Autohydrolysis Treatment Research Articles

Cascading Recovery of Added-Value Cocoa Bean Shell Fractions Through Autohydrolysis Treatments

AbstractIn this work, an autohydrolysis treatment was applied to cocoa bean shells (CBS) to obtain different potentially added-value fractions rich in phenolic compounds with antioxidant potential and oligosaccharides with potential prebiotic properties. The final residue was enzymatically treated to deliver sugars that can undergo fermentation-based biotransformation. This hydrothermal pretreatment was assessed for maximum temperatures (Tmax) between 120 to 200 °C and severities (S0) between 1.1 and 3.4. The highest oligosaccharide concentration (5.5 g/L) was achieved at S0 of 3.4. The increase of S0 during the process allowed to increase the recovery of interesting bioactive compounds, achieving a maximum TPC and antioxidant activity of 2.8 g/L and 17178.5 µmol Fe2+/L, respectively, when the Tmax reached 200 °C. However, at this temperature, a significant amount of degradation products such as organic acids and HMF was already formed, and a compromise temperature of 160 °C was chosen for further tests. It was possible to obtain a maximum glucose yield of 71% when the pretreated solids were enzymatically hydrolysed. Hence, the use of autohydrolysis, avoiding the use of toxic chemicals, has proved to be a sustainable alternative to obtain different CBS fractions with interesting composition to be potentially employed in multiple sectors.

Autohydrolysis treatment of bamboo and potassium oxalate (K2C2O4) activation of bamboo product for CO2 capture utilization

Typically, the hydroxide agents, such as sodium hydroxide and potassium hydroxide, which have corrosive properties, are used in the carbon activation process. In this study, potassium oxalate (K2C2O4), a less toxic and non-corrosive activating reagent, was used to synthesize activated carbon from the solid residue after autohydrolysis treatment. The effect of the autohydrolysis treatment and the ratio of the K2C2O4/solid residue are presented in this study. Moreover, the comparison between the activated carbon from bamboo and biochar from the solid residue are also reported. The resulting activated carbon from the solid residue exhibited a high surface area of up to 1432 m2·g−1 and a total pore volume of up to 0.88 cm3·g−1. The autohydrolysis treatment enhanced the microporosity properties compared to those without pretreatment of the activated carbon. The microporosity of the activated carbon from the solid residue was dominated by the pore width at 0.7 nm, which is excellent for CO2 storage. At 25 °C and 1.013 × 105 Pa, the CO2 captured reached up to 4.1 mmol·g−1. On the other hand, the ratio between K2C2O4 and the solid residue has not played a critical role in determining the porosity properties. The ratio of the K2C2O4/solid residue of 2 could help the carbon material reach a highly microporous textural property that produces a high carbon capture capacity. Our finding proved the benefit of using the solid residue from the autohydrolysis treatment as a precursor material and offering a more friendly and sustainable activation carbon process.

Microwave-assisted hydrothermal processing of pine nut shells for oligosaccharide production

Pine nut shells, a biomass residue from the Mediterranean Pinus pinea pine nut industrial processing, were treated by microwave-assisted autohydrolysis to produce xylo-oligosaccharides. Microwave-assisted processes provide alternative heating that may reduce energy input and increase overall process efficiency. The autohydrolysis treatments were performed under isothermal and non-isothermal operations within a wide range of operational conditions (temperature/reaction times) covering several severity regimes (as measured by the log R0 severity factor). The composition of the autohydrolysis liquors was determined in terms of oligo- and monosaccharides, aliphatic acids and degradation compounds. The process was highly selective towards hemicelluloses hydrolysis and liquid streams containing a mixture of oligomeric compounds (mainly xylo-oligosaccharides) could be obtained under relatively mild operation conditions (190 °C, 30 min) with a maximal oligosaccharides’ concentration of 18.48 g/L. The average polymerization degree of the obtained oligosaccharides was characterised by HPLC, showing that for the optimal conditions a mixture of oligomers with DPs from 2 to 6.

Autohydrolysis Application on Vine Shoots and Grape Stalks to Obtain Extracts Enriched in Xylo-Oligosaccharides and Phenolic Compounds.

Agronomic practices and the winemaking process lead to the production of considerable quantities of waste and by-products. These are often considered waste with negative effects on environmental sustainability. However, vine shoots and grape stalks can be reused, representing a potential source of xylo-oligosaccharides and polyphenols. In this context, the purpose of this work was to obtain enriched extracts using three different autohydrolysis treatments with (i) H2O, (ii) H2O:EtOH, and (iii) H2O:Amberlyst. The obtained extracts were characterized by their xylo-oligosaccharide and polyphenol profiles using LC-MS techniques. The use of ethanol during autohydrolysis allowed for greater extraction of xylan-class compounds, especially in vine shoot samples, while an increase in antioxidant activity (128.04 and 425.66 µmol TE/g for ABTS and DPPH, respectively) and in total phenol content (90.92 mg GAE/g) was obtained for grape stalks.

