Fabrication and characterization of antibacterial nanofiber membranes modified with chitosan and imidazolidinyl urea for potential use in biological waste treatments.

An ion exchange nanofiber membrane (AEA-COOH) was developed from polyacrylonitrile (PAN) nanofibers through chemical hydrolysis. It was further modified by grafting chitosan (CS) onto its surface, creating the AEA-COOH-CS membrane. Then, both membranes were covalently immobilized with imidazolidinyl urea (IU), resulting in AEA-COOH-IU and AEA-COOH-CS-IU membranes. This study analyzed their physical properties, antibacterial efficacy (AE), and reusability. Optimal conditions were identified: 50 kDa molecular weight of chitosan, pH 8 for IU modification, and 0.05 % IU concentration. The AEA-COOH-IU membrane achieved 96.15 % AE against Escherichia coli at an initial concentration of 2.0 × 107 CFU/mL, while the AEA-COOH-CS-IU membrane achieved 100 % AE. The AEA-COOH-CS-IU membrane maintained 95.04 % efficacy over 5 cycles, demonstrating superior durability. As a result, the AEA-COOH-CS-IU membrane has high potential for environmental applications such as water purification and wastewater treatment. Its robust antibacterial properties and reusability suggest a significant impact on ensuring cleaner water resources and prospective uses in the biomedical field, including medical device coatings and healthcare applications.

Alginate and chitosan-based polyamide 56 modified nanofiber membrane for highly effective capture of Escherichia coli: Antibacterial and cytotoxicity studies.

In recent years, microbial fermentation has become a sustainable alternative to traditional petrochemical processes for producing biomass nylon 56 (i.e., PA56). This study is centered on creating a highly efficient antibacterial nanofiber membrane using bio-nylon 56 as the main material. The membrane was fabricated via a multi-step process involving sodium alginate, chitosan, and poly(hexamethylene biguanide) (PHMB). The PA56 nanofiber was chemically modified by sequential coupling with alginate (AG) and chitosan (CS), introducing a significant number of functional groups (-COOH and -NH2). This process resulted in the formation of PA56-AG and PA56-AG-CS nanofibers. Further modification with PHMB led to obtaining the PA56-AG-PHMB and PA56-AG-CS-PHMB antibacterial nanofiber membranes. The optimal preparation conditions for these membranes were determined, including the pH and concentration of AG, the molecular weight, pH, and concentration of CS, and the pH and concentration of PHMB. The PA56-based membranes demonstrated nearly 100 % antibacterial efficiency within a short time. However, the PA56-AG-PHMB membrane exhibited faster antibacterial rates and higher efficiency in repeated use compared to the PA56-AG-CS-PHMB membrane. The two-step coupling reaction in the preparation of PA56-AG-CS-PHMB may have reduced its surface accessibility to E. coli cells, resulting in slower bacterial attachment. Furthermore, the PA56-related membranes showed excellent biocompatibility, with a 100 % cell survival rate. Despite some limitations in reusability, biomass nylon PA56 stands out as an environmentally friendly material derived from renewable resources through microbial fermentation. It offers significant sustainability advantages over traditional petroleum-based nylons, as evidenced by the favorable cytotoxicity test results.

Recent progress in one-pot enzymatic synthesis and regeneration of high-value cofactors.

One-pot enzymatic synthesis is flourishing in synthetic chemistry, heralding a sustainable and green era. Recent advancements enable the creation of complex enzymatic prosthetic groups and regeneration of enzymatic cofactors such as S-adenosylmethionine. The next frontier is to develop the effective and innovative cofactors for essential micronutrients, metabolic modulators, and biomedicines.

Non-native Pathway Engineering with CRISPRi for Carbon Dioxide Assimilation and Valued 5-Aminolevulinic Acid Synthesis in Escherichia coli Nissle.

