Facile Preparation and Study of Self-healing Water-absorbing Expanding Elastomers.

The absorbent expansion elastomer plays a crucial role in engineering sealing and holds a promising future in this field as infrastructure continues to develop. Traditional materials have their limitations, especially when used in large construction projects where the integrity and reliability of the material are of utmost importance. In this work, a self-healing water-absorbing expansion elastomer was developed for continuous production at a large scale to monitor the sealing conditions of massive infrastructure projects. At room temperature, the material exhibited a repairing efficiency of 57.77% within 2 h, which increased to 84.02% after 12 h. This extended reaction time allowed for effective repairs when defects were detected. The material's strength reached approximately 3 MPa, making it suitable for a wide range of applications. The volume expansion rate of the material reached 200-400% for effective sealing, and the fictionalization of the packing made it have a good external force sensing effect and prevent heat build-up effect. The conductive detection performance of the absorbent expansion elastomer was improved by utilizing triple self-healing strategies, including dipole-dipole interaction, ion cross-linked network, and externally-aided restoration materials.

Designing Fast-Moving Antibacterial Microtorpedoes to Treat Lethal Bacterial Biofilm Infections.

Engineering fast-moving microrobot swarms that can physically disassemble bacterial biofilms and kill the bacteria released from the biofilms is a promising way to combat bacterial biofilm infections. Here, we report electrochemical design of Ag7O8NO3 microtorpedoes with outstanding antibacterial performance and meanwhile capable of moving at speeds of hundreds of body lengths per second in clinically used H2O2 aqueous solutions. These fast-moving antibacterial Ag7O8NO3 microtorpedoes could penetrate into and disintegrate the bacterial biofilms and, in turn, kill the bacteria released from the biofilms. Based on the understanding of the growth behavior of the microtorpedoes, we could fine-tune the morphology of the microtorpedoes to accelerate the moving speed and increase their penetration depth into the biofilms simply via controlling the potential waveforms. We further developed an automatic shaking method to selectively peel off the uniformly structured microtorpedoes from the electrode surface, realizing continuous electrochemical production of the microtorpedoes. Animal experiments proved that the microtorpedo swarms greatly increased the survival rate of the mice infected by lethal biofilms to >90%. We used the electrochemical method to design and massively produce uniformly structured fast-moving antibacterial microtorpedo swarms with application potentials in treatment of lethal bacterial biofilm infections.

Analytical comparison between batch and continuous direct compression processes for pharmaceutical manufacturing using an innovative UV-Vis reflectance method and chemometrics.

Advancements in industrial technologies and the application of quality by design (QbD) guidelines are shifting the attention of manufacturers towards innovative production techniques. In the pharmaceutical field, there is a significant focus on the implementation of continuous processes, in which the production stages are carried out continuously, without the need to interrupt the process and store the production intermediates, as in traditional batch production. Such innovative production techniques also require the development of proper analytical methods able to analyze the products in-line, while still being processed. The present study aims to compare a traditional batch manufacturing process with an alternative continuous one. To this end, a real pharmaceutical formulation was used, substituting the active pharmaceutical ingredient (API) with riboflavin, at the concentration of 2 %w/w. Moreover, a direct and non-destructive analytical method based on UV-Vis reflectance spectroscopy was applied for the quantification of riboflavin in the final tablets, and compared with a traditional absorbance analysis. Good results were obtained in the comparison of both the two manufacturing processes and the two analytical methods, with R2 higher than 0.9 for all the calculated calibration models and predicted riboflavin concentrations that never significantly overcame the 15 % limits recommended by the pharmacopeia. The continuous production method demonstrated to be as reliable as the batch one, allowing to save time and money in the production step. Moreover, UV-Vis reflectance was proved to be an interesting alternative to absorption spectroscopy, which, with the proper technology, could be implemented for in-line process control.

Synergistic effect of stereo-complexation and interfacial compatibility in ammonium polyphosphate grafted polylactic acid fibers for simultaneously improved toughness and flame retardancy.

