一种双层多糖水凝胶用于增强益生菌肠道靶向口服递送

Transplantation of probiotics to the intestine can positively regulate the gut microbiota,thereby promoting the immune system and treating various diseases.However,the harsh gastrointestinal environment and short retention time in the gastrointestinal tract significantly limit the bioavailability and intestinal colonization of probiotics.Herein,we present a double-layer polysaccharide hydrogel(DPH)in the form of a double-layer structure composed of a carboxymethyl cellulose(CMCL)supramolecular inner layer and a dialdehyde alginate(DAA)cross-linked carboxymethyl chitosan(CMCS)outer layer.This doublelayer structure allows DPH to encapsulate and deliver probiotics in a targeted manner within the body.In the stomach,the cage structure of the DPH is closed,and the outer layer absorbs surrounding liquids to form a barrier to protect the probiotics from gastric fluids.In the intestine,the cage structure opens and disintegrates,releasing the probiotics.Thus,DPH endows probiotics with excellent intestine-targeted delivery,improved oral bioavailability,enhanced gastrointestinal tract tolerance,and robust mucoadhesion capacity.The encapsulated probiotics exhibit almost unchanged bioactivity in the gastrointestinal tract before release,as well as improved oral delivery.In particular,probiotics encapsulated by DPH exhibit 100.1 times higher bioavailability and 10.6 times higher mucoadhesion than free probiotics in an animal model 48 h post-treatment.In addition,with a remarkable ability to survive and be retained in the intestine,probiotics encapsulated by DPH show excellent in vitro and in vivo competition with pathogens.Notably,DAA-mediated dynamic crosslinking not only maintains the overall integrity of the hydrogels but also controls the release timing of the probiotics.Thus,it is expected that encapsulated substances(probiotics,proteins,etc.)can be delivered to specific sites of the intestinal tract by means of DPH,by controlling the dynamic covalent crosslinking.

Aptasensing biosynthesized phosphatidylserine with a AuNPs nanozyme-based colorimetric aptasensor

Sensitive monitoring of the target products during the biosynthesis process is crucial,and facile analytical approaches are urgently needed.Herein,phosphatidylserine(PS)was chosen as the model target,a colorimetric aptasensor was developed for the rapid quantitation in biosynthesis samples.A chimeric aptamer was constructed with two homogeneous original PS aptamers.Specific recognition between the chimeric aptamer and PS results in the desorption of aptamer from the surface of the AuNPs nanozyme,and the peroxidase-like enzymatic activity of the AuNPs nanozyme was weakened in a relationship with the different concentrations.The developed aptasensor performed well when applied for analyzing PS in biosynthesis samples.The aptasensor offers good sensitivity and selectivity,under optimal conditions,achieving monitoring and quantitation of PS in the range of 2.5-80.0μmol/L,with a limit of detection at 536.2 nmol/L.Moreover,the aptasensor provides good accuracy,with comparison rates of 98.17%-106.40%,when compared with the HPLC-ELSD.This study provides a good reference for monitoring other biosynthesized products and promoting the development of aptamers and aptasensors in real-world applications.

P_(luxI)mutants with different promoting period and their application for quorum sensing regulated protein expression

Quorum sensing(QS)system can dynamically control the expression of proteins along with the cell growth.The promoting period of QS system has been little focused on until now.In this study,a self-induced dynamic regulated expression(SIDRE)system was constructed in Escherichia coli.To enable the system suitable for the expression of enzymes,promoter engineering was used to obtain P_(luxI)mutants.To test the SIDRE system,alginate lyase AL493 and esterase Est7 were used as target protein for expression.The enzyme activity of alginate lyase and esterase reached 96.38%and 106.71%of the control strains containing the T7 promoter.In high-density fermentation,the activity of alginate lyase expressed by the SIDRE system with P_(luxI)(T-38C)as promoter was 4.34-fold of that expressed by the T7 promoter.Therefore,the P_(luxI)mutants with different promoting periods and/or different strengths show great potential in both laboratory and industrial scale for protein expression.

A chitosan-based antibacterial hydrogel with injectable and self-healing capabilities

The presence of bacteria directly affects wound healing.Chitosan-based hydrogel biomaterials are a solution as they offer advantages for wound-healing applications due to their strong antimicrobial properties.Here,a double-cross-linking chitosanbased hydrogel with antibacterial,self-healing,and injectable properties is reported.Thiolated chitosan was successfully prepared,and the thiolated chitosan molecules were cross-linked by Ag-S coordination to form a supramolecular hydrogel.Subsequently,the amine groups in the thiolated chitosan covalently cross-linked with genipin to further promote hydrogel formation.In vitro experimental results indicate that hydrogel can release Ag^(+)over an extended time,achieving an antibacterial rate of over 99% against Escherichia coli and Staphylococcus aureus.Due to the reversible and dynamic feature of Ag-S coordination,an antibacterial hydrogel exhibited injectable and self-healing capabilities.Additionally,the hydrogel showed excellent biocompatibility and biodegradability.

