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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]

High-pressure homogenization (HPH) and alkaline-heat were both used to pretreat grass clipping in order to improve the efficiency of enzymatic hydrolysis and biogas production. Results showed that both methods were very effective. HPH and alkaline-heat pretreated grass clipping yielded 230.39 and 415.93 mg g −1 reducing sugar with enzymatic hydrolysis, showing 37.82% and 148.81% increase respectively. HPH and alkaline-heat pretreated grass clipping produced 418 and 405 ml biogas in anaerobic digestion respectively, both around 2.5 times higher than that of the control. Furthermore, both pretreated samples produced biogas immediately while the control had a two-day delay. HPH could produce more biogas in a shorter time and it could be operated in room temperature and needs no chemical, implying that HPH could be an effective pretreatment of biomass for biogas production. [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]

Different solid contents of corn stover were pretreated with rumen fluid to enhance its hydrolysis and acidification, with whole pretreatment time of 72 h. Results showed that rumen fluid pretreatment effectively enhanced the hydrolysis of corn stover. The concentration of soluble COD for 10% ( w/v ) corn stover was about 2–6.4 times and 1.5–2.5 times of that for 3% and 5% ( w/v ), respectively. The highest reducing sugar concentration for 10% ( w/v ) corn stover was about 20 folds and 5.7 folds of that for 3% and 5% ( w/v ) at 2 h, respectively. Higher solid content of corn stover produced more VFAs, however, VFAs accumulation happened during the 10% ( w/v ) corn stover pretreatment, leading to the higher VFAs concentration for 5% ( w/v ) corn stover than that for 10% ( w/v ) during the 16–36 h. After the pretreatment, the structure of corn stover changed, such as the increase of specific surface area and decrease of crystallinity. Due to the removal of hemicellulose, the relative amount of lignin increased in the treated solids illustrated by the FTIR spectra. The changes of enzymatic activities showed that the enzymes secreted by the rumen microorganisms were quickly adsorbed by the corn stover, participating in the hydrolysis, which resulted in the sharp decrease of enzymatic activities in the fluid at the first 4 h. Though the enzymatic activities increased a little during the pretreatment, they could not restore the original level. This might be caused by the pH decrease and VFAs accumulation. The practical application prospect of this study was also conducted. [ABSTRACT FROM AUTHOR]