MnO2纳米粒子固载纤维素酶用于高效水解农业废弃物制备生物乙醇

纤维素酶是一种有效的纤维质类物质水解催化剂,工业应用时可通过固定化纤维素酶来降低其成本。本文将烟曲霉原变种JCF产生的纤维素酶固定在MnO2纳米颗粒上。 MnO2可提高纤维素酶的活性,并充当一个更好的载体。采用扫描电镜表征了所制MnO2纳米粒子及其负载纤维素酶的表面性质,以傅里叶变换红外光谱分析了固定在MnO2纳米粒子上纤维素酶的官能团性质。纤维素酶在MnO2纳米粒子上最大的固定化效率为75%。考察了固定化纤维素酶的活性、操作pH值、温度、热稳定性和重复使用性等性质。结果表明,所制固定化酶的稳定性比游离酶更高。固定于MnO2纳米粒子上的纤维素酶可用于纤维质类物质的水解反应,且能在较宽的温度和pH值范围内使用。表征结果证实了该催化剂具有非常高的催化纤维素类物质水解的活性。     

A universal kinetic equation for characterising the fractal nature of delignification of lignocellulosic materials

A kinetic model was developed, based on the power law of growth and Avrami’s nuclei growth concepts, to describe the heterogeneous nature of pulping kinetics, taking into account the effects of chemical concentration and temperature. The general form of the kinetic equation is first order with a time-dependent rate coefficient. The model was statistically tested using published data obtained from delignification of lignocellulosic materials (hemp woody core, giant reed, wheat straw, cottonwood, bamboo and flax fibres). The activation energies of the delignification range from 71 to 136 kJ/mol. The p-values obtained from the regression analysis are significantly small indicating that all the estimates of the model parameters were significant with very high levels of confidence. The correlation coefficients R ² for these models range from 0.76 to 0.98.     

Pretreatment of bagasse by UCT-Solvent for the enzymatic hydrolysis

A thermochemical pretreatment of bagasse for the enzymatic hydrolysis has been carried out, in which pretreatment bagasse was autoclaved with binary solvent, composed of Water and organic solvent having upper critical temperature (UCT) on the mutual solubility curve. The pretreatment was named “UCT-solvent pretreatment.” The hydrophobic decomposition products from lignin and hemicellulose, that dissolved in organic phase at room temperature, could be easily separated from the solid and sugars in the aqueous phase. By using UCT-solvent instead of only water, the sugar recoveries from bagasse through the pretreatment and the enzymatic hydrolysis were much improved. There exists an optimal mixing ratio between organic solvent and water to maximize the effect of the pretreatment for enzymatic hydrolysis. The optimal ratio can be explained by the competitive effect between the ability of water as a reagent for the hydrolysis and the ability of solvent for the extraction of the decomposition product, and furthermore by the competitive effect between affinities of the solvent to hydrophilic hemicellulose and hydrophobic lignin. Decomposition of hemicellulose at lower temperature than 190°C was decreased, and hence the degradation of xylose during the pretreatment decreased. These favorable effects of UCT-solvent pretreatment are significantly attributed to the formation of the homogeneous single phase of organic solvent and water at high temperature and the phase separation at room temperature.     

A review of bacterial cellulose: sustainable production from agricultural waste and applications in various fields

Bacterial cellulose (BC) is a polymer with interesting conformation and properties. BC can be obtained in different shapes and is easily modified by chemical and physical means, so its applications in the production of new materials and nanocomposites for different purposes have been in the focus of many research projects. However, one of the major challenges to address in bacterium-derived polymer technology is to find suitable carbon sources as substrates that are cheap and do not compete with food production for achieving large scale industrial applications. Agricultural wastes are defined as the residues from the growing and processing of raw agricultural products such as crops, fruits, vegetables and dairy products. Their composition can vary depending on the type of agricultural activity and harvesting conditions, but these residues are suitable for the production of BC. The aim of this review is to give insight into the production of BC using agro-wastes and an overview of the most interesting and novel applications of this biopolymer in different areas i.e. environmental applications, optoelectronic and conductive devices, food ingredients and packaging, biomedicine, and 3D printing technology.

