Enzymatic Degradation of κ-Carrageenan in Aqueous Solution

Recombinant mussel protein Pvfp5β enhances cell adhesion of poly(vinyl alcohol)/k-carrageenan hydrogel scaffolds

Polymeric hydrogels are increasingly considered as scaffolds for tissue engineering due to their extraordinary resemblance with the extracellular matrix (ECM) of many tissues. As cell adhesion is a key factor in regulating important cell functions, hydrogel scaffolds are often functionalized or loaded with a variety of bioactive molecules that can promote adhesion. Interesting biomimetic approaches exploit the properties of mussel-inspired recombinant adhesive proteins. In this work, we prepared hydrogel scaffolds with a 50%w mixture of k-carrageenan (kC) and polyvinyl alcohol (PVA), by a two-step physical gelation process, and we coated them with Perna viridis foot protein-5β (Pvfp5β). The mechanical and morphological properties of hydrogels were investigated both after conditioning with typical cell culture media and also after coating with the Pvfp5β. The protein resulted strongly adsorbed onto the surface of the hydrogel and also able to penetrate in its interiors to a certain depth, mainly interacting with the kC component of the scaffold as resulted from the confocal analysis. Mouse embryonic fibroblasts NIH-3T3 were seeded on top of the hydrogels and cultured up to two weeks. The role of Pvfp5β in promoting cell adhesion, spreading and colonization of the scaffold was demonstrated.

Rapid determination of kappa-carrageenan using a biosensor from immobilized Pseudomonas carrageenovora cells

A potentiometric whole cell biosensor based on immobilized marine bacterium, Pseudomonas carrageenovora producing κ-carrageenase and glycosulfatase enzymes for specific and direct determination of κ-carrageenan, is described. The bacterial cells were immobilized on the self-plasticized hydrogen ion (H+)-selective acrylic membrane electrode surface to form a catalytic layer. Hydrogen ionophore I was incorporated in the poly(n-butyl acrylate) [poly(nBA)] as a pH ionophore. Catalytic decomposition of κ-carrageenan by the bienzymatic cascade reaction produced neoagarobiose, an inorganic sulfate ion and a proton. The latter was detectable by H+ ion transducer for indirect potentiometric quantification of κ-carrageenan concentration. The use of a disposable screen-printed Ag/AgCl electrode (SPE) provided no cleaning requirement and enabled κ-carrageenan detection to be carried out conveniently without cross contamination in a complex food sample. The SPE-based microbial biosensor response was found to be reproducible with high reproducibility and relative standard deviation (RSD) at 2.6% (n = 3). The whole cell biosensor demonstrated a broad dynamic linear response range to κ-carrageenan from 0.2-100 ppm in 20 mM phosphate buffer saline (PBS) at pH 7.5 with a detection limit at 0.05 ppm and a Nernstian sensitivity of 58.78±0.87 mV/decade (R2 = 0.995). The biosensor showed excellent selectivity towards κ-carrageenan compared to other types of carrageenans tested e.g. ι-carrageenan and λ-carrageenan. No pretreatment to the food sample was necessary when the developed whole cell biosensor was employed for direct assay of κ-carrageenan in dairy product.

Ultrathin κ-Carrageenan/Chitosan Hydrogel Films with High Toughness and Antiadhesion Property

Designing tough biopolymer-based hydrogels as structural biomaterials has both scientific and practical significances. We report a facile approach to prepare polysaccharide-based hydrogel films with remarkable mechanical performances and antiadhesion property. The hydrogel films with a thickness of 40-60 μm were prepared by mixing aqueous solutions of κ-carrageenan (κ-CG) and protonated chitosan (CS), evaporating the solvent, and then swelling the casted film in water to achieve the equilibrium state. The obtained κ-CG/CS gel films with a water content of 48-88 wt % possessed excellent mechanical properties with a breaking stress of 2-6.7 MPa and a breaking strain of 80-120%, superior to the most existing biopolymer-based hydrogels. The extraordinary mechanical properties of gel films obtained over a wide range of mass ratio of κ-CG to CS should be rooted in the synergistic effect of ionic and hydrogen bonds between the κ-CG and CS molecules. In addition, the tough gel films showed good self-recovery ability, biocompatibility, and cell antiadhesion property, making them promising as an artificial dura mater and diaphragm materials in the surgery. The design principle by incorporating multiple noncovalent bonds to toughen the biopolymer-based hydrogels should be applicable to other systems toward structural biomaterials with versatile properties.

