Experimental Response Surface Research Articles

Statistical models for predicting the higher heating value of torrefied kesambi leaves

The study investigates the effects of temperature and residence time on the energy density of kesambi leaves through experimental torrefaction, proximate analysis, and response surface methodology with a central composite design (RSM-CCD). The torrefaction process enhances the energy density of kesambi leaves by increasing fixed carbon content while reducing volatile matter. The RSM-CCD models developed in this research are both statistically significant and exhibit robust predictive accuracy for estimating higher heating value (HHV), providing valuable insights into optimal torrefaction conditions. Surface plots effectively illustrate the relationships between HHV, temperature, and residence time, enabling the identification of ideal process parameters. Additionally, a desirability analysis reveals opportunities to enhance correlations between HHV and key measured properties, such as moisture content, ash, and volatile matter. This research makes a significant contribution to understanding and optimising the torrefaction process for kesambi leaves, with practical implications for improving energy density and advancing the development of sustainable biofuel sources. By offering a novel approach to predicting HHV in kesambi leaf-based biofuels, the findings highlight the potential for optimising torrefaction processes to enhance the viability of renewable energy resources. Further research is suggested to refine these predictive models and explore additional factors influencing HHV, aiming to bolster the production of sustainable biofuels.

Enhancing aglycone isoflavones in soymilk through soybean germination and incubation

As a group of important bioactive compounds in soybeans, isoflavones are beneficial to human health, and aglycone isoflavones are more readily absorbed and utilized by the human body. Soymilk is a widely consumed soy-based beverage. The reduction in isoflavones content during soymilk production can lower its nutritional quality. This study aimed to increase the total isoflavones content and the proportion of aglycone isoflavones in soymilk through seeds germination and the followed soymilk incubation. In this study, changes in the isoflavone content and composition of soymilk made from germinated and raw soybeans were detected at different processing stages. Single-factor and response surface experiments were carried out to optimize the incubation conditions, aiming to enhance the content of aglycone isoflavones in soymilk made of germinated soybeans. The results showed that total isoflavones content increased from 3722.23 μg/g DW to 4337.93 μg/g DW in 2-day germinated soybeans, and incubation promoted the conversion of conjugated isoflavones to aglycone isoflavones in soymilk. Under the optimal incubation conditions (53.26 ± 1.0 °C for 56.64 ± 1.0 min), the content of aglycone isoflavones in soymilk significantly increased by 44.43% compared with the control, and the incubation with optimized conditions had little effect on its microbial safety, nutrients content and overall flavor, consequently leading to no significant deterioration in its quality after incubation. Therefore, the combination of germination and incubation is an efficient strategy to enhance the aglycone isoflavones content in soymilk, providing valuable information for enhancing the isoflavones bioactivity of soymilk during processing.

Enhanced operating voltage and desalination performance using ionic liquids as electrolyte for flow electrode capacitive deionisation

Flow-electrode capacitive deionisation (FCDI) technology is a promising approach for desalinating brackish water. Selecting the electrolyte with a high voltage window is essential for improving the FCDI performance. In this study, ionic liquids were used for the first time as a new electrolyte for FCDI systems. The water-desalting efficiency was selected as the evaluation index, and single-factor experiments were conducted on the activated carbon content of electrode slurry, brine flow rate, initial brine concentration, and electrolyte volume ratio, respectively. Box-Behnken design response surface experiments were used and models were constructed to analyse the desalting results of the single factor influence and interaction effects for the aqueous and ionic liquid systems respectively, to determine further the key influencing factors and optimal conditions for the brine desalination in the FCDI system. The results showed that the brine flow rate was the most significant factor affecting the desalination efficiency of the aqueous and ionic liquid FCDI systems (p < 0.0001). The optimal process conditions for the ionic liquid system fitted by the model were as follows: 6.6 wt% activated carbon content in the electrode slurry, a brine flow rate of 45 mL/min, an initial brine concentration of 1 g/L, and an electrolyte ratio of N, N-Dimethylformamide/1-ethyl-3-methylimidazolium tetrafluoroborate = 3. The desalination effect of FCDI under the above optimal process conditions was up to 99.739% at a voltage of 3.5 V, and the water-desalting efficiency was still maintained at over 95% after 20 cycles. Compared with the aqueous electrolyte, using ionic liquid electrolytes significantly improves the desalination rate and cycling stability, and this study provides new ideas and methods for developing and applying high-performance electrolytes in FCDI systems.

