Pretreatment Methods Research Articles

A Novel Green Sample Pretreatment Method Column-Free Matrix Solid-Phase Dispersion Extraction: Application in a High-Performance Liquid Chromatography Experiment for Undergraduate Chemistry

A Novel Green Sample Pretreatment Method Column-Free Matrix Solid-Phase Dispersion Extraction: Application in a High-Performance Liquid Chromatography Experiment for Undergraduate Chemistry

Effect of Pretreatments on the Chemical, Bioactive and Physicochemical Properties of Cinnamomum camphora Seed Kernel Extracts.

Cinnamomum camphora seed kernels (CCSKs) are rich in phytochemicals, especially plant extracts. Phytochemicals play a vital role in therapy due to their strong antioxidant and anti-inflammatory activities. Extracts from CCSK can be obtained through multiple steps, including pretreatment, extraction and purification, and the purpose of pretreatment is to separate the oil from other substances in CCSKs. However, C. camphora seed kernel extracts (CKEs) were usually considered as by-products and discarded, and their potential bioactive values were underestimated. Additionally, little has been known about the effect of pretreatment on CKE. This study aimed to investigate the effects of pretreatment methods (including the solvent extraction method, cold pressing method, aqueous extraction method and sub-critical fluid extraction method) on the extraction yields, phytochemical profiles, volatile compounds and antioxidant capacities of different CKE samples. The results showed that the CKE samples were rich in phenolic compounds (15.28-20.29%) and alkaloids (24.44-27.41%). The extraction yield, bioactive substances content and in vitro antioxidant capacity of CKE pretreated by the sub-critical fluid extraction method (CKE-SCFE) were better than CKEs obtained by other methods. CKE pretreated by the solvent extraction method (CKE-SE) showed the best lipid emulsion protective capacity. Moreover, the volatile substances composition of the CKE samples was greatly influenced by the pretreatment method. The results provided a fundamental basis for evaluating the quality and nutritional value of CKE and increasing the economic value of by-products derived from CCSK.

Enhanced vanadium bioleaching from stone coal employing Aspergillus niger: Optimization of stone coal pretreatment method

Vanadium is a rare metal with excellent properties. The recovery of vanadium from low-grade stone coal and vanadium-containing solid wastes using microbial leaching, has become an increasingly popular technology. In this paper, Vanadium was obtained from stone coal using Aspergillus niger as the leaching strain, and the process of vanadium bioleaching was strengthened. Compared with plasma treatment and ultrasonic pretreatment of stone coal, the leaching effect of stone coal after roasting at 900 °C was the best, and the leaching rate of vanadium was as high as 94.52 %. The vanadium bioleaching mechanism was explored by SEM-EDS, XRD, XPS and FTIR analysis. The findings indicated that Aspergillus niger has the ability to adhere to the surface of stone coal, resulting in subsequent corrosion and degradation. The roasting treatment of stone coal and bioleaching of Aspergillus niger jointly lead to the decrease of crystallinity, the increase of interplanar spacing and the decrease of stability of stone coal. Meanwhile, the valence state and binding form of vanadium changed, and V (III) was oxidized to V (IV) and V (V). The mineral structure may be distorted as a result of the distinctive peak's vibratory stretching and the influence of functional categories that include oxygen, which in turn causes the change of the coordination form of the internal metal ions, which affects the symmetry of the mineral and facilitates the dissolution of vanadium from the stone coal. Research indicates that roasting and Aspergillus niger bioleaching have a great deal of promise to increase vanadium recovery from stone coal.

Optimizing the Conditions of Pretreatment and Enzymatic Hydrolysis of Sugarcane Bagasse for Bioethanol Production.