Carbon dioxide emission and acidification during chemical biosynthesis are critical challenges toward microbial cell factories' sustainability and efficiency. Due to its acidophilic traits among workhorse lineages, the probiotic Escherichia coli Nissle (EcN) has emerged as a promising chemical bioproducer. However, EcN lacks a CO2-fixing system. Herein, EcN was equipped with a simultaneous CO2 fixation system and subsequently utilized to produce low-emission 5-aminolevulinic acid (5-ALA). Two different artificial CO2-assimilating pathways were reconstructed: the novel ribose-1,5-bisphosphate (R15P) route and the conventional ribulose-5-phosphate (Ru5P) route. CRISPRi was employed to target the pfkAB and zwf genes in order to redirect the carbon flux. As expected, the CRISPRi design successfully strengthened the CO2 fixation. The CO2-fixing route via R15P resulted in high biomass, while the engineered Ru5P route acquired the highest 5-ALA and suppressed the CO2 release by 77%. CO2 fixation during 5-ALA production in EcN was successfully synchronized through fine-tuning the non-native pathways with CRISPRi.

Tailored expression of ICCM cutinase in engineered Escherichia coli for efficient polyethylene terephthalate hydrolysis.

Enzymatic depolymerization of PET waste emerges as a crucial and sustainable solution for combating environmental pollution. Over the past decade, PET hydrolytic enzymes, such as PETase from Ideonella sakaiensis (IsPETases), leaf compost cutinases (LCC), and lipases, have been subjected to rational mutation to enhance their enzymatic properties. ICCM, one of the best LCC mutants, was selected for overexpression in Escherichia coli BL21(DE3) for in vitro PET degradation. However, overexpressing ICCM presents challenges due to its low productivity. A new stress-inducible T7RNA polymerase-regulating E. coli strain, ASIAhsp, which significantly enhances ICCM production by 72.8 % and achieves higher enzyme solubility than other strains. The optimal cultural condition at 30 °C with high agitation, corresponding to high dissolved oxygen levels, has brought the maximum productivity of ICCM and high PET-hydrolytic activity. The most effective PET biodegradation using crude or pure ICCM occurred at pH 10 and 60 °C. Moreover, ICCM exhibited remarkable thermostability, retaining 60 % activity after a 5-day reaction at 60 °C. Notably, crude ICCM eliminates the need for purification and efficiently degrades PET films.

Tailoring nitrogen and phosphorus levels for tunable glycogen and protein production in halophilic Cyanobacterium aponinum PCC10605.

Cyanobacteria hold promise for simultaneous carbon capture and chemicals production, but the regulation and effect of nitrogen (N) and phosphorus (P) remains unclear. This study investigates major productions of glycogen, protein, and C-phycocyanin (C-PC) in Cyanobacterium aponinum PCC10605 under different N/P levels, alongside changes in light and CO2. Increasing nitrate (NO3-) from 2 to 6 mM resulted in a 9.7-fold increase in C-PC and reduced glycogen to 8.9 %. On the other hand, elevating phosphorus from 0.1 to 2 mM under limited nitrogen enhanced biomass and glycogen through the upregulation of carbonic anhydrase, ADP-glucose pyrophosphorylase, and glycogen phosphorylase. Changes in phosphorus levels and CO2 inlet concentrations affected metabolites accumulation and carbon capture efficiency, leading to the best condition of 76 % uptake capacity in direct air capture (DAC). All findings underscore the trade-off between glycogen and protein, representing the importance of N/P levels in nutrient modulation of PCC10605.

ASIA: An automated stress-inducible adaptor for enhanced stress protein expression in engineered Escherichia coli.

Orthogonal T7 RNA polymerase (T7RNAP) and T7 promoter is a potent technique for protein expression in broad cells, but the energy requirements associated with this method impede the growth, leading to cell lysis when dealing with toxic and stress proteins. A Lemo21(DE3) strain denoted as L21 offers a solution by fine-tuning T7RNAP levels under rhamnose to induce T7 lysozyme (LysY) and enhance the protein production, but it requires optimization of inducer concentration, cultural temperature, and condition, even the types of carbon sources. Herein, we construct an automated stress-inducible adaptor (ASIA) employing different stress-inducible promoters from Escherichia coli. The ASIA system is designed to automatically regulate LysY expression in response to stress signals, thereby suppressing T7RNAP and amplifying the overexpression of stress protein cutinase ICCM. This approach fine-tunes T7RNAP levels and outperforms L21 in various temperatures and carbon source conditions. The ASIAhtp strain maintains ICCM yield at 91.6 mg/g-DCW even in the limiting carbon source at 1 g/L, which is 12-fold higher in protein productivity compared to using L21. ASIA as a versatile and robust tool for enhancing overexpression of stress proteins in E. coli is expected to address more difficult proteins in the future.