Optimizing Carbon Structures in Laser-Induced Graphene Electrodes Using Design of Experiments for Enhanced Electrochemical Sensing Characteristics.

In this study, we explored the morphological and electrochemical properties of carbon-based electrodes derived from laser-induced graphene (LIG) and compared them to commercially available graphene-sheet screen-printed electrodes (GS-SPEs). By optimizing the laser parameters (average laser power, speed, and focus) using a design of experiments response surface (DoE-RS) approach, binder-free LIG electrodes were achieved in a single-step process. Traditional trial-and-error methods can be time-consuming and may not capture the interactions between all variables effectively. To address this, we focused on linear resistance and substrate delamination to streamline the DoE-RS optimization process. Two LIGs, designated LIG A and LIG B, were fabricated using distinct and optimized laser settings, which resulted in a sheet resistance of 25 ± 2 Ω/sq and 21 ± 1 Ω/sq, respectively. These LIGs, characterized by scanning electron microscopy, Raman spectroscopy, and contact angle analysis, exhibited a highly porous morphology with 13% pore coverage and a contact angle <50°, which significantly increased their hydrophilicity when compared to the GS-SPE. For the electrochemical studies, the oxidation of NO2- ion by the graphene-based working electrodes was investigated, as it allowed for the direct comparison of the LIGs to the GS-SPE. These included cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulsed voltammetry studies, which revealed that LIG electrodes displayed a remarkable 500% increase in peak current during NO2- oxidation compared to the GS-SPE. The LIGs also demonstrated improved stability and sensitivity (420 ± 30 and 570 ± 10 nAμM-1 cm-2) compared to the GS-SPE (73 ± 4 nAμM-1 cm-2) in the oxidation of NO2- ions; however, LIG B was more susceptible to ionic interference than LIG A. These findings highlight the value of applying statistical approaches such as DoE-RS to systematically improve the LIG fabrication process, enabling the rapid production of optimized LIGs that outperform conventional carbon-based electrodes.

Engineered production of 5-aminolevulinic acid in recombinant Escherichia coli BL21.

5-aminolevulinic acid (ALA) is a non-protein amino acid that has been widely used in the fields of medicine and agriculture. This study aims to engineer the C5 pathway of the ALA biosynthesis in Escherichia coli BL21 to enhance ALA production. The ALA synthase genes gltX, hemA, and hemL were overexpressed in E. coli BL21 to lead to the increase in the production of ALA. The sRNA RyhB was also overexpressed to downregulate the expression of ALA dehydratase to reduce the downstream bioconversion of ALA to porphobilinogen. Next, the gene arcA was knocked out by CRISPR-Cas9 technology to open the TCA cycle to promote the respiratory metabolism of the strain to reduce the feedback inhibition of heme to ALA. The fermentation conditions of the engineered strain were optimized by response surface experiments. The time-course analysis of the ALA production was carried out in a 1 L shake flask. Through these efforts, the production of ALA in engineered strain reached 2953 mg/L in a 1 L shake flask. This study contributes to the industrial production of ALA by the engineered E. coli in the future.

Optimisation of chemically assisted mechanical polishing process parameters for polycrystalline diamond based on photo-Fenton reaction

