Xylo-oligosaccharides and lignin production from Camellia oleifera shell by malic acid hydrolysis at mild conditions

Robust holocellulose barrier films from agricultural byproduct of Camellia Oleifera shells through dilute acid and ultrasonic treatments

Camellia oleifera shells (COS) are commonly discarded as an agricultural by-product. Effective utilization of COS can not only reduce environmental pollution but also enhance the value of the tea-oil industry. The unique composition of COS, with high hemicellulose and low cellulose content, makes it suitable for the production of film materials. In this study, COS holocellulose (COSH) was isolated and treated with four different types of dilute acids (15 % acetic acid, gallic acid, citric acid, and 0.5 % sulfuric acid, 1-24 h, 75°-105 °C) to produce barrier films. Among these, citric acid treatment resulted in the strongest and toughest film. By incorporating a brief ultrasonic pretreatment (15 min, 300 w) prior to the citric acid reaction, translucent films were achieved with impressive mechanical properties, showing tensile strength, Young's modulus and elongation at break up to 75.72 MPa, 3306.11 MPa and 8.01 %, respectively. Through a comprehensive analysis of the structure-property relationships, it was discovered that the combined effects of ultrasonic and citric acid treatments disrupted the integrated holocelluose fiber structure and facilitated the formation of a robust hydrogen bond network during the film preparation process. The resulting films exhibited enhanced water vapor barrier properties, antioxidant capacity, and complete decomposition in soil, suggesting the potential application as wraps for fresh fruits.

Combined pretreatment of malic acid and kraft pulping for the production of fermentable sugars and highly active lignin

The separation and utilization of cellulose, hemicellulose, and lignin in lignocellulosic biorefineries present significant challenges. This study proposes a pretreatment method for biomass refining by combining acid and kraft pulping. Firstly, the biomass was pretreated by malic acid, resulting in the isolation of xylo-oligosaccharides (XOS) with a yield of 86.26 % with optimized conditions of 180 °C, 1 wt% concentration, 40 min. Secondly, a mixture of 12.98 wt% NaOH and 1.043 wt% Na2S is employed to achieve lignin removal efficiency up to 63.42 %. Physical refinement techniques are then applied to enhance the enzyme digestion efficiency of cellulose, resulting in an increase from 55.03 % to 91.4 % for efficient cellulose conversion. The reacted samples exhibit a lignin composition rich in β-O-4 ether bonds, facilitating their high-value utilization. The results indicated that the combined pretreatment approach demonstrates high efficiency in separating cellulose, hemicellulose, and lignin while obtaining XOS, highly active lignin, and enzyme-digested substrates.

An energy-efficient solution to sludge drying and combustion process through Camellia oleifera shells amended foaming

Foaming pretreatment has been proven effective in promoting sludge drying, however, the variation in sludge properties significantly influences the foaming efficiency. Inspired by foam stabilizer of solid particles, Camellia oleifera shells (COS) was screened out from various biomasses as an additive incorporated with the CaO for promoting the sludge foaming. For the introduction of COS, this study analyzed the drying behaviors of foamed sludge, quantified the surface cracks information, characterized the combustion performance, and evaluated the energy consumption. The results indicated that 46.72-50.10% of time could be saved in foaming the sludge to 0.70 g/mL by addition of 3.0 wt% COS. Compared with the original sludge (OS), the 0.70 g/mL foamed sludge saved 47.43% of time for sludge drying at 80 °C, and this value further increased to 53.14% with 3.0 wt% COS addition. Combining the multifractal spectra and drying kinetics analysis, the foaming promoted the formation of complex surface cracks in the warm-up period, while COS further improved the complexity of cracks in the constant rate period, and the shrinkage of isolated sludge blocks in the falling rate period, thus enhanced the moisture diffusion and heat transfer. Furthermore, the appropriate porous structure and additional volatile matters promoted the combustion performance. The 0.90 g/mL foamed sludge with COS presented the lowest activation energy of 180.362 kJ/mol in combustion. Overall, compared with OS, the 0.70 g/mL foamed sludge with COS saved 40.65% energy consumption during the foaming, drying and combustion processes, providing an energy-efficient solution for the sludge treatment and disposal.

