Corrigendum: Combination effect of engineered endolysin EC340 with antibiotics.

[This corrects the article DOI: 10.3389/fmicb.2022.821936.].

Effect of thermal characteristics on the chemical quality of real-brine treatment through hydrophilic fiber-based low-grade heat-powered humidification-dehumidification process.

Considering the increasing demand for desalination plants and their byproduct brine, this study investigated a humidification-dehumidification (HDH) system for treating membrane distillation-generated real high-salinity brine using low-grade heat (45-70 ℃) to explore its feasibility for sustainable energy-efficient minimal liquid discharge. A novel super-hydrophilic fabric was adopted for accelerated humidification, and its impact on brine droplet miscarriage characteristics was evaluated. The influence of the operating fluid thermal properties (cycle 1: air preheating; cycle 2: air and brine dual-fluid preheating; and cycle 3: air post-heating after humidification) on the brine treatment efficiency, energy consumption, and chemical quality of freshwater produced was analyzed in detail to establish their characteristic nexus. It was identified that, during humidification, increasing the brine temperature (up to 55 ℃) influenced its ionic mobility, thereby promoting efficient separation of the salts/minerals and contributing to achieving better freshwater quality. Furthermore, although cycle 3 exhibited improved system thermal efficiency (gained output ratio equal to 1.77), its non-preheated air contributed to a negative effect of the reduced humidity ratio (∼17 g/kg), leading to a lower freshwater productivity of 67% than that of cycle 2 (29 g/kg and 70%). The present study also illustrates a novel effect of evaporative deposition occurring due to air-water interaction on the fabric humidifier surface, with an exploration of its effect on reducing freshwater chemical quality. The freshwater generated from optimum thermal cycle 2 exhibited reduced pH (by ∼63%), sodium (99.9%), chloride (99.9%), toxic boron (99.7%), and other chemical contaminants, thereby satisfying the major international water reuse standards.

Comprehensive experimental and theoretical investigations on the effect of microbubble two-phase flow on the performance of direct-contact membrane distillation.

This study provides a comprehensive and systematic overview of the application of gas-liquid two-phase flow with microbubbles in the feed stream to improve heat and mass transfer in direct-contact membrane distillation (DCMD) processes for seawater desalination. A swirl-flow-type microbubble generator (MBG) was installed at the feed-side inlet of the DCMD module to investigate its effect on transmembrane flux. The maximum improvement in the MBG-assisted DCMD permeation flux was found to be approximately 18% at a lower feed temperature (40 °C) and optimal air flow rate (50 cc/min), and an optimal MBG geometry comprising a swirler, a nozzle tip of diameter 2 mm, and a diffuser at an angle of 30°. The results were observed to be related to the number density of microbubbles less than 100 µm in size, which plays an important role in improving heat and mass transfer in two-phase flow. In addition, the simulation results based on conventional heat transfer correlations of bubbly flow underestimated the experimental results. Therefore, this study also aims to propose and verify a new two-phase flow heat transfer correlation. The proposed correlation considers the effects of bubble size distribution to accurately predict the performance of MBG-assisted DCMD processes.

Combination Effect of Engineered Endolysin EC340 With Antibiotics.

Bacteriophage lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages during the final stage of the lytic cycle to enable cleavage through the host's cell wall, thus allowing the phages to burst out of their host bacteria after multiplication inside them. When applied externally to Gram-negative bacteria as recombinant proteins, lysins cannot easily reach the cell wall due to the presence of an outer membrane (OM). In this study, endolysin EC340 obtained from phage PBEC131 infecting Escherichia coli was engineered for improved OM permeability and increased activity against Gram-negative bacteria. The engineered endolysin, LNT113, was tested for potential synergistic effects with standard-of-care antibiotics. A synergistic effect was demonstrated with colistin, while an additive effect was seen with meropenem, tigecycline, chloramphenicol, azithromycin, and ciprofloxacin. Neither ceftazidime nor kanamycin showed any synergy or additive effects with the LNT113 endolysin. Moreover, synergy and additive effects could not be generalized by antibiotic class, OM traverse mechanism, molecular weight, or the bactericidal nature of each antibiotic tested.

