A newly discovered glycosyltransferase gene UGT88A1 affects growth and polysaccharide synthesis of Grifola frondosa.

Grifola frodosa polysaccharides, especially ß-D-glucans, possess significant anti-tumor, antioxidant and immunostimulatory activities. However, the synthesis mechanism remains to be elucidated. A newly discovered glycosyltransferase UGT88A1 was found to extend glucan chains in vitro. However, the role of UGT88A1 in the growth and polysaccharide synthesis of G. frondosa in vivo remains unclear. In this study, the overexpression of UGT88A1 improved mycelial growth, increased polysaccharide production, and decreased cell wall pressure sensitivity. Biomass and polysaccharide production decreased in the silenced strain, and the pressure sensitivity of the cell wall increased. Overexpression and silencing of UGT88A1 both affected the monosaccharide composition and surface morphology of G. frondosa polysaccharides and influenced the antioxidant activity of polysaccharides from different strains. The messenger RNA expression of glucan synthase (GLS), UTP-glucose-1-phosphate uridylyltransferase (UGP), and UDP-xylose-4-epimerase (UXE) related to polysaccharide synthesis, and genes related to cell wall integrity increased in the overexpression strain. Overall, our study indicates that UGT88A1 plays an important role in the growth, stress, and polysaccharide synthesis of G. frondosa, providing a reference for exploring the pathway of polysaccharide synthesis and metabolic regulation. KEY POINTS: •UGT88A1 plays an important role in the growth, stress response, and polysaccharide synthesis in G. frondosa. •UGT88A1 affected the monosaccharide composition, surface morphology and antioxidant activity of G. frondosa polysaccharides. •UGT88A1 regulated the mRNA expression of genes related to polysaccharide synthesis and cell wall integrity.

Synthesis, molecular docking, and binding Gibbs free energy calculation of ß-nitrostyrene derivatives: Potential inhibitors of SARS-CoV-2 3CL protease.

The outbreak of novel coronavirus disease 2019 (COVID-19), caused by the novel coronavirus (SARS-CoV-2), has had a significant impact on human health and the economic development. SARS-CoV-2 3CL protease (3CLpro) is highly conserved and plays a key role in mediating the transcription of virus replication. It is an ideal target for the design and screening of anti-coronavirus drugs. In this work, seven ß-nitrostyrene derivatives were synthesized by Henry reaction and ß-dehydration reaction, and their inhibitory effects on SARS-CoV-2 3CL protease were identified by enzyme activity inhibition assay in vitro. Among them, 4-nitro-ß-nitrostyrene (compound a) showed the lowest IC50 values of 0.7297 µM. To investigate the key groups that determine the activity of ß-nitrostyrene derivatives and their interaction mode with the receptor, the molecular docking using the CDOCKER protocol in Discovery Studio 2016 was performed. The results showed that the hydrogen bonds between ß-NO2 and receptor GLY-143 and the π-π stacking between the aryl ring of the ligand and the imidazole ring of receptor HIS-41 significantly contributed to the ligand activity. Furthermore, the ligand-receptor absolute binding Gibbs free energies were calculated using the Binding Affinity Tool (BAT.py) to verify its correlation with the activity of ß-nitrostyrene 3CLpro inhibitors as a scoring function. The higher correlation(r2=0.6) indicates that the absolute binding Gibbs free energy based on molecular dynamics can be used to predict the activity of new ß-nitrostyrene 3CLpro inhibitors. These results provide valuable insights for the functional group-based design, structure optimization and the discovery of high accuracy activity prediction means of anti-COVID-19 lead compounds.

Enhancing bacterial cellulose production with hypoxia-inducible factors.