The agricultural waste sugarcane bagasse (SCB) is a kind of plentiful biomass resource. In this study, different pretreatment methods (NaOH, H2SO4, and sodium percarbonate/glycerol) were utilized and compared. Among the three pretreatment methods, NaOH pretreatment was the most optimal method. Response surface methodology (RSM) was utilized to optimize NaOH pretreatment conditions. After optimization by RSM, the solid yield and lignin removal were 54.60 and 82.30% under the treatment of 1% NaOH, a time of 60 min, and a solid-to-liquid ratio of 1:15, respectively. Then, the enzymolysis conditions of cellulase for NaOH-treated SCB were optimized by RSM. Under the optimal enzymatic hydrolysis conditions (an enzyme dose of 18 FPU/g, a time of 64 h, and a solid-to-liquid ratio of 1:30), the actual yield of reducing sugar in the enzyme-treated hydrolysate was 443.52 mg/g SCB with a cellulose conversion rate of 85.33%. A bacterium, namely, Bacillus sp. EtOH, which produced ethanol and Baijiu aroma substances, was isolated from the high-temperature Daqu of Danquan Baijiu in our previous study. At last, when the strain EtOH was cultured for 36 h in a fermentation medium (reducing sugar from cellulase-treated SCB hydrolysate, yeast extract, and peptone), ethanol concentration reached 2.769 g/L (0.353%, v/v). The sugar-to-ethanol and SCB-to-ethanol yields were 13.85 and 11.81% in this study, respectively. In brief, after NaOH pretreatment, 1 g of original SCB produced 0.5460 g of NaOH-treated SCB. Then, after the enzymatic hydrolysis, reducing sugar yield (443.52 mg/g SCB) was obtained. Our study provided a suitable method for bioethanol production from SCB, which achieved efficient resource utilization of agricultural waste SCB.

Development of a targeted method for DNA adductome and its application as sensitive biomarkers of ambient air pollution exposure

DNA adducts are widely recognized as biomarkers of exposure to environmental carcinogens and associated health effects in toxicological and epidemiological studies. This study presents a targeted and sensitive method for comprehensive DNA adductome analysis using ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). The method was developed using calf thymus DNA, with careful optimization of mass spectrometric parameters, chromatographic separation conditions, and pretreatment methods. Ultimately, a targeted method was established for 41 DNA adducts, which showed good linearity (R2 ≥0.992), recovery (80.1–119.4 %), accuracy (81.3–117.8 %), and precision (relative standard deviation <14.2 %). The established method was employed to analyze DNA adducts in peripheral blood cells from pregnant women in Shanxi and Beijing. Up to 23 DNA adducts were successfully detected in samples of varying sizes. From 2 μg of maternal DNA samples, seven specific adducts were identified: 5-methyl-2'-deoxycytidine (5-MedC), 5-hydroxymethyl-2'-deoxycytidine (5-HmdC), N6-methyl-2'-deoxyadenosine (N6-MedA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), 5-hydroxy-2'-deoxycytidine (5-OHdC), 1,N6-etheno-2'-deoxyadenosine (1,N6-εdA), and N2-methyl-2'-deoxyguanosine (N2-MedG). This study reveals that exposure to higher concentrations of ambient air pollutants may elevate the levels of DNA methylation and oxidative damage at different base sites, highlighting the application potential of DNA adducts as sensitive biomarkers of air pollution exposure.

Quantification and analyses of seven tyrosine kinase inhibitors targeting hepatocellular carcinoma in human plasma by QuEChERS and UPLC-MS/MS

Tyrosine kinase inhibitors (TKIs) are commonly used to treat various cancers. Literature suggests that the blood concentration of TKIs strongly correlates with their efficacy and adverse effects. Therefore, establishing a Therapeutic Drug Monitoring (TDM) methodology for TKI drugs is crucial to improving their clinical efficacy and minimizing the treatment-related adverse effects. However, quantifying their concentrations in the plasma using existing methods to avoid potential toxicity is challenging. Herein, seven TKIs, namely sorafenib tosylate, axitinib, erlotinib, cediranib, brivanib, linifanib, and golvatinib, were successfully analyzed in human plasma by following a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment method combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Briefly, biological samples were extracted using 1 mL of methanol, followed by the sequential addition of 250 mg of anhydrous magnesium sulfate and 25 mg of N-propylethylenediamine (PSA) for salinization and purification by adsorption, respectively. In this study, dovitinib was used as the internal standard. The seven TKIs were detected by the gradient elution method for 4 min in the positive ion electrospray mode. The mobile phase comprised methanol (phase A) and 0.1 % aqueous formic acid solution (phase B) on the Agilent Zorbax RRHD Stablebond Aq, (2.1 × 50 mm; 1.8 μm). Brivanib, linifanib, axitinib, sorafenib tosylate, and golvatinib exhibited good linearity in the range of 5–500 ng/mL, and erlotinib and cediranib exhibited good linearity in the range of 10–1000 ng/mL, with linear correlation coefficients (R2) ≥ 0.99. The limits of detection and quantification were 0.60–0.18 ng/mL and 5–10 ng/mL, respectively. The intraday and interday accuracy values ranged from −6.12 % to 7.31 %, with a precision (RSD) of ≤ 10.57 %. The method was rapid, accurate, specific, simple, reproducible, and suitable for the quantitative determination of the seven TKIs in human plasma.