A green process for producing xylooligosaccharides via autohydrolysis of plasma-treated sugarcane bagasse

Due to alarming energy consumption and population growth, the transition to a circular economy is being pursued by searching for alternative resources to produce chemicals and energy. In this regard, lignocellulosic biomass, as the most abundantly accessible plant material, is a suitable alternative for satisfying this high demand. Sustainable lignocellulose biorefineries could convert cellulose, hemicellulose, and lignin into high-value products. Most available approaches prioritize cellulose and lignin over hemicellulose. In this work, autohydrolysis treatment of sugarcane bagasse is developed to produce xylooligosaccharides (XOS) with a variable degree of polymerization (2−6) using low-temperature atmospheric-pressure plasma and ball-mill treatment on raw bagasse. The reactive oxygen, ozone, hydronium ions (H3O+), and nitrogen species generated by plasma increase hemicellulose conversion. XOS hydrolysate obtained from plasma pre-treated samples (41.1%) was quantified for xylobiose (12.1%), xylotriose (10.1%), xylotetrose (6.9%), xylopentaose (7.1%), and xylohexaose (4.9%) (6 h of autohydrolysis at 135 °C). Xylan hydrolysate was also yielded 21.2% xylose, and 2.2% furfural, respectively. The entire process (plasma and autohydrolysis) was conducted in water without using any other chemicals. These results suggest the potential role of plasma pre-treatment prior to hydrothermal treatments to selectively produce XOS.

Potential use of Sargassum muticum as source of plant biostimulants after three different drying methods

Seaweed derived biostimulants are gaining attention as an important tool in sustainable agriculture. This offers a unique opportunity to alleviate the environmental impact of Sargassum muticum (Ochrophyta, Phaeophyceae) as an invasive species by finding new applications for its biomass. In this sense, incorporating green extraction technologies is fundamental to ensure environmental-friendly goals. This research was initiated in an attempt to contribute to an integral valorization system of S. muticum biomass, exploring the biostimulant potential of the solubles obtained from pressed solids, through an autohydrolysis treatment. In addition, we compared the effect of three different liquid phase drying techniques (spray-drying, freeze-drying and convective air-drying). Low stress drying techniques as spray-drying showed better conservation of bioactive compounds and biostimulant potential. A bioassay with Nastrium officinale showed no phytotoxic effects despite high electric conductivity in most of the extracts and concentrations. Dried extracts showed mainly an amorphous structure but occasional crystal formation when spray-dried at low temperatures (Tout = 50 ºC) and after convective air drying (T = 40 ºC). Significant increases in root development were achieved at a concentration of 5 mg L−1 of spray-dried extracts and 50 mg L−1 in case of freeze-dried extracts. Munoo-Liisa vitality index showed best results with 50 mg L−1 of freeze-dried extracts. This study provides important information about the influence of different drying techniques on the physicochemical properties and biostimulant potential of S. muticum aqueous extracts and contributes to the integral valorization of its biomass.

Process Design for Value-Added Products in a Biorefinery Platform from Agro and Forest Industrial Byproducts

Agroforestry wastes are industrial byproducts available locally such as eucalyptus sawdust (EUC) and sugarcane bagasse (SCB). These byproducts can be used as lignocellulosic raw materials to produce high-value products. This study is a techno-economic analysis of four potential scenarios to produce polyhydroxybutyrate (PHB) and levulinic acid (LA) from hemicellulosic sugars by a fermentative pathway in a biomass waste biorefinery. Mass and energy balances were developed, and technical and economic assessments were carried out to obtain gas, char, and tar from residual solids from autohydrolysis treatment. It was determined that microbial culture could be an attractive option for added-value product production. More than 1500 t/year of PHB and 2600 t/year of LA could be obtained by the proposed pathways. Microbial and enzymatic conversion of LA from sugars could significantly improve energy consumption on the conversion strategy. The products from solid residual valorization (char and tar) are the most important for economic performance. Finally, a variation in specific variables could mean substantial improvements in the final indicators of the processes, reaching a higher NPV than USD 17 million.

Effects of Hydrothermal Processing on Miscanthus × giganteus Polysaccharides: A Kinetic Assessment.

