Different Levels of Skin Whitening Activity among 3,6-Anhydro-l-galactose, Agarooligosaccharides, and Neoagarooligosaccharides

A review: Structure, bioactivity and potential application of algal polysaccharides in skin aging care and therapy

Skin is the first barrier of body which stands guard for defending aggressive pathogens and environmental pressures all the time. Cutaneous metabolism changes in harmful exposure, following with skin dysfunctions and diseases. Lots of researches have reported that polysaccharides extracted from seaweeds exhibited multidimensional bioactivities in dealing with skin disorder. However, few literature systematically reviews them. The aim of the present paper is to summarize structure, bioactivities and structure-function relationship of algal polysaccharides acting on skin. Algal polysaccharides show antioxidant, immunomodulating, hydration regulating, anti-melanogenesis and extracellular matrix (ECM) regulating abilities via multipath ways in skin. These bioactivities are determined by various parameters, including seaweed species, molecular weight, monosaccharides composition and substitute groups. In addition, potential usages of algae-derived polysaccharides in skin care and therapy are also elaborated. Algal polysaccharides are potential ingredients in formulation that providing anti-aging efficacy for skin.

Agarose biodegradation by deep-sea bacterium Vibrio natriegens WPAGA4 with the agarases through horizontal gene transfer

This study aimed to reveal the importance of horizontal gene transfer (HGT) for the agarose-degrading ability and the related degradation pathway of a deep-sea bacterium Vibrio natriegens WPAGA4, which was rarely reported in former works. A total of four agarases belonged to the GH50 family, including Aga3418, Aga3419, Aga3420, and Aga3472, were annotated and expressed in Escherichia coli cells. The agarose degradation products of Aga3418, Aga3420, and Aga3472 were neoagarobiose, while those of Aga3419 were neoagarobiose and neoagarotetraose. The RT-qPCR analysis showed that the expression level ratio of Aga3418, Aga3419, Aga3420, and Aga3472 was stable at about 1:1:1.5:2.5 during the degradation, which indicated the optimal expression level ratio of the agarases for agarose degradation by V. natriegens WPAGA4. Based on the genomic information, three of four agarases and other agarose-degrading related genes were in a genome island with a G + C content that was obviously lower than that of the whole genome of V. natriegens WPAGA4, indicating that these agarose-degrading genes were required through HGT. Our results demonstrated that the expression level ratio instead of the expression level itself of agarase genes was crucial for agarose degradation by V. natriegens WPAGA4, and HGT occurred in the deep-sea environment, thereby promoting the deep-sea carbon cycle and providing a reference for studying the evolution and transfer pathways of agar-related genes.

Comparative study on different immobilization sites of immobilized β-agarase based on the biotin/streptavidin system

β-Agarase was biotinylated and immobilized onto streptavidin-conjugated magnetic nanoparticles to provide insights into the effect of immobilization sites on β-agarase immobilization. Results showed that, compared with free enzyme, the stability of prepared immobilized β-agarases through amino or carboxyl activation were both significantly improved. However, the amino-activated immobilized β-agarase showed higher thermostability and catalytic efficiency than the carboxyl-activated immobilized β-agarase. The relative activity of the former was 65.00 % after incubation at 50 °C for 1 h, which was 1.77-fold higher than that of the latter. Additionally, amino-activated immobilization increased the affinity of the enzyme to the substrate, and its maximum reaction rate (0.68 μmol/min) was superior to that of carboxyl-activated immobilization (0.53 μmol/min). The visualization results showed that the catalytic site of β-agarase after carboxyl-activated immobilization was more susceptible to the immobilization process, and the orientation of the enzyme may also hinder substrate binding and product release. These results suggest that by pre-selecting appropriate activation sites and enzyme orientation, immobilized enzymes with higher catalytic activity and stability can be obtained, making them more suitable for the application of continuous production.

Anti-obesity effect of Neoagaro-oligosaccharides with overweight and obese subjects: a 16-week, randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

This trial aimed to evaluate the anti-obesity effects and safety of Neoagaro-oligosaccharides (NAOs) in humans in a 16 week, randomized, double-blind, placebo-controlled clinical trial.

METHODS

One hundred overweight or obese subjects with a body mass index of 23 to 34.9 kg/m2 and a percent body fat of > 25% for males or > 30% for females were enrolled. NAOs or placebo products were administered at 3 g (twice a day, four capsules once) each for 16 weeks. Efficacy and safety biomarkers were measured before and after intervention.

RESULTS

After 16 weeks of intervention, the group administered with NAOs had statistically significant decreases in visceral fat area and visceral-subcutaneous fat area ratio compared to the placebo group. The NAOs group suppressed the increase in weight and BMI compared to the placebo group, which was significant between groups. High-density lipoprotein- cholesterol was increased in the group administered with NAOs, which showed a significant trend compared to the placebo group. Clinical changes were not observed for any safety biomarkers.

CONCLUSIONS

These results suggest that NAOs have a beneficial effect on obesity. Thus, NAOs could be used as an anti-obesity supplement without side effects.

TRIAL REGISTRATION

cris.nih.go.kr: (KCT0006640, 07/10/2021).

Rehashing Our Insight of Seaweeds as a Potential Source of Foods, Nutraceuticals, and Pharmaceuticals

In a few Southeast Asian nations, seaweeds have been a staple of the cuisine since prehistoric times. Seaweeds are currently becoming more and more popular around the world due to their superior nutritional value and medicinal properties. This is because of rising seaweed production on a global scale and substantial research on their composition and bioactivities over the past 20 years. By reviewing several articles in the literature, this review aimed to provide comprehensive information about the primary and secondary metabolites and various classes of bioactive compounds, such as polysaccharides, polyphenols, proteins, and essential fatty acids, along with their bioactivities, in a single article. This review also highlights the potential of seaweeds in the development of nutraceuticals, with a particular focus on their ability to enhance human health and overall well-being. In addition, we discuss the challenges and potential opportunities associated with the advancement of pharmaceuticals and nutraceuticals derived from seaweeds, as well as their incorporation into different industrial sectors. Furthermore, we find that many bioactive constituents found in seaweeds have demonstrated potential in terms of different therapeutic attributes, including antioxidative, anti-inflammatory, anticancer, and other properties. In conclusion, seaweed-based bioactive compounds have a huge potential to play an important role in the food, nutraceutical, and pharmaceutical sectors. However, future research should pay more attention to developing efficient techniques for the extraction and purification of compounds as well as their toxicity analysis, clinical efficacy, mode of action, and interactions with regular diets.

Production of Ethyl-agarobioside, a Novel Skin Moisturizer, by Mimicking the Alcoholysis from the Japanese Sake-Brewing Process

Agarobiose (AB; d-galactose-β-1,4-AHG), produced by one-step acid hydrolysis of agarose of red seaweed, is considered a promising cosmetic ingredient due to its skin-moisturizing activity. In this study, the use of AB as a cosmetic ingredient was found to be hampered due to its instability at high temperature and alkaline pH. Therefore, to increase the chemical stability of AB, we devised a novel process to synthesize ethyl-agarobioside (ethyl-AB) from the acid-catalyzed alcoholysis of agarose. This process mimics the generation of ethyl α-glucoside and glyceryl α-glucoside by alcoholysis in the presence of ethanol and glycerol during the traditional Japanese sake-brewing process. Ethyl-AB also showed in vitro skin-moisturizing activity similar to that of AB, but showed higher thermal and pH stability than AB. This is the first report of ethyl-AB, a novel compound produced from red seaweed, as a functional cosmetic ingredient with high chemical stability.

