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Phosphatidylserine (PS) and docosahexaenoic acid-phosphatidylserine (DHA-PS) have significant nutritional and biological functions, which are extensively used in functional food industries. Phospholipase D (PLD)-mediated transphosphatidylation of phosphatidylcholine (PC) or DHA-PC with l -serine, is an effective method for PS and DHA-PS preparation. However, because of the hydrolysis activity of PLD, PC and DHA-PC would be converted to the undesirable byproduct, phosphatidic acid (PA) and DHA-PA. In this study, a novel phospholipase D (PLD a2 ) was firstly cloned from Acinetobacter radioresistens a2 with high transphosphatidylation activity and no hydrolysis activity. In the PLD-catalyzed synthesis process (12 h), both the transphosphatidylation conversion rate and selectivity of PS and DHA-PS were about 100%, which is the only PLD enzyme reported with this superiority up till now. In comparison with the majority of other known PLDs, PLD a2 exerted the highest activity at neutral pH, and it was stable from pH 4.0 to pH 9.0. In addition, PLD a2 had excellent thermal stability, with an optimum reaction temperature of 40 °C and keeping more than 80% activity from 20 °C to 60 °C. The high catalytic selectivity mechanism of PLD a2 was explained by utilizing homology modeling, two-step docking, and binding energy and conformation analysis. PLD a2 ensured a stable supply of the biocatalyst with its most preponderant transphosphatidylation activity and PS selectivity, and had great potential in phospholipids industrial production. [ABSTRACT FROM AUTHOR]

Shrimp has constituted a major part of crustacean consumption in recent years. Solid wastes, including the head, shell, and tail portions, accumulate owing to shrimp processing. The accumulated biowastes without appropriate utilization have resulted in a squander of sources and problems of waste disposal and environmental pollution. Proper shrimp waste processing is an approach to recover biomaterials such as chitin, protein, lipids, astaxanthin, flavor compounds, and calcium carbonate. These active components have large-scale applications in biology as well as in food, pharmaceutical, agricultural, cosmetic, pulp, and textile industries. Traditionally, methods applied for the utilization of shrimp waste are chemical procedures using corrosive or hazardous reagents (such as HCl and NaOH), which are known to cause environmental pollution and resource wastage (or incomprehensive utilization) and increase the associated costs. However, new environment-friendly and clean technologies are emerging. In this review, we briefly analyze the bioactive compounds recovered from shrimp waste. A concise overview of the comprehensive utilization of shrimp waste in recent years has been included. Biotechnological methods such as biocatalysis and biotransformation with enzymes and microorganisms have also been described. The rapid development of corresponding biotechnology enables a simple, fast, effective, clean, economic, and controllable bioprocess for the comprehensive utilization of crustacean waste. [ABSTRACT FROM AUTHOR]

Antarctic krill was efficiently fermented by Bacillus subtilis OKF04 after the optimization of fermentation conditions. Bio-active substances were detected in fermentation broth, including polypeptides (9.5 g/L), phenols (1.1 g/L), polysaccharides (200.8 mg/L), and free amino acids (3469.4 mg/L). The fermentation broth was found to be rich in essential amino acids and non-protein amino acids, particularly methionine, leucine, lysine, and taurine. The fermentation broth was separated into 4 fractions: AKF-I (<1 kDa), AKF-II (1–3 kDa), AKF-III (3–5 kDa), and AKF-IV (>5 kDa), using membrane ultrafiltration. Antioxidative properties of the fermentation broth fractions were investigated, using DPPH (2, 2-diphenyl-1-picryl-hydrazyl-hydrate) scavenging activity, metal chelating activity and reducing capacity. The results showed that AKF-I and AKF-II had higher antioxidant activities than other fractions and the entire fermentation broth. These results indicate that bio-active substrates could be effectively and cleanly produced using fermentation of Antarctic krill by B. subtilis , and the antioxidant activity (DPPH scavenging activity, metal chelating activity and reducing capacity) of the fermentation broth is enhanced by ultrafiltration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microbial programmed death is divided into autolytic death, apoptosis-like death and the toxin-antitoxin system. • Ultraviolet, gamma radiation, cold plasma, ultrasound and H 2 O 2 oxidative stress cause divergent PCD in microbe. • Microbial PCD can be further developed and utilized in searching for new antimicrobial targets, development of new preservatives, engineering design of PCD modules, and optimization of fermentation strains. In recent years, programmed cell death (PCD) has attracted the attention of many scholars as an active death process. PCD refers to an active extinction process that occurs after cells receive a certain signal or are stimulated by certain factors in order to maintain the stability of the internal environment. It is orchestrated by precise molecular circuitry. Initially, PCD was thought to exhibit altruistic behavior of "active devotion", a physiological characteristic of multicellular organisms. However, many evidences show that PCD also exists in microbe, and researchers in recent years have found that some stressors during modern food processing could cause microbe undergo different forms of programmed death, including ultraviolet, gamma radiation, cold plasma, ultrasound, weak carboxylic acids and H 2 O 2. The attention to these situations will help researchers to explore novel mechanisms of sterilization. At present, microbial PCD can be further divided into three types, including apoptosis-like death, autolytic death, and toxin-antitoxin systems based on the differences in their intrinsic mechanisms. In order to better utilize these PCD mechanisms, four directions are provided from searching for new antimicrobial targets, development of new types of preservatives, engineering design in the field of synthetic biology and modification of fermentation strains. We believe that this review can provide useful help for scholars to carry out further research on microbial PCD. [ABSTRACT FROM AUTHOR]

agWH50C, a novel β-agarase gene, was cloned from Agarivorans gilvus WH0801 by degenerate PCR and nested PCR. The gene agWH50C comprized a 2,223-bp, encoding a protein of 740 amino acids. Sequencing results demonstrated that AgWH50C shared 45 % sequence identity with a well characterized β-agarase, Aga50D, from Saccharophagus degradans 2-40. The mature agarase was expressed in Escherichia coli and purified by affinity chromatography. The optimum pH and temperature for AgWH50C activity were 6.0 and 30 °C. The K and V values for agarose were 12.55 mg/ml and 1.17 U/mg. Analysis of the hydrolysis products using linear ion trap mass spectrometry, Fourier transform-nuclear magnetic resonance spectrometry and thin-layer chromatography confirmed that the reaction product of AgWH50c was α-neoagarobiose alone. Therefore, our novel agarase has the potential for industrial applications to produce neoagarobiose as well as provides a key β-agarase for fermentation of agar biomass. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two β-agarases were purified from Agarivorans albus OAY2 isolated from seaweed. [•] Fermentation process was optimized with enzyme activity improving to 2.65U/ml. [•] Purification resulted high specific activity of 2715 and 1338U/mg, respectively. [•] Hydrolysis products of agarose by agarase-a included diverse NAOS: NA2, NA4, NA6. [•] The products of agarose by agarase-a were different from those of the agarases of GH118 family. [ABSTRACT FROM AUTHOR]

Highlights: [•] We cloned and characterised a novel β-agarase from Agarivorans gilvus WH0801. [•] Compared with other known β-agarases, the identity of amino acid sequence was 53%. [•] The agarase was purified and characterised. [•] An exo-glycoside agarase which produced neoagarotetraose was first revealed. [•] This study laid a foundation for the preparation of neoagarotetraose in future. [Copyright &y& Elsevier]