Meta-Analisis Pengaruh Blansir terhadap Total Fenolik Buah dan Sayur

Blanching is the most common pretreatment method for fruits and vegetables to maintain product quality. Numerous studies revealed desirable impacts of the process to total phenolic content, while the others showed opposite results. In addition, some differences in the blanching condition such as methods and classification of fruits and vegetables were also known able to affect total phenolic content. This study aimed to analyze the effect of blanching on total phenolic content in vegetables and fruits through a meta-analysis approach. Study selection was conducted with a PRISMA method. There were 28 articles and 82 data used for meta-analysis. The data were analyzed by Hedges’d to calculate the effect size with confidence interval (CI) utilizing OpenMee software. The result showed that blanching demonstrated significant effects on the rise of total phenolic content (hedges’d[95% CI]: 0.782 [0.037 to 1.527]; p&lt;0.05). Based on fruits and vegetables subgroups, the blanching significantly affected the increase of total phenolic content in leaves (hedges’d[95% CI]: 1.484 [0.185–2.782]) and fruits (hedges’d[95% CI]: 2.504 [0.153–4.854] compared to stems and stalks, fruits as vegetable, shoots and sprouts, pulse, and flowers. Meanwhile, in terms of blanching method subgroups, hot water blanching (hedges’d[95% CI]: 1.096 [0.234–1.959]) had significant effects on the rise of total phenolic content compared to steam blanching. Moreover, this meta-analysis was robust against publication bias.

Jerusalem Artichoke Tuber Processing: Influence of Pre-Treatment Methods, Lactic Acid, and Propionic Acid Bacteria Strains on Functional Fermented Beverage Production.

Fermented plant-based products are rapidly gaining popularity. Jerusalem artichoke is a medicinal plant that can be used to make fermented beverages. Samples were subjected to pretreatment (ultrasound at 35kHz for 2, 4, and 6min, freezing at -80°C and -17°C) while an untreated sample was used as control. It was shown that all types of pretreatments did not lead to an increase in protein, solids, polyphenols, and carbohydrates compared to the control sample. The greatest decrease in the values of these indicators occurs when pre-freezing tubers are used for Jerusalem artichoke dispersion production. It was also found that samples frozen at -80°C had a significantly higher concentration of Ca, Si, Mg, and P whereas untreated samples frozen at -17°C had more Al, K, Cu, Sr, and Cr. The processing method can affect the sensory descriptors of Jerusalem artichoke tuber dispersions to different extents, but the preference was for the control sample without pre-treatment. The fermentation of Jerusalem artichoke tuber dispersions demonstrated that S. thermophilus induced the most rapid fermentation (pH 4.75 in 5h). The highest antioxidant activity after fermentation (55.39% FRSA) was shown for L. acidophilus H9, while the highest % FRSA value during the storage period was for L. bulgaricus (67.5%) on day 5 after fermentation. The highest viability among all selected microorganisms was detected for L. bulgaricus, L. acidophilus AT-41, and B. coagulans MTCC 5856 with the increase in biomass content by 2.3, 2.27, and 2.12 log10CFU/ml after fermentation. According to the results of sensory evaluation using hybrid hedonic scale the best results were shown for samples fermented with L. bulgaricus.