Extracellular production of a thermostable Cellvibrio endolytic β-agarase in Escherichia coli for agarose liquefaction

Four GH16 family β-agarases (GH16A, GH16B, GH16C, and GH16D), originated from an agarolytic bacterium Cellvibrio sp. KY-GH-1, were expressed in an Escherichia coli system and their activities were compared. Only GH16B (597 amino acids, 63.8 kDa), with N-terminal 22-amino acid signal sequence, was secreted into the culture supernatant and demonstrated a robust endolytic agarose hydrolyzing activity for producing neoagarotetraose (NA4) and neoagarohexaose (NA6) as end products. The optimal temperature and pH for the enzyme activity were 50 °C and 7.0, respectively. The enzyme was stable up to 50 °C and over a pH range of 5.0-8.0. The kinetic parameters, including Km, Vmax, kcat, and kcat/Km, of GH16B β-agarases for agarose were 14.40 mg/mL, 542.0 U/mg, 576.3 s^-1, and 4.80 × 10⁶ s^-1 M^-1, respectively. The addition of 1 mM MnCl₂ and 15 mM tris(2-carboxyethyl)phosphine enhanced the enzymatic activity. When agarose or neoagaro-oligosaccharides were used as substrates, the end products of enzymatic catalysis were NA4 and NA6, whereas agaropentaose was produced along with NA4 and NA6 when agaro-oligosaccharides were used as substrates. Treatment of 9%[w/v] melted agarose with the enzyme (1.6 µg/mL) under continuous magnetic stirring at 50 °C for 14 h resulted in efficient agarose liquefaction into NA4 and NA6. Purification of NA4 and NA6 from the enzymatic hydrolysate (9%[w/v] agarose, 20 mL) via Sephadex G-15 column chromatography yielded ~ 650 mg NA4/~ 900 mg NA6 (i.e., ~ 85.3% of the theoretical maximum yield). These findings suggest that the recombinant thermostable GH16B β-agarase is useful for agarose liquefaction to produce NA4 and NA6.

Natural antimicrobial oligosaccharides in the food industry

An increase in the number of antibiotic resistance genes burdens the environment and affects human health. Additionally, people have developed a cautious attitude toward chemical preservatives. This attitude has promoted the search for new natural antimicrobial substances. Oligosaccharides from various sources have been studied for their antimicrobial and prebiotic effects. Antimicrobial oligosaccharides have several advantages such as being produced from renewable resources and showing antimicrobial properties similar to those of chemical preservatives. Their excellent broad-spectrum antibacterial properties are primarily because of various synergistic effects, including destruction of pathogen cell wall. Additionally, the adhesion of harmful microorganisms and the role of harmful factors may be reduced by oligosaccharides. Some natural oligosaccharides were also shown to stimulate the growth probiotic organisms. Therefore, antimicrobial oligosaccharides have the potential to meet food processing industry requirements in the future. The latest progress in research on the antimicrobial activity of different oligosaccharides is demonstrated in this review. The possible mechanism of action of these antimicrobial oligosaccharides is summarized with respect to their direct and indirect effects. Finally, the extended applications of oligosaccharides from the food source industry to food processing are discussed.

Enzymatic preparation and potential applications of agar oligosaccharides: a review

Oligosaccharides derived from agar, that is, agarooligosaccharides and neoagarooligosaccharides, have demonstrated various kinds of bioactivities which have been utilized in a variety of fields. Enzymatic hydrolysis is a feasible approach that principally allows for obtaining specific agar oligosaccharides in a sustainable way at an industrial scale. This review summarizes recent technologies employed to improve the properties of agarase. Additionally, the relationship between the degree of polymerization, bioactivities, and potential applications of agar-derived oligosaccharides for pharmaceutical, food, cosmetic, and agricultural industries are discussed. Engineered agarase exhibited general improvement of enzymatic performance, which is mostly achieved by truncation. Rational and semi-rational design assisted by computational methods present the latest strategy for agarase improvement with greatest potential to satisfy future industrial needs. Agarase immobilized on magnetic Fe3O4 nanoparticles via covalent bond formation showed characteristics well suited for industry. Additionally, albeit with the relationship between the degree of polymerization and versatile bioactivities like anti-oxidants, anti-inflammatory, anti-microbial agents, prebiotics and in skin care of agar-derived oligosaccharides are discussed here, further researches are still needed to unravel the complicated relationship between bioactivity and structure of the different oligosaccharides.

Natural products in cosmetics

The global cosmetics market reached US$500 billion in 2017 and is expected to exceed US$800 billion by 2023, at around a 7% annual growth rate. The cosmetics industry is emerging as one of the fastest-growing industries of the past decade. Data shows that the Chinese cosmetics market was US$60 billion in 2021. It is expected to be the world's number one consumer cosmetics market by 2050, with a size of approximately US$450 billion. The influence of social media and the internet has raised awareness of the risks associated with the usage of many chemicals in cosmetics and the health benefits of natural products derived from plants and other natural resources. As a result, the cosmetic industry is now paying more attention to natural products. The present review focus on the possible applications of natural products from various biological sources in skin care cosmetics, including topical care products, fragrances, moisturizers, UV protective, and anti-wrinkle products. In addition, the mechanisms of targets for evaluation of active ingredients in cosmetics and the possible benefits of these bioactive compounds in rejuvenation and health, and their potential role in cosmetics are also discussed.

Agarose-Degrading Characteristics of a Deep-Sea Bacterium Vibrio Natriegens WPAGA4 and Its Cold-Adapted GH50 Agarase Aga3420

Up until now, the characterizations of GH50 agarases from Vibrio species have rarely been reported compared to GH16 agarases. In this study, a deep-sea strain, WPAGA4, was isolated and identified as Vibrio natriegens due to the maximum similarity of its 16S rRNA gene sequence, the values of its average nucleotide identity, and through digital DNA-DNA hybridization. Two circular chromosomes in V. natriegens WPAGA4 were assembled. A total of 4561 coding genes, 37 rRNA, 131 tRNA, and 59 other non-coding RNA genes were predicted in the genome of V. natriegens WPAGA4. An agarase gene belonging to the GH50 family was annotated in the genome sequence and expressed in E. coli cells. The optimum temperature and pH of the recombinant Aga3420 (rAga3420) were 40 °C and 7.0, respectively. Neoagarobiose (NA2) was the only product during the degradation process of agarose by rAga3420. rAga3420 had a favorable stability following incubation at 10-30 °C for 50 min. The Km, Vmax, and kcat values of rAga3420 were 2.8 mg/mL, 78.1 U/mg, and 376.9 s-1, respectively. rAga3420 displayed cold-adapted properties as 59.7% and 41.2% of the relative activity remained at 10 3 °C and 0 °C, respectively. This property ensured V. natriegens WPAGA4 could degrade and metabolize the agarose in cold deep-sea environments and enables rAga3420 to be an appropriate industrial enzyme for NA2 production, with industrial potential in medical and cosmetic fields.

