Abstract
Deep eutectic solvents (DES) are new ‘green’ solvents that have a high potential for biomass processing because of their low cost, low toxicity, biodegradability, and easy recycling. When Loblolly pine trees are harvested, their branches with needles are typically left in brush piles and decompose very slowly. Exploring the effect of DES pretreatment on waste pine needles was the goal of the present work. Loblolly pine needles were treated with three types of DES to prepare the biomass for enzymatic hydrolysis to glucose, a subject not readily found in the literature. The resulting products were analyzed by Fourier transform infrared spectroscopy, fiber analysis, and high-performance liquid chromatography. Glucose yields after pretreatment and hydrolysis were found to be six times that for untreated biomass with two of the DES. Fiber analysis indicated removal of lignin, hemicellulose, and ash from the needle biomass. Enhanced glucose yield was due to removal of lignin and disruption of biomass structure during pretreatment, so that the pretreated biomass was rich in cellulosic content. Based on the results shown in this study, among the three types of DES, formic acid:choline chloride and acetic acid:choline chloride pretreatment had better potential for biomass pretreatment compared to lactic acid:choline chloride.
Highlights
IntroductionProduction of biofuels is feasible by fermenting cellulose and hemicellulose (polysaccharides) into ethanol or butanol, provided that an optimized pretreatment of the biomass to separate out lignin has occurred [2]
3:1 molar ratio (AA:CC), the percentage of mass yield for the biomass was 61.25%, with a standard error of 2.63%. This mass yield was high when compared to the biomass yields for pretreatment with lactic acid:choline chloride 10:1 molar ratio (LA:CC) and formic acid:choline chloride 2:1 molar ratio (FA:CC) (Figure 1)
Pine needle biomass had the potential to act as a substrate for pretreatment with Deep eutectic solvents (DES)
Summary
Production of biofuels is feasible by fermenting cellulose and hemicellulose (polysaccharides) into ethanol or butanol, provided that an optimized pretreatment of the biomass to separate out lignin has occurred [2]. Pine (Pinus taeda), known as southern yellow pine, has a rapid growth rate and is one of the most abundant species in the United States [5] It has significant commercial importance in the pulp and paper industry, as well as for construction. The needles have a significantly different structure and lignin content compared to the wood and do not readily compost into the soil [6]. If these needles were harvested, they could constitute a resource for producing biofuel or other bioproducts that do not require extensive grinding.
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