Miscanthus × giganteus samples were characterized for composition and treated with hot compressed water (hydrothermal or autohydrolysis treatments) at temperatures in the range of 190-240 °C. The liquid phases from treatments were analyzed to assess the breakdown of susceptible polysaccharides into a scope of soluble intermediates and reaction products. The experimental concentration profiles determined for the target compounds (monosaccharides, higher saccharides, acetic acid and sugar-decomposition products) were interpreted using a pseudohomogeneous kinetic mechanism involving 27 reactions, which were governed by kinetic coefficients showing an Arrhenius-type temperature dependence. The corresponding activation energies were calculated and compared with data from the literature. The kinetic equations allowed a quantitative assessment of the experimental results, providing key information for process simulation and evaluation.

Evaluating process of auto-hydrolysis prior to kraft pulping on production of chemical pulp for end used paper-grade products

The objective of this work is to systematically evaluate the performance of the hydrolysis-based kraft pulping process and associated pulp and black liquor characteristics. Acacia wood chips were auto-hydrolyzed under various severities, then the hydrolyzed wood chips were kraft pulping. The results indicated that the yield of pulp significantly dropped with intensifying the auto-hydrolysis severity. Meanwhile, the removal rate of pentosan reached 98.6% in the screened pulp at the P-factor of 1 000. The fiber length, fines and fiber crimp of the screened pulp were not affected by the auto-hydrolysis treatment. Auto-hydrolyzed pulps deteriorated fibrillation and beating response of the pulp in a refining process. However, fiber length and fines changed obviously after beating treatment. After auto-hydrolysis, the tensile index of the paper matrices decreased, some particle substances were found on the surface of the pulp fiber, and the solid and organic content of the black liquor were improved.

Evaluating process of auto-hydrolysis prior to kraft pulping on production of chemical pulp for end used paper-grade products

The objective of this work is to systematically evaluate the performance of the hydrolysis-based kraft pulping process and associated pulp and black liquor characteristics. Acacia wood chips were auto-hydrolyzed under various severities, then the hydrolyzed wood chips were kraft pulping. The results indicated that the yield of pulp significantly dropped with intensifying the auto-hydrolysis severity. Meanwhile, the removal rate of pentosan reached 98.6% in the screened pulp at the P-factor of 1 000. The fiber length, fines and fiber crimp of the screened pulp were not affected by the auto-hydrolysis treatment. Auto-hydrolyzed pulps deteriorated fibrillation and beating response of the pulp in a refining process. However, fiber length and fines changed obviously after beating treatment. After auto-hydrolysis, the tensile index of the paper matrices decreased, some particle substances were found on the surface of the pulp fiber, and the solid and organic content of the black liquor were improved.

Deconstruction of H-bonding and crystallite in directly prepared cellulose nanofibrils after autohydrolysis of eucalyptus

In this study, cellulose nanofibrils (CNFs) were directly prepared after autohydrolysis of eucalyptus raw materials. The effect of different autohydrolysis times on the hydrogen bond structure, micro-structure and properties of CNFs were analyzed by FTIR peak fitting, two-dimensional infrared, TGA, TEM and X-ray diffractometer. The results showed that the autohydrolysis treatments could obviously lead to the sequence of hydrogen bond changes in CNFs as follows: v(weak hydrogen bond) >v(free hydroxyl) >v(O(3)H.O(5)) >v(O(2)H.O(6)) > v(O(6)H.O(3′)), and further impact in crystallite size of CNFs. With the increase of the autohydrolysis strength, the crystallite size of CNFs on the 11¯0 crystal plane could be reduced by up to 26%, but the crystallite size on the 110 crystal plane and the 200 crystal plane increased by 24.5% and 22.6%, respectively. These microstructure changes finally increased the crystallinity index of CNFs, and then resulted in their high thermal stability.

OPTIMIZATION OF XYLAN EXTRACTION PROCESS FROM RICE STRAW FOR PRODUCTION OF AUTOHYDROLYSATES RICH IN PREBIOTIC XYLOOLIGOSACCHARIDES