Abstract: Medium compositions for the production of the novel derivatives of FR-008/Candicidin which was produced by a mutant of Streptomyces sp. FR-008 were optimized using two statistical methods including Plackett–Burman design (P–B), which was applied to find the key ingredients for the best medium composition, and response surface methodology (RSM), which was used to determine the optimal concentrations of these components. Results indicated that peptone, copper sulfate and glycerol had significant effects on the production. Under the proposed optimized conditions, the CS101 experimental yield (191.259mg/L) closely matched the yield (203.536mg/L) predicted by the statistical model. The optimization of the medium contributed to 10-fold higher antibiotic production than that of the control. It was first revealed that copper could stimulate FR-008/Candicidin and their derivatives synthesis at an optimal concentration in this paper, moreover, the basis of this phenomenon was also explained by investigating the enhancement of the enzymatic pathways. [Copyright &y& Elsevier]

[Display omitted] • Days 4 and 7 were significant for quality changes in refrigerated crab. • 369 differential abundant proteins were detected on days 0, 4 and 7. • 66 DAPs served as potential biomarkers for gazami crab muscle quality. • KEGG pathway ribosomes and autophagy were highest on day 7. Gazami crab (Portunus trituberculatus) is prone to spoilage during storage and transportation. More research is needed to determine how to reliably show its freshness and explain the mechanism of quality deterioration. We hypothesized that proteins extracted from crabs can be biomarkers to detect crab muscle quality changes. This work used physicochemical and proteomic approaches to investigate protein biomarkers and molecular mechanisms driving changes in gazami crab muscle quality after long-term refrigeration. It was shown that 66 differentially abundant proteins (DAPs) were closely associated with pH and texture and can be used as biomarkers to assess crab muscle freshness. According to bioinformatics studies, ribosomes and autophagy were significant mechanisms in crab rotting. These findings provided new concepts and a theoretical foundation for evaluating the freshness of refrigerated gazami crab and help uncover the molecular mechanism of its quality deterioration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amphiphilic halloysite nanosheets were prepared as carriers for immobilizing CALB. • The obtained amphiphilic halloysite nanosheet can stabilize Pickering emulsions. • The catalytic rate of immobilized CALB was almost twice that of free CALB. Lipase B from Candida antarctica (CALB) plays a prominent role as a biocatalyst in several industries, especially for biphasic conversion of functional lipids. Herein, an amphiphilic Janus halloysite nanosheet (JHNS) was fabricated and employed simultaneously as a solid surfactant for stabilizing Pickering emulsion and as a carrier for immobilizing CALB, with the aim to realize highly efficient biphasic bioconversion. The obtained JHNS could stabilize Pickering emulsion for at least 7 days. Immobilization of CALB on JHNS improved the substrate affinity, catalytic efficiency, thermal stability, and alkaline tolerance of the enzyme. Moreover, JHNS-based immobilized CALB was exploited as a biocatalytic platform for the conversion of retinyl acetate, with almost twice increase in conversion efficiency. Taken together, the JHNS-based immobilized CALB paves the way for the design of efficient biphasic conversion system for the production of added-value lipids. [ABSTRACT FROM AUTHOR]

A thermostable and alkaline-stable novel esterase (Est7) was identified through the whole genome sequencing of Stenotrophomonas maltophilia OUC_Est10. The open reading frame of this gene encoded 617 amino acid residues. After heterologous expression in Escherichia coli BL21 (DE3), the purified Est7 was separated as a single protein and presented a molecular mass of 70.6 kDa. Multiple sequence alignment indicated that Est7 had a typical catalytic triad (Ser-Asp-His) and the conserved sequence (GDSL) typical of the family II lipid hydrolase proteins. Est7 showed good stability in alkaline buffers, especially in Tris-HCl buffer at pH 9.0 (residual activity 93.8% after 96 h at 4 °C) and in the medium temperature conditions (residual activity 70.2% after 96 h at 45 °C and pH 8.0). The enzyme also retained higher stability toward several hydrophilic and hydrophobic organic solvents (e.g., after incubation in 100% acetonitrile or in n-hexane the enzyme retained about 97% and 84% of the activity in the absence of organic solvent, respectively). Furthermore, Est7 could catalyze the transesterification reaction of vinylacetate with 2-phenylethanol and cis-3-hexen-1-ol to their corresponding acetate esters in petroleum ether or tert-butyl methyl ether. These results indicate Est7 as a promising biocatalyst for applications of Est7 in non-aqueous media. [ABSTRACT FROM AUTHOR]

Phospholipids are distinctive, adaptable molecules that are crucial to numerous biological systems. Additionally, their various architectures and amphiphilic characteristics support their unrivaled crucial functions in scientific and industrial applications. Due to their enormous potential for use in the fields of medicine, food, cosmetics, and health, structured phospholipids, which are modified phospholipids, have garnered increased attention. Traditional extraction methods, however, are pricy, resource-intensive, and low-yielding. The process of enzyme-catalyzed conversion is effective for producing several types of structured phospholipase. However, most frequently employed catalytic procedures involve biphasic systems with organic solvents, which have a relatively large mass transfer resistance and are susceptible to solvent residues and environmental effects due to the hydrophobic nature of phospholipids. Therefore, the adoption of innovative, successful, and environmentally friendly enzyme-catalyzed conversion systems provides a new development route in the field of structured phospholipids processing. Several innovative catalytic reaction systems are discussed in this mini-review, including aqueous-solid system, mixed micelle system, water-in-oil microemulsion system, Pickering emulsion system, novel solvent system, three-liquid-phase system, and supercritical carbon dioxide solvent system. However, there is still a glaring need for a thorough examination of these systems for the enzymatic synthesis of structural phospholipids. In terms of the materials utilized, applicability, benefits and drawbacks, and comparative effectiveness of each system, this research establishes further conditions for the system's selection. To create more effective biocatalytic processes, it is still important to build green biocatalytic processes with improved performance. Key points: • The latest catalytic systems of phospholipase D are thoroughly summarized. • The various systems are contrasted, and their traits are enumerated. • Different catalytic systems' areas of applicability and limitations are discussed. [ABSTRACT FROM AUTHOR]

Phospholipids are distinctive, adaptable molecules that are crucial to numerous biological systems. Additionally, their various architectures and amphiphilic characteristics support their unrivaled crucial functions in scientific and industrial applications. Due to their enormous potential for use in the fields of medicine, food, cosmetics, and health, structured phospholipids, which are modified phospholipids, have garnered increased attention. Traditional extraction methods, however, are pricy, resource-intensive, and low-yielding. The process of enzyme-catalyzed conversion is effective for producing several types of structured phospholipase. However, most frequently employed catalytic procedures involve biphasic systems with organic solvents, which have a relatively large mass transfer resistance and are susceptible to solvent residues and environmental effects due to the hydrophobic nature of phospholipids. Therefore, the adoption of innovative, successful, and environmentally friendly enzyme-catalyzed conversion systems provides a new development route in the field of structured phospholipids processing. Several innovative catalytic reaction systems are discussed in this mini-review, including aqueous-solid system, mixed micelle system, water-in-oil microemulsion system, Pickering emulsion system, novel solvent system, three-liquid-phase system, and supercritical carbon dioxide solvent system. However, there is still a glaring need for a thorough examination of these systems for the enzymatic synthesis of structural phospholipids. In terms of the materials utilized, applicability, benefits and drawbacks, and comparative effectiveness of each system, this research establishes further conditions for the system's selection. To create more effective biocatalytic processes, it is still important to build green biocatalytic processes with improved performance. Key points: • The latest catalytic systems of phospholipase D are thoroughly summarized. • The various systems are contrasted, and their traits are enumerated. • Different catalytic systems' areas of applicability and limitations are discussed. [ABSTRACT FROM AUTHOR]