A perspective on the complexity of dietary fiber structures and their potential effect on the gut microbiota

Even though there are many factors that determine the human colon microbiota composition, diet is an important one because most microorganisms in the colon obtain energy for their growth by degrading complex dietary compounds, particularly dietary fibers. While fiber carbohydrates that escape digestion in the upper gastrointestinal tract are recognized to have a range of structures, the vastness in number of chemical structures from the perspective of the bacteria is not well appreciated. In this article, we introduce the concept of "discrete structure" that is defined as a unique chemical structure, often within a fiber molecule, which aligns with encoded gene clusters in bacterial genomes. The multitude of discrete structures originates from the array of different fiber types coupled with structural variations within types due to genotype and growing environment, anatomical parts of the grain or plant, discrete regions within polymers, and size of oligosaccharides and small polysaccharides. These thousands of discrete structures conceivably could be used to favor bacteria in the competitive colon environment. A global framework needs to be developed to better understand how dietary fibers can be used to obtain predicted changes in microbiota composition for improved health. This will require a multi-disciplinary effort that includes biological scientists, clinicians, and carbohydrate specialists.

Characterization of a κ-carrageenase from marine Cellulophaga lytica strain N5-2 and analysis of its degradation products

A carrageenan-degrading marine Cellulophaga lytica strain N5-2 was isolated from the sediment of carrageenan production base. A κ-carrageenase (EC 3.2.1.83) with high activity was purified to electrophoretic homogeneity from the culture supernatant by a procedure of ammonium sulfate precipitation, dialyzing and gel filtration on SephadexG-200 and SephadexG-75. The purified enzyme was verified as a single protein on SDS-PAGE, and whose molecular weight was 40.8 kDa. The κ-carrageenase yielded a high activity of 1170 U/mg protein. For κ-carrageenase activity, the optimum temperature and pH were 35 °C and pH 7.0, respectively. The enzyme was stable at 40 °C for at least 2.5 h. The enzyme against κ-carrageenan gave a K_m value of 1.647 mg/mL and a V_max value of 8.7 μmol/min/mg when the reaction was carried out at 35 °C and pH 7.0. The degradation products of the κ-carrageenase were analyzed by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), electrospray ionization time-of-flight mass spectroscopy (ESI-TOF-MS) and ¹³C-NMR spectroscopy, and the results indicated that the enzyme was specific of the β-1,4 linkage and hydrolyzed κ-carrageenan into κ-neocarraoctaose-sulfate and κ-neocarrahexaose-sulfate first, and then broke κ-neocarraoctaose-sulfate into κ-neocarrabiose-sulfate and κ-neocarrahexaose-sulfate.

Polysaccharides of the red algae

Red algae (Rhodophyta) are known as the source of unique sulfated galactans, such as agar, agarose, and carrageenans. The wide practical uses of these polysaccharides are based on their ability to form strong gels in aqueous solutions. Gelling polysaccharides usually have molecules built up of repeating disaccharide units with a regular distribution of sulfate groups, but most of the red algal species contain more complex galactans devoid of gelling ability because of various deviations from the regular structure. Moreover, several red algae may contain sulfated mannans or neutral xylans instead of sulfated galactans as the main structural polysaccharides. This chapter is devoted to a description of the structural diversity of polysaccharides found in the red algae, with special emphasis on the methods of structural analysis of sulfated galactans. In addition to the structural information, some data on the possible use of red algal polysaccharides as biologically active polymers or as taxonomic markers are briefly discussed.

Antibacterial Activities of Kappa-Carrageenan Oligosaccharides

Κ-carrageenan oligosaccharides were prepared by enzymatic degradation. The inhibiting activities of the prepared κ-carrageenan oligosaccharides against Escherichia coli (E.coli ), Staphylococcus aureus (S.aureus), Saccharomyces cerevisiae (S.cere), Penicillium citrinum (P.citr) and Mucor.sp were determined and compared by measuring the inhibitory zone diameter. The results indicate that all tested κ-carrageenan oligosaccharides have inhibiting activity against the five bacteria, but the inhibiting activities against Saccharomyces cerevisiae is higher than against any other four bacteria. The inhibiting concentration (MIC) of κ-carrageenan oligosaccharides are 1mg/ml, 5mg/ml, 20mg/ml, and antibacterial activity of κ-carrageenan oligosaccharides was inversely affected by concentration, with the highest activity at the concentration of 5mg/ml.