Flammability and poor toughness of unmodified PLA limit its applications in various fields. Though ammonium polyphosphate (APP) is a green and effective flame retardant, it has poor compatibility with the matrix, leading to a decrease in mechanical properties. Stereo-complexation greatly improves the strength and heat resistance of traditional PLA. However, the effect of flame retardants on the formation of stereo-complexed crystals and the impact of stereo-complexation on flame retardancy have not been studied previously. In this research, PDLA chains were first in-situ reacted with APP particles for improved interfacial compatibility. By utilizing the characteristic of PLA enantiomers that can form stereo-complexed crystals, near-complete stereo-complexed PLA fibers with flame retardancy were produced via clean and continuous melt spinning. The compatibility between PDLA-g-APP and PLLA matrix was studied by SEM, rheological analyses and DSC. Strength and flexibility of the fibers were simultaneously enhanced compared to traditional PLA due to the synergistic effect of interfacial compatibility and stereo-complexation. Compared to traditional PLA, the peak heat release rate and total heat release in microcalorimetry test were reduced by 33 % and 22 %, respectively. The flame-retardant fibers achieved a V-0 rating in the UL-94 test, and an increase in LOI value from 19.4 % to 28.2 %.

Continuous Production of Functionalized Graphene Inks by Soft Solution Processing.

The continuous production of high-quality, few-layer graphene nanosheets (GNSs) functionalized with nitrogen-containing groups was achieved via a two-stage reaction method. The initial stage produces few-layer GNSs by utilizing our recently developed glycine-bisulfate ionic complex-assisted electrochemical exfoliation of graphite. The second stage, developed here, uses a radical initiator and nitrogen precursor (azobisisobutyronitrile) under microwave conditions in an aqueous solution for the efficient nitrogen functionalization of the initially formed GNSs. These nitrile radical reactions have great advantages in green chemistry and soft processing. Raman spectra confirm the insertion of nitrogen functional groups into nitrogen-functionalized graphene (N-FG), whose disorder is higher than that of GNSs. X-ray photoelectron spectra confirm the insertion of edge/surface nitrogen functional groups. The insertion of nitrogen functional groups is further confirmed by the enhanced dispersibility of N-FG in dimethyl formamide, ethylene glycol, acetonitrile, and water. Indeed, after the synthesis of N-FG in solution, it is possible to disperse N-FG in these liquid dispersants just by a simple washing-centrifugation separation-dispersion sequence. Therefore, without any drying, milling, and redispersion into liquid again, we can produce N-FG ink with only solution processing. Thus, the present work demonstrates the 'continuous solution processing' of N-FG inks without complicated post-processing conditions. Furthermore, the formation mechanism of N-FG is presented.

Gamma-Glutamylcysteine Production Using Phytochelatin Synthase-Like Enzyme Derived from Nostoc sp. Covalently Immobilized on a Cellulose Carrier.

Gamma-glutamylcysteine (γ-EC) is an intermediate generated in the de novo synthesis of glutathione (GSH). Recent studies have revealed that the administration of γ-EC shows neuroprotective effects against oxidative stress in age-related disorders and chronic diseases like Alzhiemer's disease in model animals, which is not expected function in GSH. A phytochelatin synthase-like enzyme derived from Nostoc sp. (NsPCS) mediates γ-EC synthesis from GSH. To achieve low-cost and stable commercial level supply, the availability of immobilized NsPCS for γ-EC production was investigated in this study. Among the tested immobilization techniques, covalent binding to the cellulose carrier was most effective, and could convert GSH completely to γ-EC without decreasing the yield. The stable conversion of γ-EC from 100 mM GSH was achieved by both batch repeated and continuous reactions using the immobilized NsPCS on cellulose sheet and column shape monolith, respectively. The immobilization of NsPCS on those carriers is promising alternative technique for high-yielding and cost-effective production of γ-EC on its commercial applications.

Electrochemical Reactors for Continuous Decentralized H2 O2 Production.