Polyhydroxyalkanoates bioproduction from bench to industry: Thirty years of development towards sustainability.

The pursuit of carbon neutrality goals has sparked considerable interest in expanding bioplastics production from microbial cell factories. One prominent class of bioplastics, polyhydroxyalkanoates (PHA), is generated by specific microorganisms, serving as carbon and energy storage materials. To begin with, a native PHA producer, Cupriavidus necator (formerly Ralstonia eutropha) is extensively studied, covering essential topics such as carbon source selection, cultivation techniques, and accumulation enhancement strategies. Recently, various hosts including archaea, bacteria, cyanobacteria, yeast, and plants have been explored, stretching the limit of microbial PHA production. This review provides a comprehensive overview of current advancements in PHA bioproduction, spanning from the native to diversified cell factories. Recovery and purification techniques are discussed, and the current status of industrial applications is assessed as a critical milestone for startups. Ultimately, it concludes by addressing contemporary challenges and future prospects, offering insights into the path towards reduced carbon emissions and sustainable development goals.

Challenges and opportunities for engineered Escherichia coli as a pivotal chassis toward versatile tyrosine-derived chemicals production.

Growing concerns over limited fossil resources and associated environmental problems are motivating the development of sustainable processes for the production of high-volume fuels and high-value-added compounds. The shikimate pathway, an imperative pathway in most microorganisms, is branched with tyrosine as the rate-limiting step precursor of valuable aromatic substances. Such occurrence suggests the shikimate pathway as a promising route in developing microbial cell factories with multiple applications in the nutraceutical, pharmaceutical, and chemical industries. Therefore, an increasing number of studies have focused on this pathway to enable the biotechnological manufacture of pivotal and versatile aromatic products. With advances in genome databases and synthetic biology tools, genetically programmed Escherichia coli strains are gaining immense interest in the sustainable synthesis of chemicals. Engineered E. coli is expected to be the next bio-successor of fossil fuels and plants in commercial aromatics synthesis. This review summarizes successful and applicable genetic and metabolic engineering strategies to generate new chassis and engineer the iterative pathway of the tyrosine route in E. coli, thus addressing the opportunities and current challenges toward the realization of sustainable tyrosine-derived aromatics.

Tunable T7 Promoter Orthogonality on T7RNAP for cis-Aconitate Decarboxylase Evolution via Base Editor and Screening from Itaconic Acid Biosensor.

The deaminase-fused T7 RNA polymerase (T7RNAP) presents a promising toolkit for in vivo target-specific enzyme evolution, offering the unique advantage of simultaneous DNA modification and screening. Previous studies have reported the mutation efficiency of base editors relying on different resources. In contrast, the mechanism underlying the T7RNAP/T7 system is well-understood. Therefore, this study aimed to establish a new platform, termed dT7-Muta, by tuning the binding efficiency between T7RNAP and the T7 promoter for gene mutagenesis. The strategy for proof-of-concept involves alterations in the fluorescence distribution through dT7-Muta and screening of the mutants via flow cytometry. The cis-aconitate decarboxylase from Aspergillus terreus (AtCadA) was evolved and screened via an itaconate-induced biosensor as proof-of-function of enzyme evolution. First, the degenerated codons were designed within the binding and initial region of T7 promoters (dT7s), including upstream (U), central (C), and downstream (D) regions. Three strength variants of dT7 promoter from each design, i.e., strong (S), medium (M), and weak (W), were used for evaluation. Mutation using dT7s of varying strength resulted in a broader fluorescence distribution in sfGFP mutants from the promoters CW and DS. On the other hand, broader fluorescence distribution was observed in the AtCadA mutants from the original promoter T7, UW, and DS, with the highest fluorescence and itaconic acid titer at 860 a.u. and 0.51 g/L, respectively. The present platform introduces a novel aspect of the deaminase-based mutagenesis, emphasizing the potential of altering the binding efficiency between T7RNAP and the T7 promoter for further efforts in enzyme evolution.