Chitosan derivates with varying degrees of polymerization (DP) have attracted great concern due to their excellent biological activities. Increasing the abundance of chitosanases with different degradation modes contributes to revealing their catalytic mechanisms and facilitating the production of chitosan derivates. However, the identification of endo-chitosanases capable of producing chitobiose and D-glucosamine (GlcN) from chitosan substrates has remained elusive. Herein, an endo-chitosanase (CsnCA) belonging to the GH46 family was identified based on structural analysis in phylogenetic evolution. Moreover, we demonstrate that CsnCA acts in a random endo-acting manner, producing chitosan derivatives with DP ≤ 2. The in-depth analysis of CsnCA revealed that (GlcN)3 serves as the minimal substrate, undergoing cleavage in the mode that occupies the subsites − 2 to + 1, resulting in the release of GlcN. This study succeeded in discovering a chitosanase with distinctive degradation modes, which could facilitate the mechanistic understanding of chitosanases, further empowering the production of chitosan derivates with specific DP. Key points: • Structural docking and evolutionary analysis guide to mining the chitosanase. • The endo-chitosanase exhibits a unique GlcN-producing cleavage pattern. • The cleavage direction of chitosanase to produce GlcN was identified. [ABSTRACT FROM AUTHOR]

Many by-products that are harmful to the environment and human health are generated during food processing. However, these wastes are often potential resources with high-added value. For example, crustacean waste contains large amounts of chitin. Chitin is one of the most abundant polysaccharides in natural macromolecules, and is a typical component of crustaceans, mollusks, insect exoskeleton and fungal cell walls. Chitosan is prepared by deacetylation of chitin and a copolymer of D-glucosamine and N -acetyl-D-glucosamine through β-(1 → 4)-glycosidic bonds. Chitosan has better solubility, biocompatibility and degradability compared with chitin. This review introduces the preparation, physicochemical properties, chemical and physical modification methods of chitosan, which could help us understand its biological activities and applications. According to the latest reports, the antibacterial activity, antioxidant, immune and antitumor activities of chitosan and its derivatives are summarized. Simultaneously, the various applications of chitosan and its derivatives are reviewed, including food, chemical, textile, medical and health, and functional materials. Finally, some insights into its future potential are provided, including novel modification methods, directional modification according to structure-activity relationship, activity and application development direction, etc. • The utilization of chitosan is effective solution to improve the value of waste. • The physicochemical properties and modification of chitosan were reviewed. • Chitosan and its derivatives have many biological activities. • Chitosan and its derivatives can be used in various industrial fields. [ABSTRACT FROM AUTHOR]

Ionizing radiation is increasingly used to successfully diagnose many human health problems, but ionizing radiation may cause damage to organs/tissues in the living organisms such as the spleen, liver, skin, and brain. Many radiation protective agents have been discovered, with the deepening of radiation research. Unfortunately, these protective agents have many side effects, which cause drug resistance, nausea, vomiting, osteoporosis, etc. The polysaccharides extracted from natural sources are widely available and low in toxicity. In vivo and in vitro experiments have demonstrated that polysaccharides have anti-radiation activity through anti-oxidation, immune regulation, protection of hematopoietic system and protection against DNA damage. Recently, some studies have shown that polysaccharides were resistant to radiation. In the review, the anti-radiation activities of polysaccharides from different sources are summarized, and the anti-radiation mechanisms are discussed as well. It can be used to develop more effective anti-radiation management drugs. • Natural polysaccharides have shown great potential for anti-radiation activity. • Summarize the anti-radiation activity of polysaccharides from different sources • The mechanism of polysaccharide radiation resistance was reviewed. [ABSTRACT FROM AUTHOR]

Agar is a polysaccharide mixture extracted from red algae. Agar has been widely used in food, medicine and biochemistry, because of its gelling properties and stability. However, sulfate groups in the structure of agar weaken the gel strength of agar; hence, sulfate removal is necessary to improve the agar quality. The commonly used alkali desulfation greatly pollutes the environment, and enzymatic desulfation is costly due to the need for a large amount of the enzyme. In this work, microorganisms were for the first time used for agar desulfation, taking advantage of the sulfur demand of microorganisms themselves. This allows the removal of agar sulfate groups to be eco-friendly and effective. Firstly, microorganism strains were screened with agar as the sole sulfur source. Then 4 microorganism-based agar desulfation techniques, sulfate removal from agar liquid at 60 °C, from an solid agar plate at 37 °C, from freshly-prepared agar slices in liquid medium, and from agar strips without pretreatment (ASWP) in liquid medium, were established and compared. Finally, by using Priestia megaterium WMX, the sulfate removal rate from ASWP reached 74.67%, and the gel strength increased by 187%, reaching 1173 g cm−2. Therefore, the agar quality was greatly improved by sulfate removal with microorganisms. The microorganism-based agar desulfation technique established in this work is easy-to-perform, cost effective, and an eco-friendly way to improve agar quality and has the potential to be applied on the industrial scale. [ABSTRACT FROM AUTHOR]

A novel chitinase gene of 888 bp from Streptomyces bacillaris was cloned and expressed in Escherichia coli BL21. The purified recombinant enzyme (SbChiAJ103) was identified as the first microbial-derived family 19 endochitinase that showed exochitinase activity. SbChiAJ103 exhibited the substrate preference for N-acetylchitooligosaccharides with even degrees of polymerization and the capability to specifically hydrolyze colloidal chitin into (GlcNAc)2. Mono-methyl adipate was employed as a novel linker for the efficient covalent immobilization of chitinase on magnetic nanoparticles (MNPs). The immobilized SbChiAJ103, SbChiAJ103@MNPs, exhibited superior pH tolerance, temperature stability, and storage stability than free SbChiAJ103. Even after incubation at 45 °C for 24 h, SbChiAJ103@MNPs could retain more than 60.0% initial activity. As a result, the enzymatic hydrolysis yield of SbChiAJ103@MNPs increased to 1.58 times that of free SbChiAJ103. Moreover, SbChiAJ103@MNPs could be reused by convenient magnetic separation. After 10 recycles, SbChiAJ103@MNPs could retain almost 80.0% of its initial activity. The immobilization of the novel chitinase SbChiAJ103 paves the way to the efficient and eco-friendly commercial production of (GlcNAc)2. Key points: • The first microbial GH19 endochitinase with exochitinase activity was reported. • Mono-methyl adipate was first employed to immobilize chitinase. • SbChiAJ103@MNPs showed excellent pH stability, thermal stability, and reusability. [ABSTRACT FROM AUTHOR]

