The effect of autohydrolysis on the production of second generation bioethanol from extracted olive pomace (original) (raw)
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Bioethanol production from extracted olive pomace: dilute acid hydrolysis
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Olive table industry, olive mills and olive pomace oil extraction industries annually generate huge amounts of olive stones. One of their potential applications is the production of bioethanol by fractionation of their lignocellulose constituents and subsequent fermentation of the released sugars using yeasts. In this work, we studied the influence of temperature (175–225 °C) and residence time (0–5 min) in the liquid hot-water pre-treatment of olive stones as well as the initial enzyme loading (different mixtures of cellulases, hemicellulases and β–glucosidases) in the later enzymatic hydrolysis on the release of fermentable sugars. The Chrastil’s model was applied to the d-glucose data to relate the severity of pre-treatment to enzyme diffusion through the pre-treated cellulose. Finally, the hydrolysate obtained under the most suitable conditions (225 °C and 0 min for pre-treatment; 24 CE initial enzyme concentration) was fermented into ethanol using the yeast Pachysolen tannophil...
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Production of Bioethanol from Olive Solid Waste "JEFT
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Olive solid residue (JEFT) is the solid waste generated during olive oil production process in three-phase olive mills. It consists of the remaining pulp of olive processing after the extraction of oil, as well as the cracked seeds of the olive fruits. As a lignocellulosic material, the hemicellulose, cellulose and lignin are the main components of olive stone. The present study standardized production of ethanol from olive solid wastes using Saccharomyces cerevisiae isolates. S. cerevisiae isolated from yogurt, grape and sugarcane. These isolates were identified according to morphological and biochemical characterization tests. The alcohol tolerance test indicated that S. cerevisiae tolerated up to 10% of ethanol in the medium. Optimization of culture conditions such as pH and temperature of yeast isolates was did. 10g JEFT subjected to hydrolysis to sugar by different concentrations of diluted sulfuric and hydrochloric acids. Among acid treatment, the maximum amount of reducing su...
Bio-based fractions by hydrothermal treatment of olive pomace: Process optimization and evaluation
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Olive pomace is an important lignocellulosic biomass for Mediterranean countries which is released in large quantities during industrial olive oil production and used for heating purposes for many years. In this study, the aim was to investigate the use of olive pomace to obtain value added fractions namely, proteins, fermentable sugars and lignin by sustainable biorefinery approach applying a sequence of high pressure extraction and hydrolysis. After pretreatment steps, 93.7% of the fermentable sugars and 94.4% of the lignin that present in the biomass were recovered. Liquid hot water (LHW) pretreatment was shown to enhance the yield of enzymatic hydrolysis by an increase of 95.23%. The obtained sugars were used to produce bioethanol and based on the consumed sugar the yield and productivity were determined as 15.25% and 0.086 kg/m 3 h respectively.
Ethanolic fermentation of phosphoric acid hydrolysates from olive tree pruning
Industrial Crops and Products, 2007
The objective of this work was to study the feasibility of using phosphoric acid to hydrolyze the hemicellulosic fraction of olive tree pruning, as a step in the bioconversion process to produce ethanol. Milled olive tree pruning was submitted to hydrolysis at 90 • C by phosphoric acid in a concentration range 0.3-8N for 240 min. The hydrolysates were then fermented by Pachysolen tannophilus. The hydrolysis stage was evaluated by the evolution of glucose and reducing sugars generated and by the conversion of hemicellulose fraction. The main parameters determined in the fermentation were: maximum specific growth rate, specific substrate consumption rate, specific ethanol production rate and ethanol yield. The maximum ethanol yield (0.38 kg/kg, equivalent to 74.5% of the theoretical yield) was obtained when hydrolysing with 0.5N phosphoric acid. Hemicellulose conversion is however incomplete at these operational conditions. Higher acid concentrations lead to higher hydrolysis of hemicellulose, but the ethanol yields resulting from the fermentation are lower.
Renewable Energy, 2015
Olive stones are an agro-industrial by-product in Mediterranean countries that can be regarded as a potential source of bio-fuels and bioactive compounds. In this work, olive stones were pretreated with liquid hot water (LHW), dilute sulphuric acid (DSA) and organosolv delignification at temperatures in the range 190 Ce230 C. The resulting solids from pretreatments were subjected to simultaneous saccharification and fermentation (SSF) with the yeast Saccharomyces cerevisiae IR2-9a for fuel-ethanol production. The composition of prehydrolysates from LHW and DSA pretreatments were strongly dependent of reactor temperature. The highest yields of D-xylose (0.21 kg kg À1) and D-glucose (0.11 kg kg À1) were achieved in DSA assays at 200 C and 230 C, respectively, while LHW processes provided the maximum oligosaccharide recovery (0.17 kg kg À1) at 210 C. The addition of sulphuric acid in organosolv pretreatments was particularly effective to increase the cellulose content of the pretreated solids till percentages close to 83%. Finally, the maximum ethanol concentration achieved by SSF was 47.1 kg m À3 , and 13 kg ethanol were obtained from 100 kg of raw material.
Environmental Science and Pollution Research, 2020
The present study investigated the effect of thermo-chemical pretreatment on the enhancement of enzymatic digestibility of olive mill stones (OMS), as well as its possible valorisation via bioconversion of the generated free sugars to alcohols. Specifically, the influence of parameters such as reaction time, temperature, type and concentration of dilute acids and/or bases, was assessed during the thermo-chemical pretreatment. The hydrolysates and the solids remaining after pretreatment, as well as the whole pretreated slurries, were further evaluated as potential substrates for the simultaneous production of ethanol and xylitol via fermentation with the yeast Pachysolen tannophilus. The digestibility and overall saccharification of OMS were considerably enhanced in all cases, with the maximum enzymatic digestibility observed for dilute sodium hydroxide (almost 4-fold) which also yielded the highest total saccharification yield (91% of the total OMS carbohydrates). Ethanol and xylitol yields from the untreated OMS were 28 g/kg OMS and 25 g/kg OMS, respectively, and were both significantly enhanced by pretreatment. The highest ethanol yield was 79 g/kg OMS and was achieved by the alkali pretreatment and separate fermentation of hydrolysates and solids, whereas the highest xylitol yield was 49 g/kg OMS and was obtained by pretreatment with sulphuric acid and separate fermentation of hydrolysates and solids.
Ensilage and Bioconversion of Grape Pomace into Fuel Ethanol
Journal of Agricultural and Food Chemistry, 2012
Two types of grape pomace were ensiled with eight strains of lactic acid bacteria (LAB). Both fresh grape pomace (FrGP) and fermented grape pomace (FeGP) were preserved through alcoholic fermentation but not malolactic conversion. Water leaching prior to storage was used to reduce water-soluble carbohydrates and ethanol from FrGP and FeGP, respectively, to increase malolactic conversion. Leached FeGP had spoilage after 28 days of ensilage, whereas FrGP was preserved. Dilute acid pretreatment was examined for increasing the conversion of pomace to ethanol via Escherichia coli KO11 fermentation. Dilute acid pretreatment doubled the ethanol yield from FeGP, but it did not improve the ethanol yield from FrGP. The ethanol yields from raw pomace were nearly double the yields from the ensiled pomace. For this reason, the recovery of ethanol produced during winemaking from FeGP and ethanol produced during storage of FrGP is critical for the economical conversion of grape pomace to biofuel.