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In this study, the production of two-stage metal-free catalysts from pistachio shells, which are abundant in Turkey and the world, is designed. The first stage of the study includes activated carbon(AC) production, and the second stage includes the production of heteroatom-doped catalysts as a result of hydrothermal heating of the obtained activated carbon with nitric acid. These metal-free catalysts obtained were used for the production of hydrogen (H2) from sodium borohydride (NaBH4) in methanol. In H2 production experiments, the NaBH4 concentration effect, temperature effect and catalyst amount effect and catalyst reusability parameters were investigated. HGR values obtained from the methanolysis using metal-free catalysts treated by the nitric acid/water ratio: 1:2, 1:3, 1:4, 1:5 are 8041, 8955, 10600 and 8333 ml min−1 g−1, respectively. The activation energy (Ea) of the production of H2 from NaBH4(NaBH4–H2–P) in methanol by the metal-free catalyst was 18.19 kJ mol−1. Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), CHNS elemental analysis, scanning electron microscopy (SEM), and nitrogen adsorption analyses were performed for the characterization of the metal-free catalysts obtained. In addition, the mechanism of the obtained metal-free catalysts on the NaBH4–H2–P in methanol is discussed.

The present analysis deals with the ability of Thermomyces lanuginosus to degrade pre-treated low-density polyethylene (LDPE). The synergistic effect of UV irradiation, heat, and acid pre-treatments on the biodegradability of the polymer was thoroughly assessed. Oxidative structural modifications such as the appearance of carboxylate and carbonyl groups in LDPE chains were recorded post the UV and heat treatments. Furthermore, the nitric acid treatment incorporated NO 2 groups into the polymer matrix. Alterations in the polymer thermal stabilities and surface morphologies after each pre-treatment were analyzed using thermogravimetric analysis and scanning electron microscopy (SEM), respectively. The gravimetric analysis revealed a reduction in the weight of the pre-treated LDPE films by 9.21 ± 0.84% after 1 month of the incubation period with Thermomyces lanuginosus. An increase in the thermal stability, disappearance of the incorporated hydrophilic functional groups, and reduction in the carbon content of the polymer samples post the incubation period further justified the biodegradation process. SEM analysis showed modifications in the morphology and texture patterns in pre-treated LDPE after inoculation with Thermomyces lanuginosus . The findings suggest that Thermomyces lanuginosus could be efficient for the decomposition of pre-treated LDPE under laboratory conditions.

Fruit development and ripening are controlled by multiple plant hormones; for strawberries, recent evidence supports the role of abscisic acid (ABA) as a promoter of fruit ripening. Fruit softening during ripening is mainly a consequence of the solubilization and depolymerization of cell wall components mediated by the action of a complex set of enzymes and proteins. In the present work, we performed a comparative study (ABA-treatment vs. control) of the changes in the physiological properties of the cell wall-associated polysaccharide contents of strawberry fruit (Fragaria x ananassa ‘Camarosa’) via analysis of thermogravimetry (TG) combined with analysis of mRNA abundance, enzymatic activity and physiological characteristics. ‘Camarosa’ did not show a decline in the fruit firmness at 48 h post-treatment; however, we observed changes in cell wall stability based on the TG and differential thermogravimetric (DTG) analysis curves, which demonstrated the degradation of the cell wall polymers after ABA hormone treatment for 48 h, principally for hemicellulose polymers. Additionally, DTG analysis showed that dried samples derived from the treatment of the fruit with the ABA biosynthesis inhibitor fluridone maintained the same thermal stability as the control samples. Finally, the existence of a relationship between thermal stability, transcriptional analysis and enzymatic activity after hormone treatment was demonstrated, which provides the basis for a model for understanding the changes in the cell wall polymers of F. x ananassa mediated by the ABA hormone during fruit ripening.Graphic abstract