Towards sustainable circular brine reclamation using seawater reverse osmosis, membrane distillation and forward osmosis hybrids: An experimental investigation.

Desalination and wastewater treatment technologies require an effective solution for brine management to ensure environmental sustainability, which is closely linked with efficient process operations, reduction of chemical dosages, and valorization of brines. Within the scope of desalination brine reclamation, a circular system consisting of seawater reverse osmosis (SWRO), membrane distillation (MD), and forward osmosis (FO) three-process hybrid is investigated. The proposed design increases water recovery from SWRO brine (by MD) and dilutes concentrated brine to seawater level (by FO) for SWRO feed. It ultimately reduces SWRO process brine disposal and improves crystallization efficiency for a zero-liquid discharge application. The operating range of the hybrid system is indicated by a seawater volumetric concentration factor (VCF) ranging from 1.0 to 2.2, which covers practical and sustainable operation in full-scale applications. Within the proposed VCF range, different operating conditions of the MD and FO processes were evaluated in series with concentrated seawater as well as real SWRO brine from a full-scale desalination plant. Water quality and membrane surface were analyzed before and after experiments to assess the impact of the SWRO brine. Despite their low concentration (0.13 mg/L as phosphorous), antiscalants present in SWRO brine alleviated the flux decline in MD operations by 68.3% compared to operations using seawater concentrate, while no significant influence was observed on the FO process. A full spectrum of water quality analysis of real SWRO brine and Red Sea water is made available for future SWRO brine reclamation studies. The operating conditions and experimental results have shown the potential of the SWRO-MD-FO hybrid system for a circular brine reclamation.

Detailed modeling and simulation of an out-in configuration vacuum membrane distillation process.

In this study, a detailed rigorous theoretical model was developed to predict the transmembrane flux of a shell-and-tube type vacuum membrane distillation (VMD) module for seawater desalination. Two modes of operation are used for performing the VMD, namely lumen-side feed (in-out) configuration and shell-side feed (out-in) configuration. In this study, detailed mathematical formulations are derived for an out-in configuration that is commonly used in seawater desalination applications. Experimental results and model predictions for mean permeate flux are compared and shown to be in good agreement. The results indicate that although the simple VMD model that maintains a constant permeate pressure is easy to use, it is likely to significantly overestimate the mean permeate flux when compared to the detailed model that considers the pressure build-up in the fiber lumen. The pressure build-up of water vapor in the fiber lumen is identified as the crucial factor that significantly affects the VMD performance because it directly reduces the driving force for vapor permeation through the membrane pores. Additionally, its effect is more pronounced at longer fiber lengths and higher permeate fluxes, and this is achieved at higher feed temperatures and velocities and at lower feed salinities. In conclusion, the results of the study are extremely important in module design for the practical applications of VMD processes.

A novel multi-stage direct contact membrane distillation module: Design, experimental and theoretical approaches.

An economic desalination system with a small scale and footprint for remote areas, which have a limited and inadequate water supply, insufficient water treatment and low infrastructure, is strongly demanded in the desalination markets. Here, a direct contact membrane distillation (DCMD) process has the simplest configuration and potentially the highest permeate flux among all of the possible MD processes. This process can also be easily instituted in a multi-stage manner for enhanced compactness, productivity, versatility and cost-effectiveness. In this study, an innovative, multi-stage, DCMD module under countercurrent-flow configuration is first designed and then investigate both theoretically and experimentally to identify its feasibility and operability for desalination application. Model predictions and measured data for mean permeate flux are compared and shown to be in good agreement. The effect of the number of module stages on the mean permeate flux, performance ratio and daily water production of the MDCMD system has been theoretically identified at inlet feed and permeate flow rates of 1.5 l/min and inlet feed and permeate temperatures of 70 °C and 25 °C, respectively. The daily water production of a three-stage DCMD module with a membrane area of 0.01 m2 at each stage is found to be 21.5 kg.

A novel integrated thermal-/membrane-based solar energy-driven hybrid desalination system: Concept description and simulation results.

