Purification and Characterisation of κ-Carrageenan Oligosaccharides Prepared by κ-Carrageenase from Thalassospira sp. Fjfst-332

Systematic review on carrageenolytic enzymes: From metabolic pathways to applications in biotechnology

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.

Effect of xanthan gum (XG) and carrageenan (CG) ratio on casein (CA)-XG-CG ternary complex: Used to improve the stability of liquid diabetes formula food for special medical purposes

Poor storage stability limits the application of liquid diabetes formula food for special medical purposes (L-D-FSMP) in maintaining blood sugar stability in diabetic patients. This work aims to improve the stability of L-D-FSMP by adjusting the ratio of xanthan gum (XG) and carrageenan (CG) in casein (CA)-XG-CG ternary complex. The centrifugal sedimentation rate results showed that the compound ratio of XG and CG had a greater impact on L-D-FSMP storage stability. Transmission electron microscopy (TEM) results showed that the combination of CA, XG and CG occurred. Fourier transform infrared spectroscopy (FTIR) results showed that CA, XG and CG were mainly combined through hydrogen bonds and ionic bonds to form a CA-XG-CG ternary complex. When the ratio of XG and CG was 1:1, the number of disulfide bonds was the largest. The results of three-phase contact angle and emulsifying ability confirmed that when the ratio of XG and CG was 1:1, CA-XG-CG had the strongest emulsifying ability. The particle size distribution and zeta-potential results showed that when the ratio of XG and CG was 1:1, L-D-FSMP had the narrowest particle size distribution range and the strongest stability. These results may provide valuable information for the production of stable L-D-FSMP.

Separation, purification and structural characterization of marine oligosaccharides: A comprehensive and systematic review of chromatographic methods

Marine oligosaccharides have now been applied in a wide range of industry due to various kinds of physiological activities. However, the oligosaccharides with different polymeric degrees (Dps) differed in physiological activities and applicable fields. So it is promising and essential to separate, purify and structurally characterize these oligosaccharides for understanding their structure-function relationship. This review will summarize the lasted developments in the separation, purification and structural characterization of marine oligosaccharides, including the alginate oligosaccharides, carrageenan oligosaccharides, agar oligosaccharides, chitin oligosaccharides and chitosan oligosaccharides, emphasizing the successful examples of methods for separation and purification. Furthermore, an outlook for preparation of functional oligosaccharides in food biotechnology and agriculture fields is also included. This comprehensive review could definitely promote the utilization of marine functional polysaccharides for food and agriculture.

Advances in oligosaccharides production from algal sources and potential applications

In recent years, algal-derived glycans and oligosaccharides have become increasingly important in health applications due to higher bioactivities than plant-derived oligosaccharides. The marine organisms have complex, and highly branched glycans and more reactive groups to elicit greater bioactivities. However, complex and large molecules have limited use in broad commercial applications due to dissolution limitations. In comparison to these, oligosaccharides show better solubility and retain their bioactivities, hence, offering better applications opportunity. Accordingly, efforts are being made to develop a cost-effective method for enzymatic extraction of oligosaccharides from algal polysaccharides and algal biomass. Yet detailed structural characterization of algal-derived glycans is required to produce and characterize the potential biomolecules for improved bioactivity and commercial applications. Some macroalgae and microalgae are being evaluated as in vivo biofactories for efficient clinical trials, which could be very helpful in understanding the therapeutic responses. This review discusses the recent advancements in the production of oligosaccharides from microalgae. It also discusses the bottlenecks of the oligosaccharides research, technological limitations, and probable solutions to these problems. Furthermore, it presents the emerging bioactivities of algal oligosaccharides and their promising potential for possible biotherapeutic application.