Komagataeibacter xylinus is an aerobic strain that produces bacterial cellulose (BC). Oxygen levels play a critical role in regulating BC synthesis in K. xylinus, and an increase in oxygen tension generally means a decrease in BC production. Fumarate nitrate reduction protein (FNR) and aerobic respiration control protein A (ArcA) are hypoxia-inducible factors, which can signal whether oxygen is present in the environment. In this study, FNR and ArcA were used to enhance the efficiency of oxygen signaling in K. xylinus, and globally regulate the transcription of the genome to cope with hypoxic conditions, with the goal of improving growth and BC production. FNR and ArcA were individually overexpressed in K. xylinus, and the engineered strains were cultivated under different oxygen tensions to explore how their overexpression affects cellular metabolism and regulation. Although FNR overexpression did not improve BC production, ArcA overexpression increased BC production by 24.0% and 37.5% as compared to the control under oxygen tensions of 15% and 40%, respectively. Transcriptome analysis showed that FNR and ArcA overexpression changed the way K. xylinus coped with oxygen tension changes, and that both FNR and ArcA overexpression enhanced the BC synthesis pathway. The results of this study provide a new perspective on the effect of oxygen signaling on growth and BC production in K. xylinus and suggest a promising strategy for enhancing BC production through metabolic engineering. KEY POINTS: • K. xylinus BC production increased after overexpression of ArcA • The young's modulus is enhanced by the ArcA overexpression • ArcA and FNR overexpression changed how cells coped with changes in oxygen tension.

The production of bacterial cellulose in Gluconacetobacter xylinus regulated by luxR overexpression of quorum sensing system.

Quorum sensing is a mechanism that facilitates cell-to-cell communication. Through signal molecular density for signal recognition, which leads to the regulation of some physiological and biochemical functions. Gluconacetobacter xylinus CGMCC 2955, which produces bacterial cellulose (BC), synthesizes the LuxR protein belonging to the LuxI/LuxR type QS system. Here, a luxR overexpression vector was transformed into G. xylinus CGMCC 2955. The overexpression of luxR increased the yield of BC by 15.6% after 16 days static culture and reduced the cell density by 15.5% after 120-h-agitated culture. The glucose was used up by G. xylinus-pMV24-luxR at 72-h-agitated fermentation, which 12 h earlier than the wild-type (WT). The total N-acylhomoserine lactones (AHL) content of the luxR-overexpressing strain and the WT strain attained 1367.9 ± 57.86 mg/L and 842.9 ± 54.22 mg/L, respectively. The C12-HSL and C14-HSL contents of G. xylinus-pMV24-luxR were 202 ± 21.66 mg/L and 409.6 ± 0.91 mg/L, which were significantly lower than that of WT. In contrast, C6-HSL showed opposite results. The difference of AHL content proved that overexpression of luxR improved the binding of AHL and showed preference for some specific AHL. The metabolic results demonstrated that upon glucose exhaustion, the consumption of gluconic acid was promoted by luxR overexpression, and the content of D- ( +)-trehalose, an antiretrograde metabolite, increased significantly. KEY POINTS: • The overexpression of luxR increased the yield of bacterial cellulose • The content of signal molecules was significantly different • Differential metabolites were involved in multiple metabolic pathways.

Tailoring bacterial cellulose structure through CRISPR interference-mediated downregulation of galU in Komagataeibacter xylinus CGMCC 2955.

Diverse applications of bacterial cellulose (BC) have different requirements in terms of its structural characteristics. culturing Komagataeibacter xylinus CGMCC 2955, BC structure changes with alterations in oxygen tension. Here, the K. xylinus CGMCC 2955 transcriptome was analyzed under different oxygen tensions. Transcriptome and genome analysis indicated that BC structure is related to the rate of BC synthesis and cell growth, and galU is an essential gene that controls the carbon metabolic flux between the BC synthesis pathway and the pentose phosphate (PP) pathway. The CRISPR interference (CRISPRi) system was utilized in K. xylinus CGMCC 2955 to control the expression levels of galU. By overexpressing galU and interfering with different sites of galU sequences using CRISPRi, we obtained strains with varying expression levels of galU (3.20-3014.84%). By testing the characteristics of BC, we found that the porosity of BC (range: 62.99-90.66%) was negative with galU expression levels. However, the crystallinity of BC (range: 56.25-85.99%) was positive with galU expression levels; galU expression levels in engineered strains were lower than those in the control strains. Herein, we propose a new method for regulating the structure of BC to provide a theoretical basis for its application in different fields.