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Effects of chemical composition,mild alkaline pretreatment and particle size on mechanical,thermal, and structural properties of binderless lignocellulosic biopolymers prepared by hot-pressing raw microfibrillated Phoenix dactylifera and Cocos nucifera fibers and leaves

We developed value-added, high-strength lignocellulosic biopolymers by exploiting high-lignin biomass waste of palms. Lignocellulosic biopolymers were prepared by hot-pressing microfibrillated raw and alkaline pre-treated date and coconut fibers and leaves powders consisting of (≤53–≤106 μm) particles in the range 140–180 °C. The obtained biopolymers were subjected to three-point bending strength, water resistance, structural morphology (SEM), thermal stability (TGA/DTG), spectroscopy (FTIR), and crystallinity (XRD) analyses. Findings showed that raw fiber-based and alkaline-pretreated biopolymers exhibited bending strength, water resistance, and thermal stability (~200 °C) superior to those of leaf-based biopolymers. Furthermore, lignocellulosic biopolymers prepared from smaller particles showed enhanced bending and thermal properties, compared to those prepared from large particles. By mechanical and thermal properties, the optimum results were observed for biopolymers pre-treated with 1 wt% NaOH, except for coconut leaf-based biopolymers. Results were correlated to chemical composition and particle size of milled lignocellulosic biomass, allowing for efficient lignin condensation.     

Semicarbazones and thiosemicarbazones,XIII: Study of the hydrolysis of coordinated thiosemicarbazones

Summary The hydrolysis of coordinated thiosemicarbazones was studied. It was found that the nickel(II) ion promotes the reaction. Steric and electronic influences were found. The hydrolysis ofATSC in the trigonal bipyramid compounds [M(ATSC)₂Cl]Cl [M=Fe(II), Co(II), Ni(II)], is higher with the Ni(II) complex, the compound with the shorterM-N distance.

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Semicarbazone und Thiosemicarbazone, 13. Mitt.: Untersuchungen zur Hydrolyse koordinierter Thiosemicarbazone

Zusammenfassung Bei der Hydrolyse von koordinierten Thiosemicarbazonen wurde festgestellet, daß das Nickel(II)-Ion die Reaktion begünstigt. Es wurden sterische und elektronische Einflüsse gefunden. Die Hydrolysengeschwindigkeit desATSC im trigonal bipyramidalen Komplex [M(ATSC)₂Cl]Cl [M=Fe(II), Co(II), Ni(II)] ist höher mit dem Ni(II)-Komplex, der Verbindung mit der kürzerenM-N-Distanz.

     

A Comparison Between Lime and Alkaline Hydrogen Peroxide Pretreatments of Sugarcane Bagasse for Ethanol Production

Pretreatment procedures of sugarcane bagasse with lime (calcium hydroxide) or alkaline hydrogen peroxide were evaluated and compared. Analyses were performed using 2³ factorial designs, with pretreatment time, temperature, and lime loading and hydrogen peroxide concentration as factors. The responses evaluated were the yield of total reducing sugars (TRS) and glucose released from pretreated bagasse after enzymatic hydrolysis. Experiments were performed using the bagasse, as it comes from an alcohol/sugar factory and bagasse, in the size, range from 0.248 to 1.397 mm (12–60 mesh). The results show that, when hexoses and pentoses are of interest, lime should be the pretreatment agent chosen, as high TRS yields are obtained for non-screened bagasse using 0.40 g lime/g dry biomass at 70 °C for 36 h. When the product of interest is glucose, the best results were obtained with lime pretreatment of screened bagasse. However, the results for alkaline peroxide and lime pretreatments of non-screened bagasse are not very different.     