Background Sunflower stalk pith, residue from the processing of sunflower, is rich in pectin and cellulose, thereby acting as an economic raw material for the acquisition of these compounds. In order to increase the commercial value of sunflower processing industry, a two-step dilute sulfuric acid treatment process was conducted on spent sunflower stalk pith to obtain the value-added products, pectin and glucose. Results In this study, pectin was firstly extracted under mild acid condition to avoid pectin degradation, which was conducted at 90 °C with a pH of 2.0 for 2 h, and ~0.14 g/g of pectin could be recovered. Then the remaining solids after pectin extraction were subjected to the reinforced treatment process with 0.75% H2SO4 at 150 °C for 30 min to further improve enzymatic hydrolysis efficiency. Moreover, by combining a fed-batch enzymatic hydrolysis strategy, a solid loading content of 16% was successfully achieved and the glucose titer reached 103.1 g/L with a yield of 83.6%. Conclusion Finally, ~140 g pectin and 260 g glucose were produced from 1 kg of raw sunflower stalk pith using the integrated biorefinery process. This work puts forward a two-step dilute acid pretreatment combined with enzymatic hydrolysis method to produce pectin and glucose from sunflower spent waste.

The removal of free cyanide from aqueous solutions was investigated by kaolin, calcined kaolin (metakaolin), and acid-treated metakaolin. The kaolin in raw form had no ability for cyanide adsorption, but calcination and acid treatment significantly improve its adsorptive properties. The best calcination conditions were determined to be at temperature of 600 °C and calcination time of 1 h. The scanning electron microscope (SEM), wavelength-dispersive X-ray (WDX), X-ray fluorescence (XRF), and X-ray diffraction (XRD) analysis methods were used to explain the adsorptive properties of the adsorbents. The loading capacity of metakaolin increased from 0.66 to 5.32 mg/g, and the loading capacity of acid-treated metakaolin increased from 1.33 to 10.67 mg/g by increasing the initial cyanide concentration from 25 to 531 mg/L. The kinetics of cyanide adsorption onto both adsorbents increases by increasing the initial cyanide concentration (25–531 mg/L) and solution temperature (30–50 °C). The equilibrium and kinetic data on both adsorbents are best fitted by the Freundlich isotherm and pseudo-second-order kinetic models, respectively. The thermodynamic study showed that the cyanide adsorption onto both adsorbents is endothermic and spontaneous in nature. The activation energy for the cyanide adsorption onto metakaolin and acid-treated metakaolin was determined to be 16.68 and 5.79 kJ/mol which indicates that the adsorption of cyanide ions onto metakaolin is chemisorption and onto the acid-treated metakaolin is a physicochemical process.

One of the targets of the Sustainable Development Goals is clean and affordable energy. This is also the aim of the Biofuels Act of 2007 in the Philippines. However, this law is confronted with challenges such as the limitation of lignocellulosic feedstock, specifically available for bioethanol production. The present study sought to address the issue by exploring the potential of mango seed husk (MSH), a by-product of the mango industry, in bioethanol production. MSH is considered a waste material and its utilization also permit value-addition as this can serve as an alternative and affordable source of feedstock in energy production. Two pretreatment strategies are employed to exploit the cellulose and hemicellulose content of MSH, namely, dilute acid treatment and enzymatic hydrolysis. Results show that the %H2SO4 resulting in the highest glucose concentration and yield is 4% v/v at 95 °C hydrolysis temperature, 1:10 (w/v) solid-to-solvent ratio, and 60-min hydrolysis time. For enzymatic hydrolysis using a commercial enzyme preparation, the reaction time up to 72 h did not affect glucose concentration and yield at the following conditions: 50 °C hydrolysis temperature, 150 rpm, pH 5.0, 10% solids loading, and 4% enzyme loading. This could be attributed to the lignin and non-structural compounds present in MSHs. However, a combined process strategy of dilute acid pretreatment followed by enzymatic hydrolysis in the pretreatment of MSH contributes to an increased concentration and yield of sugars in the hydrolysates, which is advantageous for bioethanol production.

