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Open AccessFeature PaperArticle

Acid and Enzymatic Fractionation of Olive Stones for Ethanol Production Using Pachysolen tannophilus

1
Department of Chemical, Environmental and Materials Engineering, University of Jaén, Campus ‘Las Lagunillas’, 23071 Jaén, Spain
2
Center for Advanced Studies in Olive Grove and Olive Oils, Science and Technology Park GEOLIT, 23620 Mengibar, Spain
3
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Seville, Spain
*
Authors to whom correspondence should be addressed.
Processes 2020, 8(2), 195; https://doi.org/10.3390/pr8020195
Received: 29 December 2019 / Revised: 30 January 2020 / Accepted: 31 January 2020 / Published: 6 February 2020
Olive stones are an abundant lignocellulose material in the countries of the Mediterranean basin that could be transformed to bioethanol by biochemical pathways. In this work, olive stones were subjected to fractionation by means of a high-temperature dilute-acid pretreatment followed by enzymatic hydrolysis of the pretreated solids. The hydrolysates obtained in these steps were separately subjected to fermentation with the yeast Pachysolen tannophilus ATCC 32691. Response surface methodology with two independent variables (temperature and reaction time) was applied for optimizing D-xylose production from the raw material by dilute acid pretreatment with 0.01 M sulfuric acid. The highest D-xylose yield in the liquid fraction was obtained in the pretreatment at 201 °C for 5.2 min. The inclusion of a detoxification step of the acid prehydrolysate, by vacuum distillation, allowed the fermentation of the sugars into ethanol and xylitol. The enzymatic hydrolysis of the pretreated solids was solely effective when using high enzyme loadings, thus leading to easily fermentable hydrolysates into ethanol. The mass macroscopic balances of the overall process illustrated that the amount of inoculum used in the fermentation of the acid prehydrolysates strongly affected the ethanol and xylitol yields. View Full-Text
Keywords: bioethanol; dilute acid pretreatment; enzymatic hydrolysis; olive stones; Pachysolen tannophilus; response surface methodology bioethanol; dilute acid pretreatment; enzymatic hydrolysis; olive stones; Pachysolen tannophilus; response surface methodology
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MDPI and ACS Style

Cuevas, M.; Saleh, M.; García-Martín, J.F.; Sánchez, S. Acid and Enzymatic Fractionation of Olive Stones for Ethanol Production Using Pachysolen tannophilus. Processes 2020, 8, 195.

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