Structural characterization of lignin from the green pretreatments for co-producing xylo-oligosaccharides and glucose: Toward full biomass utilization

Three green non-enzymatic catalysis pretreatments (NECPs) including autohydrolysis, subcritical CO2-assisted seawater autohydrolysis, and inorganic salt catalysis were utilized to simultaneously produce xylo-oligosaccharides (XOS), glucose, and cellulolytic enzyme lignin (CEL) from sugarcane bagasse (SCB). The yield of XOS in all three NECPs was over 50 % with a competitive glucose yield of enzymatic hydrolysis. And the effects of different pretreatments on the chemical structure and composition of CEL samples were also investigated. The pretreatments significantly increased the thermal stability, yield, and purity of the CEL samples. Moreover, the net yield of lignin was 58.3 % with lignin purity was 98.9 % in the autohydrolysis system. Furthermore, there was a decrease in the molecular weight of CEL samples as the pretreatment intensity increased. And the original lignin structural units sustained less damage during the NECPs, due to the cleavage of the β-O-4 bonds dominating lignin degradation. Meanwhile, these pretreatments increased the phenolic-OH in CEL samples, making the lignin more reactive, and enhancing its subsequent modification and utilization. Collectively, the described techniques have demonstrated practical significance for the coproduction of XOS and glucose, and lignin, providing a promising strategy for full utilization of biomass.

Efficient co-production of xylo-oligosaccharides and fermentable sugars from sugarcane bagasse by glutamic acid pretreatment

In the production of xylo-oligosaccharides (XOS) by organic acid pretreatment, it is often difficult to isolate organic acids from XOS. Here, an acidic amino acid, glutamic acid (GA), was used to pretreat sugarcane bagasse (SCB) to prepare XOS and fermentable sugars. The effects of GA concentration, hydrolysis temperature, and pretreatment time on the yield and polymerization distribution of XOS were investigated. After hydrolysis by 0.2 M GA at 140 °C for 30 min, the maximum yield of X2-5 was 53.3%, and the concentrations of xylose and furfural were 1.8 g/L and 0.1 g/L, respectively. Meanwhile, GA increased the pore size and porosity of SCB as well as the number of functional groups of amino acid residues, which improved the enzymatic efficiency and the maximum yield of glucose was 95.3%. Thus, GA pretreatment provides a more economical, environmentally friendly and sustainable method for the co-production of XOS and glucose from SCB.

Novel dual-action vanillic acid pretreatment for efficient hemicellulose separation with simultaneous inhibition of lignin condensation

Aromatic acids play a selective role in the separation of hemicellulose. Phenolic acids have demonstrated an inhibitory effect on lignin condensation. In the current study, vanillic acid (VA), which combines the characteristics of aromatic and phenolic acids, is used to separate eucalyptus. The efficient and selective separation of hemicellulose is achieved simultaneously at 170 °C, 8.0% VA concentration, and 80 min. The separation yield of xylose increased from 78.80% to 88.59% compared to acetic acid (AA) pretreatment. The separation yield of lignin decreased from 19.32% to 11.19%. In particular, the β-O-4 content of lignin increased by 5.78% after pretreatment. The results indicate that VA, as a "carbon positive ion scavenger", it preferentially reacts with the carbon-positive ion intermediate of lignin. Surprisingly, the inhibition of lignin condensation is achieved. This study provides a new starting point for the development of an efficient and sustainable commercial technology by organic acid pretreatment.

Pretreatment of moso bamboo with p-toluenesulfonic acid for the recovery and depolymerization of hemicellulose

Bamboo and its mechanical processing residues have broad prospects for high value-added utilization. In this research, p-toluenesulfonic acid was used for the pretreatment of bamboo to investigate the effects of extraction and depolymerization of hemicellulose. The response and behavior of changes of cell-wall chemical components were investigated after different solvent concentration, time, and temperature pretreatment. Results indicated that the maximum extraction yield of hemicellulose was 95.16 % with 5 % p-toluenesulfonic acid at 140 °C for 30 min. The depolymerized components of hemicellulose in the filtrate were mainly xylose and xylooligosaccharide, with xylobiose accounting for 30.77 %. The extraction of xylose from the filtrate reached a maximum of 90.16 % with 5 % p-toluenesulfonic acid at 150 °C for 30 min pretreatment. This research provided a potential strategy for the industrial production of xylose and xylooligosaccharide from bamboo and for the future conversion and utilization.

Rapid and mild fractionation of hemicellulose through recyclable mandelic acid pretreatment

The development of organic acid pretreatments from biological sources is essential to facilitate the progress of green and sustainable chemistry. In this study, the effectiveness of mandelic acid pretreatment (MAP) was analyzed for eucalyptus hemicellulose separation. 83.66% of xylose was separated under optimal conditions (temperature: 150 °C; concentration: 6.0 wt%; time: 80 min). The hemicellulose separation selectivity is higher than acetic acid pretreatment (AAP). The stable and effective separation efficiency (56.55%) is observed even after six reuses of the hydrolysate. Higher thermal stability, larger crystallinity index and optimized surface element distribution in the samples were demonstrated by MAP. Lignin condensation is effectively inhibited through MAP, as determined from the structural of different lignin. In particular, the demethoxylation of lignin by MA was found. These results open up a new way to construct a novel organic acid pretreatment for separating hemicellulose with high efficiency.