Characterization of a GH50 β-Agarase: A Biotechnological Tool for Preparing Oligosaccharides from Agarose and Porphyran

Agarase is of vital significance for functional agaro-oligosaccharides production from algal dived agarose. Especially, the exolytic agarases have the advantage of obtaining agaro-oligosaccharides with a specific degree of polymerization. Herein, we cloned and expressed a novel glycoside hydrolase (GH) 50 family β-agarase OUC-PgJC50 from Photobacterium gaetbulicola. The degradation pattern analysis indicated that OUC-PgJC50 not only showed an exolytic activity with main products of neoagarotetraose from hydrolyzing agarose but also show a hydrolytic activity to transform neoagarotetraose into neoagarobiose. This is the first time that the discovery of a neoagarotetraose-producing exolytic GH50 β-agarase possesses the activity to transform neoagarotetraose into neoagarobiose, which provided new insight into the recognition of the degradation mode of agarases. Molecular docking and sequence alignment analysis further revealed the His₆₅₄ residue in OUC-PgJC50 may play a vital role in forming a strong force with l-AHG residue at -4 subsite that helps to produce neoagarotetraose from catalyzing agarose. Moreover, the catalytic ability of OUC-PgJC50 toward another agar polysaccharide porphyran was also described that could hydrolyze porphyran into sulfated oligosaccharides, in which the LA6S-d-Gal was the main products. This study is of vital significance for developing the application range of GH50 β-agarases.

Simultaneous quantification of marine neutral neoagaro-oligosaccharides and agar-oligosaccharides by the UHPLC-MS/MS method: application to the intestinal transport study by using the Caco-2 cell monolayer

A sensitive and robust ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the first time to simultaneously quantify marine neutral neoagaro-oligosaccharides (NAOS) and agar-oligosaccharides (AOS) with different degrees of polymerization (DP) in Hanks' balanced salt solution (HBSS). The separation was achieved on a BEH amide column using a mobile phase of acetonitrile-10 mmol L^-1 ammonium acetate (58 : 42, v/v) with an isocratic elution program. The total analysis time was 3.5 min. The mass spectra were acquired in the multiple reaction monitoring (MRM) pattern by using a heated-electrospray ionization (H-ESI) source operating in the positive ionization mode. The linear range was 40-20 000 nmol L^-1. The accuracy and precision ranged from 91.5 to 110.0% and 0.9 to 10.4%, respectively. The extraction recovery was consistent and reproducible. The stability was within 90.3-110.8%. The matrix effect, carryover, and dilution integrity were all satisfactory. Moreover, the validated method was successfully applied to the intestinal transport study by using the Caco-2 cell monolayer in vitro. The results revealed that neoagarobiose, neoagarotetraose, neoagarohexaose, agarotriose, agaropentose, and agaroheptose were transported by a paracellular pathway.

Characterization of Agarolytic Pathway in a Terrestrial Bacterium Cohnella sp. LGH

Previously, we have reported that an endo-type β-agarase AgaW was responsible for the hydrolysis of agarose into the major product neoagarotetraose in a terrestrial agar-degrading bacterium Cohnella sp. LGH. Here, we identify and characterize the following depolymerization pathway in strain LGH through the genomic and enzymatic analysis. In the pathway, neoagarotetraose was depolymerized by a novel α-neoagarooligosaccharide (NAOS) hydrolase CL5012 into 3,6-anhydro-α-L-galactose (L-AHG) and agarotriose; Agarotriose was further depolymerized by a novel agarolytic β-galactosidase CL4994 into D-galactose and neoagarobiose; Neoagarobiose was finally depolymerized by CL5012 into L-AHG and D-galactose. Although α-agarase has not been identified in strain LGH, the combined action of CL5012 and CL4994 unexpectedly plays a critical role in the depolymerization of agarotetraose, one theoretical product of α-agarase hydrolysis of agarose. In this pathway, agarotetraose was depolymerized by CL4994 into D-galactose and neoagarotriose; Neoagarotriose was then depolymerized by CL5012 into L-AHG and agarobiose. Furthermore, another novel endo-type β-agarase CL5055 was identified as an isozyme of AgaW with different pH preference in the hydrolysis of agarose into α-NAOSs. Strain LGH seemed to lack a common exo-type β-agarase responsible for the direct depolymerization of agarose or neoagarooligosaccharide into neoagarobiose. These results highlight the diversity of agarolytic manner in bacteria and provide a novel insight on the diversity of agarolytic pathways.

Synergistic effects of novel herbal decoctions from Panax ginseng and Morus alba on tyrosinase activity and melanogenesis in vitro

Many medicinal plants such as a Panax ginseng and Morus alba (mulberry tree) have been widely used as depigmenting agents in Asia. To maximize their synergistic effects on melanogenesis, new herbal decoctions were created by mixing Ginseng Radix Alba (GR) and Mori Radicis Cortex (MC) at a ratio of 3:2 which called GMC decoction. A decoction of GR and Mori Ramulus (MR), which called GMR, was also formulated in order to compare the anti-melanogenic capacity. Combined decoctions, GMC and GMR, significantly decreased mushroom tyrosinase activity in vitro; however, single extracts, including MC and MR, showed weaker inhibitory activity. Melanin content assay and Fontana–Masson staining confirmed that two decoctions showed stronger inhibitory effects on the forskolin-induced melanin level in B16 cells, without cytotoxicity. Our findings suggest that ginseng in combination with mulberry tree enhances the anti-melanogenic effect in vitro.

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.

A Novel Agarase, Gaa16B, Isolated from the Marine Bacterium Gilvimarinus agarilyticus JEA5, and the Moisturizing Effect of Its Partial Hydrolysis Products

We recently identified a β-agarase, Gaa16B, in the marine bacterium Gilvimarinus agarilyticus JEA5. Gaa16B, belonging to the glycoside hydrolase 16 family of β-agarases, shows less than 70.9% amino acid similarity with previously characterized agarases. Recombinant Gaa16B lacking the carbohydrate-binding region (rGaa16Bc) was overexpressed in Escherichia coli and purified. Activity assays revealed the optimal temperature and pH of rGaa16Bc to be 55 °C and pH 6–7, respectively, and the protein was highly stable at 55 °C for 90 min. Additionally, rGaa16Bc activity was strongly enhanced (2.3-fold) in the presence of 2.5 mM MnCl₂. The K_m and V_max of rGaa16Bc for agarose were 6.4 mg/mL and 953 U/mg, respectively. Thin-layer chromatography analysis revealed that rGaa16Bc can hydrolyze agarose into neoagarotetraose and neoagarobiose. Partial hydrolysis products (PHPs) of rGaa16Bc had an average molecular weight of 88–102 kDa and exhibited > 60% hyaluronidase inhibition activity at a concentration of 1 mg/mL, whereas the completely hydrolyzed product (CHP) showed no hyaluronidase at the same concentration. The biochemical properties of Gaa16B suggest that it could be useful for producing functional neoagaro-oligosaccharides. Additionally, the PHP of rGaa16Bc may be useful in promoting its utilization, which is limited due to the gel strength of agar.