κ-Selenocarrageenan Oligosaccharides Prepared by Deep-Sea Enzyme Alleviate Inflammatory Responses and Modulate Gut Microbiota in Ulcerative Colitis Mice

κ-Selenocarrageenan (KSC) is an organic selenium (Se) polysaccharide. There has been no report of an enzyme that can degrade κ-selenocarrageenan to κ-selenocarrageenan oligosaccharides (KSCOs). This study explored an enzyme, κ-selenocarrageenase (SeCar), from deep-sea bacteria and produced heterologously in Escherichia coli, which degraded KSC to KSCOs. Chemical and spectroscopic analyses demonstrated that purified KSCOs in hydrolysates were composed mainly of selenium-galactobiose. Organic selenium foods through dietary supplementation could help regulate inflammatory bowel diseases (IBD). This study discussed the effects of KSCOs on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in C57BL/6 mice. The results showed that KSCOs alleviated the symptoms of UC and suppressed colonic inflammation by reducing the activity of myeloperoxidase (MPO) and regulating the unbalanced secretion of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10). Furthermore, KSCOs treatment regulated the composition of gut microbiota, enriched the genera Bifidobacterium, Lachnospiraceae_NK4A136_group and Ruminococcus and inhibited Dubosiella, Turicibacter and Romboutsia. These findings proved that KSCOs obtained by enzymatic degradation could be utilized to prevent or treat UC.

Characterization and Gel Properties of Low-Molecular-Weight Carrageenans Prepared by Photocatalytic Degradation

Low-molecular-weight carrageenan has attracted great interest because it shows advantages in solubility, absorption efficiency, and bioavailability compared to original carrageenan. However more environment-friendly and efficient methods to prepare low-molecular-weight carrageenan are still in great need. In the present study, a photocatalytic degradation method with only TiO₂ has been developed and it could decrease the average molecular weight of κ-carrageenan to 4 kDa within 6 h. The comparison of the chemical compositions of the degradation products with those of carrageenan by FT-IR, NMR, etc., indicates no obvious removement of sulfate group, which is essential for bioactivities. Then 20 carrageenan oligosaccharides in the degradation products were identified by HPLC-MSⁿ, and 75% of them possessed AnGal or its decarbonylated derivative at their reducing end, indicating that photocatalysis is preferential to break the glycosidic bond of AnGal. Moreover, the analysis results rheology and Cryo-SEM demonstrated that the gel property decreased gradually. Therefore, the present study demonstrated that the photocatalytic method with TiO₂ as the only catalyst has the potential to prepare low-molecular-weight carrageenan with high sulfation degree and low viscosity, and it also proposed the degradation rules after characterizing the degradation products. Thus, the present study provides an effective green method for the degradation of carrageenan.

Beneficial effects of seaweed-derived dietary fiber: Highlights of the sulfated polysaccharides

Seaweeds and their derivatives are important bioresources of natural bioactive compounds. Nutritional studies indicate that dietary fibers derived from seaweeds have great beneficial potentials in human health and can be developed as functional food. Moreover, sulfated polysaccharides are more likely to be the main bioactive components which are widely distributed in various species of seaweeds including Phaeophyceae, Rhodophyceae and Chlorophyceae. The catabolism by gut microbiota of the seaweeds-derived dietary fibers (DFs) may be one of the pivotal pathways of their physiological functions. Therefore, in this review, we summarized the latest results of the physiological characteristics of seaweed-derived dietary fiber and highlighted the roles of sulfated polysaccharides in the potential regulatory mechanisms against disorders. Meanwhile, the effects of different types of seaweed-derived dietary fiber on gut microbiota were discussed. The analysis of the structure-function correlations and gut microbiota related mechanisms and will contribute to further better applications in food and biotherapeutics.

Marine microbial enzymes for the production of algal oligosaccharides and its bioactive potential for application as nutritional supplements

Marine macroalgae have a very high carbohydrate content due to complex algal polysaccharides (APS) like agar, alginate, and ulvan in their cell wall. Despite numerous reports on their biomedical properties, their hydrocolloid nature limits their applications. Algal oligosaccharides (AOS), which are hydrolyzed forms of complex APS, are gaining importance due to their low molecular weight, biocompatibility, bioactivities, safety, and solubility in water that makes it a lucrative alternative. The AOS produced through enzymatic hydrolysis using microbial enzymes have far-reaching applications because of its stereospecific nature. Identification and characterization of novel microorganisms producing APS hydrolyzing enzymes are the major bottlenecks for the efficient production of AOS. This review will discuss the marine microbial enzymes identified for AOS production and the bioactive potential of enzymatically produced AOS. This can improve our understanding of the biotechnological potential of microbial enzymes for the production of AOS and facilitate the sustainable utilization of algal biomass. Enzymatically produced AOS are shown to have bioactivities such as antioxidant, antiglycemic, prebiotic, immunomodulation, antiobesity or antihypercholesterolemia, anti-inflammatory, anticancer, and antimicrobial activity. The myriad of health benefits provided by the AOS is the need of the hour as there is an alarming increase in physiological disorders among a wide range of the global population.