Rice straw, an abundant agricultural waste, possesses immense potential to serve as renewable, eco-friendly and non-edible feedstock to generate value-added products. Therefore, the present study aimed to obtain prebiotic neutral xylooligosaccharides (XOS)-rich autohydrolysate from rice straw xylan. The central composite design of response surface methodology was employed to optimize the conditions for the alkaline extraction of xylan, i.e. NaOH concentration (6-14%, w/v), reaction time (1-3.5 h) and temperature (50-100 °C). Autohydrolysis of xylan was carried out at 121 °C and 15 psi for varied hydrolysis times (10, 25 and 40 min) and sulphuric acid concentrations (0.1, 0.5 and 1.0M) to obtain XOS-rich autohydrolysate. The optimum conditions were found to be as follows: 11.04% (w/v) NaOH, 3.126 h and 80.146 °C, so that the maximum xylan yield of 19.97% was predicted by the software. This value was quite close to the experimental yield of 19.4%, with 80.83% xylan being recovered per gram of rice straw. The best autohydrolysis treatment for xylan was found to be using 0.1M sulphuric acid for 10 min, which allowed 34.5% of 100 mg xylan to be depolymerized to produce neutral XOS (degree of polymerization up to 7), with xylose, xylobiose and xylotriose constituting 4.45, 10.14 and 7.83 mg, respectively. These autohydrolysates promoted higher growth of Lactobacillus rhamnosus and Lactobacillus casei than established prebiotic fructooligosaccharides. The study attempts to solve disposal issues of rice straw through production of XOS-rich autohydrolysates in demand on the global nutraceuticals market.

Hemicellulosic Bioethanol Production from Fast-Growing Paulownia Biomass

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S0 of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach.

Influence of the heating mechanism during the aqueous processing of vine shoots for the obtaining of hemicellulosic oligosaccharides

This work deals with the revalorization of an important winery residue such as the vine shoots by the obtaining of oligosaccharides with potential prebiotic activity. The manufacture of these added-value products was performed by an autohydrolysis treatment assisted with microwaves to make the process less time consuming and more environmentally friendly. The influence of the reaction time (0–40 min) and the temperature (140–200) on the production of oligosaccharides during the microwave-assisted autohydrolysis was evaluated. The highest concentration of oligosaccharides (168.3 g/Kg oven-dried vines shoots) was achieved during the treatment carried out at 180 °C for 20 min. To assess the benefits of the assistance of the autohydrolysis treatment with the microwaves a conventionally heated treatment was performed using conditions (180 °C for 15 min) that provoked similar effects on the solubilisation of the hemicellulosic fraction. This treatment permitted the obtaining of 203.5 g oligosaccharides/Kg oven-dried vines shoots using 61.0% more of the time needed to carry out the microwaves-assisted autohydrolysis. Although the microwave-assisted treatment permitted the manufacture of a lower amount of oligosaccharides, only consumed 28.8% of the energy needed to perform the conventionally heated treatment. The oligosaccharides manufactured by the two treatments were substituted xyloglucans with different polymerization and acetylation degrees, which due to their potential prebiotic activity could be highly appreciated by pharmaceuticals and food industries. Thus, this work demonstrated the environmental sustainability of the microwave-assisted autohydrolysis for the revalorisation of the vine shoots.

Assessment of the effect of autohydrolysis treatment in banana’s pseudostem pulp

Banana’s pseudostem pulp (BPP) is a potential by-product obtained in the mechanical fiber extraction of banana’s pseudostem. Its chemical characterization revealed to have an interesting composition, with a high polysaccharides content and low content in lignin, which makes it particularly relevant for the biorefinery’s biochemical platform. Autohydrolysis pretreatment, studied under isothermal (140 °C) and non-isothermal conditions (140–220 °C), yielded oligosaccharides, mainly gluco-oligosaccharides, as the main soluble products. The highest oligosaccharides production (24 g/100 g raw material) was obtained at a severity factor of 2.3. Autohydrolysis pretreatment effectively disrupted the structure of the material, inducing an improvement of the enzymatic digestibility from 73% for the raw material up to 90% for the most severe conditions. Two stage autohydrolysis, with increasing severity, was also studied, allowing to obtain a higher amount of oligosaccharides (32 g/100 g raw material) and higher digestibility of the remaining solid (up to 97%).

Two‐Step Autohydrolysis Pretreatment: Towards High Selective Full Fractionation of Wheat Straw

AbstractPretreatment is necessary to increase the enzymatic digestibility of lignocellulosic biomass. Here, degradation reactions of solubilized pentoses to furfural and others are undesired regarding the reduced product yield and increasing downstream processing efforts. In this work, the use of the unit operation configuration was successfully shown to reduce degradation reactions. In the used two‐step autohydrolysis pretreatment, the reaction is stopped before degradation takes place. The pentoses are removed by water leaching to make them unavailable for degradation in a second autohydrolysis treatment. The overall sugars yield is increased, and the furfural formation is decreasing while maintaining the high lignin purity using the two‐step autohydrolysis pretreatment.

