Organosolv pretreatment of sorghum bagasse using a low concentration of hydrophobic solvents such as 1-butanol or 1-pentanol

Abstract

BackgroundThe primary components of lignocellulosic biomass such as sorghum bagasse are cellulose, hemicellulose, and lignin. Each component can be utilized as a sustainable resource for producing biofuels and bio-based products. However, due to their complicated structures, fractionation of lignocellulosic biomass components is required. Organosolv pretreatment is an attractive method for this purpose. However, as organosolv pretreatment uses high concentrations of organic solvents (>50 %), decreasing the concentration necessary for fractionation would help reduce processing costs. In this study, we sought to identify organic solvents capable of efficiently fractionating sorghum bagasse components at low concentrations.ResultsFive alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-pentanol) were used for organosolv pretreatment of sorghum bagasse at a concentration of 12.5 %. Sulfuric acid (1 %) was used as a catalyst. With 1-butanol and 1-pentanol, three fractions (black liquor, liquid fraction containing xylose, and cellulose-enriched solid fraction) were obtained after pretreatment. Two-dimensional nuclear magnetic resonance analysis revealed that the lignin aromatic components of raw sorghum bagasse were concentrated in the black liquor fraction, although the major lignin side-chain (β-O-4 linkage) was lost. Pretreatment with 1-butanol or 1-pentanol effectively removed p-coumarate, some guaiacyl, and syringyl. Compared with using no solvent, pretreatment with 1-butanol or 1-pentanol resulted in two-fold greater ethanol production from the solid fraction by Saccharomyces cerevisiae.ConclusionsOur results revealed that a low concentration (12.5 %) of a highly hydrophobic solvent such as 1-butanol or 1-pentanol can be used to separate the black liquor from the solid and liquid fractions. The efficient delignification and visible separation of the lignin-rich fraction possible with this method simplify the fractionation of sorghum bagasse.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0427-z) contains supplementary material, which is available to authorized users.

Selective Primary Alcohol Oxidation of Lignin Streams from Butanol‐Pretreated Agricultural Waste Biomass

“…In addition, due to the frequent use of acidic conditions, some organosolv lignins are still condensed. Our group and others have previously reported the use of biorenewable butanol as a pretreatment solvent for woody‐biomass sources, using both hardwoods and softwoods . Under the acidic butanosolv conditions, the hydroxy at the α position of the β‐ O ‐4 unit is replaced by butanol leading to stabilization of the β‐ O ‐4 unit in a “protected” form (structure 2 , Figures and S1).…”

From mannan to bioethanol: cell surface co-display of β-mannanase and β-mannosidase on yeast Saccharomyces cerevisiae

“…The quantities of major sugar components contained in 1,4-β- d -mannan and ivory nut mannan were determined by following a previously described procedure [36] according to the NREL method [37]. …”

Alternatives for Chemical and Biochemical Lignin Valorization: Hot Topics from a Bibliometric Analysis of the Research Published During the 2000–2016 Period

“…In order to avoid excessive costs, the solvents employed for organosolv process must be bulk commodity chemicals. Low molecular weight alcohols have been preferred: ethanol appears as the most frequent solvent [102][103][104][105][106], but examples that use methanol [107][108][109], propanol [110][111][112], and butanol [113][114][115] can be found as well. Low molecular weight organic acids, mainly formic and acetic acids, are other relevant solvents for organosolv treatments [116][117][118][119][120][121] and include the optional addition of hydrogen peroxide to produce in situ performic and peracetic acids [122][123][124].…”