Background The dense structure of cellulose lowers its reactivity and hinders its applications. Concentrated sulfuric acid is an ideal solvent to dissolve cellulose and thus has been used widely to treat cellulose. However, the changes of cellulose after reaction with concentrated sulfuric acid at near-limit S/L ratio and its effect on enzymatic saccharification still need further investigation. Results In this study, the interactions between cellulose (Avicel) and 72% sulfuric acid at very low acid loading conditions of 1:2 to 1:3 (S/L ratio) were studied for the enhanced production of glucose. The Avicel gradually transformed from cellulose I structure to cellulose II structure during the sulfuric acid treatment. Other physicochemical characteristics of Avicel also changed dramatically, such as the degree of polymerization, particle size, crystallinity index, and surface morphology. After acid treatment, both the yield and productivity of glucose from cellulose increased significantly under a very low enzyme loading of 5 FPU/g-cellulose. The glucose yields for raw cellulose and acid-treated (30 min) were 57% and 85%, respectively. Conclusion Low loadings of concentrated sulfuric acid were proven to be effective to break the recalcitrance of cellulose for enzymatic saccharification. A positive correlation between cellulose CrI and glucose yield was found for concentrated sulfuric acid-treated cellulose, which was opposite to previous reports. Cellulose II content was found to be an important factor that affects the conversion of cellulose to glucose.

Torularhodin is a fungus-derived carotenoid, and the lack of downstream processing of torularhodin is still a challenge for its large-scale production. To support the industrial production of torularhodin, this work initially evaluated the efficiency of carotenoid release from Rhodotorula mucilaginosa using thermal acid treatment, saponification and ultrasound-assisted enzymatic lysis. Based on the polarity, torularhodin was then purified using methanol/acetone/hexane (2/2/1, v/v/v) solution eluting from a silica cartridge. Thermal acid treatment was considered the most appropriate method for total carotenoid release and torularhodin recovery. The highest carotenoid content was 121.3 ± 7.0 μg/g dry cell weight and 63.0 ± 6.1% of torularhodin (50.5 ± 3.0 μg/g dry cell weight in total) was recovered after purification. To fast quantify the content of torularhodin extracted from yeast, the absorption coefficient (E1cm1% = 3342) of torularhodin dissolved in chloroform was assayed. With the developed strategy for torularhodin recovery, purification and quantification, the potential of this yeast to produce torularhodin using xylose and glycerol was further evaluated. It was found that carbon sources may influence the proportion of carotenoids in this yeast, but torularhodin was still the dominant pigment. The results obtained in this study identified the feasibility of sustainable production of torularhodin from Rhodotorula mucilaginosa with high efficiency and purity.

Exogenous abiotic stimulant treatments are a straightforward and effective method for enhancing secondary metabolites in plants. In this study, the response surface optimization method was used to optimize the conditions for enriching flavonoids in short-germinated black soybeans under a slight acid treatment, and the mechanism of flavonoid accumulation during black soybean germination was explored. The results show that the use of a 126.2 mM citric acid–sodium citrate buffer (pH 5.10) as a slight acid treatment resulted in the highest flavonoid content when the black soybeans were germinated for 24 h. Under these conditions, the isoflavonoid (glycitin, daidzein, and genistein) increased significantly, and the flavonoid content reached 2.32 mg/g FW. The microacidified germination treatment significantly increased the activities and relative gene expression levels of key enzymes involved in flavonoid metabolism (4-coumarate-CoA ligase and cinnamic acid 4-hydroxylase, etc.). However, the slight acid treatment inhibited the growth of the black soybeans and caused damage to their cells. This was evidenced by significantly higher levels of malondialdehyde, superoxide anion, and hydrogen peroxide compared to the control group. Furthermore, the antioxidant system in the short-germinated soybeans was activated by the slight acid treatment, leading to a significant increase in the activities and relative gene expression levels of catalase and peroxidase. The results above show that a slight acid treatment was beneficial in inducing the accumulation of flavonoids during the growth of black soybean sprouts. This lays a technical foundation for producing black soybean products that are rich in flavonoids.

A method was developed for the high-yield preparation of cellulose nanofibers (CNFs) using glycerol and a small quantity of sulfuric acid with a colloid milling mechanical dispersion. The glycerol together with a small quantity of sulfuric acid was employed to break hydrogen bonds between cellulose fibrils, after which the excessively swelled cellulose bundles could be easily disassembled to nanosize by a simple mechanical treatment. Reaction conditions, including the amount of sulfuric acid, the temperature and the preferred acid treatment time, were optimized to be 0.64% w/w sulfuric acid (based on the whole reaction system), 100 °C and 2 h respectively. Under the optimized conditions, CNFs with a width less than 100 nm and a length of several microns were obtained from various raw materials with high yield (above 85%), high crystallinity and an average degrees of polymerization (DP v ) of 200. Graphical abstract