Applications of cellulose and chitin/chitosan derivatives and composites as antibacterial materials: current state and perspectives.

The bacterial infections have always a serious problem to public health. Scientists are developing new antibacterial materials to overcome this problem. Polysaccharides are promising biopolymers due to their diverse biological functions, low toxicity, and high biodegradability. Chitin and chitosan have antibacterial properties due to their cationic nature, while cellulose/bacterial cellulose does not possess any antibacterial activity. Moreover, the insolubility of chitin in common solvents, the poor solubility of chitosan in water, and the low mechanical properties of chitosan have restricted their biomedical applications. In order to solve these problems, chemical modifications such as quaternization, carboxymethylation, cationization, or surface modification of these polymers with different antimicrobial agents, including metal and metal oxide nanoparticles, are carried out to obtain new materials with improved physiochemical and biological properties. This mini review describes the recent progress in such derivatives and composites with potential antibacterial applications.

Identification of Quorum-Sensing Molecules of N-Acyl-Homoserine Lactone in Gluconacetobacter Strains by Liquid Chromatography-Tandem Mass Spectrometry.

Many Gram-negative bacteria can regulate gene expression in a cell density-dependent manner via quorum-sensing systems using N-acyl-homoserine lactones (AHLs), which are typical quorum-sensing signaling molecules, and thus modulate physiological characteristics. N-acyl-homoserine lactones are small chemical molecules produced at low concentrations by bacteria and are, therefore, difficult to detect. Here, a biosensor system method and liquid chromatography-tandem mass spectrometry were combined to detect and assay AHL production. As demonstrated by liquid chromatography-tandem mass spectrometry, Gluconacetobacter xylinus CGMCC No. 2955, a Gram-negative acetic acid-producing bacterium and a typical bacterial cellulose (BC) biosynthesis strain, produces six different AHLs, including N-acetyl-homoserine lactone, N-butanoyl-homoserine lactone, N-hexanoyl-homoserine lactone, N-3-oxo-decanoyl-homoserine lactone, N-dodecanoyl-homoserine lactone, and N-tetradecanoyl-homoserine lactone. Gluconacetobacter sp. strain SX-1, another Gram-negative acetic acid-producing bacterium, which can synthesize BC, produces seven different AHLs including N-acetyl-homoserine lactone, N-butanoyl-homoserine lactone, N-hexanoyl-homoserine lactone, N-3-oxo-octanoyl-homoserine lactone, N-decanoyl-homoserine lactone, N-dodecanoyl-homoserine lactone, and N-tetradecanoyl-homoserine lactone. These results lay the foundation for investigating the relationship between BC biosynthesis and quorum-sensing systems.

Comparative proteomic analysis of Nostoc flagelliforme reveals the difference in adaptive mechanism in response to different ultraviolet-B radiation treatments.

Nostoc flagelliforme is a pioneer organism in the desert and highly resistant to ultraviolet B (UV-B) radiation, while the involved adaptive mechanism has not been fully explored yet. To elucidate the responsive mechanism, two doses of UV-B radiation (low: 1 W/m2 and high: 5 W/m2) were irradiated for 6 h and 48 h, respectively, and their effects on global metabolism in N. flagelliforme were comprehensively investigated. In this study, we used iTRAQ-based proteomic approach to explore the proteomes of N. flagelliforme, and 151, 172, 124 and 148 differentially expressed proteins were identified under low and high UV-B doses for 6 h and 48 h, respectively. Functional classification analysis showed these proteins were mainly involved in photosynthesis, amino acid metabolism, antioxidant activity and carbohydrate metabolism. Further analysis revealed that UV-B imposed restrictions on primary metabolism including photosynthesis, Calvin cycle, and amino acid metabolism, and cells started defense mechanism through repair of DNA and protein damage, increasing antioxidant activity, and accumulating extracellular polysaccharides to minimize the damage. Moreover, high UV-B dose imposed more severe restrictions and activated stronger defense mechanism compared with low dose. The results would improve the understanding of molecular mechanisms of UV-B-stress adaption in N. flagelliforme.