A Comparison between Lime and Alkaline Hydrogen Peroxide Pretreatments of Sugarcane Bagasse for Ethanol Production

Pretreatment procedures of sugarcane bagasse with lime (calcium hydroxide) or alkaline hydrogen peroxide were evaluated and compared. Analyses were performed using 2 × 2 × 2 factorial designs, with pretreatment time, temperature, and lime loading and hydrogen peroxide concentration as factors. The responses evaluated were the yield of total reducing sugars (TRS) and glucose released from pretreated bagasse after enzymatic hydrolysis. Experiments were performed using the bagasse as it comes from an alcohol/sugar factory and bagasse in the size range of 0.248 to 1.397 mm (12–60 mesh). The results show that when hexoses and pentoses are of interest, lime should be the pretreatment agent chosen, as high TRS yields are obtained for nonscreened bagasse using 0.40 g lime/g dry biomass at 70 °C for 36 h. When the product of interest is glucose, the best results were obtained with lime pretreatment of screened bagasse. However, the results for alkaline peroxide and lime pretreatments of nonscreened bagasse are not very different.     

Current technologies for analysis of biomass thermochemical processing: A review

Pyrolysis and gasification are two of the more promising utilization methods for the conversion of biomass toward a clean fuel source. To truly understand and model these processes requires detailed knowledge ranging from structural information of raw biomass, elemental composition, gas-phase reaction kinetics and mechanisms, and product distributions (both desired and undesired). The various analytical methods of biomass pyrolysis/gasification processing are discussed, including reactor types, analytical tools, and recent examples in the areas of (a) compositional analysis, (b) structural analysis, (c) reaction mechanisms, and (d) kinetic studies on biomass thermochemical processing.     

Accelerated hydrolysis of α-halo and α-cyano pyridinium relative to uracil derivatives: a model for ODCase-catalyzed hydrolysis of 6-cyanoUMP

α-Halo and α-cyano pyridiniums were found to undergo facile hydrolysis, in contrast to the sluggish reactions of corresponding uracils. The greatly enhanced rates found with pyridinium compounds have indicated a possible source of the rate acceleration seen in the hydrolysis of 6-cyanouridine 5′-monophosphate catalyzed by orotidine 5′-monophosphate decarboxylase.     

Biofuels from microalgae biomass: A review of conversion processes and procedures

Achieving the EU 2030 vision of a 15% minimum amount of biofuels utilized in the road transportation require more research on biofuel production from biomass feedstock. To this end, this review study examines the use of green, deep eutectic solvents and direct transesterification approaches for biomass conversion to biofuels. Next, biogas production from anaerobic co-digestion of microalgae biomass is presented. Lastly, the effect of operating conditions, as well as advantages and limitations of several biomass conversion techniques are outlined. Of note, this study presents promising microalgae conversion processes which could be progressed are the use of bio-based solvents and supercritical fluids for biodiesel production, hydrothermal liquefaction for biogas production, microwave-induced pyrolysis for syngas production, and ultrasound/microwave enhanced extraction for bio-oil production. These are based on the possibility of high yield and process economics. We have also enumerated knowledge gaps needed to propel future studies.     

Preliminary studies on the processing sequence for southern red oak and municipal solid waste using a hybrid dilute acid/ enzymatic hydrolysis process for ethanol production

Based on this preliminary study, a metric ton of dry southern red oak chips subjected to a first-stage dilute sulfuric acid hydrolysis would yield 132 kg of xylose and 40 kg of glucose and mannose. A second-stage dilute sulfuric acid hydrolysis on the first-stage residue would yield only 128 kg of additional glucose, but a second-stage cellulytic enzyme hydrolysis on the first-stage residue would yield an additional 265 kg of glucose. Fermentation of these hydrolyzates would show that the hybrid process would yield over 50% more ethanol. Results on other biomass are also included.     

