Abstract
Loblolly pine residues have enormous potential to be the raw material for advanced biofuel production due to extensive sources and high cellulose content. Hot water (HW) pretreatment, while being a relatively economical and clean technology for the deconstruction of lignocellulosic biomass, could also inhibit the ensuing enzymatic hydrolysis process because of the production of inhibitors. In this study, we investigated the effect of oligosaccharide fractions purified from HW pre-hydrolyzate of pinewood using centrifugal partition chromatography (CPC) on three recombinant cellulolytic enzymes (E1, CBHI and CBHII), which were expressed in the transgenic corn grain system. The efficiency of recombinant enzymes was measured using either a 4-methylumbelliferyl-β-D-cellobioside (MUC) or a cellulose-dinitrosalicylic acid (DNS) assay system. The results showed that HW pre-hydrolyzate CPC fractions contain phenolics, furans, and monomeric and oligomeric sugars. Among CPC fractions, oligomers composed of xylan, galactan, and mannan were inhibitory to the three recombinant enzymes and to the commercial cellulase cocktail, reducing the enzymatic efficiency to as low as 10%.
Highlights
Considering the large volume of logging residues of both softwood and hardwood from existing wood processing plants, the forestry industry has recently expressed strong interest in becoming providers of biomass for bioenergy and biofuel production (Bioenergy, 2008)
This is the first time we report the fractionation of mannan, glucan and galactan oligosaccharides from Loblolly pinewood hydrolyzate using the centrifugal partition chromatography (CPC) technique
Pinewood oligosaccharides were purified from the liquid fraction of hot water (HW) pretreatment using CPC
Summary
Considering the large volume of logging residues of both softwood and hardwood from existing wood processing plants, the forestry industry has recently expressed strong interest in becoming providers of biomass for bioenergy (heat and power generation) and biofuel production (Bioenergy, 2008). During the pretreatment process, a number of byproducts are formed from the degradation of holocellulose and lignin such as phenolics, furans, organic acids, and unfermentable monomeric and oligomeric sugars (xylose, mannose, xylan, mannan, etc.). All these compounds have been shown to negatively affect the saccharification step during biofuel production by inhibiting the cellulolytic enzymes (Duarte et al, 2012; Gao et al, 2014; González-Bautista et al, 2017)
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