Organosolv pretreatment of olive tree biomass for fermentable sugars

Abstract

Olive tree pruning biomass is one of the main agricultural residues available in Mediterranean countries and is currently lacking commercial applications. To take advantage of its sugar content, a pretreatment is necessary to enhance enzyme accessibility of the cellulose fraction of the residue. This paper describes for the first time the use of organosolv pretreatment in this regard. The main process variables such as pretreatment temperature, residence time, and solvent composition (aqueous ethanol) are studied. Results show that organosolv pretreatment causes delignification and hydrolysis of hemicelluloses and improves the enzymatic digestibility of olive tree pruning biomass. A higher pretreatment severity and ethanol content of the solvent were found to increase delignification (up to 64% at 66% w/w aqueous ethanol, 2108C, 60 min). By contrast, xylan hydrolysis was promoted by a lower ethanol content (maximum 92%). The highest enzymatic hydrolysis yield (90% of the structural glucan present in the raw material) has been obtained after pretreatment with 43% w/w aqueous ethanol at 2108C for 15 min. Organosolv pretreatment was found to be the most effective pretreatment for enzymatic hydrolysis of olive tree pruning biomass.

Lignocellulosic biomass to biofuels and biochemicals: A comprehensive review with a focus on ethanol organosolv pretreatment technology

“…In the actual pretreatment process, the optimal ethanol concentration is usually in the range of 50–60 wt% (X. Zhao et al, ). Higher ethanol concentration can promote delignification, but it is not good for hydrolysis of hemicellulose (Díaz et al, ). Therefore, delignification and hydrolysis of hemicellulose have to be taken into consideration for the selection of the optimal ethanol concentration.…”

“…In the past few decades, autocatalyzed pretreatment has been successfully applied to improving the enzymatic hydrolysis of lignocellulosic biomass, such as Eucalytus (Mou & Wu, ; Muñoz, Baeza, Freer, & Mendonça, ; Yáñez‐S et al, ), Triploid of Populus tomentosa Carr . (Guo et al, ), hybrid polar (Pan, Kadla, Ehara, Gilkes, & Saddler, ), olive tree biomass (Díaz et al, ), southwest birch (Wen, Xue, Sun, & Sun, ), bagasse (Wei, Wu, & Xu, ), and wheat straw (Chen et al, ). Muñoz et al () pretreated the tension and opposite wood of Eucalyptus globulus using 60% ethanol solution at 180°C and 200°C for 30–120 min.…”

High value‐added monomer chemicals and functional bio‐based materials derived from polymeric components of lignocellulose by organosolv fractionation

“…Ethanol concentration is a key factor for lignin solubilization in aqueous ethanol solution. The maximum solubility of lignin has been reported to be 75 wt% ethanol aqueous solution, but 50–60 wt% ethanol aqueous solution is normally used for fractionation, because a higher water content is good for hemicellulose hydrolysis . Catalysts have significant influence on ethanol‐based organosolv fractionation.…”

Optimization of sulfuric acid-assisted glycerol pretreatment of sugarcane bagasse

“…Organosolv processes, which have been investigated as alternative to traditional pulping methods (Puls 1987 ), have a certain potential as a pretreatment for enzymatic hydrolysis (Zhao et al 2009 ;D í az et al 2011 ). However, the limitation is the risk of high-pressure operations with highly volatile and flammable solvents.…”