Expanding the application range of theκ‑carrageenase OUC‑FaKC16A when preparing oligosaccharides fromκ‑carrageenan and furcellaran

Carrageenan oligosaccharides are important products that have demonstrated numerous bioactivities useful in the food,medicine,and cosmetics industries.However,the specifc structure–function relationships of carrageenan oligosaccharides are not clearly described due to the defciency of high specifc carrageenases.Here,a truncated mutant OUC-FaKC16Q based on the reportedκ-neocarratetrose(Nκ4)-producingκ-carrageenase OUC-FaKC16A from Flavobacterium algicola was constructed and further studied.After truncating the C-terminal Por_Secre_tail(PorS)domain(responsible for substrate binding),the catalytic efciency and temperature stability decreased to a certain extent.Surprisingly,this truncation also enabled OUC-FaKC16Q to hydrolyze Nκ4 intoκ-neocarrabiose(Nκ2).The ofset of Arg265 residue in OUC-FaKC16Q may explain this change.Moreover,the high catalytic abilities,the main products,and the degradation modes of OUC-FaKC16A and OUC-FaKC16Q toward furcellaran were also demonstrated.Data suggested OUC-FaKC16A and OUC-FaKC16Q could hydrolyze furcellaran to produce mainly the desulfated oligosaccharides DA-G-(DA-G4S)2 and DA-G-DA-G4S,respectively.As a result,the spectrum of products ofκ-carrageenase OUC-FaKC16A has been fully expanded in this study,indicating its promising potential for application in the biomanufacturing of carrageenan oligosaccharides with specifc structures.

一株从红藻中分离出的产芳基硫酸酯酶的海单胞菌FW-1的全基因组测序及结果分析（英文）

【目的】海单胞菌Marinomonas sp. FW-1是1株经验证可以获得高活性芳基硫酸酯酶的菌株。为深入研究FW-1菌株产芳基硫酸酯酶机制,进一步筛选高活性的芳基硫酸酯酶基因片段,有必要解析FW-1菌株的全基因组序列信息。【方法】本研究采用高通量测序技术对FW-1进行全基因组测序,使用相关软件对测序数据进行基因组装、基因预测与功能注释、COG聚类分析等。结合异源表达的方法对其不同基因片段所产生的芳基硫酸酯酶活性进行分析。【结果】全基因组测序结果表明该基因组大小为3964876 bp,GC含量为44.03%,编码3590个蛋白基因,含有78个tRNA和25个rRNA操纵子。从全基因组测序结果中找到22个可能具有芳基硫酸酯酶活性的基因,对其中4个进一步异源表达后发现FW-1中至少含有的3个具有芳基硫酸酯酶活性的基因,其均含有芳基硫酸酯酶的特异性氨基酸基团C-X-P-X-R基团。【结论】本研究首次报道了1株含有多个芳基硫酸酯酶基因序列的菌株FW-1的全基因组序列,分析了基因组的基本特征,为芳基硫酸酯酶的进一步应用提供了思路。

An efficient method for chitin production from crab shells by a natural deep eutectic solvent

Crab shells are an important feedstock for chitin production.However,their highly compact structure significantly limits their use for the production of chitin under mild conditions.Here,a green and efficient approach using a natural deep eutectic solvent(NADES)to produce chitin from crab shells was developed.Its effectiveness in isolating chitin was investigated.The results showed that most proteins and minerals were removed from crab shells and the relative crystallinity of the isolated chitin reached 76%.The quality of the obtained chitin was comparable to chitin isolated by the acid–alkali method.This is the first report on a green method for efficient chitin production from crab shells.This study is expected to open new avenues for green and efficient production of chitin from crab shells.

Characterization of TEMPO-oxidized chitin nanofbers with various oxidation times and its application as an enzyme immobilization support

Chitin nanofbers have recently received increased attention and are considered to be a promising material for a wide range of applications because of their excellent characteristics.In this study,2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)-oxidized chitin nanofbers(CNFs)with various oxidation times were prepared and characterized.CNFs with diferent oxidation times were then utilized for enzyme immobilization,using chymotrypsin as a model enzyme.The efects of oxidation time on enzyme immobilization were explored.Results showed characteristics of chitin nanofbers can be controlled by adjusting oxidation time.CNFs treated with TEMPO for 360 min showed the lowest crystallinity(79.13±1.43%),the shortest length(241.70±74.61 nm),the largest width(12.67±3.43 nm),and the highest transmittance(73.01%at 800 nm).The activity of immobilized enzymes and enzyme loading showed good correlation to the carboxylate content of CNFs.The enzyme efciency based on CNFs and the content of carboxylate groups peaked at the oxidization time of 60 min.When the additional amount of chymotrypsins(CTs)was 500 or 2000 mg/g carrier,the highest loading amount of CTs was 307.17±4.08 or 726.82±12.05 mg/g carrier,respectively.