Polycrystalline diamond (PCD) has ultra-high thermal conductivity and is suitable for use as a thermal substrate material for semiconductor power devices. However, the high hardness, good wear resistance and chemical inertness of PCD lead to low machining efficiency and poor machined surface quality. Chemically assisted mechanical polishing based on the photo-Fenton reaction enables efficient PCD processing and high surface quality. In this study, Box-Behnken response surface experiments were employed to investigate the influence of the photo-Fenton reaction polishing process parameters (H₂O₂ concentration, light intensity, polishing pressure and abrasive concentration) and their interactions on the polishing process. Regression equations were constructed to model the material removal rate (MRR) and surface roughness (Ra) and to optimise the process parameters. Finally, the polishing mechanism was analysed. The results demonstrated that the effects of polishing pressure, polishing pressure-abrasive concentration, abrasive concentration and H2O2 concentration on the material removal rate were statistically significant. Furthermore, the effects of polishing pressure, H2O2 concentration, abrasive concentration, polishing pressure-abrasive concentration, H2O2 concentration-light intensity and light intensity on the surface roughness were also found to be statistically significant. The optimal process parameters were identified as a light intensity of 150 mW/cm2, a H₂O₂ concentration of 15 wt%, a polishing pressure of 0.89 MPa, and an abrasive concentration of 5 wt%. These parameters yielded a material removal rate of up to 666.9 nm/h and a surface roughness of Ra 2.58 nm. The polishing mechanism of the photo-Fenton reaction on PCD can be described as follows: the photo-Fenton reaction produces •OH, which then oxidises the PCD surface to generate an oxide layer. This layer is subsequently removed by the mechanical action of the abrasive, and the oxidation and mechanical removal continue to occur on the exposed new PCD surface. It has been demonstrated that, under the condition of balance between the mechanical action and the chemical action, a better quality of the surface can be obtained. This paper offers further evidence in support of the use of the photo-Fenton reaction in the context of PCD polishing.

Experimental Investigation and NSGA-III Multi-Criteria Optimization of 60CrMoV18-5 Cold-Work Tool Steel Machinability Under Dry CNC Hard Turning Conditions

This work concerns an experimental investigation dealing with the machinability of 60CrMoV18-5 cold-work tool steel under dry CNC hard turning conditions using a CBN cutting insert. A response surface experiment based on the central composite design was set to conduct dry CNC hard-turning experiments with three different levels for cutting conditions, cutting speed Vc (m/min), feed rate f (mm/rev), and depth of cut α (mm) while selecting main cutting force and surface roughness Ra as the two machinability responses. The results were analyzed by applying analysis of variance (ANOVA). The effect of cutting conditions on main cutting force and surface roughness was studied through contour plots. Full quadratic regression models were generated to model the relationships between inputs and outputs. Finally, the NSGA-III algorithm was applied to simultaneously optimize the selected machinability parameters by providing beneficial values for determining cutting conditions. The results have shown that surface roughness is mainly affected by feed rate and cutting speed, whereas main cutting force is affected by depth of cut and feed rate.

Optimization of fermentation conditions for 3-methylthio-1-propanol production by Saccharomycopsis fibuligera Y1402 in tobacco matrix

3-methylthio-1-propanol (3-Met) is widely used as a flavoring substance in food flavoring. In this study, the fermentation conditions of Saccharomycopsis fibuligera Y1402 for 3-Met production were optimized in the tobacco matrix. Firstly, the optimization of the culture medium components and culture conditions was carried out through a single factor design. Then, a Plackett-Burman design was used to screen out factors that most significantly affected the production of 3-Met by S. fibuligera Y1402. The steepest ascending path design was used to identify the most significant response region. The optimal conditions for the production of 3-Met were determined using the Box-Behnken experimental design and response surface analysis. These conditions included a particle size of tobacco between 60 and 80 mesh, ammonium sulphate as the nitrogen source with a concentration of 2.4 g/L, L-methionine (L-Met) concentration of 3.1 g/L in the nutrient solution, an incubation time of 145 h, a moisture content of 83%, an initial pH of 5.5, a temperature of 29 °C, and an inoculation size of 1.6%. Under these conditions, the production of 3-Met reached 342.07 mg/g of tobacco. When the culture was scaled up, the conversion yield of 3-Met reached 1.07 g/g of tobacco. This suggests that fermenting this strain can increase the amount of 3-Met in tobacco leaves. This research offers a reference value for employing this strain to enhance the flavor components of crushed tobacco leaves, low-quality tobacco leaves, or tobacco stems, facilitating the processing of inferior tobacco leaves.