Optimization of 4-aminobutyric acid feeding strategy and clustered regularly interspaced short palindromic repeats activation for enhanced value-added chemicals in halophilic Chlorella sorokiniana.

Chlorella sorokiniana (CS) is a prominent microalga with vast potential as a biocarrier for carbon mitigation toward a green process. However, challenges remain in achieving high biomass levels and production rates. Therefore, a systematic feeding strategy using 4-aminobutyric acid (GABA) and CRISPR technology was applied to improve microalgal productivity. At first, GABA increased protein content by 1.4-fold, while intermittent supplementation during cultivation resulted in a 1.58-fold and 2.13-fold increase in biomass and pigment content, respectively. Under halophilic conditions, the optimal approach involved repeated feeding of 5 mM GABA at the initial and mid-log phases of growth, resulting in biomass, protein, and pigment levels of 6.74 g/L, 3.24 g/L, and 49.87 mg/L. CRISPRa mediated glutamate synthase and using monosodium glutamate (MSG) as a cheap precursor for GABA has effectively enhanced the biomass, protein, and lutein content, thus offers a cost-effective approach to commercialize high-valued chemical using algae towards a low-carbon paradigm.

Enhanced carbon capture, lipid and lutein production in Chlamydomonas reinhardtii under meso-thermophilic conditions using chaperone and CRISPRi system.

Microalgae are widely recognized as a promising bioresource for producing renewable fuels and chemicals. Microalgal biorefinery has tremendous potential for incorporation into circular bioeconomy, including sustainability, cascading use, and waste reduction. In this study, genetic engineering was used to enhance the growth, lipid and lutein productivity of Chlamydomonas reinhardtii including strains of CC400, PY9, pCHS, and PG. Notably, CRISPRi mediated on phosphoenolpyruvate carboxylase (PEPC1) gene to down-regulate the branch pathway from glycolysis to partitioning more carbon flux to lipid was explored under meso-thermophilic condition. The best chassis PGi, which has overexpressed chaperone GroELS and applied CRISPRi resulting in the highest biomass of 2.56 g/L and also boosted the lipids and lutein with 893 and 23.5 mg/L, respectively at 35°C. Finally, all strains with CRISPRi exhibited higher transcriptional levels of the crucial genes from photosynthesis, starch, lipid and lutein metabolism, thus reaching a CO2 assimilation of 1.087 g-CO2/g-DCW in mixotrophic condition.

Microbial itaconic acid bioproduction towards sustainable development: Insights, challenges, and prospects.

Microbial biomanufacturing is a promising approach to produce high-value compounds with low-carbon footprint and significant economic benefits. Among twelve "Top Value-Added Chemicals from Biomass", itaconic acid (IA) stands out as a versatile platform chemical with numerous applications. IA is naturally produced by Aspergillus and Ustilago species through a cascade enzymatic reaction between aconitase (EC 4.2.1.3) and cis-aconitic acid decarboxylase (EC 4.1.1.6). Recently, non-native hosts such as Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, and Yarrowia lipolytica have been genetically engineered to produce IA through the introduction of key enzymes. This review provides an up-to-date summary of the progress made in IA bioproduction, from native to engineered hosts, covers in vivo and in vitro approaches, and highlights the prospects of combination tactics. Current challenges and recent endeavors are also addressed to envision comprehensive strategies for renewable IA production in the future towards sustainable development goals (SDGs).

High value ferulic acid biosynthesis using modular design and spent coffee ground in engineered Escherichia coli chassis.