Strategy for clean phosphate recovery from polymerized aluminum chloride-treated sludge by alkaline anion exchange resins: High alkalinity and desorption

Polyaluminum chloride (PAC) is commonly used as a flocculant in wastewater treatment plants to aid in the removal of phosphorus (P) from wastewater. As a result, the P element present in PAC-treated sludge is predominantly in the form of Al-P. This study proposes the use of alkaline anion exchange resin (AAER) as a pretreatment method for PAC-treated sludge to enhance P extraction and achieve cleaner P recovery from this type of sludge. The findings of the study indicate that the optimal concentration of AAER is 12 g/g TS, resulting in a P extraction efficiency of 67.2 %. This represents a 26.5 % increase compared to alkali treatment at the same pH (pH = 12.23). Stepwise extraction analysis and molecular dynamics simulations suggest that during AAER treatment, Al(OH)3 is converted into dissolved [Al(OH)4]−. These species then agglomerate with PO43− and subsequently get adsorbed by the N(CH3)+ groups on the AAER. Furthermore, even after undergoing five regeneration cycles, the AAER still exhibits a significant adsorption capacity for P. Ultimately, high-purity Ca10(PO4)6(OH)2 is obtained as the final product with a recovery rate of 90.5 %. Meanwhile, the Al extracted by AAER can be reused as a feedstock for polymerized aluminum chloride. This demonstrates that AAER extraction is a promising and efficient waste management strategy for the clean recovery of P and Al from PAC sludge.

Nano-modified recycled aggregates via vacuum impregnation: Towards stronger and durable recycled concrete

For the first time, this study aimed to enhance the quality of recycled aggregates (RAs) by employing nano-silica (NS) and the vacuum impregnation technique. Specifically, RAs experienced water immersion, ordinary and vacuum impregnation with 2 % NS slurry, and vacuum impregnation with 4 % NS slurry. Subsequently, these nano-modified RAs were incorporated into concrete mixes, and their strength and durability were assessed. Following this, an examination of the pore structures and properties of the interfacial transitional zones (ITZs) in recycled concrete was conducted. The results demonstrate that in contrast to ordinary pretreatment methods, concrete containing nano-modified recycled aggregates after vacuum impregnation exhibits better compressive strength (+18.39 %) and reduced chloride ion penetration (−17.90 %), which is attributable to a more compact pore structure and enhanced ITZs. The findings prove that vacuum impregnation significantly enhances the modification impact of NS on RAs when compared to conventional impregnation methods, owing to the reduced agglomeration effect of NS in concrete.

Organic solvent-assisted ethylenediamine pretreatment to improve the high-value utilization efficiency of corn stalk

In order to achieve the goal of carbon neutrality, it is an important way and a great challenge to realize the full-component conversion of lignocellulosic biomass via bio-refinery. In this study, the pretreatment method of organic solvent-assisted ethylenediamine was used to separate cellulose, hemicellulose, and lignin in corn stalk. The effects of different organic solvents on the separation ability were studied, and the separated products were transformed into high-value products. Specifically, the structures of solid residue, regenerated hemicellulose, and regenerated lignin were analyzed and applied to pyrolysis saccharification (at 500℃ for 30 min), information anti-counterfeiting, and selective detection of Fe3+ respectively. The results showed that the lignin removal ratio of 1-butyl-3-lethylimidazolyl chloride/ethylenediamine (IL/EDA) system could reach 96.05 % under the pretreatment condition of 200℃ for 2 h, and the yield of Levoglucosan obtained from pyrolysis bio-oil reached 169.70 mg·g−1 with high selectivity. Moreover, IL/EDA pretreatment increased the nitrogen content of lignin and hemicellulose, enhanced the fluorescence intensity, and effectively realized selective detection and information encryption. Furthermore, Density functional theory (DFT) calculation proved that the addition of organic solvents was beneficial to the reaction between lignin and ethylenediamine (EDA). The Fukui function was used to explore the reaction site between EDA and lignin. In addition, the mass balance of the pretreatment process was also described. This study realized the high-value application of all components of lignocellulose and provided a new process for the efficient utilization of green carbon resources.