The global utilization of H2 O2 is currently around 4 million tons per year and is expected to continue to increase in the future. H2 O2 is mainly produced by the anthraquinone process, which involves multiple steps in terms of alkylanthraquinone hydrogenation/oxidation in organic solvents and liquid-liquid extraction of H2 O2 . The energy-intensive and environmentally unfriendly anthraquinone process does not meet the requirements of sustainable and low-carbon development. The electrocatalytic two-electron (2 e- ) oxygen reduction reaction (ORR) driven by renewable energy (e.g. solar and wind power) offers a more economical, low-carbon, and greener route to produce H2 O2 . However, continuous and decentralized H2 O2 electrosynthesis still poses many challenges. This Minireview first summarizes the development of devices for H2 O2 electrosynthesis, and then introduces each component, the assembly process, and some optimization strategies.

In Vitro and In Vivo Studies of a Verapamil-Containing Gastroretentive Solid Foam Capsule.

Gastroretentive systems may overcome problems associated with incomplete drug absorption by localized release of the API in the stomach. Low-density drug delivery systems can float in the gastric content and improve the bioavailability of small molecules. The current publication presents verapamil-HCl-containing solid foam prepared by continuous manufacturing. Production runs were validated, and the foam structure was characterized by micro-CT scans and SEM. Dissolution properties, texture changes during dissolution, and floating forces were analyzed. An optimized formulation was chosen and given orally to Beagle dogs to determine the pharmacokinetic parameters of the solid foam capsules. As a result, a 12.5 m/m% stearic acid content was found to be the most effective to reduce the apparent density of capsules. Drug release can be described by the first-order model, where 70% of verapamil dissolved after 10 h from the optimized formulation. The texture analysis proved that the structures of the solid foams are resistant. Additionally, the floating forces of the samples remained constant during their dissolution in acidic media. An in vivo study confirmed the prolonged release of the API, and gastroscopic images verified the retention of the capsule in the stomach.

Biocatalysis in Continuous-Flow Microfluidic Reactors.

The implementation of continuous-flow transformations in biocatalysis has received remarkable attention in the last few years. Flow microfluidic reactors represent a crucial technological tool that has catalyzed this trend by promising tremendous improvement in biocatalytic processes across a host of different levels, including bioprocess development, intensification of reactions, implementation of new methods of reaction screening, and enhanced reaction scale-up. However, the full realization of this promise requires a synergy between these biocatalytic reaction features and the design and operation of microfluidic reactors. Here an overview on the different applications of flow biocatalysis is provided according to the format of the enzyme used: free vs immobilized form. Until now, flow biocatalysis has been implemented on a case-by-case approach but challenges and limitations are discussed in order to be overcome, and making continuous-flow microfluidic reactors as universal tool a reality.

Efficient enzymatic synthesis of L-ascorbyl palmitate using Candida antarctica lipase B-embedded metal-organic framework.

The Candida antarctica lipase B (CALB) was embedded in the metal-organic framework, zeolitic imidazolate framework-8 (ZIF-8), and applied in the enzymatic synthesis of L-ascorbic acid palmitate (ASP) for the first time. The obtained CALB@ZIF-8 achieved the enzyme loading of 80 mg g-1 with 11.3 U g-1 (dry weight) unit activity, 59.8% activity recovery, and 92.7% immobilization yield. Under the optimal condition, ASP was synthesized with over 75.9% conversion of L-ascorbic acid in a 10-batch reaction. Continuous synthesis of ASP was subsequently performed in a packed bed bioreactor with an outstanding average space-time yield of 58.1 g L-1  h-1 , which was higher than ever reported continuous ASP biosynthesis reactions.

In Vitro Biosynthesis of Isobutyraldehyde Through the Establishment of a One-Step Self-Assembly-Based Immobilization Strategy.

The in vitro biosynthesis of high-value compounds has become popular and attractive. The convenient and simple strategy of enzyme immobilization has been significant for continuous and efficient in vitro biosynthesis. On the basis of that, this work established a one-step self-assembly-based immobilization strategy to efficiently biosynthesize isobutyraldehyde in vitro. Isobutyraldehyde is a crucial precursor for the synthesis of foods and spices. The established CipA scaffold-based strategy can express and immobilize enzymes at the same time, and purification requires only one centrifugation step. Structural simulations indicated that this scaffold-dependent self-assembly did not influence the structure or catalytic mechanisms of the isobutyraldehyde production-related enzymes leucine dehydrogenase (LeuDH) and ketoisovalerate decarboxylase (Kivd). Immobilized LeuDH and Kivd displayed a higher conversion capacity and thermal stability than the free enzymes. Batch conversion experiments demonstrated that the recovered immobilized LeuDH and Kivd have similar conversion capacities to the enzymes used in the first round of reaction. The continuous production of isobutyraldehyde was achieved by filling the immobilized enzymes into the column of a constructed device. This study not only expands the application range of self-assembly systems but also provides guidance for the in vitro production of value-added compounds.