Structural characterization and in vitro fermentation by rat intestinal microbiota of a polysaccharide from Porphyra haitanensis

A sulfated polysaccharide (PHP1) produced by the marine red alga Porphyra haitanensis was structurally characterized, and its effect on rat fecal microbiota fermentations and short chain fatty acids production were investigated. PHP1 was mainly composed of galactose and the main linkage types were identified as → 3)G4Sβ(1 → 3)G(1 → 6)G4Sα(1 → 4)LA(1 → 6)G4Sα(1→. The surface morphology of dried PHP1 films appears to be related to its chemical structure. PHP1 promoted the growth of both propionic acid-producing bacteria and propionic acid production, as well as influencing the composition and abundance of beneficial microbiota species in rats, which may be related to its high level of sulfation. The molecular weight of PHP1 decreased significantly after fermentation, which may result from hydrolysis of the galactan (with α- and β-linkages between galactose residues) by α- or β-galactosidase secreted by the microbiota. These results provided new insights into the structure-activity relationships between P. haitanensis polysaccharide and its regulation of microbiota in vivo.

Low Molecular Weight Kappa-Carrageenan Based Microspheres for Enhancing Stability and Bioavailability of Tea Polyphenols

Tea polyphenols (TP) are a widely acknowledged bioactive natural product, however, low stability and bioavailability have restricted their application in many fields. To enhance the stability and bioavailability of TP under certain moderate conditions, encapsulation technique was applied. Kappa–Carrageenan (KCG) was initially degraded to a lower molecular weight KCG (LKCG) by H2O2, and was selected as wall material to coat TP. The obtained LKCG (Mn = 13,009.5) revealed narrow dispersed fragments (DPI = 1.14). FTIR and NMR results demonstrated that the main chemical structure of KCG remained unchanged after degradation. Subsequently, LK-CG and TP were mixed and homogenized to form LK-CG-TP microspheres. SEM images of the microspheres revealed a regular spherical shape and smooth surface with a mean diameter of 5–10 μM. TG and DSC analysis indicated that LK-CG-TP microspheres exhibited better thermal stability as compared to free TP. The release profile of LK-CG-TP in simulated gastric fluid (SGF) showed a slowly release capacity during the tested 180 min with the final release rate of 88.1% after digestion. Furthermore, in vitro DPPH radical scavenging experiments revealed that LK-CG-TP had an enhanced DPPH scavenging rate as compared to equal concentration of free TP. These results indicated that LK-CG-TP microspheres were feasible for protection and delivery of TP and might have extensive potential applications in other bioactive components.

Module function analysis of a full-length κ-carrageenase from Pseudoalteromonas sp. ZDY3

κ-Carrageenan oligosaccharides with many excellent biological properties could be produced by κ-carrageenases selectively. In this study, based on the encoding gene of full length κ-carrageenase obtained from Pseudoalteromonas sp. ZDY3 and the reported mature secreted κ-carrageenase composed of 275 amino acid residues (N26-T300), CgkPZ_GH16 was expressed in E. coli, but no soluble active protein could be detected. Fortunately, the signal peptide of wild-type κ-carrageenase was recognized, and cleaved in the soluble and folding form in E. coli, the K_m and k_cat values of CgkPZ_SP_GH16 was 1.007 mg/mL and 362.8 s^-1. By molecular dynamics simulations, it was showed that YjdB domain might affect the activity of κ-carrageenase. Due to the absence of mature processing modification system in E. coli, YjdB was remained in recombinant full length κ-carrageenase, and the lost catalytic efficiency of CgkPZ was compensated by expression level and thermal stability. Interestingly, CgkPZ_GH16_YjdB was expressed soluble without the signal peptide, which indicated that YjdB could contribute to the expression and folding of κ-carrageenase. These results provide new insight into the effects of different modules of κ-carrageenase on the expression and properties of enzyme.