Zosteric acid (ZA) is a Zostera species-derived, sulfated phenolic acid compound with antifouling activity and has gained much attention due to its nontoxic and biodegradable characteristics. However, the yield of Zostera species available for ZA extraction is limited by natural factors, such as season, latitude, light, and temperature. Here we report the development of metabolically engineered Escherichia coli strains capable of producing ZA from glucose and glycerol. First, intracellular availability of the sulfur donor 3′-phosphoadenosine-5′-phosphosulfate (PAPS) was enhanced by knocking out the cysH gene responsible for PAPS consumption and overexpressing the genes required for PAPS biosynthesis. Co-overexpression of the genes encoding tyrosine ammonia-lyase, sulfotransferase 1A1, ATP sulfurylase, and adenosine 5′-phosphosulfate kinase constructed ZA producing strain with enhanced PAPS supply. Second, the feedback-resistant forms of aroG and tyrA genes (encoding 3-deoxy- d -arabinoheptulosonate 7-phosphate synthase and chorismate mutase, respectively) were overexpressed to relieve the feedback regulation of L- tyrosine biosynthesis. Third, the pykA gene involved in phosphoenolpyruvate-consuming reaction, the regulator gene tyrR , the competing pathway gene pheA , and the ptsHIcrr genes essential for the PEP:carbohydrate phosphotransferase system were deleted. Moreover, all genes involved in the shikimate pathway and the talA , tktA , and tktB genes in the pentose phosphate pathway were examined for ZA production. The PTS-independent glucose uptake system, the expression vector system, and the carbon source were also optimized. As a result, the best-performing strain successfully produced 1.52 g L−1 ZA and 1.30 g L−1 p -hydroxycinnamic acid from glucose and glycerol in a 700 mL fed-batch bioreactor. • Multi-level metabolic engineering of E. coli allowed p -hydroxycinnamic acid and zosteric acid production. • Knockout of cysH and overexpression of ATPSL and APSK synergically improved intracellular PAPS content. • Accumulation of p -hydroxycinnamic acid hindered sulfation in zosteric acid biosynthesis. • Fed-batch culture produced 1.52 g L−1 zosteric acid and 1.30 g L−1 p -hydroxycinnamic acid. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple ball-milling method with the aid of ionic liquid was successfully applied to product cellulose nanofibrils. • A one-step immobilizing procedure was developed to produce the immobilized-on-cellulose enzyme. • The CNF-CBD1 was used as Pickering emulsions stabilizers for efficient synthesis of phosphatidylserine. • The Pickering emulsion obtained was an attractive Pickering interfacial biocatalysis platform. An efficient and attractive platform for synthesizing phosphatidylserine is indispensable for driving large-scale industrial applications. Given the interfacial effect of phospholipase D (PLD), an adequate oil-water interface surface is essential for the catalytic efficiency of PLD. Herein, a simple ball-milling method with ionic liquid was successfully applied to produce cellulose nanofibrils and immobilized PLD with the cellulose-binding domain through a one-step procedure. Each droplet in the Pickering reaction system was regarded as a microreactor to provide sufficient oil-water interface to the active sites of PLD. The constructed Pickering emulsion system exhibited outstanding catalytic activity, achieving 95.4 % conversion after 2 h with the minimal amount of catalyst (0.8 wt% of CNF-CBD1 addition amount), which was 6-fold higher than the previously reported immobilized MCC-CBD1 and 21-fold higher than free PLD-CBD1. These results demonstrated a sustainable and high-performance biocatalysis method, paving the way for the efficient synthesis of novel phospholipids. [ABSTRACT FROM AUTHOR]

Chitin deacetylase can be used in the green and efficient preparation of chitosan from chitin. Herein, a novel chitin deacetylase SbCDA from Streptomyces bacillaris was heterologously expressed and comprehensively characterized. SbDNA exhibits its highest deacetylation activity at 35 °C and pH 8.0. The enzyme activity is enhanced by Mn2+ and prominently inhibited by Zn2+, SDS, and EDTA. SbCDA showed better deacetylation activity on colloidal chitin, (GlcNAc)5, and (GlcNAc)6 than other forms of the substrate. Molecular modification of SbCDA was conducted based on sequence alignment and homology modeling. A mutant SbCDA63G with higher activity and better temperature stability was obtained. The deacetylation activity of SbCDA63G was increased by 133% compared with the original enzyme, and the optimal reaction temperature increased from 35 to 40 °C. The half-life of SbCDA63G at 40 °C is 15 h, which was 5 h longer than that of the original enzyme. The improved characteristics of the chitin deacetylase SbCDA63G make it a potential candidate to industrially produce chitosan from chitin. [ABSTRACT FROM AUTHOR]

Chitosanase, a glycoside hydrolase (GH), catalyzes the cleavage of β-1,4-glycosidic bonds in polysaccharides and is widely distributed in nature. Many organisms produce chitosanases, and numerous chitosanases in the GH families have been intensely studied. The reported chitosanases mainly cleaved the inter-glucosamine glycosidic bonds, while substrate specificity is not strictly unique due to the existence of bifunctional or multifunctional activity profiles. The promiscuity of chitosanases is essential for the different pathways of biomass polysaccharide conversion and understanding of the chitosanase evolutionary process. However, the reviews for this aspect are completely unknown. This review provides an overview of the promiscuous activities, also considering the substrate and product specificity of chitosanases observed to date. These contribute to important implications for the future discovery and research of promiscuous chitosanases and applications related to biomass conversion. Key points: • The promiscuity of chitosanases is reviewed for the first time. • The current review provides insights into the substrate specificity of chitosanases. • The mode-product relationship and prospect of promiscuous chitosanases are highlighted. [ABSTRACT FROM AUTHOR]

Here, a novel double‐crosslinked hydrogel dressing with enhanced antibacterial and anti‐inflammatory activities is reported. Carboxymethyl chitosan is crosslinked with silane and Ca2+ to form a double‐crosslinked hydrogel, and silver nanoparticles are loaded to introduce antibacterial properties to the hydrogel. The covalent crosslinking preserves the integrity of the hydrogel matrix, while the ionic crosslinking dissipates the energy under deformation. It combines high stretchability, toughness, tissue adhesion, and antimicrobial function. This hydrogel exhibits excellent cytocompatibility and hemocompatibility. Moreover, in vitro and in vivo investigations demonstrate its efficacy in accelerating bacterial‐infected wound healing. Given its excellent cytocompatibility and mechanical properties, this hydrogel is anticipated to be widely used in bacteria‐associated wound management. [ABSTRACT FROM AUTHOR]

A new α-neoagarobiose hydrolase (NABH) called AgaWH117 was cloned from Agarivorans gilvus WH0801. The gene encoding this hydrolase consists of 1,086 bp and encodes a protein containing 361 amino acids. This new NABH showed 74% amino acid sequence identity with other known NABHs. The molecular mass of the recombinant AgaWH117 was estimated to be 41 kDa. Purified AgaWH117 showed endolytic activity during neoagarobiose degradation, yielding 3,6-anhydro- l-galactose ( l-AHG) and d-galactose as products. It showed a maximum activity at a temperature of 30 °C and a pH of 6.0 and was stable at temperatures below 30 °C. Its Km and Vmax values were 2.094 mg/mL and 6.982 U/mg, respectively. The cloning strategy used and AgaWH117 isolated in this study will provide information on the saccharification process of marine biomass. This study provides a method to produce l-AHG from agarose by using AgaWH117 without an acid and describes its one-step purification by using Bio-Gel P2 chromatography. [ABSTRACT FROM AUTHOR]

[Display omitted] • Complete inactivation of PPO by 3–9 V/cm DC electric field was realized. • The inactivation kinetics conforms to Weibull model with n > 1. • Structural change of PPO in electric field was analyzed by MD simulation the first time. • The receptor binding domain of catechol in PPO was altered by DC field, and bonding energy decreased. In this study, inactivation of mushroom polyphenol oxidase (PPO) by low intensity direct current (DC) electric field and its molecular mechanism were investigated. In the experiments under 3 V/cm, 5 V/cm, 7 V/cm and 9 V/cm electric fields, PPOs were all completely inactivated after different exposure times. Under 1 V/cm, a residual activity of 11.88 % remained. The inactivation kinetics confirms to Weibull model. Under 1–7 V/cm, n value closes to a constant about 1.3. The structural analysis of PPO under 3 V/cm and 5 V/cm by fluorescence emission spectroscopy and molecular dynamics (MD) simulation showed that the tertiary structure was slightly changed with increased radius of gyration, higher potential energy and rate of C-alpha fluctuation. After exposure to the electric field, most of the hydrophobic tryptophan (TRP) residues turned to the hydrophilic surface, resulting the fluorescence red-shifted and quenched. Molecular docking indicated that the receptor binding domain of catechol in PPO was changed. PPO under electric field was MD simulated the first time, revealing the changing mechanism of the electric field itself on PPO, a binuclear copper enzyme, which has a metallic center. All these suggest that the low intensity DC electric field would be a promising option for enzymatic browning inhibition or even enzyme activity inactivation. [ABSTRACT FROM AUTHOR]