Study on the mechanical properties of PES-HmA samples printed by selective laser sintering under various pre-heating conditions

The purpose of this study is to investigate the influence of pre-heating characteristics on the mechanical properties and forming process of selective laser sintering (SLS) printed PES-HmA samples. An experimental setup with four heating tubes was designed to study the pre-heating temperature distribution on the powder bed. The pre-heating temperature distribution on the powder bed was captured using a thermal imaging camera. A method for evaluating pre-heating temperature distribution based on the average and standard deviation of surface temperature was proposed. The heating tube installation position was optimized using a response surface experiment study based on the temperature distribution evaluation. By optimizing the installation position of the tubes, the temperature distribution on the powder bed tends to become uniform. The effect of pre-heating temperature value and distribution on the mechanical properties of the SLS printed PES-HmA samples was also experimentally investigated. The cross sectional microstructure of the printed samples were examined by scanning electron microscope to analyze the layer formation process at different pre-heating temperature. By increasing the pre-heating temperature from 70°C to 100°C, the material diffusion at the layers interface was improved, which made the tensile strength of sample increased by 376%, and the flexural strength increased by 224%.

A new enrichment strategy of dissimilatory iron-reducing bacteria for remediation of organic-contaminated river sediments: Process, performance, and mechanism

Dissimilatory iron-reducing bacteria (DIRB) have been widely applied to organic matter metabolism in sediments due to their specific biological properties, which are significantly affected by environmental factors. Until now, there has been no systematic study on applying these effects of environmental factors to DIRB enrichment. In this study, we identified the critical environmental factors through RDA, PLS-PM, and correlation analysis and then adjusted the proportion of these factors (C/Fe, C/N, and Fe/S) through single-factor and response surface experiments to enrich DIRB. The performance of the enriched DIRB in carbon metabolism of organic-rich sediments was analyzed by remediation experiment, and the metabolic mechanism was revealed through iron-reducing performance, community structure, and functional genes. The results showed that the carbon, nitrogen, phosphorus, and sulfur were crucial factors influencing the activity of DIRB in river sediments, and the enriched mud-bacteria mixture containing a large amount of DIRB (referred to as “DMB”) obtained by domestication under C/Fe = 0.492 and C/N = 13.659 showed the highest iron reduction rate of 55.51% ± 2.53%. The DMB exhibited better-sustained removal of total organic matter (TOM), which was higher than the control (MB) by 8.81%. Moreover, we discovered that the enriched DIRB: (1) had a better reduction effect on different Fe(III) forms, especially in carbon-limited and iron-limited conditions. (2) increased in abundance and established a beneficial symbiotic relationship with hydrolytic acidifying bacteria. (3) showed an increased abundance of functional pathways associated with organismal systems and signal processing (such as ABC transporters and Translation). These findings revealed the reasons for the improved efficiency of organic matter metabolism.

Revealing the Potential of Star Anise Essential Oil: Comparative Analysis and Optimization of Innovative Extraction Methods for Enhanced Yield, Aroma Characteristics, Chemical Composition, and Biological Activities.

Star anise has been used for a long time in improving human health and curing diseases, owing to its unlimited components with complex chemical structures and a wide range of bioactivities. This study is aimed to investigate the influence of extraction methods (steam distillation, ethanol Soxhlet extraction, supercritical carbon dioxide extraction, subcritical n-butane extraction) on the yield, aroma properties, chemical composition, and bioactivity of star anise essential oils. Electronic nose detection revealed the essential oils from subcritical extraction exhibited the most intense aroma, while the essential oils from ethanol Soxhlet extraction had a more complex aroma profile. Fourier-transform infrared analysis showed the presence of benzene rings, carbonyl groups, C=C, and aromatic ether bonds in the essential oils extracted through different methods. The major components were heterocyclic olefins, heterocyclic oxygenates, and aromatic oxygenates, as well as certain amounts of flavonoids and polyphenols. Correlation analysis revealed the relative contents of volatile trans-anethole, wormwood, d-limonene, cineole, and trans-α-citronelene were strongly associated with the antibacterial activity of the essential oils. Similarly, the contents of volatile components (d-limonene, cineole) and non-volatile components (total flavonoids and total polyphenols) were strongly correlated with the DPPH scavenging activity of the essential oils. These results confirm the effectiveness of the ethanol Soxhlet extraction method in retaining the bioactivity of the essential oils. Finally, with a Box-Behnken central composite design of response surface and single-factor experiments, the optimal extraction conditions for the ethanol Soxhlet method were determined: ultrasonic frequency of 80 kHz, crushing particle size of 60 meshes, liquid-material ratio of 8:1 (mL:g), and ultrasonic time of 35 min. Under these conditions, the essential oil yield was 25.51% ± 0.21%. Overall, these findings highlight the significance of extraction methods in obtaining high-quality star anise essential oils with desirable aroma properties and potent bioactivities.