Effects of pretreatment methods on the flavor profile and sensory characteristics of Kiwi wine based on 1H NMR, GC-IMS and E-tongue

The pretreatment method of fruit before fermentation is a crucial step in fruit wine production, exerting a considerable influence on its overall quality, particularly on sensory characteristics and flavor profile. In this study, Pujiang kiwifruits as raw material, four pretreatment methods were employed in kiwi wine (KW) production, namely kiwi fruit crushing with peel (KCP), crushing without peel (KCW), kiwi fruit squeezing juice with peel (KJP), and squeezing juice without peel (KJW). The sensory characteristics and flavor profile of KW were evaluated using sensory evaluation, E-tongue, GC-IMS, and 1H NMR. KW produced through KCP method achieved the highest sensory evaluation score, compared to the others. E-tongue could effectively differentiate the taste features among KW produced by different pretreatment methods. A total of 137 compounds were characterized by the combination of GC-IMS and 1H NMR. Moreover, among the molecules quantified by GC-IMS and 1H NMR, the concentrations of 52 and 58 compounds, respectively, exhibited significant differences among the four groups, primarily comprising esters, organic acids and alcohols. Furthermore, enrichment analysis indicated that several metabolic pathways could be altered by different pretreatment methods. This study serves as a theoretical reference and application basis for the quality improvement of KW and offers insights on the reduction and utilization of winemaking by-products.

Superparamagnetic nanofluid based on target-specific deep eutectic solvent for determination of multiple perfluoroalkyl substances in edible oils

Deep eutectic solvents (DESs) are recognized as sustainable mediums, and DES-related materials have been used for the detection of perfluoroalkyl substances (PFASs). However, such studies were usually limited to only one category of PFASs among the massive target PFASs compounds. Additionally, the selectivity of the related detection method still needs improvement. In this study, a convenient and effective method for the direct selective microextraction of multiple PFASs was developed based on a target-specific DES-based superparamagnetic nanofluid. Parameters such as DES compositions, amount of DES-based nanofluid, and microextraction time were systematically investigated to establish a straightforward, rapid, sensitive, and efficient green pretreatment method. Under optimal conditions, the method demonstrated high sensitivity, good precision, a detection limit of 0.04–8.71 ng kg−1, a spike recovery of 80.49–119.95%, and low matrix effects (<20%). The potential mechanism was elucidated by ab initio molecular dynamics (AIMD) simulations. The solvent system exhibited diverse interaction modes with analytes of varying types, including hydrogen bond acceptors (HBA)···PFASs, HBA···FAAs···hydrogen bond donors (HBD), and hetero-halogen interactions. Finally, this method was applied to the monitoring of 13 PFASs compounds in 17 edible oil samples, and targets were detected in the range of 0.05–10.04 ng kg−1.

Pressurized microwave-assisted hydrothermal treatment with various salts for efficient production of monosaccharides from rice straw

This study proposed a two-stage pressurized microwave hydrothermal treatment with a catalyst, followed by enzymatic saccharification, as a pretreatment method for efficiently converting cellulose and hemicellulose from rice straw into glucose and xylose. The use of various inorganic salts and dilute sulfuric acid as catalysts enhances sugar production. Using 1 wt% sulfuric acid as a catalyst at 150 °C for 5 min for the first-stage and then 180 °C for 5 min for the second-stage yielded the highest sugar production from rice straw compared with other inorganic salts tested. The filtrate and enzymatic saccharification solution contained a total sugar of 0.434 g/g-untreated rice straw (i.e. 0.302 g-glucose/g-untreated rice straw and 0.132 g-xylose/g-untreated rice straw). When inorganic salts such as NaCl, MgCl2, CaCl2, and FeCl3 were used as catalysts, the highest sugar yield of 0.414 g/g-untreated rice straw (i.e. 0.310 g-glucose/g-untreated rice straw and 0.104 g-xylose/g-untreated rice straw) was obtained when using 1 wt% FeCl3 at 170 °C for 5 min in the first-stage and 190 °C for 5 min in the second-stage, with a value close to that of 1 wt% sulfuric acid. These findings suggest that two-stage treatment with a catalyst is a suitable pretreatment method for the production of glucose and xylose from rice straw owing to the different hydrolysis temperatures of cellulose and hemicellulose.