Recent advances in marine algae oligosaccharides: structure, analysis, and potential prebiotic activities

Marine algae contain abundant polysaccharides that support a range of health-promoting activities; however, the high molecular weight, high viscosity, and low solubility of marine algae polysaccharides (MAPs) limit their application in food, agriculture and medicine. Thus, as the degradation products of MAPs, marine algae oligosaccharides (MAOs) have drawn increasing attention. Most MAOs are non-digestible by digestive enzyme in the human gastrointestinal tract, but are fermented by bacteria in the gut and converted into short-chain fatty acids (SCFAs). MAOs can selectively enhance the activities of some populations of beneficial bacteria and stimulate a series of prebiotic effects, such as anti-oxidant, anti-diabetic, anti-tumour. However, the exact structures of MAOs and their prebiotic activities are, to a large extent, unexplored. This review summarizes recent advances in the sources, categories, and structure analysis methods of MAOs, emphasizing their effects on gut microbiota and its metabolite SCFAs as well as the resulting range of probiotic activities.

Overview on Microbial Enzymatic Production of Algal Oligosaccharides for Nutraceutical Applications

Global requirement for algal foods is increasing, as they are progressively consumed for its nutrition and health. Macroalgae is a proven source of metabolites, proteins, pigments, bioactive compounds, and algal polysaccharides. The unique polysaccharides such as agar, carrageenan, porphyran, alginate, fucoidan, laminarin, and ulvan are known for its wide range of bioactivities and extensively used for applications from tissue engineering to drug delivery. However, there are few limitations due to its high molecular size, low compatibility, and hydrocolloid nature. Hence, the enzymatically produced algal oligosaccharides have drawn tremendous attention due to its green synthesis, solubility, and lower molecular size. They are reported to have bioactivities including antioxidant, antiglycemic, immunostimulatory, anti-inflammatory, and prebiotic activities, which can be used in the healthcare and nutraceutical industry for the manufacture of functional foods and dietary supplements. However, identification of potential microorganisms, producing polysaccharide hydrolyzing enzymes, remains a major bottle neck for efficient utilization of bioactive algal oligosaccharides. This review summarizes the recent developments in the identification and characterization of microbial enzymes for the production of bioactive algal oligosaccharides. This can improve our understanding of bioactive algal oligosaccharides and pave way for efficient utilization of macroalgae to prevent various chronic diseases.

κ/β-Carrageenan oligosaccharides promoting polarization of LPS-activated macrophage and their potential in diabetes wound healing

Here we prepared a low-degree-sulfated κ/β-carrageenan oligosaccharide (L-DS-KOS) by DMSO-methanol desulfation method, and fabricated a sponge dressing for the wound healing of diabetic rats. The immunomodulatory effects of L-DS-KOS on M1-like macrophages were evaluated. Results showed that L-DS-KOS could effectively promote the secretion of anti-inflammatory factors and accelerate polarization of LPS-activated macrophages from M1 to M2 type. The gross examination result showed that the sponge dressing with the mass ratio of L-DS-KOS: collagen = 3: 7 could effectively accelerate the repair process of the full-thickness excisional wound in diabetic rats; and H&E and Masson staining results disclosed that the L-DS-KOS/collagen dressing could better shorten the inflammation period of the wound site, and improve the process of collagen deposition and epithelial formation, thereby promote the repair of skin wounds in diabetic rats. These results demonstrate that L-DS-KOS has potential to be used as a new type of immunomodulatory biomaterial for diabetic wound dressings.