A high cell density perfusion process for Modified Vaccinia virus Ankara production: Process integration with inline DNA digestion and cost analysis.

By integrating continuous cell cultures with continuous purification methods, process yields and product quality attributes have been improved over the last 10 years for recombinant protein production. However, for the production of viral vectors such as Modified Vaccinia virus Ankara (MVA), no such studies have been reported although there is an increasing need to meet the requirements for a rising number of clinical trials against infectious or neoplastic diseases. Here, we present for the first time a scalable suspension cell (AGE1.CR.pIX cells) culture-based perfusion process in bioreactors integrating continuous virus harvesting through an acoustic settler with semi-continuous chromatographic purification. This allowed obtaining purified MVA particles with a space-time yield more than 600% higher for the integrated perfusion process (1.05 × 1011 TCID50 /Lbioreactor /day) compared to the integrated batch process. Without further optimization, purification by membrane-based steric exclusion chromatography resulted in an overall product recovery of 50.5%. To decrease the level of host cell DNA before chromatography, a novel inline continuous DNA digestion step was integrated into the process train. A detailed cost analysis comparing integrated production in batch versus production in perfusion mode showed that the cost per dose for MVA was reduced by nearly one-third using this intensified small-scale process.

Leloir glycosyltransferases enabled to flow synthesis: Continuous production of the natural C-glycoside nothofagin.

C-glycosyltransferase (CGT) and sucrose synthase (SuSy), each fused to the cationic binding module Zbasic2 , were co-immobilized on anionic carrier (ReliSorb SP400) and assessed for continuous production of the natural C-glycoside nothofagin. The overall reaction was 3'-C-ß-glycosylation of the polyphenol phloretin from uridine 5'-diphosphate (UDP)-glucose that was released in situ from sucrose and UDP. Using solid catalyst optimized for total (∼28 mg/g) as well as relative protein loading (CGT/SuSy = ∼1) and assembled into a packed bed (1 ml), we demonstrate flow synthesis of nothofagin (up to 52 mg/ml; 120 mM) from phloretin (≥95% conversion) solubilized by inclusion complexation in hydroxypropyl ß-cyclodextrin. About 1.8 g nothofagin (90 ml; 12-26 mg/ml) were produced continuously over 90 reactor cycles (2.3 h/cycle) with a space-time yield of approximately 11 mg/(ml h) and a total enzyme turnover number of up to 2.9 × 103 mg/mg (=3.8 × 105 mol/mol). The co-immobilized enzymes exhibited useful effectiveness (∼40% of the enzymes in solution), with limitations on the conversion rate arising partly from external liquid-solid mass transfer of UDP under packed-bed flow conditions. The operational half-life of the catalyst (∼200 h; 30°C) was governed by the binding stability of the glycosyltransferases (≤35% loss of activity) on the solid carrier. Collectively, the current study shows integrated process technology for flow synthesis with co-immobilized sugar nucleotide-dependent glycosyltransferases, using efficient glycosylation from sucrose via the internally recycled UDP-glucose. This provides a basis from engineering science to promote glycosyltransferase applications for natural product glycosides and oligosaccharides.

Process Optimization for the Continuous Production of a Gastroretentive Dosage Form Based on Melt Foaming.