Characterization and activity enhancement of a novel exo-type agarase Aga575 from Aquimarina agarilytica ZC1

The novel β-agarase gene aga575 from the agarolytic bacterium Aquimarina agarilytica ZC1 is composed of 2142 bp, and the encoded protein Aga575 has the highest amino acid sequence homology of only 65.2% with known agarases. Though carrying a domain of glycoside hydrolase family 42 in the C-terminal, Aga575 should belong to glycoside hydrolase family 50 according to the phylogenetic analysis. Gene aga575 was successfully cloned and overexpressed in Escherichia coli Rosetta (DE3) cells. The recombinant protein had the maximal agarase activity at pH 8.0 and 37 °C. The values K_m and V_max toward agarose were 8.4 mg/mL and 52.2 U/mg, respectively. Aga575 hydrolyzed agarose and neoagarooligosaccharides to yield neoagarobiose as the sole product. The agarose hydrolysis pattern of Aga575 indicated that it was an exo-type β-agarase. Random mutagenesis was carried out to obtain two beneficial mutants M1 (R534G) and M2 (S4R-R424G) with higher activities. The results showed that the agarase activity of mutant M1 and M2 reached 162% and 192% of the wild-type agarase Aga575, respectively. Moreover, the activity of the mixed mutant M1/M2 (S4R-R424G-R534G) increased to 227%. KEY POINTS: • Aga575 is a novel exo-type β-agarase degrading agarose to yield neoagarobiose as the sole product. • Though owning a domain of glycoside hydrolase family GH42, Aga575 should belong to family GH50. • The agarase activity of one mutant increased to 227% of the wild-type Aga575.

Expression and Characterization of a Novel Cold-Adapted and Stable β-Agarase Gene agaW1540 from the Deep-Sea Bacterium Shewanella sp. WPAGA9

The neoagaro-oligosaccharides, degraded from agarose by agarases, are important natural substances with many bioactivities. In this study, a novel agarase gene, agaW1540, from the genome of a deep-sea bacterium Shewanella sp. WPAGA9, was expressed, and the recombinant AgaW1540 (rAgaW1540) displayed the maximum activity under the optimal pH and temperature of 7.0 and 35 °C, respectively. rAgaW1540 retained 85.4% of its maximum activity at 0 °C and retained more than 92% of its maximum activity at the temperature range of 20-40 °C and the pH range of 4.0-9.0, respectively, indicating its extensive working temperature and pH values. The activity of rAgaW1540 was dramatically suppressed by Cu²⁺ and Zn²⁺, whereas Fe²⁺ displayed an intensification of enzymatic activity. The K_m and V_max of rAgaW1540 for agarose degradation were 15.7 mg/mL and 23.4 U/mg, respectively. rAgaW1540 retained 94.7%, 97.9%, and 42.4% of its maximum activity after incubation at 20 °C, 25 °C, and 30 °C for 60 min, respectively. Thin-layer chromatography and ion chromatography analyses verified that rAgaW1540 is an endo-acting β-agarase that degrades agarose into neoagarotetraose and neoagarohexaose as the main products. The wide variety of working conditions and stable activity at room temperatures make rAgaW1540an appropriate bio-tool for further industrial production of neoagaro-oligosaccharides.

Enhanced production of neoagarobiose from agar with Corynebacterium glutamicum producing exo-type and endo-type β-agarases

Neoagarobiose (NA2) derived from agar marine biomass is a rare reagent that acts as an anti-melanogenesis reagent and moisturizer. Here, for the economical manufacturing of NA2, we developed the co-secretory production system of endo-type β-agarases (DagA) and exo-type β-agarases (EXB3) in Corynebacterium glutamicum. For this purpose, we first developed a secretory system of DagA via Tat pathway. To improve the secretion efficiency, we coexpressed two Tat pathway components (TatA and TatC), and to improve the purity of secreted DagA in the culture supernatant, two endogenous protein genes (Cg2052 and Cg1514) were removed. Using the engineered strain (C. glutamicum SP002), we confirmed that DagA as high as 1.53 g l^-1 was successfully produced in the culture media with high purity (72.7% in the supernatant protein fraction). Next, we constructed the expression system (pHCP-CgR-DagA-EXB3) for the simultaneous secretion of EXB3 via Sec-pathway together with DagA, and it was clearly confirmed that DagA and EXB3 were successfully secreted as high as 54% and 24.5%, respectively. Finally, using culture medium containing DagA and EXB3, we successfully demonstrated the conversion of high-concentration agar (40 g l^-1 ) into NA2 via a two-stage hydrolysis process.

Metabolic and enzymatic elucidation of cooperative degradation of red seaweed agarose by two human gut bacteria

Various health beneficial outcomes associated with red seaweeds, especially their polysaccharides, have been claimed, but the molecular pathway of how red seaweed polysaccharides are degraded and utilized by cooperative actions of human gut bacteria has not been elucidated. Here, we investigated the enzymatic and metabolic cooperation between two human gut symbionts, Bacteroides plebeius and Bifidobacterium longum ssp. infantis, with regard to the degradation of agarose, the main carbohydrate of red seaweed. More specifically, B. plebeius initially decomposed agarose into agarotriose by the actions of the enzymes belonging to glycoside hydrolase (GH) families 16 and 117 (i.e., BpGH16A and BpGH117) located in the polysaccharide utilization locus, a specific gene cluster for red seaweed carbohydrates. Then, B. infantis extracted energy from agarotriose by the actions of two agarolytic β-galactosidases (i.e., Bga42A and Bga2A) and produced neoagarobiose. B. plebeius ultimately acted on neoagarobiose by BpGH117, resulting in the production of 3,6-anhydro-l-galactose, a monomeric sugar possessing anti-inflammatory activity. Our discovery of the cooperative actions of the two human gut symbionts on agarose degradation and the identification of the related enzyme genes and metabolic intermediates generated during the metabolic processes provide a molecular basis for agarose degradation by gut bacteria.

Advances in agaro-oligosaccharides preparation and bioactivities for revealing the structure-function relationship

Agaro-oligosaccharides originating from red algae have attracted increasing attention in both basic theoretical research and applied fields due to their excellent bioactivities, which indicates the wide prospects of agaro-oligosaccharides for application in the food, pharmaceutical and cosmetic industries. Thus, a considerable number of studies regarding functional agaro-oligosaccharides preparation as well as the bioactivities exploration have been carried out. Based on these studies, this review first introduced different methods that have been used in agar extraction from red algae, and further provided research progress on arylsulfatase. Then, different methods used for agaro-oligosaccharides production were summarized. Moreover, the abundant bioactivities of agaro-oligosaccharides were described in detail. Finally, this review has discussed current research problems and further provided critical aspects, which may be helpful for revealing the structure-function relationship of agaro-oligosaccharide.