Optimization protocols and improved strategies of cross-linked enzyme aggregates technology: current development and future challenges.

Cross-linked enzyme aggregate (CLEA) technology has been regarded as an effective carrier-free immobilization method. This method is very attractive due to its simplicity and robustness, as well as for the possibility of using the crude enzyme extract and the opportunity to co-immobilize multiple different enzymes. The resulting CLEAs generally exhibit high catalyst productivities, improved storage and operational stability and are easy to recycle. Nowadays, although the technology has been applied to various enzymes, some undesirable properties have limited its further application. To overcome these limitations, novel strategies have been developing in recent years. This mini-review focuses on process optimization, new improved strategies and the latest advances on CLEAs technology.

Comparison of bacterial community structures of terrestrial cyanobacterium Nostoc flagelliforme in three different regions of China using PCR-DGGE analysis.

Filamentous Nostoc flagelliforme form colloidal complex, with beaded cells interacting with other bacteria embedded in the complex multilayer sheath. However, the species of bacteria in the sheath and the interaction between N. flagelliforme and associated bacteria remain unclear. In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial communities of N. flagelliforme from three regions of China. DGGE patterns showed variations in all samples, exhibiting 25 discrete bands with various intensities. The diversity index analysis of bands profiles suggested the high similarity of bacterial communities to each other but also the dependence of microbial composition on each location. Phylogenetic affiliation indicated that the majority of the sequences obtained were affiliated with Actinobacteria, Cyanobacteria, Proteobacteria, Acidobacteria, Bacteroidetes, of which Cyanobacteria was dominant, followed the Proteobacteria. Members of the genus Nostoc were the most abundant in all samples. Rhizobiales and Actinobacteria were identified, whereas, Craurococcus, Caulobacter, Pseudomonas, Terriglobus and Mucilaginibacter were also identified at low levels. Through comparing the bacterial composition of N. flagelliforme from different regions, it was revealed that N. flagelliforme could facilitate the growth of other microorganisms including both autotrophic bacteria and heterotrophic ones and positively contributed to their harsh ecosystems. The results indicated N. flagelliforme played an important role in diversifying the microbial community composition and had potential application in soil desertification.

Biotechnological production and applications of microbial phenylalanine ammonia lyase: a recent review.

Phenylalanine ammonia lyase (PAL) catalyzes the nonoxidative deamination of l-phenylalanine to form trans-cinnamic acid and a free ammonium ion. It plays a major role in the catabolism of l-phenylalanine. The presence of PAL has been reported in diverse plants, some fungi, Streptomyces and few Cyanobacteria. In the past two decades, PAL has gained considerable significance in several clinical, industrial and biotechnological applications. Since its discovery, much knowledge has been gathered with reference to the enzyme's importance in phenyl propanoid pathway of plants. In contrast, there is little knowledge about microbial PAL. Furthermore, the commercial source of the enzyme has been mainly obtained from the fungi. This study focuses on the recent advances on the physiological role of microbial PAL and the improvements of PAL biotechnological production both from our laboratory and many others as well as the latest advances on the new applications of microbial PAL.

Integrating kinetics with thermodynamics to study the alkaline extraction of protein from Caragana korshinskii Kom.