Preparation and characterizations of oil palm fronds cellulose nanocrystal (OPF-CNC) as reinforcing filler in epoxy-Zn rich coating for mild steel corrosion protection

Oil palm frond (OPF) is one of largest contributions to the biomass waste from oil palm plantation. In this work, OPF has been successfully utilized to prepare cellulose nanocrystal (OPF-CNC) by acid hydrolysis. OPF was initially treated with autohydrolysis treatment. The obtained OPF-CNC was characterized via complementary analyses. The produced OPF-CNC showed a high crystallinity index value (60%) and high BET surface area (26.10 m2 g−1) as compared to α-cellulose (crystallinity index: 54% and BET surface area:7.14 m2g−1). The surface analyses via scanning electron microscope (SEM) and transmission electron microscopy (TEM) demonstrated that the OPF-CNC has a smooth surface with a needle-like shape, where the average length and diameter are 95.09 nm and 6.81 nm, respectively. The corrosion analyses via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) illustrate that the coated mild steel with the inclusion of 0.5 wt% OPF-CNC has managed to sharply reduce the corrosion (99%). The coated mild steel with the inclusion of 0.5 wt% OPF-CNC showed the highest hydrophobicity (100.5 ± 0.7°) and has lowest amount of O via water contact angle and energy dispersive X-ray spectroscopy (EDX) analyses respectively, indicating lowest corrosion rate.

Design of an industrial autohydrolysis pretreatment plant for annual lignocellulose

Three concepts for a 3000 t/a continuous autohydrolysis plant aiming at a full fractionation of agricultural residues (wheat straw as model substrate) into streams rich in xylose, glucose, and lignin, respectively, are developed. For this purpose, two kinetic models based on batch liquid-hot water experiments (30 mL, 170–230 °C, 10–60 min) were investigated. The solid hemicellulose conversion was described with a first-order rate model. The concentration and conversion profile investigation of the solid and liquid phases using the severity factor resulted in a linear equation describing the hemicellulose solubilization: XHC = (0.5839 ∗ log(R0) − 1.7027) ± 0.06. Here, specific process parameter boarders for the maximal hemicellulose concentration and furfural formation at log(R0) = 4.0 considering the liquid phase were identified. These findings were used to propose a multi-step hydrothermal processing approach, with intermediate sugar extraction, tailored to the compositional requirements of the product streams. Seven reactor types were evaluated for its feasibility; in this regard, the screw conveyor reactor (SCR) was evaluated as most promising. For the concepts, the SCR reactors were scaled, based on the generated data. It was found that the process temperature is a major parameter determining the reactor size. It is considered more important than the number of autohydrolysis treatment steps. In brief, the fractionation of agricultural residues using a multi-step continuous plant is evaluated to be very promising for the industrial application, regarding selectivity, handling, investment, and process costs.

Evaluation of hardwood and softwood fractionation using autohydrolysis and ionic liquid microwave pretreatment

Differences in hardwood and softwood, elucidates their behaviour against pretreatments varies. In this work, microwave ionic liquid (IL) and autohydrolysis (AH) pretreatments were applied to Eucalyptus globulus (as a model of hardwood) and Pinus radiata (as a model of softwood). The comparison between hardwood and softwood of microwave ionic liquid (IL) and autohydrolysis (AH) were evaluated in terms of chemical composition of pretreated solids, liquid by streams composition (hemicellulose and lignin extraction) and, substrates enzymatic digestibility. Furthermore, micrographs using scanning electron microscopy (SEM) and confocal fluorescence microscopy supported results obtained. In this study, it has been demonstrated that autohydrolysis pretreatment effectiveness, through maximizing enzymatic digestibility, is opposite in hardwood (73 g glucan/100 g glucan introduced at severe conditions) and softwood (10 g/100 g glucan). IL pretreatment has been especially effective in softwood with higher digestibilities (78 g glucan/100 g glucan introduced) than those obtained in hardwood (68 g glucan/100 g glucan introduced). Confocal fluorescence microscopy images, together with SEM images have resulted to be a clarifying technique to explain enzymatic digestibility results. Final sugars yields after the whole process have shown that low solid yields recoveries obtained in AH treatments have considerably worsened final glucose production, mainly in softwood. IL microwave pretreatment have resulted in higher glucose yields in softwood than in hardwood.

Autohydrolyzed Low-Cost Biomass and Adsorbent Aging

Autohydrolysis or self-hydrolysis or hydrothermal treatment of lignocellulosic materials like sawdust and straw is already used in bioethanol industry for water soluble fermentable sugars production. The main idea in this paper is the use of the autohydrolysis and other thermochemical treatments’ solid residue as an adsorbent. In this study continuous fixed-bed-column systems were investigated. Continue-flow experiments were carried out on stainless steel columns with dimensions 15 × 2.5 and 25 × 2.5 cm. In chemical processing, a packed bed is a hollow tube, pipe, or other vessel that is filled with a packing material.