“…A previous study reported that the chemical pretreatment could increase the crystallinity of the lignocellulosic biomass due to the removal of hemicellulose or lignin components [45]. Kainthola et al [46] reported that the fungal pretreatment of rice straw decrystallized the crystalline part of the substrate, thereby decreasing the crystallinity. These differences may be related to the types of biomass, the conditions of pretreatment and actions of cellulase.Fig.…”
BackgroundThe efficient utilization of lignocellulosic biomass for biofuel production has received increasing attention. Previous studies have investigated the pretreatment process of biomass, but the detailed enzymatic hydrolysis process of pretreated biomass remains largely unclear. Thus, this study investigated the pretreatment efficiency of dilute alkali, acid, hydrogen peroxide and its ultimate effects on enzymatic hydrolysis. Furthermore, to better understand the enzymatic digestion process of alkali-pretreated sweet sorghum straw (SSS), multimodal microscopy techniques were used to visualize the enzymatic hydrolysis process.ResultAfter pretreatment with alkali, an enzymatic hydrolysis efficiency of 86.44% was obtained, which increased by 99.54% compared to the untreated straw (43.23%). The FTIR, XRD and SEM characterization revealed a sequence of microstructural changes occurring in plant cell walls after pretreatment, including the destruction of lignin–polysaccharide interactions, the increase of porosity and crystallinity, and reduction of recalcitrance. During the course of hydrolysis, the cellulase dissolved the cell walls in the same manner and the digestion firstly occurred from the middle of cell walls and then toward the cell wall corners. The CLSM coupled with fluorescent labeling demonstrated that the sclerenchyma cells and vascular bundles in natural SSS were highly lignified, which caused the nonproductive bindings of cellulase on lignin. However, the efficient delignification significantly increased the accessibility and digestibility of cellulase to biomass, thereby improving the saccharification efficiency.ConclusionThis work will be helpful in investigating the biomass pretreatment and its structural characterization. In addition, the visualization results of the enzymatic hydrolysis process of pretreated lignocellulose could be used for guidance to explore the lignocellulosic biomass processing and large-scale biofuel production.
“…A previous study reported that the chemical pretreatment could increase the crystallinity of the lignocellulosic biomass due to the removal of hemicellulose or lignin components [45]. Kainthola et al [46] reported that the fungal pretreatment of rice straw decrystallized the crystalline part of the substrate, thereby decreasing the crystallinity. These differences may be related to the types of biomass, the conditions of pretreatment and actions of cellulase.Fig.…”
BackgroundThe efficient utilization of lignocellulosic biomass for biofuel production has received increasing attention. Previous studies have investigated the pretreatment process of biomass, but the detailed enzymatic hydrolysis process of pretreated biomass remains largely unclear. Thus, this study investigated the pretreatment efficiency of dilute alkali, acid, hydrogen peroxide and its ultimate effects on enzymatic hydrolysis. Furthermore, to better understand the enzymatic digestion process of alkali-pretreated sweet sorghum straw (SSS), multimodal microscopy techniques were used to visualize the enzymatic hydrolysis process.ResultAfter pretreatment with alkali, an enzymatic hydrolysis efficiency of 86.44% was obtained, which increased by 99.54% compared to the untreated straw (43.23%). The FTIR, XRD and SEM characterization revealed a sequence of microstructural changes occurring in plant cell walls after pretreatment, including the destruction of lignin–polysaccharide interactions, the increase of porosity and crystallinity, and reduction of recalcitrance. During the course of hydrolysis, the cellulase dissolved the cell walls in the same manner and the digestion firstly occurred from the middle of cell walls and then toward the cell wall corners. The CLSM coupled with fluorescent labeling demonstrated that the sclerenchyma cells and vascular bundles in natural SSS were highly lignified, which caused the nonproductive bindings of cellulase on lignin. However, the efficient delignification significantly increased the accessibility and digestibility of cellulase to biomass, thereby improving the saccharification efficiency.ConclusionThis work will be helpful in investigating the biomass pretreatment and its structural characterization. In addition, the visualization results of the enzymatic hydrolysis process of pretreated lignocellulose could be used for guidance to explore the lignocellulosic biomass processing and large-scale biofuel production.
“…The λ values ranged between 2.669 and 7.871 in the ML model, and 2.205 and 8.454 in the MG models. In a study of the AD of rice straw, Logistic modeling resulted in a lag phase ranging from 2.54 to 4.31 80 . In this study, the lag time was found to be relatively higher, one possible reason for which is that the raw materials used in this study have larger amounts of lignocellulosic components.…”
In this study, anaerobic co-digestion was investigated for mixtures of walnut shells (WS) and cattle manure (CM), which are lignocellulosic wastes, in various different carbon: nitrogen (C/N) ratios. The best mixing ratio for WS and CM in anaerobic digestion (AD) was determined to be 1:3, offering a methane yield of 173.2 ml/g volatile solid (VS) added. Effects of various alkaline pretreatments including calcium hydroxide (Ca(OH) 2), sodium hydroxide (NaOH) and potassium hydroxide (KOH) were studied in the concentration range 1-5% wt/wt for the best mixing ratio of WS and CM. The optimal KOH and NaOH concentrations were each found to be 4%, giving methane yields of 312.6 ± 5.1 and 342.5 ± 9.6 ml/g VS added , respectively, where these yields were found to increase by 80.5 and 97.2%, respectively, compared to the control reactor. By contrast, a 3% Ca(OH) 2 concentration was found to increase the methane yield by 67% compared to the untreated reactor. NaOH pretreatments resulted in relatively higher lignocellulosic solubilization and soluble chemical oxygen demand compared to KOH and Ca(OH) 2 pretreatments. This study contributes to our understanding of the alkaline pretreatment in taking advantage of CM and WS for methane productions in future applications.
“…48424, a white‐rot fungus with high laccase activity which is one of the important ligninolytic enzymes responsible for lignin degradation (Fan et al ., 2011; Niu et al ., 2015), has also been used in RSM pretreatment. Lignin, which is hydrophobic and crosslinks other structures, has been recognized one of the most natural recalcitrant factors and has played a negative role in efficient utilization of lignocellulosic substrates, such as RSM (Croat et al ., 2017; Kainthola et al ., 2019; You et al ., 2019). Our results also demonstrated that Trametes sp.…”
Fungal pretreatment is the most common strategy for improving the conversion of rapeseed meal (RSM) into value-added microbial products. It was demonstrated that Bacillus amyloliquefaciens CX-20 could directly use RSM as the sole source of all nutrients except the carbon source for iturin A fermentation with high productivity. However, whether fungal pretreatment has an impact on iturin A production is still unknown. In this study, the effects of fungal pretreatment and direct bio-utilization of RSM for iturin A fermentation were comparatively analysed through screening suitable fungal species, and evaluating the relationships between iturin A production and the composition of solid fermented RSM and liquid hydrolysates. Three main unconventional adverse effects were identified. (1) Solid-state fermentation by fungi resulted in a decrease of the total nitrogen for B. amyloliquefaciens CX-20 growth and metabolism, which caused nitrogen waste from RSM. (2) The released free ammonium nitrogen in liquid hydrolysates by fungal pretreatment led to the reduction of iturin A. (3) The insoluble precipitates of hydrolysates, which were mostly ignored and wasted in previous studies, were found to have beneficial effects on producing iturin A. In conclusion, our study verifies the unconventional adverse effects of fungal pretreatment on iturin A production by B. amyloliquefaciens CX-20 compared with direct bioutilization of RSM.
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