Production of a thermo-tolerant κ-carrageenase via a food-grade host and anti-oxidant activity of its enzymatic hydrolysate

κ-Carrageenase cleaves the β-(1-4) linkages of κ-carrageenan into κ-carrageenan oligosaccharides (κ-COS), which exhibit various biological activities. In this study, a glycoside hydrolase (GH) family 16 κ-carrageenase gene, cgkA, was cloned from the marine bacterium Vibrio sp. SY01 and secretory expressed in a food-grade host, Yarrowia lipolytica. The specific activity of the purified CgkA was 12.5 U/mg. Determination of biochemical properties showed that CgkA was a thermo-tolerant enzyme, and 59.9% of the initial enzyme activity was recovered by immediately placing the sample at 20 °C for 30 min after enzymatic inactivation by boiling for 5 min. The recombinant CgkA was an endo-type enzyme, the main enzymatic product was κ-carradiaose (accounting for 87.6% of total products), and κ-carratetraose was the minimum substrate. Additionally, in vitro and in vivo analyses indicated that enzymatic κ-carradiaose possesses anti-oxidant activity. These features make CgkA as a promising candidate for biotechnological applications in the production of anti-oxidant κ-COS.

Marine oligosaccharides originated from seaweeds: Source, preparation, structure, physiological activity and applications

Marine polysaccharides originated from seaweeds, including agar, alginate, carrageenan, and fucoidan, possess various kinds of physiological activities and have been widely used in food, agricultural and medical areas. However, the application has been greatly limited by their poor solubility and low bioavailability. Thus marine oligosaccharides, as the degradation products of those polysaccharides, have drawn increasing attentions due to their obvious biological activities, good solubility and excellent bioavailability. This review will summarize the recent advances on the source, molecular structure and physiological activity of marine oligosaccharides, emphasizing their application as functional food additives. Furthermore, the relationship between the structure and the physiological activity of marine oligosaccharides is also elucidated and highlighted. The review concludes with an outlook toward potential applications for preparing the functional oligosaccharides in food biotechnology and agriculture fields.

In vitro antitumor and immunotropic activity of carrageenans from red algae Chondrus armatus and their low-molecular weight degradation products

Antitumor and immunotropic effects of κ-, λ-carrageenan from red marine algae Chondrus armatus and their low-molecular weight (LMW) degradation products were explored. Effects on human esophageal cancer cell lines KYSE30 and FLO1 viability and ability to induce production of pro- and anti-inflammatory cytokines by human monocytes was assessed. All polysaccharides demonstrated antimetabolic and cytostatic activity towards cancer lines, with high-molecular weight carrageenans possessing higher antimetabolic and lower cytostatic activity than their LMW degradation products. All carrageenans induced monocytes to produce pro-inflammatory cytokines IL1β, IL6, IL18, and TNFα. However, secretion of anti-inflammatory cytokine IL10 was induced only by LMW λ-carrageenan, which exhibited the highest cytokine production inducing efficacy overall. We demonstrate that LMW carrageenan degradation products not only retain biological activity of their precursors, but also increase their efficacy in type-dependent manner, allowing for their future development for pharmacological practice.

Proteomic Analysis Reveals Inflammation Modulation of κ/ι-Carrageenan Hexaoses in Lipopolysaccharide-Induced RAW264.7 Macrophages

κ/ι-Carrageenan hexaoses (κ/ι-neocarrahexaoses, KCO-4) are a type of carrageenan oligosaccharide that have a broad spectrum of bioactivities due to the presence of sulfate groups. However, the anti-inflammatory capacity of purified carrageenan oligosaccharides and the underlying mechanism has not been completely elucidated. The present study aimed to investigate inflammatory signaling modulation of KCO-4 in LPS-induced macrophages using a quantitative proteomic strategy. KCO-4 inhibited the oversecretion of inflammatory mediators (i.e., NO, TNF-α, IL-1β, IL-8, iNOS, and COX-2). KCO-4 treatment altered proteome profile, and metabolic processes in mitochondria were significantly disrupted. The IPA network analysis proposed that KCO-4 triggered the NF-κB signaling pathway-dependent anti-inflammation process through the inhibition of CD14/Rel@p50 in LPS-induced RAW264.7 macrophages. These data improve our understanding of the anti-inflammatory mechanism and contribute to exposure biomarker screening of κ-carrageenan oligosaccharides.