Development of binderless fiberboard from poplar wood residue with Trametes hirsuta

The utilization of agricultural and forestry residues for the development and preparation of green binderless fiberboard (BF) is an effective way to realize high-value utilization of lignocellulose biomass resources. This study focuses on the fabrication of BF with excellent mechanical and waterproof properties, utilizing poplar wood residue (PWR) as raw material and Trametes hirsuta as a pretreatment method. During the fermentation process, lignin-degrading enzymes and biological factors, such as sugars, were produced by T. hirsuta, which activated lignin by depolymerizing lignin bonds and modifying structural functional groups, and forming new covalent bonds between poplar fibers, ultimately enhancing adhesion. Additionally, the activated lignin molecules and sugar molecules coalesce under high temperatures and pressures, forming a dense carbonization layer that bolsters the mechanical properties of the fiberboard and effectively shields it from rapid water infiltration. The bio-pretreated BF for 10 days shows a MOR and MOE of up to 36.1 Mpa and 3704.3 Mpa, respectively, which is 261% and 247.8% higher than that of the bio-untreated fiberboard, and the water swelling ratio (WSR) rate is only 5.6%. Chemical composition analysis revealed that repolymerization occurred among lignin, cellulose, and hemicellulose, especially the molecular weight of lignin changed significantly, with the Mw of lignin increasing from 312066 g/mol to 892362 g/mol, and then decreasing to 825021 g/mol. Mn increased from 277790 g/mol to 316987.5 g/mol and then decreased to 283299.5 g/mol at 21 days. Compared to other artificial fiberboards prepared through microbial pretreatment, the BF prepared by microorganisms in this study exhibited the highest mechanical properties among the poplar wood biobased panels.

Optimization of ultrasonication and alkalinization as pretreatment methods for leachate co-digested with food waste toward maximum synergistic effects

Anaerobic co-digestion (AcoD) of food waste (FW) and landfill leachate has shown promising results in enhancing the methane yield. However, leachate includes toxic and refractory compounds that may impact the decomposition process. In this research, co-digested leachate was pretreated using ultrasonication and alkalinization to manipulate its characteristics toward improved synergism with FW. Experimental optimization was conducted through biochemical methane potential (BMP) assays to identify the optimum operating conditions of the pretreatment methods. The study evaluated the synergistic effects of co-digestion with raw and pretreated leachate on enhancing the performance in terms of feedstock solubilization and methane production. The BMP test demonstrated that alkalinization and ultrasonication improved the total methane generation by 35% and 27%, respectively, yielding around 397 and 375 mL CH4 per g of volatile solids. Moreover, ultrasonication and alkalinization enhanced the synergistic effects by 28% and 36%, respectively, compared to co-digestion with untreated leachate. Optimization by response surface methodology revealed that maximum performance could be achieved with leachate sonication at 212 W for 37.5 min or augmenting 788 g NaOH per kg of volatile solids. Kinetic and statistical models were derived to simulate and assess the impacts of the pretreatment parameters on the AcoD process. The results indicated that the ultrasonication energy had a higher influence on total solubility and methane production than alkaline dosage. Additionally, energy efficiency analyses were performed to examine the overall viability of the examined management approach and found that alkalinization increased the net energy efficiency by 23%, whereas ultrasonication was inefficient within the examined laboratory conditions despite the improved performance. The findings support an integrated organic waste management system where separated FW is co-treated with landfill leachate.

