Abstract
Purple Alfalfa is an inexpensive, abundant, readily available lignocellulosic material. This work was attempted to develop an efficient combination pretreatment by sequential HClO4–ethyl glycol–H2O (1.2:88.8:10, w/w/w) extraction at 130 °C in 0.5 h and urea/NaOH (urea 12 wt%, NaOH 7 wt%) soaking at −20 °C for 0.5 h for the pretreatment of purple alfalfa. The porosity, morphology, and crystallinity of pretreated purple alfalfa were characterized with SEM, FM, XRD, and FTIR. This combination pretreatment had a significant influence on hemicellulose removal and delignification. The above changes could enhance cellulose accessibility to enzymes and improve the enzymatic digestibility of cellulose. High yields of reducing sugars from pretreated purple alfalfa were obtained at 93.4%. In summary, this combination pretreatment has high potential application in the future.
Highlights
Saccharification of Purple Alfalfa viaWith an expanding world population and increasing resource demand, lignocellulosic biomass has gained more and more attention due to its abundance and renewability, which has been transformed into biofuel molecules and value-added bio-based compounds [1].Alfalfa (Medicago sativa) is known as a commercial crop cultivated domestically throughout the whole world with an output of over 0.1 billion tons/year
While UN-purple alfalfa (PAF), ethylene glycol (EG)-PAF, urea/NaOH soaking and EG–HClO4 –H2 O extraction (UN–EG)-PAF, and EG–UN-PAF had significant cracks and rougher surfaces compared to untreated PAF (UT-PAF). These results indicated that more cellulose was exposed on the surface after the pretreatment, crystallinity index (CrI)
This work aimed at evaluating the feasibility of using combination pretreatment to enhance the enzymatic saccharification of PAF
Summary
Alfalfa (Medicago sativa) is known as a commercial crop cultivated domestically throughout the whole world with an output of over 0.1 billion tons/year. In China, alfalfa is planted in a large area, and its annual output is about 1.0 million tons. Alfalfa has been widely utilized as animal feed, and bioenergy crops [2,3], and its leaves and stems have been utilized for biofuel production [4,5]. Alfalfa is a kind of typical lignocellulosic material, which is mainly composed of lignin, hemicellulose, cellulose [6]. Pretreatment is a crucial prerequisite step for the biotransformation of lignocellulosic materials into liquid biofuels and chemicals [3,12,13,14,15]. Numerous pretreatment techniques, including chemical, physical, physical-chemical, biological strategies, and their combinations have been utilized to enhance the enzyme digestion of lignocellulose [16,17,18,19,20,21]
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