Pretreatment with ammonia water for enzymatic hydrolysis of corn husk, bagasse, and switchgrass

Bagasse, corn husk, and switchgrass were pretreated with ammonia water to enhance enzymatic hydrolysis. The sample (2 g) was mixed with 1–6 mL ammonia water (25–28% ammonia) and autoclaved at 120°C for 20 min. After treatment, the product was vacuum-dried to remove ammonia gas. The dried solid could be used immediately in the enzymatic hydrolysis without washing. The enzymatic hydrolysis was effectively improved with more than 0.5 and 1 mL ammonia water/g for corn husk and bagasse, respectively. In bagasse, glucose, xylose, and xylobiose were the main products. The adsorption of CMCase and xylanase was related to the initial rate of enzymatic hydrolysis. In corn husks, arabinoxylan extracted by pretreatment was substantially unhydrolyzed because of the high ratio of arabinose to xylose (0.6). The carbohydrate yields from cellulose and hemicellulose were 72.9% and 82.4% in bagasse, and 86.2% and 91.9% in corn husk, respectively. The ammonia/water pretreatment also benefited from switchgrass (Miscanthus sinensis and Solidago altissima L.) hydrolysis.     

On-line desalting and carbohydrate analysis for immobilized enzyme hydrolysis of waste cellulosic biomass by column-switching high-performance liquid chromatography

An innovative green column-switching high-performance liquid chromatographic (HPLC) technique was developed by coupling traditional and Pb²⁺ ion-exclusion columns to study enzyme hydrolysis components of waste cellulosic biomass. Pure water was used as the mobile phase to separate neutral polar analytes in high salt content solution. The column-switching HPLC-RI was connected on-line to the immobilized enzyme reactor for successive on-line desalting and simultaneous analysis of six carbohydrates (cellobiose, glucose, xylose, galactose, mannose, and arabinose) in the hydrolysate of waste paper and waste tree branch by incorporating the heart-cut and the elution-time-difference techniques. Six internal standard calibration curves in the linear concentration range of 0–2000 μg mL⁻¹ were prepared. Xylitol was used as the internal standard to give excellent linear correlation coefficients (0.9984–0.9999). The limits of detection and quantification for cellobiose, glucose, xylose, galactose, mannose, and arabinose varied between 0.12–4.88 and 0.40–16.3 μg mL⁻¹, respectively, with an accuracy of 90–102% and a precision of 0.1–7.8%. Cellulose and hemicellulose contents were higher in waste paper than in waste tree branch.     

Potential of using a single fermenter for biomass build-up,starch hydrolysis,and ethanol production

Data on conversion of starch on biomass and ethanol bySchwanniomyces castellii in an aerobic-anaerobic solid state fermentation is reported.Schwanniomyces castellii grew exponentially in the aerobic phase (12 h) and simultaneously hydrolyzed nearly half (55%) of the starch initially present. The accumulation of glucose increased up to 12 h, whereas maltose was nearly absent beyond 7 h. Shift of metabolism from oxidative to fermentative pattern was observed about 10 h as a result of the build-up of CO₂ level and faster utilization of O₂. The ethanol production in the anaerobic phase reached the level of 89.3 mg ethanol/g initial dry matter by the end of 30 h. A total of 92.9% of the starch is utilized during the fermentation. The overall ethanol conversion yields are 57.8% of the theoretical value, whereas in the anaerobic phase it was found to be 94.4%. The cell shape, its morphology, and the type of attachment to the solid support were found to be similar in aerobic and anaerobic phases of fermentation. Data given in this work indicate the feasibility of using one single fermenter for aerobic growth to generate inoculum as well as to simultaneously hydrolyze the starch and subsequent anaerobic fermentation to produce ethanol.     

New understanding of aconitine hydrolysis pathway: Isolation,identification and toxicity evaluation based on intermediate products

Aconitine hydrolysis is deemed to be the guarantee for the safe application of Aconitum phytomedicine. Studies have suggested that hydrolysates of aconitine not only include benzoylaconitine and aconine, but other hydrolysates. Moreover, these hydrolysates maybe have a mutual transformation relationship, which has not been confirmed. Herein, hydrolysates of aconitine and their mutual transformation relationship were studied by the theoretical quantum chemistry, UPLC-Q-TOF-MS, the separation and identification of target products, etc. Then the toxicity of its hydrolysates was evaluated. The results demonstrate that the probability is the same for aconitine hydrolysis to pyroaconitine and benzoylaconitine, but they are difficult to convert to each other. Aconitine hydrolysis has three independent hydrolysis pathways, 1) to indaconitine, 2) to benzoylaconitine, and aconine, 3) to pyroaconitine and to 16-epi-pyroaconine. The result of embryotoxicity evaluation on zebrafish was aconitine > indaconitine > benzoylaconitine > α-pyroaconitine > β- pyroaconitine > aconine > 16-epi-pyroaconine. In conclusion, aconitine have three independent hydrolysis pathways and the hydrolysates of different pathways cannot be transformed into each other. Pyroaconitine is a hydrolysate of aconitine except for benzoylaconitine, and its toxicity is lower than benzoylaconitine. More importantly, it clarifies the long-standing debate and provides scientific evidence for the processing and detoxification of Aconitum phytomedicine.     