In this paper, a hybrid desalination system consisting of vacuum membrane distillation (VMD) and adsorption desalination (AD) units, designated as VMD-AD cycle, is proposed. The synergetic integration of the VMD and AD is demonstrated where a useful effect of the AD cycle is channelled to boost the operation of the VMD process, namely the low vacuum environment to maintain the high pressure gradient across the microporous hydrophobic membrane. A solar-assisted multi-stage VMD-AD hybrid desalination system with temperature modulating unit is first designed, and its performance is then examined with a mathematical model of each component in the system and compared with the VMD-only system with temperature modulating and heat recovery units. The total water production and water recovery ratio of a solar-assisted 24-stage VMD-AD hybrid system are found to be about 21% and 23% higher, respectively, as compared to the VMD-only system. For the solar-assisted 24-stage VMD-AD desalination system having 150 m(2) of evacuated-tube collectors and 10 m(3) seawater storage tanks, both annual collector efficiency and solar fraction are close to 60%.

Phage-encoded colanic acid-degrading enzyme permits lytic phage infection of a capsule-forming resistant mutant Escherichia coli strain.

In this study, we isolated a bacteriophage T7-resistant mutant strain of Escherichia coli (named S3) and then proceeded to characterize it. The mutant bacterial colonies appeared to be mucoid. Microarray analysis revealed that genes related to colanic acid production were upregulated in the mutant. Increases in colanic acid production by the mutant bacteria were observed when l-fucose was measured biochemically, and protective capsule formation was observed under an electron microscope. We found a point mutation in the lon gene promoter in S3, the mutant bacterium. Overproduction of colanic acid was observed in some phage-resistant mutant bacteria after infection with other bacteriophages, T4 and lambda. Colanic acid overproduction was also observed in clinical isolates of E. coli upon phage infection. The overproduction of colanic acid resulted in the inhibition of bacteriophage adsorption to the host. Biofilm formation initially decreased shortly after infection but eventually increased after 48 h of incubation due to the emergence of the mutant bacteria. Bacteriophage PBECO4 was shown to infect the colanic acid-overproducing mutant strains of E. coli. We confirmed that the gene product of open reading frame 547 (ORF547) of PBECO4 harbored colanic acid-degrading enzymatic (CAE) activity. Treatment of the T7-resistant bacteria with both T7 and PBECO4 or its purified enzyme (CAE) led to successful T7 infection. Biofilm formation decreased with the mixed infection, too. This procedure, using a phage cocktail different from those exploiting solely receptor differences, represents a novel strategy for overcoming phage resistance in mutant bacteria.

Antitumor activity of 3,4-dihydroquinazoline dihydrochloride in A549 xenograft nude mice.

In the previous article we have reported that 3,4-dihydroquinazoline 1 is a potent and selective T-type calcium channel blocker that exhibited strong anti-cancer activity in vitro. Compound 1·2HCl was further in vivo evaluated against A549 xenograft in BALB/c nude mice, which exhibited 49% tumor-weight inhibition through intravenous administration of 2 mg/kg of body weight and was more potent than doxorubicin. Moreover, compound 1·2HCl has an oral bioavailability of 98% with LD(50) values of 693 mg/kg (p.o. route) and 40.0 mg/kg (i.v. route) of body weight. In addition, its efficient scale-up synthetic method was developed.

Total synthesis and biological evaluation of methylgerambullone.

First total synthesis of methylgerambullone (MGB, 1) isolated from Glycosmis angustifolia was completed via a convergent route. The effect of MGB on the contractile responses of the isolated guinea-pig ileum induced by acetylcholine was investigated. As a result, it showed a potent relaxation rate (78.66+/-4.30% at 100mg/L) in a concentration-dependent manner on longitudinal smooth muscle contraction of isolated guinea-pig ileum induced by 1microM acetylcholine.

T-type Ca2+ channel blockers suppress the growth of human cancer cells.

In order to further clarify the role of T-type Ca(2+) channels in cell proliferation, we have measured the growth inhibition of human cancer cells by using our potent T-type Ca(2+) channel blockers. As a result, KYS05090, a most potent T-type Ca(2+) channel blocker, was found to be as potent as doxorubicin against some human cancer cells without acute toxicity. Therefore, this letter provides the biological results that T-type calcium channel is important in regulating the important cellular phenotype transition leading to cell proliferation, and thus novel T-type Ca(2+) channel blocker presents new prospects for cancer treatment.