Sophisticated genetic engineering enables microbial hosts to derive high-value aromatics in a green manner. Ferulic acid (FA) is one of the noteworthy aromatics due to its potent pharmacokinetic properties. However, the current approaches to FA biosynthesis still decamp from time- and cost-effectiveness. Herein, FA pathway was artificially reconstructed in Escherichia coli using modular designs. Comprehensive screening of E. coli lineages was reckoned for efficient synthesis of p-coumaric acid (pCA) as a precursor and FA eventually. The modular design was further advanced by harboring tyrosine transporter, adapting the heterologous codon, utilizing pCA symporter, and enriching FADH2 cofactor pools via in vivo regeneration. Taken together with simultaneous optimization of culture condition, a remarkable FA yield of 972.6 mg/L with 89.4 % conversion was achieved in 48 h, circumventing the time-consuming issue. Moreover, this study successfully exported inexpensive precursor from spent coffee ground for the first time, paving the economical way of FA biosynthesis.

High-level itaconic acid (IA) production using engineered Escherichia coli Lemo21(DE3) toward sustainable biorefinery.

Itaconic acid (IA) serves as a prominent building block for polyamides as sustainable material. In vivo IA production is facing the competing side reactions, byproducts accumulation, and long cultivation time. Therefore, the utilization of whole-cell biocatalysts to carry out production from citrate is an alternative approach to sidestep the current limitations. In this study, in vitro reaction of IA was obtained 72.44 g/L by using engineered E. coli Lemo21(DE3) harboring the aconitase (Acn, EC 4.2.1.3) and cis-aconitate decarboxylase (CadA, EC 4.1.1.6) which was cultured in glycerol-based minimal medium. IA productivity enhancement was observed after cold-treating the biocatalysts in - 80 °C for 24 h prior to the reaction, reaching 81.6 g/L. On the other hand, a new seeding strategy in Terrific Broth (TB) as a nutritionally rich medium was employed to maintain the biocatalysts stability up to 30 days. Finally, the highest IA titer of 98.17 g/L was attained using L21::7G chassis, that has a pLemo plasmid and integration of GroELS to the chromosome. The high-level of IA production along with the biocatalyst reutilization enables the economic viability toward a sustainable biorefinery.

Investigation of enzymatic quality and quantity using pyridoxal 5'-phosphate (PLP) regeneration system as a decoy in Escherichia coli.

Pyridoxal 5'-phosphate (PLP), an essential cofactor for multiple enzymes, was used as a protein decoy to prompt enzyme expression and activity for the first time. The best chassis, denoted as WJK, was developed using a pyridoxal kinase (PdxK) and integrated at the HK022 phage attack site of Escherichia coli W3110. When compared with the original strain, the amount and activity of lysine decarboxylase (CadA) in WJK were significantly increased by 100 % and 120 %, respectively. When supplementary nineteen amino acids as second carbon source, cell growth and protein trade-off were observed. The transcriptional levels of genes from glycolysis to TCA cycle, adhE, argH and gdhA were dominating and redirected more flux into α-ketoglutarate, thus facilitated cell growth. Stepwise improvement was conducted with pyridoxal and nitrogen-rich medium; hence, CadA activity was increased to 60 g-cadaverine/g-dry cell weight/h. By reutilizing the whole-cell biocatalysts in two repeated reactions with the supplementation of fresh cells, a total cadaverine of 576 g/L was obtained even without additional PLP. Notably, PLP decoy augment the enzymatic activities of 5-aminolevulinic acid synthase and glutamate/lysine/arginine decarboxylases by over 100 %. Finally, a conserved PLP-binding pocket, Ser-His-Lys, was identified as a vital PLP sponge site that simultaneously improved protein quality and quantity.

Heterologous Expression of Toxic White Spot Syndrome Virus (WSSV) Protein in Eengineered Escherichia coli Strains.

Aquacultural shrimps suffer economic lost due to the white spot syndrome virus (WSSV) that is the most notorious virus for its fatality and contagion, leading to a 100% death rate on infected shrimps within 7 days. However, the infection of mechanism remains a mystery and crucial problem. To elucidate the pathogenesis of WSSV, a high abundance of protein is required to identify and characterize its functions. Therefore, the optimal WSSV355 overexpression was explored in engineered Escherichia coli strains, in particular C43(DE3) as a toxic tolerance strain remedied 40% of cell growth from BL21(DE3). Meanwhile, a trace amount of WSSV355 was observed in both strains. To optimize the codon of WSSV355 using codon adaption index (CAI), an overexpression was observed with 1.32 mg/mL in C43(DE3), while the biomass was decreased by 35%. Subsequently, the co-expression with pRARE boosted the target protein up to 1.93 mg/mL. Finally, by scaling up production of WSSV355 in the fermenter with sufficient oxygen supplied, the biomass and total and soluble protein were enhanced 67.6%, 44.9%, and 7.8% compared with that in flask condition. Herein, the current approach provides efficacious solutions to produce toxic proteins via codon usage, strain selection, and processing optimization by alleviating the burden and boosting protein production in E. coli.