Recent advances of use of the supercritical carbon dioxide for the biomass pre-treatment and extraction: A mini-review

Biomass is considered as the most sustainable and renewable resource for the synthesis of value added potential platform chemicals. Various techniques are utilized to extract or to pre-treat or to isolate various value added chemicals from biomass. Pre-treatment of the biomass is a very essential aspect to enhance the biomass processing yield which is attributed to reduced lignin content/delignification, cellulose crystallinity and hemi-cellulose hydration. In search of efficient extraction and processing for biomass treatment, supercritical fluid (SCF) has been considered as the green technique to obtain the value added chemicals with higher efficiency than conventional technique. The use of the supercritical carbon dioxide (SC–CO₂) pre-treatment on biomass not only enhances glucose yield effectively but also delignify, hydrolyse hemi-cellulose component and allows extraction of various compounds from the biomass. However, very limited research articles are available for the use of SC-CO₂ for biomass processing to obtain value-added chemicals. In view of this, the present review article focus on the recent advances of applications of SC-CO₂ in (i) extraction of value added chemicals from biomass processing, (ii) biomass pre-treatment, (iii) factors affecting SC-CO₂ processing efficiency, (iv) scale-up scenario (v) challenges and opportunities in this field.     

Acyclic phenylalkanediols as substrates for the study of enzyme recognition: synthesis of substrates and enzymatic resolution via hydrolysis and transesterification

Different racemic or prochiral phenyl alkane (l,n)-diols were synthesized, and their resolution was carried out by two different strategies: enzymatic transesterification with vinyl acetate, or enzymatic hydrolysis of their corresponding diacetates, in both cases catalysed by porcine pancreatic lipase (PPL). The absolute configuration of the optically enriched reaction products was determined by formation of Mosher's esters or by the use of the Benzene Sector and Benzene Chirality Rules as obtained from the Circular Dichroism spectra.     

New phosphoroamidate compounds: Synthesis,structural characterization and studies on ZnCl2 assisted hydrolysis of the P–N bond

A variety of phosphorodiamidate compounds were synthesized from the corresponding phosphorodichloridate intermediates and phosphorus oxychloride. These were completely characterized using different spectroscopic methods and single crystal X-ray diffraction studies on one of them. Studies revealed that water in the presence of a mild Lewis acid like ZnCl₂ was found to assist the hydrolysis of the P–N linkage. The proof of this concept was effectively realized through the hydrolysis of hexamethylphosphoramide.     

Synthesis, crystallization and hydrolysis of aromatic-aliphatic copolyester: Poly(trimethylene terephthalate)-co-poly(l-lactic acid)

In this study, poly(trimethylene terephthalate)-co-poly(l-lactic acid) (PTT-co-PLLA) copolyesters with different compositions were synthesized by melt polycondensation. The crystal morphologies of PTT-co-PLLA copolyesters were investigated with polarized light microscope (PLM). It was found that PTT-co-PLLA copolyesters exhibited banded spherulites with smaller band spacing at the same degree of super-cooling compared with PTT homopolymer. The PLLA segments in those copolyesters ranged from 0 to 28.4 mol% and did not form crystals during crystallization. Hydrolysis study on PTT homopolymer and PTT-co-PLLA copolyesters was carried out in buffer solutions. PTT-co-PLLA copolyesters represented pronounced hydrolytic degradation, which increased with the content of lactyl units. And it was concluded that degradation of PTT-co-PLLA was mainly attributed to the scission of PLLA segments.