Metabolic profiling of cytotoxic metabolites from five Tabebuia species supported by molecular correlation analysis

Tabebuia is the largest genus among the family Bignoniaceae. Tabebuia species are known for their high ornamental and curative value. Here, the cytotoxic potential of extracts from the leaves and stems of five Tabebuia species was analyzed. The highest activity was observed for T. rosea (Bertol.) DC. stem extract against HepG2 cell line (IC₅₀ 4.7 µg/mL), T. pallida L. stem extract against MCF-7 cell line (IC₅₀ 6.3 µg/mL), and T. pulcherrima stem extract against CACO2 cell line (IC₅₀ 2.6 µg/mL). Metabolic profiling of the ten extracts using liquid chromatography–high-resolution mass spectrometry for dereplication purposes led to annotation of forty compounds belonging to different chemical classes. Among the annotated compounds, irridoids represent the major class. Principle component analysis (PCA) was applied to test the similarity and variability among the tested species and the score plot showed similar chemical profiling between the leaves and stems of both T. pulcherrima and T. pallida L. and unique chemical profiling among T. rosea (Bertol.) DC., T. argentea Britton, and T. guayacan (Seem.) Hemsl. leaf extracts and the stem extract of T. rosea (Bertol.) DC. Additionally, a molecular correlation analysis was used to annotate the bioactive cytotoxic metabolites in the extracts and correlate between their chemical and biological profiles.

Novel and emerging prebiotics: Advances and opportunities

Consumers are conscientiously changing their eating preferences toward healthier options, such as functional foods enriched with pre- and probiotics. Prebiotics are attractive bioactive compounds with multidimensional beneficial action on both human and animal health, namely on the gastrointestinal tract, cardiometabolism, bones or mental health. Conventionally, prebiotics are non-digestible carbohydrates which generally present favorable organoleptic properties, temperature and acidic stability, and are considered interesting food ingredients. However, according to the current definition of prebiotics, application categories other than food are accepted, as well as non-carbohydrate substrates and bioactivity at extra-intestinal sites. Regulatory issues are considered a major concern for prebiotics since a clear understanding and application of these compounds among the consumers, regulators, scientists, suppliers or manufacturers, health-care providers and standards or recommendation-setting organizations are of utmost importance. Prebiotics can be divided in several categories according to their development and regulatory status. Inulin, galactooligosaccharides, fructooligosaccharides and lactulose are generally classified as well established prebiotics. Xylooligosaccharides, isomaltooligosaccharides, chitooligosaccharides and lactosucrose are classified as "emerging" prebiotics, while raffinose, neoagaro-oligosaccharides and epilactose are "under development." Other substances, such as human milk oligosaccharides, polyphenols, polyunsaturated fatty acids, proteins, protein hydrolysates and peptides are considered "new candidates." This chapter will encompass actual information about the non-established prebiotics, mainly their physicochemical properties, market, legislation, biological activity and possible applications. Generally, there is a lack of clear demonstrations about the effective health benefits associated with all the non-established prebiotics. Overcoming this limitation will undoubtedly increase the demand for these compounds and their market size will follow the consumer's trend.

The degradation activities for three seaweed polysaccharides of Shewanella sp. WPAGA9 isolated from deep-sea sediments

Seaweed oligosaccharides possess great bioactivities. However, different microbial strains are required to degrade multiple polysaccharides due to their limited biodegradability, thereby increasing the cost and complexity of production. Shewanella sp. WPAGA9 was isolated from deep-sea sediments in this study. According to the genomic and biochemical analyses, the extracellular fermentation broth of WPAGA9 had versatile degradation abilities for three typical seaweed polysaccharides including agar, carrageenan, and alginate. The maximum enzyme activities of the extracellular fermentation broth of WPAGA9 were 71.63, 76.4, and 735.13 U/ml for the degradation of agar, alginate, and carrageenan, respectively. Moreover, multiple seaweed oligosaccharides can be produced by the extracellular fermentation broth of WPAGA9 under similar optimum conditions. Therefore, WPAGA9 can simultaneously degrade three types of seaweed polysaccharides under similar conditions, thereby greatly reducing the production cost of seaweed oligosaccharides. This finding indicates that Shewanella sp. WPAGA9 is an ideal biochemical tool for producing multiple active seaweed oligosaccharides at low costs and is also an important participant in the carbon cycle process of the deep-sea environment.

Cellulose nanocrystal preparation from Gelidium amansii and analysis of its anti-inflammatory effect on the skin in vitro and in vivo

Treated Gelidium amansii cellulose nanocrystal (TGa CNC) was prepared from treated Gelidium amansii (TGa) and evaluated for its anti-inflammatory effect on human keratinocytes and mice skin. Using three independent cell lines, TGa CNC showed no cytotoxicity in HaCaT, Beas-2B, and Raw 264.7 cells. A non-toxic dose of TGa CNC suppressed ultraviolet (UV) B-induced AP (activated protein)-1, and subsequent cyclooxygenase (COX)-2 gene and protein expression in HaCaT cells. TGa CNC suppressed translocation of c-Jun from the cytosol to the nucleus responds to UVB irradiation. Additionally, TGa CNC suppressed UVB-induced extracellular signal-regulated kinases (ERKs)1/2/MEK/2/B-Raf, c-Jun N-terminal kinase (JNK)1/2/MKK4/7, Akt, and epidermal growth factor receptor (EGFR) phosphorylation in HaCaT cells. Dorsal treatment of TGa CNC significantly suppressed acute UVB-induced increase in epidermal thickness and COX-2 expression in mice skin. Overall, these results indicate that TGa CNC exerts potent anti-inflammatory activity through the inhibition of abnormal COX-2 expression and mitogen-activated protein kinases (MAPK)s signaling pathways.

Production of Neoagaro-Oligosaccharides With Various Degrees of Polymerization by Using a Truncated Marine Agarase

Bioactivities, such as freshness maintenance, whitening, and prebiotics, of marine neoagaro-oligosaccharides (NAOS) with 4-12 degrees of polymerization (DPs) have been proven. However, NAOS produced by most marine β-agarases always possess low DPs (≤6) and limited categories; thus, a strategy that can efficiently produce NAOS especially with various DPs ≥8 must be developed. In this study, 60 amino acid residues with no functional annotation result were removed from the C-terminal of agarase AgaM1, and truncated recombinant AgaM1 (trAgaM1) was found to have the ability to produce NAOS with various DPs (4-12) under certain conditions. The catalytic efficiency and stability of trAgaM1 were obviously lower than the wild type (rAgaM1), which probably endowed trAgaM1 with the ability to produce NAOS with various DPs. The optimum conditions for various NAOS production included mixing 1% agarose (w/v) with 10.26 U/ml trAgaM1 and incubating the mixture at 50°C in deionized water for 100 min. This strategy produced neoagarotetraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagarodecaose (NA10), and neoagarododecaose (NA12) at final concentrations of 0.15, 1.53, 1.53, 3.02, and 3.02 g/L, respectively. The NAOS served as end-products of the reaction. The conditions for trAgaM1 expression in a shake flask and 5 L fermentation tank were optimized, and the yields of trAgaM1 increased by 56- and 842-fold compared with those before optimization, respectively. This study provides numerous substrate sources for production and activity tests of NAOS with high DPs and offers a foundation for large-scale production of NAOS with various DPs at a low cost.

