya M, Castro E, Ruiz E, Bravo V, 2007b. Fermentation of olive tree pruning acid-hydrolysates by Pachysolen tannophilus. Biochem Eng J 36: 108-115.
http://dx.doi.org/10.1016/j.bej.2007.02.006

Snchez S, Bravo V, Castro E, Moya AJ, Camacho F, 1999. Comparative study of the fermentation of D-glucose/D-xylose mixtures with Pachysolen tannophilus and Candida shehatae. Bioprocess Eng 21: 525-532.

Zhao L, Yu J, Zhang X, Tan T, 2010. The ethanol tolerance of Pachysolen tannophilus in fermentation on xylose. Appl Biochem Biotechnol 160: 378-385.
http://dx.doi.org/10.1007/s12010-008-8308-y
PMid:18651246




DOI: 10.5424/sjar/2012103-2631