Carrageenan, the major carbohydrate component of some red algae, is an important renewable bioresource with very large annual outputs. Different types of carrageenolytic enzymes in the carrageenan metabolic pathway are potentially valuable for the production of carrageenan oligosaccharides, biofuel, and other chemicals obtained from carrageenan. However, these enzymes are not well-developed for oligosaccharide or biofuel production. For further application, comprehensive knowledge of carrageenolytic enzymes is essential. Therefore, in this review, we first summarize various carrageenolytic enzymes, including the recently discovered β-carrageenase, carrageenan-specific sulfatase, exo -α-3,6-anhydro-D-galactosidase (D-ADAGase), and exo-β-galactosidase (BGase), and describe their enzymatic characteristics. Subsequently, the carrageenan metabolic pathways are systematically presented and applications of carrageenases and carrageenan oligosaccharides are illustrated with examples. Finally, this paper discusses critical aspects that can aid researchers in constructing cascade catalytic systems and engineered microorganisms to efficiently produce carrageenan oligosaccharides or other value-added chemicals through the degradation of carrageenan. Overall, this paper offers a comprehensive overview of carrageenolytic enzymes, providing valuable insights for further exploration and application of these enzymes. [ABSTRACT FROM AUTHOR]

Polymerized guluronates (polyG)-specific alginate lyase with lower polymerized mannuronates (polyM)-degrading activity, superior stability, and clear action mode is a powerful biotechnology tool for the preparation of AOSs rich in M blocks. In this study, we expressed and characterized a polyG-specific alginate lyase OUC-FaAly7 from Formosa agariphila KMM3901. OUC-FaAly7 belonging to polysaccharide lyase (PL) family 7 had highest activity (2743.7 ± 20.3 U/μmol) at 45 °C and pH 6.0. Surprisingly, its specific activity against polyG reached 8560.2 ± 76.7 U/μmol, whereas its polyM-degrading activity was nearly 0 within 10 min reaction. Suggesting that OUC-FaAly7 was a strict polyG-specific alginate lyase. Importantly, OUC-FaAly7 showed a wide range of temperature adaptations and remarkable temperature and pH stability. Its relative activity between 20 °C and 45 °C reached >90 % of the maximum activity. The minimum identifiable substrate of OUC-FaAly7 was guluronate tetrasaccharide (G4). Action process and mode showed that it was a novel alginate lyase digesting guluronate hexaose (G6), guluronate heptaose (G7), and polymerized guluronates, with the preferential generation of unsaturated guluronate pentasaccharide (UG5), although which could be further degraded into unsaturated guluronate disaccharide (UG3) and trisaccharide (UG2). This study contributes to illustrating the catalytic properties, substrate recognition, and action mode of novel polyG-specific alginate lyases. [Display omitted] [ABSTRACT FROM AUTHOR]

• Incorporation of proline improved water-holding capacity of frozen shrimp. • Interactions between proline, water, and myosin were studied. • Proline improved the stability of shrimp myosin. • Proline may form a glassy state around shrimp myosin. • Proline inhibited ice crystal formation by forming hydrogen bonds with water. This study aimed to investigate the cryoprotective properties of proline (1% and 3% (w/v)) on shrimp. The cryoprotective mechanism was studied using physico-chemical experiments and molecular simulations. Proline had a notable positive impact on the thawing loss and texture of shrimp in comparison to the control. The denaturation of myosin in frozen shrimp was delayed by proline. Microscopy analysis demonstrated that proline effectively lowered the harm caused by ice crystals to shrimp muscle. Molecular simulations indicated that proline potentially exerted a cryoprotective effect primarily through the "water substitution" and "glassy state" hypotheses. Proline formed hydrogen bonds with myosin to replace the water molecules around myosin. Additionally, proline interacted with water molecules to form a glassy state, impeding the growth of ice crystals. Consequently, the stability of shrimp myosin was enhanced during freezing. In conclusion, proline demonstrated promise as an efficacious cryoprotectant for aquatic products. [ABSTRACT FROM AUTHOR]

Non-homogeneous enzyme-catalyzed systems are more widely used than homogeneous systems. Distinguished from the conventional biphasic approach, Pickering emulsion stabilized by ultrafine solid particles opens up an innovative platform for biocatalysis. Their vast specific surface area significantly enhances enzyme-substrate interactions, dramatically increasing catalytic efficiency. This review comprehensively explores various aspects of Pickering emulsion biocatalysis, provides insights into the multiple types and mechanisms of its catalysis, and offers strategies for material design, enzyme immobilization, emulsion formation control, and reactor design. Characterization methods are summarized for the determination of drop size, emulsion type, interface morphology, and emulsion potential. Furthermore, recent reports on the design of stimuli-responsive reaction systems are reviewed, enabling the simple control of demulsification. Moreover, the review explores applications of Pickering emulsion in single-step, cascade, and continuous flow reactions and outlines the challenges and future directions for the field. Overall, we provide a review focusing on Pickering emulsions catalysis, which can draw the attention of researchers in the field of catalytic system design, further empowering next-generation bioprocessing. • Pickering emulsion biocatalysis is focused and systematically reviewed. • Design principles for Pickering emulsion systems are introduced in different design stages. • Different stimuli-responsive reaction systems used for demulsification are reviewed. • Detailed methods for Pickering emulsion characterization are summarized. • Applications and promising prospects of Pickering emulsion biocatalysis are proposed. [ABSTRACT FROM AUTHOR]

Aquatic foods, also known as blue foods, contain a wide range of unique bioactive substances. Among these substances, aquatic foods-derived bioactive peptides exhibit diverse structures and activities, including blood pressure reduction, antibacterial effects, uric acid level reduction, and antioxidant effects. As a result, these peptides show considerable potential for application in functional foods. Existing reviews on aquatic foods-derived bioactive peptides have focused primarily on their functional activities and preparation methods, while neglecting the latest trends in rapid discovery and large-scale production of peptides. Therefore, in addition to summarizing the most recent preparation methods of aquatic foods-derived bioactive peptides, this paper also examines the structure-activity relationships and strategies for large-scale production of active peptides. The use of bioinformatics techniques, such as docking and data mining, can significantly expedite the process of discovering and purifying of aquatic foods-derived bioactive peptides. Furthermore, the precise design and optimization of peptides based on their structure-activity relationships can effectively enhance their activity. Heterologous biosynthesis via the modification of host and target peptides holds promise for enabling large-scale production of these peptides. These methods represent the future direction of research on aquatic foods-derived bioactive peptides. • Bioinformatics accelerates the discovery of aquatic foods derived-active peptides. • Active peptide can be rationally designed based on structure-activity relationship. • Heterologous biosynthesis could facilitate the large-scale preparation of peptides. [ABSTRACT FROM AUTHOR]

Here, a multifunctional film (MFF) as an alternative tissue adhesive in the form of an interpenetrating network consisting of self‐crosslinked aldehyde‐functionalized chitosan (AC) and crosslinked poly(acrylic acid) (PAA) further coordinated with Ag+ is reported. The MFF combines enhanced toughness and stretchability, which is attributed to the synergistic effects of the double‐network design. Covalent crosslinking maintains the overall integrity of the MFF matrix, while noncovalent crosslinking dissipates energy under deformation. Upon contact, the MFF quickly dries the tissue surface followed by instant physical crosslinking to the tissue. Subsequent covalent crosslinking between the aldehyde groups of the MFF and the primary amine groups on the surface of the tissue further stabilizes the adhesion. Meanwhile, Ag+ provides strong antibacterial properties to the MFF. Notably, in vivo studies demonstrate that the MFF allows facile and tough attachment to the wet and dynamic surface of rabbit liver and presents superior hemostasis and sealing properties. Furthermore, the MFF can be safely degraded without causing abnormal defects in vivo. The outstanding physicochemical properties of the MFF can potentially be a good alternative to existing sutures or staples and has potential for use in clinical practice. [ABSTRACT FROM AUTHOR]