Agarose degradation for utilization: Enzymes, pathways, metabolic engineering methods and products

Red algae are important renewable bioresources with very large annual outputs. Agarose is the major carbohydrate component of many red algae and has potential to be of value in the production of agaro-oligosaccharides, biofuels and other chemicals. In this review, we summarize the degradation pathway of agarose, which includes an upstream part involving transformation of agarose into its two monomers, D-galactose (D-Gal) and 3,6-anhydro-α-L-galactose (L-AHG), and a downstream part involving monosaccharide degradation pathways. The upstream part involves agarolytic enzymes such as α-agarase, β-agarase, α-neoagarobiose hydrolase, and agarolytic β-galactosidase. The downstream part includes the degradation pathways of D-Gal and L-AHG. In addition, the production of functional agaro-oligosaccharides such as neoagarobiose and monosaccharides such as L-AHG with different agarolytic enzymes is reviewed. Third, techniques for the setup, regulation and optimization of agarose degradation to increase utilization efficiency of agarose are summarized. Although heterologous construction of the whole agarose degradation pathway in an engineered strain has not been reported, biotechnologies applied to improve D-Gal utilization efficiency and construct L-AHG catalytic routes are reviewed. Finally, critical aspects that may aid in the construction of engineered microorganisms that can fully utilize agarose to produce agaro-oligosaccharides or as carbon sources for production of biofuels or other value-adding chemicals are discussed.

Therapeutic Uses of Red Macroalgae

Red Seaweed “Rhodophyta” are an important group of macroalgae that include approximately 7000 species. They are a rich source of structurally diverse bioactive constituents, including protein, sulfated polysaccharides, pigments, polyunsaturated fatty acids, vitamins, minerals, and phenolic compounds with nutritional, medical, and industrial importance. Polysaccharides are the main components in the cell wall of red algae and represent about 40–50% of the dry weight, which are extensively utilized in industry and pharmaceutical compounds, due to their thickening and gelling properties. The hydrocolloids galactans carrageenans and agars are the main red seaweed cell wall polysaccharides, which had broad-spectrum therapeutic characters. Generally, the chemical contents of seaweed are different according to the algal species, growth stage, environment, and external conditions, e.g., the temperature of the water, light intensity, nutrient concentrations in the ecosystem. Economically, they can be recommended as a substitute source for natural ingredients that contribute to a broad range of bioactivities like cancer therapy, anti-inflammatory agents, and acetylcholinesterase inhibitory. This review touches on the main points of the pharmaceutical applications of red seaweed, as well as the exploitation of their specific compounds and secondary metabolites with vital roles.

Comparative Genomic and Secretomic Analysis Provide Insights Into Unique Agar Degradation Function of Marine Bacterium Vibrio fluvialis A8 Through Horizontal Gene Transfer

Agarose-oligosaccharide production from agar degradation by agarase exhibits lots of advantages and good application prospects. In this study, a novel agar-degrading bacterium Vibrio sp. A8 was isolated from a red algae in the South China Sea. The whole genome sequencing with comparative genomic and secretomic analysis were used to better understand its genetic components about agar degradation. This strain exhibited good agarase production in artificial seawater after culture optimization. The complete genome (4.88 Mb) of this strain comprised two circular chromosomes (3.19 and 1.69 Mb) containing 4,572 protein-coding genes, 108 tRNA genes and 31 rRNA genes. This strain was identified as Vibrio fluvialis A8 by comparative genomic analysis based on genome phylogenetic tree and average nucleotide identity (ANI) similarity. Different from other 20 similar strains including three strains of the same species, V. fluvialis A8 possessed unique agar degradation ability with four β-agarases (GH50) and one α-1,3-L-NA2 hydrolase (GH117) due to the horizontal gene transfer. Secretomic analysis showed that only β-agarase (gene 3152) was abundantly expressed in the secretome of V. fluvialis A8. This agarase had a good substrate specificity and wide work conditions in complex environments, suggesting its potential application for agarose-oligosaccharide production.

Quantification of 3,6-anhydro-galactose in red seaweed polysaccharides and their potential skin-whitening activity

This study determined the composition of the monosaccharide, 3, 6-anhydrogalactose (AnGal), in red algae and explored the potential whitening activity of the extract. Using gas chromatography-mass spectrometry (GC-MS), the AnGal composition of six different species of red seaweed (Porphyra haitanensis, Gracilaria chouae, Gracilaria blodgettii, Gracilaria lemaneiformis, Eucheuma galetinae, and Gelidium amansii) was successfully analyzed, revealing molar ratios ranging from 1.0:1.0 to 1.0:3.1 of AnGal and galactose (Gal), respectively. Employing the tyrosinase inhibition assay, the skin-whitening effect of AnGal red seaweed polysaccharides was determined. Polysaccharides from P. haitanensis, G. chouae, and G. blodgettii as well as their degradation products showed higher tyrosinase inhibitory activity (inhibition rates 24.2-26.8%). These results suggest that the GC-MS approach could conveniently be used in quality control or for the quantitative determination of AnGal and Gal in red seaweed polysaccharides as well as exploring their potential application in cosmetic and functional food products. The findings here exhibited that red seaweed polysaccharides and their degradation products were potential ingredients for cosmeceutical industries.

Dual Agarolytic Pathways in a Marine Bacterium, Vibrio sp. Strain EJY3: Molecular and Enzymatic Verification

Vibrio sp. strain EJY3 is an agarolytic marine bacterium that catabolizes 3,6-anhydro-l-galactose (AHG), a monomeric sugar unit of agarose. While the AHG catabolic pathway in EJY3 has been discovered recently, the complete agarolytic system of EJY3 remains unclear. We have identified five enzymes, namely, the β-agarases VejGH50A, VejGH50B, VejGH50C, and VejGH50D and the α-neoagarooligosaccharide (NAOS) hydrolase VejGH117, involved in the agarolytic system of EJY3. Based on the characterization of recombinant enzymes and intracellular metabolite analysis, we found that EJY3 catabolizes agarose via two different agarolytic pathways. Among the four β-agarases of EJY3, VejGH50A, VejGH50B, and VejGH50C were found to be extracellular agarases, producing mainly neoagarotetraose (NeoDP4) and neoagarobiose. By detecting intracellular NeoDP4 in EJY3 grown on agarose, NeoDP4 was observed being taken up by cells. Intriguingly, intracellular NeoDP4 acted as a branching point for the two different downstream agarolytic pathways. First, via the well-known agarolytic pathway, NeoDP4 was depolymerized into monomeric sugars by the exo-type β-agarase VejGH50D and the α-NAOS hydrolase VejGH117. Second, via the newly found alternative agarolytic pathway, NeoDP4 was depolymerized into AHG and agarotriose (AgaDP3) by VejGH117, and AgaDP3 then was completely depolymerized into monomeric sugars by sequential reactions of the agarolytic β-galactosidases (ABG) VejABG and VejGH117. Therefore, by experimentally verifying agarolytic enzymatic activity and transport of NeoDP4 into EJY3 cells, we revealed that EJY3 possesses both the known pathway and the newly discovered alternative pathway that involves α-NAOS hydrolase and ABG.IMPORTANCE Agarose is the main polysaccharide of red macroalgae and is composed of galactose and 3,6-anhydro-l-galactose. Many marine bacteria possess enzymes capable of depolymerizing agarose into oligomers and then depolymerizing the oligomers into monomers. Here, we experimentally verified that both a well-known agarolytic pathway and a novel agarolytic pathway exist in a marine bacterium, Vibrio sp. strain EJY3. In agarolytic pathways, agarose is depolymerized mainly into 4-sugar-unit oligomers by extracellular enzymes, which are then transported into cells. The imported oligomers are intracellularly depolymerized into galactose and 3,6-anhydro-l-galactose by two different agarolytic pathways, using different combinations of intracellular enzymes. These results elucidate the depolymerization routes of red macroalgal biomass in the ocean by marine bacteria and provide clues for developing industrial processes for efficiently producing sugars from red macroalgae.