Several drugs have poor oral bioavailability due to low or incomplete absorption which is affected by various effects as pH, motility of GI, and enzyme activity. The gastroretentive drug delivery systems are able to deal with these problems by prolonging the gastric residence time, while increasing the therapeutic efficacy of drugs. Previously, we developed a novel technology to foam hot and molten dispersions on atmospheric pressure by a batch-type in-house apparatus. Our aim was to upgrade this technology by a new continuous lab-scale apparatus and confirm that our formulations are gastroretentive. At first, we designed and built the apparatus and continuous production was optimized using a Box-Behnken experimental design. Then, we formulated barium sulfate-loaded samples with the optimal production parameters, which was suitable for in vivo imaging analysis. In vitro study proved the low density, namely 507 mg/cm3, and the microCT record showed high porosity with 40 µm average size of bubbles in the molten suspension. The BaSO4-loaded samples showed hard structure at room temperature and during the wetting test, the complete wetting was detected after 120 min. During the in vivo study, the X-ray taken showed the retention of the formulation in the rat stomach after 2 h. We can conclude that with our device low-density floating formulations were prepared with prolonged gastric residence time. This study provides a promising platform for marketed active ingredients with low bioavailability.

Recovery of carbon black from waste tire in continuous commercial rotary kiln pyrolysis reactor.

Environmental problems caused by waste tires have become so glaring that it has attracted wide attention. This case study seeks to examine the properties of carbon black from waste tires continuous commercial scale pyrolysis. This work aims to contribute to this growing area of research by exploring the difference between the properties of products under the condition of mass production and those under the condition of laboratory scale or pilot scale production. A pyrolysis prototype, with a waste tire mass flow rate of 50-60 t d-1 was constructed and introduced. Steel-included tire granulates were pyrolyzed in micro-negative pressure furnace at about 420 ± 20 °C. This kind of nonstripping, micro-negative pressure and low-temperature continuous thermal pyrolysis technology can reduce the stripping process between rubber and steel wire, reduce the requirement of equipment sealing, and improve the utilization rate of resources. All three products including pyrolytic carbon black (CBp), tire pyrolysis oil (TPO) and pyrolysis gas showed good characteristics. Pyrolysis gas had been successfully re-used for pyrolysis furnaces and dryers. The higher heating value of TPO estimated to 37-40 MJ/ kg, which was comparable to diesel fuel through further treatment. Results of proximate analysis, element analysis, XPS, FTIR, XRD and surface structure confirmed that CBp with commercial scale production showed no apparent data difference with those in other small scale research cases. The morphological changes of carbon black particles were suggested, revealing a possible internal structure of CBp aggregates in commercial scale pyrolysis. This study is an attempt to push the existing research in this field to commercial production. This work generates fresh insight into the viability of continuous commercial pyrolysis and demonstrates the feasibility of the operation, providing reference for many researchers and units who study the pyrolysis technology of waste tires with the feasibility of industrial production.

Continuous production of fructooligosaccharides by recycling of the thermal-stable ß-fructofuranosidase produced by Aspergillus niger.

OBJECTIVE: To achieve continuous production of fructooligosaccharides (FOS) by recycling of the mycelial cells containing the thermal-stable ß-fructofuranosidase in Aspergillus niger without immobilization. RESULTS: The thermal-stable ß-fructofuranosidase FopA-V1 was successfully expressed in A. niger ATCC 20611 under the control of the constitutive promoter PgpdA. The engineered A. niger strain FV1-11 produced the ß-fructofuranosidase with improved thermostability, which remained 91.2% of initial activity at 50 °C for 30 h. Then its mycelial ß-fructofuranosidase was recycled for the synthesis of FOS. It was found that the enzyme still had 79.3% of initial activity after being reused for six consecutive cycles, whereas only 62.3% ß-fructofuranosidase activity was detected in the parental strain ATCC 20611. Meanwhile, the FOS yield of FV1-11 after six consecutive cycles reached 57.1% (w/w), but only 51.0% FOS yield was detected in ATCC 20611. CONCLUSIONS: The thermal-stable ß-fructofuranosidase produced by A. niger can be recycled to achieve continuous synthesis of FOS with high efficiency, providing a powerful and economical strategy for the industrial production of FOS.

Production of Modified Vaccinia Ankara Virus by Intensified Cell Cultures: A Comparison of Platform Technologies for Viral Vector Production.