PbWO4 improved the efficient photocatalytic adsorption and degradation of tetracycline and doxycycline by Cu2O

Cu2O/PbWO4 was prepared via a mechanical composite method, demonstrating that polyhedral Cu2O was deposited on coral-like and rod-shaped PbWO4. Cu2O/PbWO4 exhibited superior photoelectric performance compared to Cu2O and PbWO4, reaching a photocurrent and photovoltage reached of 0.0518 mA·cm−2 and 0.00133 V, respectively. Cu2O/PbWO4 achieved 92.4 % and 97.6 % tetracycline and doxycycline degradation within 60 min under visible light, respectively, and >83 % tetracycline degradation continued to be achieved after 5 cycles. The enhanced photocatalytic performance of Cu2O/PbWO4 compared to Cu2O was mainly attributed to the formation of heterojunctions, which increased the charge transfer rate, effectively improving charge lifetime and separation efficiency. The response surface experiments demonstrated that optimal tetracycline degradation (96.4 %) could be achieved using 37.5 mg·L−1 tetracycline and 18.3 mg Cu2O/PbWO4 at a solution pH of 7.1. Four possible tetracycline degradation pathways were proposed and 14 degradation intermediates were detected, which were further degraded into low-molecular-weight substances such as CO2 and H2O through further photocatalytic reactions.

Study on the Optimization of Culture Parameters of Oxygen-Consuming Bacterium for Preventing CSC and Its Effect on the Coal Oxidation Characteristic

ABSTRACT Microorganisms can work together to prevent coal spontaneous combustion (CSC) by consuming oxygen and changing coal oxidation characteristics. In order to explore the influence of oxygen-consuming microorganisms on coal spontaneous combustion characteristics, a highly oxygen-consuming bacterium was isolated and identified from the soil near mine drainage, named ZQ-1. The oxygen consumption characteristics of microorganisms were investigated and optimized by single-factor and response surface experiments. Further, the effect of microorganisms on CSC was analyzed from both macroscopic and microscopic perspectives by using programmed warming, simultaneous thermal analysis, and Fourier-transform infrared spectroscopy (FTIR). The results revealed that the isolated bacterium was Pseudomonas aeruginosa. Its optimal culture conditions were pH = 6.98, temperature 28.15°C, and carbon nitrogen ratio (C/N) = 12.94 when the oxygen consumption rate was maximum. After bacterial action, coal showed a decrease in the release of the indicator gas CO during the combustion process, a delay in the cross point temperature (CPT) by 18.63°C, and an increase in the residual mass at the end of combustion. In addition, the average activation energy of the coal samples in the oxidative combustion stage was increased by 2.05721 kJ/mol. Finally, the FTIR results showed that microorganisms were able to destroy the reactive groups in the coal samples, especially hydroxyl, aliphatic hydrocarbon, and oxygen-containing functional groups, which resulted in the inhibition of CSC. This paper has important theoretical research value and practical significance for CSC prevention and control.

Production-optimized fermentation of antifungal compounds by bacillus velezensis LZN01 and transcriptome analysis.