Plectasin is a promising and potent antimicrobial peptide isolated from the fungus Pseudoplectania nigrella which has been heterologously expressed in various hosts. In this study, a four-copy cassette of plectasin was constructed via 2A peptide assembly to further increase its expression level in recombinant Pichia pastoris. The yeast transformant 4Ple-61 harboring four-copy cassette of plectasin could secrete 183.2 mg/L total protein containing 60.8% of plectasin at the flask level within 120 h, which was 2.3 times higher than that of the yeast transformant Ple-6 carrying one-copy cassette of plectasin. Western blot confirmed the significant peptide expression level in the transformant 4Ple-61. Furthermore, it yielded as high as 426.3 mg/L total protein within 120 h during a 5-L fermentation. The purified plectasin shows superior stability and good antimicrobial activity against conventional Staphylococcus aureus ATCC 26,001 and some food-borne antibiotic-resistant S. aureus strains with the MICs ranging from 8 to 32 μg/mL. Therefore, the strategy based on 2A peptide assembly can enhance the expression of plectasin and further expand its application prospect. Key points: • A yeast transformant 4Ple-61 with four-copy cassette of plectasin was constructed. • The plectasin level yield by the transformant 4Ple-61 was boosted by 2.3 times. • The plectasin showed good activity against food-borne antibiotic-resistant S. aureus. [ABSTRACT FROM AUTHOR]

This study aimed to identify saltiness-enhancing peptides from yeast protein and elucidate their mechanisms by molecular docking. Yeast protein hydrolysates with optimal saltiness-enhancing effects were prepared under conditions determined using an orthogonal test. Ten saltiness-enhancing peptide candidates were screened using an integrated virtual screening strategy. Sensory evaluation demonstrated that these peptides exhibited diverse taste characteristics (detection thresholds: 0.13–0.50 mmol/L). Peptides NKF, LGLR, WDL, NMKF, FDSL and FDGK synergistically or additively enhanced the saltiness of a 0.30% NaCl solution. Molecular docking revealed that these peptides predominantly interacted with TMC4 by hydrogen bonding, with hydrophilic amino acids from both peptides and TMC4 playing a pivotal role in their binding. Furthermore, Leu217, Gln377, Glu378, Pro474 and Cys475 were postulated as the key binding sites of TMC4. These findings establish a robust theoretical foundation for salt reduction strategies in food and provide novel insights into the potential applications of yeast proteins. • Yeast protein derived saltiness-enhancing peptide candidates were virtually screened. • NKF, LGLR, WDL, NMKF, FDSL, FDGK were sensory confirmed to enhance NaCl's saltiness. • Interaction with TMC4 via H-bond promotes the saltiness enhancement of peptides. • Leu217/Gln377/Glu378/Pro474/Cys475 were deduced as the key binding sites of TMC4. [ABSTRACT FROM AUTHOR]

Advanced analytical techniques are emerging in the food industry. Aptamer-based biosensors achieve rapid and highly selective analysis, thus drawing particular attention. Aptamers are oligonucleotide probes screened via in vitro Systematic Evolution of Ligands by EXponential Enrichment (SELEX), which can bind with their specific targets by folding into three-dimensional configurations and accept various modifications to be incorporated into biosensors, showing great potential in food analysis. Unfortunately, aptamers obtained by SELEX may not possess satisfactory affinity. Post-SELEX strategies were proposed to optimize aptamers' configuration and enhance the binding affinity, with specificity confirmed. Sequence-based optimization strategies exhibit great advantages in simple operation, good generalization, low cost, etc. This review summarizes the latest study (2015–2023) on generating robust aptamers for food targets by sequence-based configuration optimization, as well as the generated aptamers and aptasensors, with an expectation to provide inspirations for developing aptamer and aptasensors with high performance for food analysis and to safeguard food quality and safety. [Display omitted] • Robust aptamer generation for food targets is of great significance. • Methods utilizing sequence-based configuration optimization were succinctly reviewed. • Performance of generated aptamers and developed aptasensors was concisely summarized. • Critical discussion and perspective of aptamer generation and application were given. [ABSTRACT FROM AUTHOR]

Although chitooligosaccharide (COS) has attracted the attention of some researchers due to its good solubility and broad-spectrum antibacterial activity, our study found that Staphylococcus aureus treated with low concentration of COS actively entered the viable-but-nonculturable (VBNC) state to resist this environmental stress. In this study, the transcriptome of VBNC-state S. aureus after COS treatment was analyzed by RNA-sequencing. Compared with the control group, pathway enrichment analysis showed that COS-treated S. aureus adopted a series of adaptive adjustment strategies for survival, including significant up-regulation of the differential genes' expression of such as ABC transporters (metI , tagG), Sec dependent transport pathway (secDF), peptidoglycan synthesis pathway (murG) and alteration of their physiological metabolic patterns, where ATP depletion played a key role in the formation of the VBNC-state S. aureus. Further, by using oxidative phosphorylation uncoupling agent to adjust the initial level of ATP in S. aureus , it was found that the reduction of intracellular ATP level could accelerate the formation of VBNC state. Overall, our results preliminarily elucidated the molecular mechanism of COS inducing the VBNC-state S. aureus. It provided an important theoretical reference for further achieving effective bacterial inactivation by COS. [Display omitted] [ABSTRACT FROM AUTHOR]

For the first time, the efficacy of low intensity (1–7 V/cm) direct-current (DC) electric field in preventing browning in apple juice is examined. The results show that applying a 5 V/cm electric field can inactivate 89.24% of polyphenol oxidase (PPO) within 90 min and achieve complete inactivation of peroxidase (POD) within 70 min, maintaining the juice temperature below 30 °C throughout the process. The Weibull model fits the PPO and POD inactivation effectively, suggesting varied responses among isoenzymes. Under the optimal conditions (5 V/cm for 90 min), a 15.89% increase in total phenolic content (TPC) was observed alongside significant improvements in antioxidant activity. Furthermore, this method preserved the natural flavor and lightened the color of the apple juice, enhancing its sensory appeal. These findings indicate that low intensity DC electric field is an innovative and effective choice for preventing juice browning, offering significant potential for application in the food industry. • Anti-browning of apple juice was feasible using a DC electric field of 5–7 V/cm at below 30 °C. • First-order kinetic model fitted the PPO inactivation more reasonable. • Exposure to 5 V/cm for 90 min gave the apple juice favorable characteristics. [ABSTRACT FROM AUTHOR]

Cheese is the potential great source of umami peptides, while studies on umami peptides in cheese are scant and current sensory-guided strategies are difficult for rapid and high-throughput screening umami peptides. Herein, the peptidomics of Cheddar cheese was conducted and 6 potential umami peptides (LEEL, EKNRLNFLK, DERF, NAVPITPTLNREQ, NMAINPSKENL, GKEKVNELSK) were screened by an integrated bioinformatics approach. Peptides except LEEL were validated as umami peptides while LEEL and DERF exhibited significant umami-enhancing effects. Molecular docking revealed that hydrogen bonds formed by hydrophilic amino acids between peptides and T1R1/T1R3 are critical for the binding of umami peptides to umami receptors. Furthermore, Phe247, Gln278 of T1R1 and Pro106 of T1R3 were inferred as key binding sites. In silico gastrointestinal digestion indicated that peptides except DERF have hypoglycemic and hypotensive potential. This work lays the foundation for high-throughput umami peptide screening and advances to understand the umami mechanism of cheese. • Peptidomics and bioinformatics were jointly used to screen umami peptides. • Six novel umami/umami-enhancing peptides were identified from Cheddar cheese. • Peptide-T1R1/T1R3 H-bonds formed by hydrophilic AAs are vital for umami perception. • Phe247, Gln278 of T1R1 and Pro106 of T1R3 were also key binding sites. • The other 5 peptides except DERF have hypoglycemic and hypotensive potential. [ABSTRACT FROM AUTHOR]