Extraction and recovery of protein from abundant plant biomass is one potential way to improve the economic feasibility of biorefineries. However, valorization of the protein fraction is challenging due to its low yield (kg protein extraction/kg biomass). In order to reveal the limiting operation parameters, the alkaline extraction process of protein from Caragana korshinskii Kom. was investigated by an integrative analysis of kinetics and thermodynamics. Both a two-site kinetic extraction model and a second-order model indicated that particle size is the most pivotal factor affecting protein extraction yield. In a two-site model, most proteins are extracted quickly from broken cells, while protein removal from the intact cells takes much longer; these are the faster and slower processes, respectively. A decrease of particle size from 20-40 to 60-80 mesh resulted in a decrease of C2 (protein yield in the slower process) from 14.02 to 7.32 mg g(-1), but a great increase of C1 (protein yield in the faster process) from 20.61 to 59.07 mg g(-1) . However, the protein yield was dominated by the faster process when the average particle size is under 80 mesh. The maximum initial extraction rate was 72.20 mg g(-1) min(-1) with the particle size of 60-80 mesh, almost ninefold of that with 20-40 mesh. Thermodynamic analysis revealed that the enthalpy change (ΔH) and entropy change (ΔS) in the protein extraction process were calculated as 21.08 kJ mol(-1) and 84.76 J K(-1), respectively. The standard free energy (ΔG) had a magnitude from -3.77 to -5.46, suggesting that the extraction process was spontaneous and physically feasible.

Metabolomic approach to optimizing and evaluating antibiotic treatment in the axenic culture of cyanobacterium Nostoc flagelliforme.

The application of antibiotic treatment with assistance of metabolomic approach in axenic isolation of cyanobacterium Nostoc flagelliforme was investigated. Seven antibiotics were tested at 1-100 mg L(-1), and order of tolerance of N. flagelliforme cells was obtained as kanamycin > ampicillin, tetracycline > chloromycetin, gentamicin > spectinomycin > streptomycin. Four antibiotics were selected based on differences in antibiotic sensitivity of N. flagelliforme and associated bacteria, and their effects on N. flagelliforme cells including the changes of metabolic activity with antibiotics and the metabolic recovery after removal were assessed by a metabolomic approach based on gas chromatography-mass spectrometry combined with multivariate analysis. The results showed that antibiotic treatment had affected cell metabolism as antibiotics treated cells were metabolically distinct from control cells, but the metabolic activity would be recovered via eliminating antibiotics and the sequence of metabolic recovery time needed was spectinomycin, gentamicin > ampicillin > kanamycin. The procedures of antibiotic treatment have been accordingly optimized as a consecutive treatment starting with spectinomycin, then gentamicin, ampicillin and lastly kanamycin, and proved to be highly effective in eliminating the bacteria as examined by agar plating method and light microscope examination. Our work presented a strategy to obtain axenic culture of N. flagelliforme and provided a method for evaluating and optimizing cyanobacteria purification process through diagnosing target species cellular state.

Metabolic flux analysis of Gluconacetobacter xylinus for bacterial cellulose production.

Metabolic flux analysis was used to reveal the metabolic distributions in Gluconacetobacter xylinus (CGMCC no. 2955) cultured on different carbon sources. Compared with other sources, glucose, fructose, and glycerol could achieve much higher bacterial cellulose (BC) yields from G. xylinus (CGMCC no. 2955). The glycerol led to the highest BC production with a metabolic yield of 14.7 g/mol C, which was approximately 1.69-fold and 2.38-fold greater than that produced using fructose and glucose medium, respectively. The highest BC productivity from G. xylinus CGMCC 2955 was 5.97 g BC/L (dry weight) when using glycerol as the sole carbon source. Metabolic flux analysis for the central carbon metabolism revealed that about 47.96 % of glycerol was transformed into BC, while only 19.05 % of glucose and 24.78 % of fructose were transformed into BC. Instead, when glucose was used as the sole carbon source, 40.03 % of glucose was turned into the by-product gluconic acid. Compared with BC from glucose and fructose, BC from the glycerol medium showed the highest tensile strength at 83.5 MPa, with thinner fibers and lower porosity. As a main byproduct of biodiesel production, glycerol holds great potential to produce BC with superior mechanical and microstructural characteristics.

Salicylic Acid and Jasmonic Acid Increase the Polysaccharide Production of Nostoc flagelliforme via the Regulation of the Intracellular NO Level.