Clustered regularly interspaced short palindromic repeats (CRISPR) technology and genetic engineering strategies for microalgae towards carbon neutrality: A critical review.

Carbon dioxide is the major greenhouse gas and regards as the critical issue of global warming and climate changes. The inconspicuous microalgae are responsible for 40% of carbon fixation among all photosynthetic plants along with a higher photosynthetic efficiency and convert the carbon into lipids, protein, pigments, and bioactive compounds. Genetic approach and metabolic engineering are applied to accelerate the growth rate and biomass of microalgae, hence achieve the mission of carbon neutrality. Meanwhile, CRISPR/Cas9 is efficiently to enhance the productivity of high-value compounds in microalgae for it is easier operation, more affordable and is able to regulate multiple genes simultaneously. The genetic engineering strategies provide the multidisciplinary concept to evolute and increase the CO2 fixation rate through Calvin-Benson-Bassham cycle. Therefore, the technologies, bioinformatics tools, systematic engineering approaches for carbon neutrality and circular economy are summarized and leading one step closer to the decarbonization society in this review.

A direct enzymatic evaluation platform (DEEP) to fine-tuning pyridoxal 5'-phosphate-dependent proteins for cadaverine production.

Pyridoxal 5'-phosphate (pyridoxal phosphate, PLP) is an essential cofactor for multiple enzymatic reactions in industry. However, cofactor engineering based on PLP regeneration and related to the performance of enzymes in chemical production has rarely been discussed. First, we found that MG1655 strain was sensitive to nitrogen source and relied on different amino acids, thus the biomass was significantly reduced when PLP excess in the medium. Then, the six KEIO collection strains were applied to find out the prominent gene in deoxyxylulose-5-phosphate (DXP) pathway, where pdxB was superior in controlling cell growth. Therefore, the clustered regularly interspaced short palindromic repeats interference (CRISPRi) targeted on pdxB in MG1655 was employed to establish a novel direct enzymatic evaluation platform (DEEP) as a high-throughput tool and obtained the optimal modules for incorporating of PLP to enhance the biomass and activity of PLP-dependent enzymes simultaneously. As a result, the biomass has increased by 55% using PlacI promoter driven pyridoxine 5'-phosphate oxidase (PdxH) with a trace amount of precursor. When the strains incorporated DEEP and lysine decarboxylase (CadA), the cadaverine productivity was increased 32% due to the higher expression of CadA. DEEP is not only feasible for high-throughput screening of the best chassis for PLP engineering but also practical in fine-tuning the quantity and quality of enzymes.

Prospective and challenges of live bacterial therapeutics from a superhero Escherichia coli Nissle 1917.

Escherichia coli Nissle 1917 (EcN), the active component of Mutaflor(R), is a notable probiotic from Gram-negative to treat Crohn's disease and irritable bowel syndrome. Therefore, a comprehensive genomic database maximizes the systemic probiotic assessment to discover EcN's role in human health. Recently, advanced synthetic and genetic tools have opened up a rich area to execute EcN as "living medicines" with controllable functions. Incorporating unique biomarkers allows the engineered EcN to switch genes on and off in response to environmental cues. Since EcN holds promise as a safe nature vehicle, more studies are desired to fully realize a wide range of probiotic potential for disease treatment. This review aims to deliver a historical origin of EcN, discuss the recent promising genetic toolbox in the rational design of probiotics, and pinpoint the clinical translation and evaluation of engineered EcN in vitro and in vivo. The summary of safety concerns, strategies of biotherapeutics development, and the challenges and prospects of engineered EcN is also concluded.