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Catalpa sawdust, a promising biofuel production biomass, was pretreated by microwave-water, -NaOH, and -Ca(OH) 2 to enhance enzymatic digestibility. After 48 h enzymatic hydrolysis, microwave-Ca(OH) 2 pretreated sample showed the highest reducing sugar yield. The content of hemicellulose and lignin in catalpa sawdust decreased after microwave-alkali pretreatment. SEM observation showed that the catalpa sawdust surface with microwave-Ca(OH) 2 pretreatment suffered the most serious erosion. Crystallinity index of catalpa sawdust increased after all three kinds of pretreatment. The optimum conditions of microwave-Ca(OH) 2 pretreatment were particle size of 40 mesh, Ca(OH) 2 dosage of 2.25% (w/v), microwave power of 400 W, pretreatment time of 6 min, enzyme loading of 175 FPU/g, and hydrolysis time of 96 h, and the reducing sugar yield of microwave-Ca(OH) 2 pretreated catalpa sawdust reached 402.73 mg/g, which increased by 682.15% compared with that of raw catalpa sawdust. The catalpa sawdust with microwave-Ca(OH) 2 pretreatment is promising for biofuel production with great potential. [ABSTRACT FROM AUTHOR]

Grass clipping, a cellulose-rich raw material, has great potential to produce biofuels, but must be firstly hydrolyzed to liberate fermentable sugars. In this study, grass clipping was pretreated with ultrasound (US), Ca(OH) 2 , NaOH, US-Ca(OH) 2 and US-NaOH at relatively low temperature to enhance its enzymatic hydrolysis. The solubilization of hemicellulose and lignin, and crystallinity index of cellulose increased after US-alkaline pretreatment, leading to a significant increase of enzyme accessibility to cellulose. Compared with another four pretreatments, US-Ca(OH) 2 pretreatment of grass clipping showed the best improvement for reducing sugar yield. X-ray diffraction (XRD) determination and scanning electron microscope (SEM) observation showed that the crystallinity index of grass clipping increased and the grass clipping surface suffered from serious erosion after US-Ca(OH) 2 pretreatment. Then, the operating conditions of US-Ca(OH) 2 pretreatment and enzymatic hydrolysis were systematically optimized, and the suitable operating conditions were as follows: US power density of 0.65 W/ml, US pretreatment time of 30 min, Ca(OH) 2 concentration of 0.75%, pretreatment temperature of 75 °C, enzyme loading of 125 FPU/g, and hydrolysis time of 72 h. The reducing sugar yield of grass clipping pretreated by US-Ca(OH) 2 reached 414 mg/g, increasing by 3.5 times compared with that of raw grass clipping. The US-Ca(OH) 2 pretreatment of grass clipping at low temperature significantly enhanced the potential of grass clipping as a promising raw material to produce biofuels. [ABSTRACT FROM AUTHOR]

In this study, physical method reinforced chemical pretreatments of Triarrhena lutarioriparia (TL) were compared to explore the higher reducing sugar yield in subsequent enzymatic hydrolysis. Four different pretreatments, namely hydrothermal pretreatment (HTP), dilute acid pretreatment (HCl-P), ultrasound assisted acid pretreatment (HCl + U) and microwave assisted acid pretreatment (HCl + M) were conducted on TL. The structural features of TL after different pretreatments were investigated by Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transformed infrared (FT-IR) techniques. The fractal-like theory was introduced to study the enzymatic hydrolysis kinetics of TL. Results showed that the reducing sugar yield of HCl-P reached 100.14 mg/g, showing 1.34 times higher than that of the raw. Due to the hemicellulose and lignin removal and lignocellulosic structure destruction, ultrasound and microwave irradiation strengthened the HCl-P, leading to a great enhancement of enzymatic hydrolysis of TL, especially the microwave irradiation. Moreover, the fractal-like theory was confirmed to be satisfactory for studying the enzymatic hydrolysis kinetics of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]