To significantly improve the polysaccharide production of Nostoc flagelliforme, a total of 12 chemicals were evaluated for their effects on polysaccharide accumulation. The results showed that salicylic acid and jasmonic acid increased the accumulation of the polysaccharides in N. flagelliforme significantly, by more than 20%. Three polysaccharides, namely control-capsule polysaccharide, salicylic acid-capsule polysaccharide, and jasmonic acid-capsule polysaccharide, were extracted and purified from N. flagelliforme under normal, salicylic acid, and jasmonic acid culture conditions, respectively. Their chemical compositions slightly differed regarding the total sugar and uronic acid contents, with average molecular weights of 2.06 × 103, 2.16 × 103 and 2.04 × 103 kDa, respectively. They presented similar Fourier transform infrared spectra and no significant difference in antioxidant activity. It was revealed that the salicylic acid and jasmonic acid significantly increased the level of nitric oxide. By investigating the effects of the exogenous nitric oxide scavenger and nitric oxide donor on the nitric oxide levels and polysaccharide yield of N. flagelliforme, the results showed that the increase in intracellular nitric oxide levels might be an important factor promoting the accumulation of polysaccharides. These findings provide a theoretical foundation for enhancing the yield of secondary metabolites by regulating the intracellular nitric oxide levels.

Four polysaccharides isolated from Poria cocos mycelium and fermentation broth supernatant possess different activities on regulating immune response.

Four polysaccharide fractions were isolated and purified from the culture supernatant and mycelium of Poria cocos, and differences in their immunomodulatory activity were investigated. The average molecular weights of EPS-0M, EPS-0.1M, IPS-0M, and IPS-0.1M were 1.77 × 103, 2.01 × 103, 0.03 × 103 and 4.97 × 103 kDa, respectively. They all mainly consisted of 5 monosaccharides, including glucose, mannose, galactose, fucose and rhamnose, but with different molar ratios. At a dose of 50 µg/mL, EPS-0M, EPS-0.1M, and IPS-0.1M significantly increased the production of nitric oxide (NO), as well as the mRNA and protein levels of pro-inflammatory factors including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1ß (IL-1ß) in RAW264.7 cells, suggesting that they enhanced macrophage-mediated innate immunity. Moreover, based on the in vitro inflammation model of lipopolysaccharide (LPS)-stimulated RAW264.7 cells, EPS-0M, EPS-0.1M and IPS-0M but not IPS-0.1M could inhibit the LPS-induced excessive inflammatory response, including NO, IL-6, TNF-α, IL-1ß production and gene transcription. Interestingly, IPS-0M showed a relatively poor immunostimulatory effect, but had the strongest inhibitory effect against the LPS-induced RAW264.7 inflammatory response. Furthermore, our results indicate that the nuclear factor-kappa B (NF-κB) pathway is associated with the immunomodulatory effects of the polysaccharide samples on RAW264.7 cells. This study can provide a reference for the more targeted application of different polysaccharide components from Poria cocos for human health.

Nostoc flagelliforme capsular polysaccharides from different culture conditions improve hyperlipidemia and regulate intestinal flora in C57BL/6J mice to varying degrees.

Two capsular polysaccharides (WL-CPS-1 and GLU-CPS-1) purified from Nostoc flagelliforme under normal and mixotrophic culture conditions were used to investigate the hypolipidemic activity and effect on intestinal flora in C57BL/6J mice respectively. Their molecular weight and monosaccharide composition have been determined in previous studies. They both improved the lipid level by affecting the expression of lipid metabolism genes. They down-regulated the TNF-α and IL-1ß levels in serum and up-regulated the activity of antioxidant enzymes in liver thus decreased the atherosclerosis index and MDA content. They up-regulated the short chain fatty acids (SCFAs) synthesis. They decreased the abundance of pathogenic bacteria and increased the abundance of probiotics positively correlated with SCFAs. Compared with WL-CPS-1, GLU-CPS-1 exhibited higher in vivo activity and enriched Odoribacter and Alloprevotella correlating with the gene expression of lipid metabolism, suggesting that the bioactivity of polysaccharides could be regulated by culture conditions. These findings contributed to application of N. flagelliforme polysaccharides with higher activity in hypolipidemia by adjusting culture conditions.

