Abstract
A shift towards a sustainable and green society is vital to reduce the negative effects of climate change associated with increased CO2 emissions. Lignocellulosic biomass is both renewable and abundant, but is recalcitrant to deconstruction. Among the methods of pretreatment available, organosolv (OS) delignifies cellulose efficiently, significantly improving its digestibility by enzymes. We have assessed the hydrolysability of the cellulose-rich solid fractions from OS-pretreated spruce and birch at 2% w/v loading (dry matter). Almost complete saccharification of birch was possible with 80 mg enzyme preparation/gsolids (12 FPU/gsolids), while the saccharification yield for spruce was only 70%, even when applying 60 FPU/gsolids. As the cellulose content is enriched by OS, the yield of glucose was higher than in their steam-exploded counterparts. The hydrolysate was a transparent liquid due to the absence of phenolics and was also free from inhibitors. OS pretreatment holds potential for use in a large-scale, closed-loop biorefinery producing fuels from the cellulose fraction and platform chemicals from the hemicellulose and lignin fractions respectively.
Highlights
There is an urgent need to produce fuels and chemicals from renewable resources, and drastic actions are required to combat the emissions of greenhouse gases, as underlined in the report by the Intergovernmental Panel on Climate Change (Houghton 2009; IPCC 2014)
Biomass is an abundant renewable feedstock (Perlack and Stokes (Leads) 2011; Limayem and Ricke 2012; Kluts et al 2017). It requires pretreatment (McCann and Carpita 2015) to release sugars that can be utilized by microorganisms to produce the products of interest. Several pretreatment methods, such as acid/alkaline hydrolysis, dilute ammonia, liquid hot water, sulfur dioxide, are available for biomass deconstruction (Mosier et al 2005), but these processes produce compounds such as hydroxyl methyl furfural (HMF), furfural and acetic acid, which are inhibitory to the microorganisms used for fermentation (Piotrowski et al 2014, 2015), or to the saccharification enzymes (Ximenes et al 2011)
No statistically significant differences were found between samples of the same wood type with and without the acid catalyst, or between various particle sizes, or ethanol concentration, the use of the acid catalyst led to somewhat higher saccharification yields
Summary
There is an urgent need to produce fuels and chemicals from renewable resources, and drastic actions are required to combat the emissions of greenhouse gases, as underlined in the report by the Intergovernmental Panel on Climate Change (Houghton 2009; IPCC 2014). Biomass is an abundant renewable feedstock (Perlack and Stokes (Leads) 2011; Limayem and Ricke 2012; Kluts et al 2017). It requires pretreatment (McCann and Carpita 2015) to release sugars that can be utilized by microorganisms to produce the products of interest. Several pretreatment methods, such as acid/alkaline hydrolysis, dilute ammonia, liquid hot water, sulfur dioxide, are available for biomass deconstruction (Mosier et al 2005), but these processes produce compounds such as hydroxyl methyl furfural (HMF), furfural and acetic acid, which are inhibitory to the microorganisms used for fermentation (Piotrowski et al 2014, 2015), or to the saccharification enzymes (Ximenes et al 2011). Tayenthal 1931) for delignification (Johansson et al 1987; Sannigrahi and Ragauskas 2013; Brosse et al 2017), has gained much interest recently
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