Co-production of fermentable sugars and highly active lignin from eucalyptus via a mild preprocessing with diethylene glycol and chromic chloride

Eucalyptus was pretreated with diethylene glycol catalyzed by 0.02 mol/L CrCl3 for 10 min, resulting in 91 % delignification and 98 % cellulose recovery, with trace fermentation inhibitors generated. After the mild pretreatment, the accessibility and affinity of cellulase to eucalyptus was enhanced, especially since enzyme adsorption rate increased by 1.6-fold. Therefore, glucose yield of pretreated eucalyptus was 7.9-fold higher than that of untreated eucalyptus after hydrolyzed 48 h, in which the maximum glucose concentration reached 62 g/L from eucalyptus by adding Tween 80. According to the characterization analysis, the structure of the eucalyptus lignin-carbohydrate complexes structure was destroyed during the pretreatment, while lignin fragments was likely reacted with diethylene glycol to form the stabilized aromatic ethers. Moreover, the extracted Deg-lignin exhibited better performances than commercial alkali lignin such as higher fluorescence intensity, less negative surface charge, and lower particle size. The mild pretreatment method with diethylene glycol and CrCl3 provided a promising approach for co-production of fermentable sugars and high activity lignin from lignocellulosic biomass.

Effects and improvement mechanisms of ultrasonic pretreatment on the quality of fermented skim milk

Fermented skim milk is an ideal food for consumers such as diabetic and obese patients, but its low-fat content affects its texture and viscosity. In this study, we developed an effective pretreatment method for fermented skim milk using low-frequency ultrasound (US), and investigated the molecular mechanism of the corresponding quality improvement. The skim milk samples were treated by optimal ultrasonication conditions (336 W power for 7 min at 3 °C), which improved the viscosity, water-holding capacity, sensory attributes, texture, and microstructure of fermented skim milk (P < 0.05). Further mechanistic analyses revealed that the US treatment enhanced the exposure of fluorescent amino acids within proteins, facilitating the cross-linking between casein and whey. The increased surface hydrophobicity of fermented milk indicates that the US treatment led to the exposure of hydrophobic amino acid residues inside proteins, contributing to the formation of a denser gel network; the average particle size of milk protein was reduced from 24.85 to 18.06 µm, which also contributed to the development of a softer curd texture. This work is the first attempt to explain the effect of a low-frequency ultrasound treatment on the quality of fermented skim milk and discuss the molecular mechanism of its improvement.

Streamlining biological recycling of poly(ethylene terephthalate) via pre-treatment methods

In this study, we validated various methods of pre-treatment of poly(ethylene terephthalate) (PET) by the engineered yeast Yarrowia lipolytica. This research compares both the effect of the type of plastic used, the processing method and enzymes with different mechanisms of action (PETase and cutinase). The investigation demonstrated that the degradation efficiency varies depending on the type of plastic used, the processing methods and the applied enzyme. Moreover, it indicated that during prolonged yeast culture under the applied conditions, enzyme activity is not impaired. Among all the methods tested, the artificial aging process had the greatest impact on the degradation level by PETase, where the amount of TPA released from commercial PET film was the highest, and yielded over 2 gL-1. The maximum yield of TPA (0.59 gL-1), for the Y. lipolytica strain overexpressing cutinase, was observed during the process with recycled PET bottles shredded into 1 mm fragments. The maximum recorded weight loss of plastic film is over 70% for commercial PET film subjected to artificial ageing process.

Effects of mechanical surface pre-treatment on integrity and corrosion of bare and coated AA6082 substrates

In this study, two classes of surface pre-treatment methods, namely three blast-cleaning methods with different abrasive materials (for initial preparation) and three mechanical methods (for repair applications) were applied to study their effects on surface morphology, composition, and corrosion of AA6082 substrates in artificial seawater. Coating adhesion and coating corrosion protection ability were investigated by applying a single-layer epoxy coating (250 μm dry film thickness) onto the substrates.The mechanical methods delivered cleaner surfaces with more regular surface morphologies, whereas the blast-cleaning methods revealed less clean surfaces and more irregular surface morphologies. The latter methods promoted the detrimental embedment of abrasive particles into the substrates. The corrosion performance of the pre-treated substrates was worse after blast-cleaning compared to mechanical treatments. However, all methods met the adhesion requirements for offshore applications. Regarding coating degradation, only the filiform corrosion test delivered meaningful results, whereas the duration of the cyclic corrosion test (3000 h) was too short to distinguish between the different methods because of neglectable degradation. Mechanical interlocking and isotropic surface morphologies are found to be more important for coating performance than a cleaner surface, and the remains of blasting material were neglectable too.