Superior separation of hemicellulose-derived sugars from eucalyptus with tropic acid pretreatment

Organic acid pretreatments can efficiently separate biomass-based hemicellulose and selectively produce hemicellulose-derived sugars. In this study, hemicellulose is separation as xylose, oligosaccharides in the tropic acid-catalyzed hydrothermal pretreatment of eucalyptus. The maximum yield of hemicellulose-derived sugars (85.78 %) with 71.25 % xylose selectivity (based on the total xylose in raw material) was achieved in the hydrolysate under optimal conditions (5 % TA, 160 ℃, 80 min). The yield of hemicellulose-derived sugar and the separation yield of hemicellulose increased by 11.06 % and 11.45 % compared with glycolic acid pretreatment in the similar severity factor. The separation yield of cellulose and lignin was decreased by 4.23 % and 0.98 %, respectively. This resulted in residual solids with higher biological stability (higher fiber crystallinity index, higher thermal stability, and higher lignin content). Therefore, higher hemicellulose separation selectivity and rich hemicellulose-derived sugars were obtained using TA pretreatment. The work would bring up a new method for biomass refining.

Production of xylo-oligosaccharides and ethanol from corncob by combined tartaric acid hydrolysis with simultaneous saccharification and fermentation

In organic acid hydrolysis for xylo-oligosaccharides (XOS) production, organic acids with low flash points and explosion limits can lead to explosion and fire risk. Herein, tartaric acid (TA) as an organic acid with high flash point and no explosion limit was used in the hydrolysis of corncob to produce XOS. Then, the TA-hydrolyzed corncob was used for ethanol production. In TA hydrolysis of corncob, a 56.4 % XOS yield was obtained from the hydrolysate with the conditions of 170 °C, 60 mM TA and 10 min. Meanwhile, 92.1 % TA was recovered from the hydrolysate by the addition of calcium hydroxide. After simultaneous saccharification and fermentation of TA-hydrolyzed corncob, an 82.4 % ethanol yield was obtained with a solid loading of 25 % (w/v, 250 g/L) by Saccharomyces cerevisiae H06. This research provided a relatively safe, simple, and efficient technology for producing XOS and ethanol from corncob.

Highly selective separation of eucalyptus hemicellulose by salicylic acid treatment with both aromatic and hydroxy acids

Aromatic and hydroxyl acid treatments demonstrate their respective characteristics for the separation of lignocellulosic biomass. In this study, the effect of salicylic acid (SA-A) treatment on the separation of eucalyptus components with both aromatic and hydroxyl acid properties was analyzed. The optimal conditions were SA-A concentration 9.0%, reaction temperature 140 °C and time 75 min. The separation yield of xylose was 85.93%. The separation of cellulose and lignin was inhibited by SA-A treatment in contrast to the separation by glycolic acid and p-toluenesulfonic acid treatment. Moreover, SA-A treatment resulted in a larger fiber crystallinity index and higher thermal stability. The SA-A-treated samples contained lignin that was rich in β-O-4 and hydroxyl groups. The degradation and condensation of lignin was inhibited. The selectivity of aromatic acids for separating hemicellulose and protecting the lignin structure using hydroxy acids was demonstrated. Thus, new and efficient organic acid treatments can be developed.

Coproduction of xylo-oligosaccharides and glucose from sugarcane bagasse in subcritical CO2-assisted seawater system

Abundant seawater resources can replace the shortage of freshwater resources. The co-production of xylo-oligosaccharides and glucose from sugarcane bagasse by subcritical CO2-assisted seawater pretreatment was studied in this paper. We investigated the effects of pretreatment conditions of temperature, CO2 pressure and reaction time on the yield of xylo-oligosaccharides in subcritical CO2-assisted seawater systems. The maximum xylo-oligosaccharide yield of 68.23% was obtained at 165 °C/2 MPa/5 min. After further enzymatic hydrolysis of the solid residue, the highest glucose yield of 94.45% was obtained. In this system, there is a synergistic effect of mixed ions in seawater and CO2 to depolymerize xylan into xylo-oligosaccharides with a lower degree of polymerization. At the same time, the addition of CO2 increased the pore size and porosity of sugarcane bagasse, improved the efficiency of enzymatic hydrolysis and increased the yield of glucose. Therefore, this study provides a more environmentally friendly and sustainable process for the co-production of xylo-oligosaccharides and glucose from sugarcane bagasse, and improves the utilization of seawater resources.