Modified Vaccinia Ankara (MVA) virus is a promising vector for vaccination against various challenging pathogens or the treatment of some types of cancers, requiring a high amount of virions per dose for vaccination and gene therapy. Upstream process intensification combining perfusion technologies, the avian suspension cell line AGE1.CR.pIX and the virus strain MVA-CR19 is an option to obtain very high MVA yields. Here the authors compare different options for cell retention in perfusion mode using conventional stirred-tank bioreactors. Furthermore, the authors study hollow-fiber bioreactors and an orbital-shaken bioreactor in perfusion mode, both available for single-use. Productivity for the virus strain MVA-CR19 is compared to results from batch and continuous production reported in literature. The results demonstrate that cell retention devices are only required to maximize cell concentration but not for continuous harvesting. Using a stirred-tank bioreactor, a perfusion strategy with working volume expansion after virus infection results in the highest yields. Overall, infectious MVA virus titers of 2.1-16.5 × 109  virions/mL are achieved in these intensified processes. Taken together, the study shows a novel perspective on high-yield MVA virus production in conventional bioreactor systems linked to various cell retention devices and addresses options for process intensification including fully single-use perfusion platforms.

Continuous Production of Water-Borne Polyurethanes: A Review.

Water-borne polyurethanes are novel functional polymers that use water as the dispersion medium. When compared with solvent-borne polyurethanes, water-borne polyurethanes are more environmentally friendly and easier to transport and store. Water-borne polyurethanes have attracted increasing attention due to their extensive applications in plastics, paints, adhesives, inks, biomaterials, and other fields. In this study, the characteristics of water-borne polyurethanes were discussed, followed by a review of studies detailing reaction procedures and mechanisms for their continuous production. Additionally, current and future applications of continuous production processes for water-borne polyurethanes are presented.

Production of L-alanyl-L-glutamine by immobilized Escherichia coli expressing amino acid ester acyltransferase.

Production of Ala-Gln by the E. coli expressing α-amino acid ester acyltransferase was a promising technical route due to its high enzyme activity, but the continuous production ability still needs to improve. Therefore, the immobilized E. coli expressing α-amino acid ester acyltransferase was applied for the continuous production of Ala-Gln. Four materials were selected as embedding medium for the whole cell entrapment of recombinant bacteria. Calcium alginate beads were found to be the most proper entrapment carrier for production of Ala-Gln. The temperature, pH, and repeatability of the immobilized cell were compared with free cells. Results showed that immobilization cell could maintain a wider range of temperature/pH and better stability than free cell (20-35 °C/pH 8.0-9.0, and 25 °C/pH 8.5, respectively). On this basis, continuous production strategy was put forward by filling the immobilized cell in the tubular reactor with multiple control conditions. The Ala-Gln by immobilization cell achieved the productivity of 2.79 mg/(min*mL-CV) without intermittent time. Consequently, these findings suggest that the immobilization technique has potential applications in the production of Ala-Gln by biotechnological method. KEY POINTS: • Immobilization helps to achieve high efficiency production of Ala-Gln. • Immobilized cells have better stability than free cells. • Sodium alginate is the most suitable immobilized material.

Acidogenic fermentation of food waste for production of volatile fatty acids: Bacterial community analysis and semi-continuous operation.

Acidogenic fermentation of food waste for production of volatile fatty acids (VFAs) contributes to both food waste minimization and resource recovery. To gain knowledge on functional bacterial communities and facilitate continuous production of VFAs, this research firstly studied the effects of initial pH values (i.e. 5, 6 and 7) and temperatures (i.e. 35 °C and 55 °C) on VFAs production, distribution, and bacterial communities during acidogenic fermentation of food waste. The optimal conditions were determined as pH 7 and 35 °C, corresponding to the highest total VFAs yield of 11.8 g COD/L with major components of acetic, propionic and butyric acid. Bioinformatic analysis showed that the relative abundance of the dominant bacterial classes (e.g. Clostridia, Bacteroidia and Bacilli) were changed by the initial pH values in both mesophilic and thermophilic reactors. NMDS analysis confirmed a significant difference between mesophilic and thermophilic communities. Finally, the feasibility of continuous production and recovery of VFAs was validated using a two-phase leachate bed bioreactor at the optimal conditions. Average concentration and yield of the total VFAs in the continuous operation were 6.3 g COD/L and 0.29 g VFA/g VSadded, respectively. The findings in this study could provide pivotal technical supports for potential pilot- and commercial-scale biorefinery plants for VFAs production from food waste.