Implications of agar and agarase in industrial applications of sustainable marine biomass

Agar, a major component of the cell wall of red algae, is an interesting heteropolysaccharide containing an unusual sugar, 3,6-anhydro-L-galactose. It is widely used as a valuable material in various industrial and experimental applications due to its characteristic gelling and stabilizing properties. Agar-derived oligosaccharides or mono-sugars produced by various agarases have become a promising subject for research owing to their unique biological activities, including anti-obesity, anti-diabetic, immunomodulatory, anti-tumor, antioxidant, skin-whitening, skin-moisturizing, anti-fatigue, and anti-cariogenic activities. Agar is also considered as an alternative sustainable source of biomass for chemical feedstock and biofuel production to substitute for the fossil resource. In this review, we summarize various biochemically characterized agarases, which are useful for industrial applications, such as neoagarooligosaccharide or agarooligosaccharide production and saccharification of agar. Additionally, we succinctly discuss various recent studies that have been conducted to investigate the versatile biological activities of agar-derived saccharides and biofuel production from agar biomass. This review provides a basic framework for understanding the importance of agarases and agar-derived saccharides with broad applications in pharmaceutical, cosmetic, food, and bioenergy industries.

Comparative Genomics and CAZyme Genome Repertoires of Marine Zobellia amurskyensis KMM 3526T and Zobellia laminariae KMM 3676T

We obtained two novel draft genomes of type Zobellia strains with estimated genome sizes of 5.14 Mb for Z. amurskyensis KMM 3526^Т and 5.16 Mb for Z. laminariae KMM 3676^Т. Comparative genomic analysis has been carried out between obtained and known genomes of Zobellia representatives. The pan-genome of Zobellia genus is composed of 4853 orthologous clusters and the core genome was estimated at 2963 clusters. The genus CAZome was represented by 775 GHs classified into 62 families, 297 GTs of 16 families, 100 PLs of 13 families, 112 CEs of 13 families, 186 CBMs of 18 families and 42 AAs of six families. A closer inspection of the carbohydrate-active enzyme (CAZyme) genomic repertoires revealed members of new putative subfamilies of GH16 and GH117, which can be biotechnologically promising for production of oligosaccharides and rare monomers with different bioactivities. We analyzed AA3s, among them putative FAD-dependent glycoside oxidoreductases (FAD-GOs) being of particular interest as promising biocatalysts for glycoside deglycosylation in food and pharmaceutical industries.

3,6-Anhydro-L-galactose increases hyaluronic acid production via the EGFR and AMPKα signaling pathway in HaCaT keratinocytes

BACKGROUND

Hyaluronic acid (HA) is an important factor in skin hydration maintenance. In mammalian keratinocytes, hyaluronan synthase 2 (HAS2) is a critical enzyme in HA production. Therefore, the promotion of HAS2 expression in keratinocytes may be a strategy for maintaining skin moisture.

OBJECTIVE

The aim was to determine the skin hydration effect and regulatory mechanisms of 3,6-anhydro-L-galactose (L-AHG), a main component of red macroalgal carbohydrates in human keratinocytes.

METHODS

L-AHG was applied to an immortalized human epidermal keratinocyte cell line (HaCaT cells). HA production, HAS2 protein and mRNA levels, and the activation of the signaling pathways involved in HAS2 expression were measured. HA levels were also evaluated for three dimensional (3D) reconstructed human skin.

RESULTS

Our results suggest that L-AHG upregulates HA production and may enhance HAS2 expression by activating EGFR-mediated ERK, PI3K/Akt, and STAT3 signaling pathways. We confirmed that L-AHG activated the AMPKα signaling pathway which in turn could regulate HAS2 expression in HaCaT cells. The effects of L-AHG on HA production were observed in the 3D reconstructed human skin model.

CONCLUSION

Our results suggest that L-AHG may enhance skin moisture retention by increasing HA synthesis in human epidermal keratinocytes.

Anti-aging Effect of Agar Oligosaccharide on Male Drosophila melanogaster and its Preliminary Mechanism

Agar oligosaccharide (AOS) is a marine prebiotic with apparent anti-inflammatory, antioxidant and anti-tumor effects. During this study, different doses of AOS are added to a basal diet to evaluate its effects on the lifespan, motor vigor and reproduction of male Drosophila melanogaster. Additionally, the activities of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and catalase (CAT) and the malondialdehyde (MDA) content in male Drosophila are examined on the 10th, 25th and 40th days. The fly midguts are removed on the 10th and 40th days for analyses of the intestinal microbial community by 16S rDNA sequencing and the expression level of intestinal immunity genes by quantitative real-time PCR (RT-PCR). The results show that AOS significantly prolonged the average and maximum lifespan and increased the antioxidant capacity of male Drosophila. Additionally, AOS significantly regulated the structure of the intestinal flora of "old" flies (40 days) and upregulated the expression of immune deficiency (IMD) genes to improve the intestinal immunity, which could be beneficial for delaying aging in old flies. The above-described results provide a theoretical basis for the application of AOS, a type of marine oligosaccharide, as a nutritional supplement or immunomodulator.

The Potential of Neoagaro-Oligosaccharides as a Treatment of Type II Diabetes in Mice

Type 2 diabetes mellitus (T2DM) accounts for more than 90% of cases of diabetes mellitus, which is harmful to human health. Herein, neoagaro-oligosaccharides (NAOs) were prepared and their potential as a treatment of T2DM was evaluated in KunMing (KM) mice. Specifically, a T2DM mice model was established by the combination of a high-fat diet (HFD) and alloxan injection. Consequently, the mice were given different doses of NAOs (100, 200, or 400 mg/kg) and the differences among groups of mice were recorded. As a result of the NAOs treatment, the fasting blood glucose (FBG) was lowered and the glucose tolerance was improved as compared with the model group. As indicated by the immunohistochemistry assay, the NAOs treatment was able to ameliorate hepatic macrovesicular steatosis and hepatocyte swelling, while it also recovered the number of pancreatic β-cells. Additionally, NAOs administration benefited the antioxidative capacity in mice as evidenced by the upregulation of both glutathione peroxidase and superoxide dismutase activity and the significant reduction of the malondialdehyde concentration. Furthermore, NAOs, as presented by Western blotting, increased the expression of p-ERK1/2, p-JNK, NQO1, HO-1, and PPARγ, via the MAPK, Nrf2, and PPARγ signaling pathways, respectively. In conclusion, NAOs can be used to treat some complications caused by T2DM, and are beneficial in controlling the level of blood glucose and ameliorating the damage of the liver and pancreatic islands.

