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Abstract: Glucomannans from Bletilla striata (bletillan) were used as excipient for controlled deliveries of drugs, genes and tissue engineering. In the present study, a controlled acetylation method was developed to improve water solubility of bletillan 70 (BT) firstly, by reacting with acetic anhydride (AA) in N,N-dimethylformamide solvent. The preparation parameters, such as reaction temperature, reaction time and molar ratio of BT/AA, were optimized based on degrees of acetyl group in addition. IR and 1H NMR spectra were applied to elucidate the reaction process and substitution pattern, which indicated that the acetylation took place at C-6 and C-2 of the hexose units in a ratio of 2:1, with DS up to 0.83. Relative viscosity analysis revealed that the resulted products had improved water solubilities. This novel method is simple, economic and easily controlled. [Copyright &y& Elsevier]

ι-Carrageenan was depolymerized in mild hydrochloric acid condition. Tetrabutylammonium (TBA) salt of ι-carrageenan fragments was acylated with succinic anhydride, 4-dimethylaminopyridine and tributylamine under homogeneous conditions in N,N-dimethylformamide at 80°C. Investigation of FT-IR spectrum of the succinylated product showed that a monoester derivative with succinyl group was formed when ι-carrageenan reacted with succinic anhydride. The 1H and 13C NMR spectroscopy has been used to characterize the fine structure of O-succinyl derivative of the ι-carrageenan. The 13C and 1H NMR chemical shifts of disaccharide unit of O-succinyl ι-carrageenan have been fully assigned using 2D NMR spectroscopic techniques. [Copyright &y& Elsevier]

Abstract: Low-molecular-weight (LMW) κ-carrageenan was achieved through mild hydrochloric acid hydrolysis of κ-carrageenan. The acylation of low-molecular-weight κ-carrageenan was performed by use of tetrabutylammonium (TBA) salt of the anionic polysaccharide fragments, maleic anhydride, 4-dimethylaminopyridine and tributylamine under homogeneous conditions in N,N-dimethylformamide at 60°C. Analysis of FT-IR spectrum of O-maleoyl κ-carrageenan showed that a monoester derivative with maleoyl group was formed when LMW κ-carrageenan reacted with maleic anhydride. Investigation of 1H NMR spectroscopy revealed that the maleoylation took place regioselectively at C-2 of the κ-carrageenan 3-linked unit. [Copyright &y& Elsevier]

Abstract: Low-molecular-weight (LMW) κ-carrageenan was achieved through mild hydrochloric acid hydrolysis of κ-carrageenan. The acylation of LMW κ-carrageenan was performed by use of tetrabutylammonium (TBA) salt of the anionic polysaccharide fragments, succinic anhydride, 4-dimethylaminopyridine and tributylamine under homogeneous conditions in N,N-dimethylformamide at 80°C. Investigation of FT-IR spectrum of the succinylated LMW κ-carrageenan showed that a monoester derivative with succinyl group was formed when LMW κ-carrageenan reacted with succinic anhydride. The 1H and 13C NMR spectroscopy has been used to characterize the fine structure of O-succinyl derivative of the LMW κ-carrageenan. The 13C and 1H NMR chemical shifts of disaccharide unit of O-succinyl LMW κ-carrageenan have been fully assigned using 2D NMR spectroscopic techniques. [Copyright &y& Elsevier]

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium , making it a promising symbiotic agent. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Mild hydrolysis of Sphingomonas sp. ATCC 31555 polysaccharide WL-26 afforded a new oligosaccharide, F21. Structural resolution based on sugar and methylation analyses as well as NMR data revealed the oligosaccharide to have the following structure: Display Omitted [Copyright &y& Elsevier]

During curdlan production by Agrobacterium sp., the secreted exopolysaccharide (EPS) gradually encapsulated Agrobacterium sp., accompanied by cell aggregation, resulted in inhibited substrate uptake and curdlan synthesis. To relieve the EPS encapsulation effect, the shake-flask culture medium was quantitatively supplemented with 2 % to 10 % endo -β-1,3-glucanase (BGN), while obtaining curdlan with a decreased weight-average molecular weight ranging from 18.99 × 104 Da to 3.20 × 104 Da. In a 7-L bioreactor, the 4 % BGN supplement substantially attenuated the EPS encapsulation, resulting in increased glucose consumption and curdlan yield to 66.41 g/L and 34.53 g/L after fermentation of 108 h, which improved 43 % and 67 %, respectively compared with the control. The disruption of EPS encapsulation with BGN treatment accelerated the regeneration of ATP and UTP, resulting in sufficient uridine diphosphate glucose for curdlan synthesis. The upregulation of related genes at the transcription level reveals that the respiratory metabolic intensity, the energy regeneration efficiency, and the curdlan synthetase activity were enhanced. This study presents a simple and novel strategy of relieving the effects of EPS encapsulation on the metabolism of Agrobacterium sp. for the high-yield and value-added production of curdlan, which could be potentially applied in producing other EPSs. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, EGCG loaded melanin-like nanoparticles (EGCG@MNPs) were incorporated into chitosan matrix to prepare an active nanocomposite food packaging film, chitosan-EGCG@MNPs (CH-EM). The influence of EGCG@MNPs on the physical and biological properties of the chitosan film was investigated. The EGCG@MNPs nanoparticles were cross-linked with chitosan through intermolecular hydrogen bonds and uniformly distributed in the matrix. Besides, the incorporation of EGCG@MNPs tremendously improved the solubility, swelling ratio and water vapor barrier properties of the film, and permitted superior ultraviolet rays blocking property. In addition, the mechanical properties, thermal stability and surface hydrophobicity have also been significantly improved. The CH-EM2.0 nanocomposite films also showed excellent oxidation resistance (58.4 ± 4.4%, DPPH and 92.4 ± 1.3%, ABTS +), and strong inhibitory ability against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The experimental results comprehensively showed that the prepared chitosan-EGCG@MNPs nanocomposite film offering excellent potential for eco-friendly active food packaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Biologically active gellan oligosaccharides (GOSs), newly found plant elicitors and biostimulants, are produced from the hydrolysis of gellan gum. Traditional hydrolysis with concentrated acid suffers from the problems of high pollution and low functional oligosaccharide yield because the process is difficult to control. Irradiation (60Co γ-ray) with a dosage ranging from 0 kGy to 175 kGy was used to degrade gellan gum efficiently and cleanly into low molecular weight (M w) gellan with an average M w ranging from 449,119 Da to 72,903 Da. The low M w gellan irradiated at 70 kGy was further hydrolyzed with low concentration acid (0.5 mol/L HCl) to produce GOSs with DPs mainly 4 and 8, indicating that the Rha-β-(1 → 3)-Glc bonds in gellan gum were easily cut to produce residues with tetrasaccharide repeat subunits. Besides antioxidant activity, GOSs were also proved with prebiotic activity by in vitro fecal fermentation in a self-designed bionic intestinal reactor. [Display omitted] • Gellan oligosaccharides were efficiently produced via coupled hydrolysis. • The structures of the hydrolysates (gellan oligosaccharides) were determined. • Specific gellan oligosaccharides (DPs 4 and 8) were isolated from the hydrolysates. • Gellan oligosaccharides were proved with prebiotic and antioxidant activities. • Biological activities of the specific oligosaccharides were compared. [ABSTRACT FROM AUTHOR]