Fusarium wilt is one of the major constraints on global watermelon production, and Fusarium oxysporum f. sp. niveum (Fon) is the causative agent of Fusarium wilt in watermelon and results in severe yield and quality losses worldwide. The enhancement of antifungal activity from antagonistic bacteria against Fon is highly practical for managing Fusarium wilt in watermelon. The aim of this study was to maximize the antifungal activity of Bacillus velezensis LZN01 by optimizing fermentation conditions and analysing its regulatory mechanism via transcriptome sequencing. The culture and fermentation conditions for strain LZN01 were optimized by single-factor and response surface experiments. The optimum culture conditions for this strain were as follows: the addition of D-fructose at 35 g/L and NH4Cl at 5 g/L in LB medium, pH 7, and incubation at 30°C for 72 h. The fungal inhibition rate for strain LZN01 reached 71.1%. The improvement of inhibition rate for strain LZN01 in optimization fermentation was supported by transcriptomic analysis; a total of 491 genes were upregulated, while 736 genes were downregulated. Transcriptome analysis revealed that some differentially expressed genes involved in carbon and nitrogen metabolism, oxidation-reduction, fatty acid and secondary metabolism; This optimization process could potentially lead to significant alterations in the production levels and types of antimicrobial compounds by the strain. Metabolomics and UPLC/Q-Exactive Orbitrap MS analysis revealed that the production yields of antimicrobial compounds, such as surfactin, fengycin, shikimic acid, and myriocin, increased or were detected in the cell-free supernatant (CFS) after the fermentation optimization process. Our results indicate that fermentation optimization enhances the antifungal activity of the LZN01 strain by influencing the expression of genes responsible for the synthesis of antimicrobial compounds.

Failure analysis-based mass reduction of an aluminium alloy engine mounting bracket using Design of Experiments approach

In this study, mass reduction of an engine mounting bracket has been performed without changing the failure mode. Firstly, failure modes were determined experimentally using failure loads provided by the vehicle manufacturer. Then critical stress concentration areas and suitable mass reduction regions were determined by using Finite Element Analysis (FEA) for these load cases. A structural optimisation process was carried out using Design of Experiment-Response Surface Methodology (DOE-RSM) to minimise the mass while keeping the failure load as constant as possible. When the stress values obtained from the preliminary structure are compared with the values obtained from the optimised part, it was seen that this target has been mostly achieved. A total mass reduction of 4.31 % was achieved in the new part through failure mode analysis. Furthermore, it was found that a financial saving of 129,000 Euro could also be achieved.

Prediction and optimization of wet bulb efficiency in solar energy-based novel evaporative cooling system: Response Surface Method Approach

Abstract The wet bulb efficiency is an essential parameter in performance of Indirect evaporative cooling systems, as it impacts efficiently cool air while minimizing energy usage. This paper focuses on model and optimize multi tubular type wet channel for indirect evaporative cooler system. The optimized wet bulb efficiency based on Box-Behnken experimental design model and response surface method. The methodology included predicting and optimizing input process and working flow parameters of indirect evaporative cooling system to maximize wet bulb efficiency. A quadratic model of response surface method was used to evaluate influence of each factor on wet bulb efficiency, which was validated through analysis of variance results. The study found a maximum WBE of 89.65% under specific conditions, with a relative error of 3.25% between predicted and experimental result. This optimization process, governed by RSM, determined essential parameters for enhancing efficiency of system. These parameters include inlet process temperature of 28°C, working air velocity of 3.5 m/s, relative humidity of 45%, and inlet working air temperature of 24°C. These results demonstrate practical significance of current research, providing useful insights for optimal design and optimization of indirect evaporative cooling systems to fulfil cooling requirements while minimising energy consumption.

Low-carbon treatment and remediation of oil sludge in mid-to-high latitude regions: A coupled approach of freeze-thaw and supercritical CO2 extraction