• Virtual strategies were integrated for high-throughput screening of umami peptides. • Six novel umami peptides CN, SM, CRD, GESMTDGF, MS and DGC were identified. • CRD, GESMTDGF, DGC had higher umami intensity and obvious umami-enhancing effects. • Umami-tasting mechanism of peptides was partly revealed by docking with T1R1/T1R3. • H-bonds formed by hydrophilic AAs of T1R1/T1R3 play key roles in umami perception. This study aimed to rapidly and precisely discover novel umami peptides from porcine type I collagen using virtual screening, sensory evaluation and molecular docking simulation. Porcine type I collagen was hydrolyzed in silico and six umami peptide candidates (CN, SM, CRD, GESMTDGF, MS, DGC) were shortlisted via umami taste, bioactivity, toxicity, allergenicity, solubility and stability predictions. The sensory evaluation confirmed that these peptides exhibited umami taste, with CRD, GESMTDGF and DGC displaying higher umami intensity and significant umami-enhancing effects in 0.35% sodium glutamate solution. Molecular docking predicted that Ser 276/384/385 of T1R1 and Asn68, Val277, Thr305, Ser306, Leu385 of T1R3 may also play critical roles in binding umami peptides. The umami taste of peptides may be perceived mainly through the formation of hydrogen bonds with the hydrophilic amino acids of T1R1/T1R3. This work provided a robust procedure and guidance to develop novel umami peptides from food byproducts. [ABSTRACT FROM AUTHOR]

In this paper, the effects of different microbial transglutaminase (mTGase) treatments (0–0.5% w/w) on the structural and functional characteristics of frozen shrimp (Litopenaeus vannamei) were investigated to explore the changes in myofibrillar protein (MP) during the catalytic process of mTGase, and further enhance the gel properties of shrimp surimi products. Fourier transform infrared spectroscopy showed that mTGase treatment caused a shift from α-helix to β-turn and β-sheet in the secondary structure of the protein, while chemical force results indicated that moderate addition of enzyme could promote the formation of disulfide bonds in the gel system, contributing to the formation of a stable three-dimensional spatial structure. These structural changes led to a significant increase in gel strength, WHC and storage modulus (G′) after mTGase-induced protein gelation, resulting in an increase in the solid properties of the gel; and the relaxation time T 22 was significantly shortened, indicating a gradual decrease in water freedom in the protein gel network. In addition, scanning electron microscopy results showed that the gel with 0.4% mTGase had a denser network structure and more uniform pores. Simultaneously, mTGase facilitated the reduction of free amino groups through deamination reaction, resulting in an elevated cross-linking degree and a reduced hydrolysis rate of pepsin. The above results indicated that appropriate mTGase treatment could improve the structure and functional properties of shrimp, benefit the quality of shrimp surimi products, and provide some references for the highly processed frozen Litopenaeus vannamei. [Display omitted] • MTGase led to the unfolding of MP conformation and raised disulfide bond contents. • Conformational change facilitated the formation of more compact microstructures. • The gelation characteristics of shrimp MP gel were enhanced by mTGase. • MTGase exerted regulatory effects on the enzymatic hydrolysis of shrimp surimi gel. [ABSTRACT FROM AUTHOR]

• Ultrasonic stress could cause active programmed death of Vibrio parahaemolyticus. • Ultrasonic stress disrupted the balance of redox reactions, mediating DNA damage. • Involvement of SOS response in the activation of apoptosis in Vibrio parahaemolyticus. • Diversity in lethal modes of Vibrio parahaemolyticus induced by ultrasonic cavitation. As an effective non-thermal sterilization method, ultrasound remains at the level of passive bacterial death despite the initial understanding of its sterilization mechanism. Here, we present the perspective that bacteria can choose to actively enter an apoptosis-like death state in response to external ultrasonic stress. In this study, Vibrio parahaemolyticus exhibited apoptotic markers such as phosphatidylserine ectropion and activated caspases when subjected to ultrasound stress. Additionally, the accumulation of reactive oxygen species (ROS) and enhanced calcium signaling were observed. Further transcriptomic analysis was conducted to investigate the regulatory mechanism of the SOS response in Vibrio parahaemolyticus during an apoptosis-like state. The results showed that the genes encoding the citrate cycle were down-regulated in Vibrio parahaemolyticus cells adapted to ultrasonic stress, leading to an apoptosis-like state and a decrease in production capacity and ability to catabolize carbon dioxide. Furthermore, the level of oxidized glutathione increased, suggesting that the bacteria were engaged in various anti-oxidative stress responses, ultimately leading to apoptosis. Moreover, the ultrasound field activated the regulatory factor CsrA, which facilitates stress survival as cells transition from rapid growth to an apoptotic state through a stringent response and catabolic inhibition system. Parallel reaction monitoring (PRM) revealed that the expression of certain key SOS proteins in Vibrio parahaemolyticus was up-regulated following ultrasound treatment, resulting in a gradual adaptation of the cells to external stress and ultimately leading to active cell death. In conclusion, the biological lethal effect of ultrasound treatment is not solely a mechanical cell necrosis process as traditionally viewed, but also a programmed cell death process regulated by cellular adaptation. This enriched the biological effect pathway of ultrasound sterilization. [ABSTRACT FROM AUTHOR]

Enteric-coated application on drug is used to prevent the drug from inactivation which are degraded by gastric enzyme. The present study is aimed at achieving controlled drug delivery in acidic medium of gastrointestinal tract (GIT) by enteric coating of hydroxy propyl methylcellulose (HPMC) and Eudragit L100 on carboxylated agarose hydrogel, creating a pH-dependent delivery system. Fourier-transformed infrared spectroscopy (FTIR) was for the detection of carboxylic group on agarose hydrogel, and scanning electron microscope (SEM) was used for the determination surface of prepared formulation. To check the pH sensitivity of enteric-coated formulation, different pH solution was used. It was found that the formulation was not dissolved in 1.2 but dissolve in pH 6.8 similarly; hydrogels lacking coating showed that tartrazine was more dissolved in pH 1.2, and less dissolved at pH 6.8. The release of tartrazine from the hydrogels was measured by using spectrophotometer and using a scanning electron microscope to examine the morphology and surface appearance of hydrogel capsules. This study revealed cracks on coated samples, while noncoated samples showed clear appearance with no cracks. Our findings revealed that this method could be useful for the development of an enteric coating drug delivery system. [ABSTRACT FROM AUTHOR]

Beta-Carotene, a type of carotenoid commonly found in plants, fungi and algae, is the most common and stable natural pigment found in nature. β-Carotene can be converted into vitamin A in the human body, where it exerts oxidation resistance, anticancer activity and anticardiovascular properties. β-carotene has therefore been widely used in food, medicine and the nutrition industry. To date, natural β-carotene is mainly extracted from plants, algae and microorganisms that can naturally accumulate β-carotene, which has the disadvantages of a high price, long growth cycle and low yield. With the development of metabolic engineering and the deepening of research related to the synthetic pathway of β-carotene, the use of metabolic engineering plays an important role in increasing the yield of β-carotene, providing another route for its production. This review covers the biosynthetic pathways of β-carotene and the production of β-carotene by naturally accumulating microorganisms and microbial metabolic engineering. Moreover, different metabolic engineering strategies and the accumulation levels of various microorganisms are considered. In addition, this paper also advances the prospect of the microbial production of β-carotene, especially the development of the production of β-carotene by microbial metabolic engineering. β-Carotene can be extracted from plants, algae and other natural resources, which has the disadvantages of environmental pollution and high production costs. In nature, in addition to plants and algae, microorganisms, such as some fungi and bacteria, can also synthesize β-carotene. At present, there are many reports on the production of β-carotene by microbial metabolic engineering, which has the advantages of low environmental pollution, low production costs and a high yield in addition to broad development prospects. To date, the major microorganisms used in the bioengineering of β-carotene metabolism are Escherichia coli and yeast. It is a feasible strategy to establish a plant to produce β-carotene by using metabolic engineering technology and optimizing the fermentation of engineered strains. • β-Carotene, a carotenoid with many applications, is significant for human health. • Microorganisms are important sources for β-carotene biosynthesis. • β-Carotene production by natural and engineered microorganisms is reviewed. • Metabolic engineering strategies for β-carotene production is summized. [ABSTRACT FROM AUTHOR]