Simple Preparation of Diverse Neoagaro-Oligosaccharides

A simple method for obtaining pure and well-defined oligosaccharides was established by hydrolyzing agar with β-agarase from Vibrio natriegens. The conditions for enzymolysis were optimized as follows: a temperature of 45 °C, a pH of 8.5, a substrate concentration of 0.3%, an enzyme amount of 100 U/g and an enzymolysis time of 20 h. Neoagaro-oligosaccharides with different degrees of polymerization were obtained by hydrolyzing agar with β-agarase for different lengths of time. After removing pigments using activated carbon and salts by dialyzing, the enzyme hydrolysis solution was separated with Bio-Gel P2 column chromatography. Neoagaro-oligosaccharides with different degrees of polymerization were acquired. By comparing with authentic standard substances, along with further confirmation by FTIR, MS and NMR, structures of the purified neoagaro-oligosaccharides were identified as neoagarobiose (NA2), neoagaroteraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagaro-decaose (NA10) and neoagarododecaose (NA12) with purities of more than 97.0%. The present study established a method for the preparation of various neoagaro-oligosaccharides that may be of great significance for further study of their bioactivities.

Biosynthetic Routes for Producing Various Fucosyl-Oligosaccharides

Fucosyl-oligosaccharides (FOSs) play physiologically important roles as prebiotics, neuronal growth factors, and inhibitors of enteropathogens. However, challenges in designed synthesis and mass production of FOSs hamper their industrial applications. Here, we report flexible biosynthetic routes to produce various FOSs, including unnatural ones, through in vitro enzymatic reactions of various sugar acceptors, such as glucose, cellobiose, and agarobiose, and GDP-l-fucose as the fucose donor by using α1,2-fucosyltransferase (FucT2). Also, the whole-cell conversion for fucosylation of various sugar acceptors by overexpressing the genes associated with GDP-l-fucose production and fucT2 gene in Escherichia coli was demonstrated by producing 17.74 g/L of 2'-fucosylgalactose (2'-FG). Prebiotic effects of 2'-FG were verified on the basis of selective fermentability of 2'-FG by probiotic bifidobacteria. These biosynthetic routes can be used to engineer industrial microorganisms for more economical, more flexible, and safer production of FOSs than chemical synthesis of FOSs.

Structure-based design of agarase AgWH50C from Agarivorans gilvus WH0801 to enhance thermostability

AgWH50C, an exo-β-agarase of GH50 isolated from Agarivorans gilvus WH0801, plays a key role in the enzymatic production of neoagarobiose, which has great application prospect in the cosmetics and pharmaceutical industry. In contrast, the poor thermostability becomes the main obstructive factor of glycoside hydrolase (GH) family 50 agarases, including AgWH50C. Herein, based on the AgWH50C crystal structure, we designed several mutants by a multiple cross-linked rational design protocol used thermostability predicting softwares ETSS, PoPMuSiC, and HotMuSiC. To our surprise, the mutant K621F increased its relative activity by as much as 45% and the optimal temperature increased to 38 °C compared to that of wild-type, AgWH50C (30 °C). The thermostability of K621F also exhibited a substantial improvement. Considering that the gelling temperature of the agarose is higher than 35 °C, K621F can be used to hydrolyze agarose for neoagarobiose production.

Beneficial Effects of Marine Algae-Derived Carbohydrates for Skin Health

Marine algae are considered to be an abundant sources of bioactive compounds with cosmeceutical potential. Recently, a great deal of interest has focused on the health-promoting effects of marine bioactive compounds. Carbohydrates are the major and abundant constituent of marine algae and have been utilized in cosmetic formulations, as moisturizing and thickening agents for example. In addition, marine carbohydrates have been suggested as promising bioactive biomaterials for their various properties beneficial to skin, including antioxidant, anti-melanogenic and skin anti-aging properties. Therefore, marine algae carbohydrates have potential skin health benefits for value-added cosmeceutical applications. The present review focuses on the various biological capacities and potential skin health benefits of bioactive marine carbohydrates.

Coimmobilization of β-Agarase and α-Neoagarobiose Hydrolase for Enhancing the Production of 3,6-Anhydro-l-galactose

Here we report a simple and efficient method to produce 3,6-anhydro-l-galactose (l-AHG) and agarotriose (AO3) in one step by a multienzyme system with the coimmobilized β-agarase AgWH50B and α-neoagarobiose hydrolase K134D. K134D was obtained by AgaWH117 mutagenesis and showed improved thermal stability when immobilized via covalent bonds on functionalized magnetic nanoparticles. The obtained multienzyme biocatalyst was characterized by Fourier transform infrared spectroscopy (FTIR). Compared with free agarases, the coimmobilized agarases exhibited a relatively higher agarose-to-l-AHG conversion efficiency. The yield of l-AHG obtained with the coimmobilized agarases was 40.6%, which was 6.5% higher than that obtained with free agarases. After eight cycles, the multienzyme biocatalyst still preserved 46.4% of the initial activity. To the best of our knowledge, this is the first report where two different agarases were coimmobilized. These results demonstrated the feasibility of the new method to fabricate a new multienzyme system onto magnetic nanoparticles via covalent bonds to produce l-AHG.

Effect of 3,6-anhydro-l-galactose on α-melanocyte stimulating hormone-induced melanogenesis in human melanocytes and a skin-equivalent model

3,6‐Anhydro‐l‐galactose (l‐AHG) is a bioactive sugar that is a major component of agarose. Recently, l‐AHG was reported to have anti‐melanogenic potential in human epidermal melanocytes (HEMs) and B16F10 melanoma cells; however, its underlying molecular mechanisms remain unknown. At noncytotoxic concentrations, l‐AHG has been shown to inhibit alpha‐melanocyte‐stimulating hormone‐induced melanin synthesis in various cell models, including HEMs, melan‐a cells, and B16F10 cells. Although l‐AHG did not inhibit tyrosinase activity in vitro, reverse transcription‐polymerase chain reaction results demonstrated that the anti‐melanogenic effect of l‐AHG was mediated by transcriptional repression of melanogenesis‐related genes, including tyrosinase, tyrosinase‐related protein‐1 (TRP‐1), tyrosinase‐related protein‐2 (TRP‐2), and microphthalmia‐associated transcription factor (MITF) in HEMs. Western blot analysis showed that l‐AHG effectively attenuated α‐melanocyte‐stimulating hormone‐induced melanogenic proteins by inhibiting cyclic adenosine monophosphate/cyclic adenosine monophosphate–dependent protein kinase, mitogen‐activated protein kinase, and Akt signaling pathways in HEMs. Topical application of l‐AHG significantly ameliorated melanin production in a 3D pigmented human skin model. Collectively, these results suggest that l‐AHG could be utilized as novel cosmetic compounds with skin‐whitening efficacy.