The oil sludge produced while extracting large oil and gas fields in the middle and high latitude regions has caused serious pollution to the surrounding soil. The key to solving this problem in the future is to unify the remediation of soil and the treatment of oil sludge. This study uses supercritical carbon dioxide(scCO2) technology to construct a low-carbon method, providing a new approach to achieve this goal. The study determines the optimal extraction conditions for black calcareous soil with 15% oil content to be 55 °C, 25 MPa, and 90 min through single factor and response surface experiments. Experiments on the scCO2 extraction coupled with freeze-thaw cycles show that oil sludge with a water content of 10% can improve the extraction efficiency of scCO2 by about 2.69% after less than five freeze-thaw cycles. The study also compares the extraction efficiency of the four soils, with a difference of 6.03% observed under the same conditions. Additionally, we analyze the impact of the extraction process on changes in the properties of the oil and soil in the oil sludge. Comprehensive tests, including scanning electron microscope (SEM), nutrient detection, X-ray powder diffractometer (XRD), fourier transform infrared spectroscopy (FTIR), and Gas Chromatography (GC), have been conducted. Results show that standalone scCO2 extraction can remove up to 98.2% of petroleum hydrocarbons from the oil sludge, while simultaneously causing small changes to the soil microstructure and the crystal structure of the oil sludge. Furthermore, this process does not lead to a significant depletion of key nutrients or the generation of new pollutants.

Particle Size Effect on Anaerobic Digestion of Fruit and Vegetable Waste

During the anaerobic digestion (AD) of fruit and vegetable waste (FVW), excessive particle size reduction can lead to the overproduction and inhibition of methanogenic microorganisms. This paper presents an in-depth analysis through experimental assays, modeling, and response surface analysis of the effect of particle size on methane production. A simple model was proposed considering the inhibition of the growth of methanogenic microorganisms and surface-based hydrolysis kinetics. The model parameters were estimated using experimental data from batch systems fed with FVW of varying particle sizes (ranging from 1.8 to 1000 μm). Response surface methodology establishes a statistical model for estimating methane production based on particle size and concentration. Numerical and statistical analyses were conducted using Matlab R2024a and Minitab 24 software. A model with an R2 of 0.89 was obtained, which determined an optimal concentration of 8.2 kg·m−3 and a particle size of 742.3 μm, yielding a methane production of 303.3 m3·kg−1 VS, similar to the experimentally obtained range of 300.95 to 316.7 m3·kg−1 VS.

Study on Optimal Production Conditions of Fibrinolytic Kinase Derived from the Nereid Worm, Perinereis aibuhitensis Grub

The fibrinolytic kinase identified in the nereid worm (Perinereis aibuhitensis Grub) displays exceptional kinase activity, stability, and specificity, suggesting its potential as a promising candidate for the advancement of new thrombolytic drugs. In this study, a process was optimized for the production of fibrinolytic kinase using Escherichia coli, and the effects of factors such as inoculum, pH, OD, temperature, inducer concentration, and time on the protein yield were investigated. The optimum points of key parameters were determined by single-factor experiments, and the initial pH, OD, and time were determined to be significant by PB (Plackett–Burman design) with six factors at two levels of experiments. The response surface experiments highlighted the key roles of initial pH and induced OD values, and the convergence of the model and experimental data confirmed the optimal conditions and reasonable fluctuation intervals, which proved the reliability of the model.

Application of Immobilized Microorganism Gel Beads in Black-Odor Water with High Nitrogen and Phosphorus Removal Performance

Black-odor water, which is caused by the excessive accumulation of nitrogen and phosphorus in water, is a significant problem. Immobilized microorganisms are considered to be an effective technical solution, but there are still many key parameters to be determined, such as organic matter dissolution, insufficient stability, and insufficient phosphorus removal capacity, among other problems. In this study, the optimum raw material ratios of immobilized microorganism gel beads were determined by means of a response surface experiment. The optimal ratio of raw materials was 5% polyvinyl alcohol (PVA), 1% sodium alginate (SA), and 6% bacterial powder. In addition, the nitrogen and phosphorus removal performance of the materials was improved by loading inorganic compounds, such as 0.5 wt.% zeolite, 0.5 wt.% iron powder, and 0.2 wt.% activated carbon. Tolerance analysis determined that these gel beads could maintain a good performance in a series of harsh environments, such as during intense agitation, at high temperatures, and at low pH values, etc. The total nitrogen (TN), ammonia nitrogen (NH3-N), and phosphorus (TP) removal efficiencies were 88.9%, 90%, and 95%.