Of note, isotope-labeled PtdGlc was observed in the brain of SP 13 sp C6-PtdGlc treated mice, which demonstrated that PtdGlc could reach to brain (Figure S4). Dear Editor, Alzheimer's disease (AD) is a commonly progressive disorder of neurodegenerative disease.1 Until now, no approach to treat the pathological progression of AD has been proven to be effective.1 Our data favored that the treatment of phosphatidylglucoside (PtdGlc), a novel glucosylated lipid enriched in the brain, protects against A and tau pathology, cognition deficits in APP/PS1 mice, and alleviates neuroinflammation through activation of PPAR and restoration of the neurotrophin signaling. Activated microglia cells and astrocytes can trigger inflammatory processes and regulate neuroinflammation in the brain.8 ASC and Caspase 1 levels were reduced by PtdGlc treatment in APP/PS1 mice, while NLRP3 expression was unchanged. To examine whether the PtdGlc reached to brain, the mice was injected with stable isotope-labeled PtdGlc ( SP 13 sp C6-D-PtdGlc) via the tail vein. [Extracted from the article]

In this study, carboxymethylation and TEMPO-mediated oxidation were compared for their ability to introduce carboxyl groups to polysaccharides, using cellulose and chitin as model polysaccharides. The carboxyl group contents and changes in the molecular weight of carboxymethylated and TEMPO-oxidized cellulose/chitin were measured. The results revealed that carboxymethylation achieved higher carboxyl group contents, with values of 4.99 mmol/g for cellulose and 4.46 mmol/g for chitin, whereas for TEMPO-oxidized cellulose and chitin, the values were 1.64 mmol/g and 1.12 mmol/g, respectively. As a consequence of TEMPO-mediated oxidation, polysaccharides underwent degradation, leading to a decrease in the molecular weight of 42.46 % for oxidized cellulose and 64.5 % for oxidized chitin. Additionally, the crystallinity of carboxymethylated polysaccharides decreased with an increase in the carboxyl group contents, whereas that of TEMPO-oxidized polysaccharides remained unchanged. Furthermore, TEMPO-mediated oxidation selectively oxidized C6 primary hydroxyls, while carboxylmethylation converted all the hydroxyl groups on the polysaccharides. [ABSTRACT FROM AUTHOR]

In this study, a novel magnetic macroporous chitin microsphere (MMCM) was developed for enzyme immobilization. Chitin nanofibers were prepared and subsequently subjected to self-assembly with magnetic nanoparticles and PMMA (polymethyl methacrylate). Following this, microspheres were formed through spray drying, achieving a porous structure through etching. The MMCM serves as an effective support for immobilizing enzymes, allowing for their covalent immobilization both on the microsphere's surface and within its pores. The substantial surface area resulting from the porous structure leads to a 2.1-fold increase in enzyme loading capacity compared to non-porous microspheres. The MMCM enhances stability of the immobilized enzymes under various pH and temperature conditions. Furthermore, after 20 days of storage at 4 °C, the residual activity of the immobilized enzyme was 2.93 times that of the free enzyme. Even after being recycled 10 times, the immobilized enzyme retained 56.7 % of its initial activity. It's noteworthy that the active sites of the enzymes remained unchanged after immobilization using the MMCM, and kinetic analysis revealed that the affinity of the immobilized enzymes rivals that of the free enzymes. [ABSTRACT FROM AUTHOR]

Litopenaeus vannamei is a highly sought-after seafood, but its short shelf life makes it highly perishable due to microbial and chemical reactions. Freezing is a common technology used for extending the shelf life of shrimp. However, it is essential to undergo a thawing process before consuming or further processing frozen shrimp. In this study, the effects of different thawing methods, including immersion (IT), ultrasonic (UT), microwave (MT), refrigerator (RT), and air thawing (AT) on the qualitative parameters and protein denaturation of shrimp were investigated. The results showed that UT reduced fat oxidation and color degradation and was more effective than other thawing treatments like AT, IT, MT, and RT at retaining water. Based on the results of surface hydrophobicity, turbidity, particle size, and Zeta potential, UT reduced the aggregation and oxidation of myofibrillar proteins (MP) during the thawing process compared to other thawing methods. Utilizing UT also minimized the amount of harm that was done to MP secondary and tertiary structures during the thawing process. In conclusion, UT is a novel thawing technique to maintain the quality of shrimp meat quickly and effectively compared with other thawing methods, which is important for the quality of subsequent processing of frozen shrimp. • Ultrasonic thawing (UT) significantly shortened thawing time of frozen shrimp. • UT delays changes in color and texture of texture and lipid oxidation compared to other thawing methods. • The microstructure of the UT group was smoother and more complete. • UT reduces oxidation and denaturation of myofibrillar protein (MP), which has the most stable structure. [ABSTRACT FROM AUTHOR]

In this study, carboxymethylation and TEMPO-mediated oxidation were compared for their ability to introduce carboxyl groups to polysaccharides, using cellulose and chitin as model polysaccharides. The carboxyl group contents and changes in the molecular weight of carboxymethylated and TEMPO-oxidized cellulose/chitin were measured. The results revealed that carboxymethylation achieved higher carboxyl group contents, with values of 4.99 mmol/g for cellulose and 4.46 mmol/g for chitin, whereas for TEMPO-oxidized cellulose and chitin, the values were 1.64 mmol/g and 1.12 mmol/g, respectively. As a consequence of TEMPO-mediated oxidation, polysaccharides underwent degradation, leading to a decrease in the molecular weight of 42.46 % for oxidized cellulose and 64.5 % for oxidized chitin. Additionally, the crystallinity of carboxymethylated polysaccharides decreased with an increase in the carboxyl group contents, whereas that of TEMPO-oxidized polysaccharides remained unchanged. Furthermore, TEMPO-mediated oxidation selectively oxidized C6 primary hydroxyls, while carboxylmethylation converted all the hydroxyl groups on the polysaccharides. [ABSTRACT FROM AUTHOR]

In this study, a novel magnetic macroporous chitin microsphere (MMCM) was developed for enzyme immobilization. Chitin nanofibers were prepared and subsequently subjected to self-assembly with magnetic nanoparticles and PMMA (polymethyl methacrylate). Following this, microspheres were formed through spray drying, achieving a porous structure through etching. The MMCM serves as an effective support for immobilizing enzymes, allowing for their covalent immobilization both on the microsphere's surface and within its pores. The substantial surface area resulting from the porous structure leads to a 2.1-fold increase in enzyme loading capacity compared to non-porous microspheres. The MMCM enhances stability of the immobilized enzymes under various pH and temperature conditions. Furthermore, after 20 days of storage at 4 °C, the residual activity of the immobilized enzyme was 2.93 times that of the free enzyme. Even after being recycled 10 times, the immobilized enzyme retained 56.7 % of its initial activity. It's noteworthy that the active sites of the enzymes remained unchanged after immobilization using the MMCM, and kinetic analysis revealed that the affinity of the immobilized enzymes rivals that of the free enzymes. [ABSTRACT FROM AUTHOR]