Fabrication of bacterial cellulose with TiO2-ZnO nanocomposites as a multifunctional membrane for water remediation.

Superhydrophilic/underwater superoleophobic (SUS) membrane technology has attracted extensive attention for water purification. However, the fabrication of multifunctional membranes to satisfy the complex wastewater treatment is still a big challenge. In this work, bacterial cellulose (BC) based multifunctional SUS membranes were designed for water purification. Membranes were prepared by blending BC nanofibers with TiO2 nanoparticles (NPs), and further modified by the in situ growth of ZnO-NPs. The composite membranes showed oil/water (o/w) separation under a small driving pressure (0.2-0.3 bar) with a flux rate of 8232.81 ± 212 L m-2h-1 and with a high separation efficiency (>99.9%). Membranes could also separate oil-in-water emulsion with a separation flux of 1498 ± 74 L m-2h-1 and with high efficiency (99.25%). Moreover, the composite membrane exhibited photocatalytic activity under visible light with a high efficiency (>92%). The composite membranes were also investigated for antibacterial activity against Gram-positive and Gram-negative bacterial strains. This work may inspire the fabrication of next-generation multifunctional membranes for wastewater treatment, particularly oily wastewater, dyes and microbial contaminated water.

Self-assembly of peptide nanofibers with chirality-encoded antimicrobial activity.

The nanostructured antimicrobial agents, self-assembled by the antimicrobial peptides (AMPs), represent an intriguing platform for the treatment of pathogens. Although the structural characteristics significantly influence antimicrobial functionality, the role of chirality is usually ignored and still unclear. Herein, two homochiral AMPs (all L- or all D-amino acids), including C16-LV4LR4 (LL) and C16-DV4DR4 (DD), and a heterochiral AMP with alternating D-/L-amino acids, C16-DV4LR4 (DL), were self-assembled into left-handed, right-handed, and right-handed helical nanofibers, respectively. The valine configuration determined the supramolecular chirality of the nanofibers. However, the DL molecules exhibited a highly aggregated propensity to form more stable helical nanofibers with a lower degree of twist and a larger helical pitch. This characteristic resulted in the optimal antimicrobial activity of the DL nanofibers against both Gram-negative and Gram-positive bacteria. Furthermore, the membrane permeability assay confirmed the higher activity for damaging the cell membrane by the DL nanofibers. These results demonstrated the significance of molecular chirality in directing the self-assembly of the amphiphilic peptides, eventually affecting their antimicrobial activity. This study opens up the possibility to fabricate promising nanostructured antimicrobial materials by controlling the chirality and structure of the materials.

In situ regulation of bacterial cellulose networks by starch from different sources or amylose/amylopectin content during fermentation.

Bacterial cellulose (BC) is a promising biopolymer, but its three-dimensional structure needs to be controllable to be used in multiple fields. BC has some advantages over other types of cellulose, not only in terms of purity and properties but also in terms of modification (in situ modification) during the synthesis process. Here, starches from different sources or with amylose/amylopectin content were added to the growth medium to regulate the structural properties of BC in-situ. The obtained BC membranes were further modified by superhydrophobic treatment for oil-water separation. Starches alter the viscosity of the medium, thus affecting bacterial motility and cellulose synthesis, and adhere to the microfibers, limiting their further polymerization and ultimately altering the membrane porosity, pore size, and mechanical properties perpendicular to the BC fibril layer direction. The average pore diameter of the BC/PS membrane increased by 1.94 times compared to the initial BC membrane. The chemically modified BC/PS membrane exhibited super-hydrophobicity (water contact angle 167°), high oil-water separation flux (dichloromethane, 23,205 Lm-2 h-1 MPa-1), high separation efficiency (>97%). The study provides a foundation for developing methods to regulate the network structure of BC and broaden its application.