3,6-anhydro-α-L-galactose (L-AHG) is one of the main monosaccharide constituents of red macroalgae. In the recently discovered bacterial L-AHG catabolic pathway, L-AHG is first oxidized by ...a NAD(P)+-dependent dehydrogenase (AHGD), which is a key step of this pathway. However, the catalytic mechanism(s) of AHGDs is still unclear. Here, we identified and characterized an AHGD from marine bacterium Vibrio variabilis JCM 19239 (VvAHGD). The NADP+-dependent VvAHGD could efficiently oxidize L-AHG. Phylogenetic analysis suggested that VvAHGD and its homologs represent a new aldehyde dehydrogenase (ALDH) family with different substrate preferences from reported ALDH families, named the L-AHGDH family. To explain the catalytic mechanism of VvAHGD, we solved the structures of VvAHGD in the apo form and complex with NADP+ and modeled its structure with L-AHG. Based on structural, mutational, and biochemical analyses, the cofactor channel and the substrate channel of VvAHGD are identified, and the key residues involved in the binding of NADP+ and L-AHG and the catalysis are revealed. VvAHGD performs catalysis by controlling the consecutive connection and interruption of the cofactor channel and the substrate channel via the conformational changes of its two catalytic residues Cys282 and Glu248. Comparative analyses of structures and enzyme kinetics revealed that differences in the substrate channels (in shape, size, electrostatic surface, and residue composition) lead to the different substrate preferences of VvAHGD from other ALDHs. This study on VvAHGD sheds light on the diversified catalytic mechanisms and evolution of NAD(P)+-dependent ALDHs.
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•3,6-anhydro-α-L-galactose (L-AHG) is the main monosaccharide constituent of red macroalgae and metabolized by marine bacteria.•AHGDs catalyze the first step of the bacterial L-AHG catabolic pathway with an unknown mechanism.•Crystal structures of VvAHGD were determined in apo and cofactor-bound states.•The catalytic mechanism of VvAHGD is proposed based on structural and mutational analyses.•VvAHGD and its homologs represent a new aldehyde dehydrogenase family.
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•Ultrasound was used as alternative technology to convectional method (CE) for macroalgae.•Ultrasonic assisted extraction(UAE) enabled increased extraction of bioactive compounds from ...L. papillosa.•UAE was faster, boost efficiency, reduction of time, least expensive compared with CE.
Currently, sustainability is one of the most critical issues confronting society today. The growing of macroalgae in ocean farms appears more sustainable than agriculture on land due to it does not require any fresh water, chemical fertiliser, or soil. Macroalgae have been shown to be a sustainable marine source of amino acids, novel bioactive phenolic and aroma compounds that can be exploitation in food, cosmetic, nutraceuticals, pharmacological applications. Despite starting the huge cultivation of macroalgae in world, bioactive compounds in the edible macroalgae have not been well characterized. Ultrasound assisted extraction (UAE) and conventional extraction (CE) techniques were compared and red macroalgae, L. papillosa extracts were characterized. The highest amount of amino acid was glutamic acid (GLU) and composed of 35% was essential amino acids. UAE at 10% amplitude for 15 min showed significantly highest (p < 0.05) phenolic (212.03±3.03 mg gallic acid equivalent/100 g) as well as antioxidant activity determined by DPPH (105.69±3.02 µmol Trolox/100 g), ABTS (238.69±2.23 µmol Trolox/100 g) radical assay and FRAP value (72.47±3.13 µmol Trolox/100 g) when in comparison with CE. Furthermore, bioactive compounds in extracts were indicated as phlorotannins, flavonoids, phenolic acids and other polyphenols using liquid chromatography coupled to diode array detection and electrospray ionisation tandem mass spectrometry (LC-DAD-ESI-MS/MS). This result confirmed higher antioxidant capacity detected with the UAE. A total of 46 volatile organic compounds were identified and quantified by GC-FID/MS with HS-SPME system. This study emerges as first report to novel extraction method used and deeply characterization of L papillosa. The results seem that significant potential application in the functional food, active packaging and nutraceuticals industry.
•Macroalgae extract has great potency as biopolymer feedstock.•Microwave-assisted dilute acid hydrolysis (MADAH) enhanced the galactose yield.•The optimum conditions for the MADAH were at 120 °C with ...0.1 M H2SO4 for 25 min.•High cell density culture exhibited a positive effect on L-lactic acid yield.•Chlorella vulgaris residues enhanced the growth of Bacillus coagulans ATCC 7050.
The development of an efficient third-generation L-lactic acid (L-LA) production process from Eucheuma denticulatum extract (EDE) was achieved in this study. Microwave-assisted dilute acid hydrolysis (MADAH) and microwave-assisted hydrothermal hydrolysis (MAHTH) were chosen as the hydrolysis of EDE for the objective of increasing galactose yield. Single-factor optimization of hydrolysis of the EDE was studied, MADAH had high performance in galactose production relative to MAHTH, in which the yield and optimal conditions for both processes were 50.7% (0.1 M H2SO4, 120 °C for 25 min) and 47.8% (0 M H2SO4,160 °C for 35 min), respectively. For fermentation, the optimal L-LA yield was achieved at the inoculum cell density of 4% (w/w) Bacillus coagulans ATCC 7050 with 89.4% and 6% (w/w) Lactobacillus acidophilus LA-14 with 87.6%. In addition, lipid-extracted Chlorella vulgaris residues (CVRs) as co-nutrient supplementation increased the relative abundance of B. coagulans ATCC 7050, thus benefiting L-LA production.
3,6-Anhydro-l-galactose (AHG) produced from agarose in red macroalgae was recently suggested as an anticariogenic sugar to replace widely used xylitol. However, the multi-step process for obtaining ...monomeric sugar AHG from agarose may be expensive. Generally, it is easier to obtain oligosaccharides than monosaccharides from polysaccharides. Therefore, a one-step process to obtain agarobiose (AB) from agarose was recently developed, and here, we suggest AB as a new anticariogenic agent, owing to its anticariogenic activity against Streptococcus mutans. Among AHG-containing oligosaccharides, AB, neoagarobiose (NAB), agarooligosaccharides (AOSs), and neoagarooligosaccharides (NAOSs), AB showed higher inhibitory activity than AOSs against the growth and lactic acid production of S. mutans; no such inhibitory activity was observed for NAB and NAOSs. This inhibitory effect of AB was comparable to the previously reported inhibitory activity of AHG against S. mutans. These results suggest that AB, which can be more economically and simply produced than AHG, may serve as an anticariogenic sugar.
A novel metabolic pathway of 3,6-anhydro-
l
-galactose (
l
-AHG), the main sugar component in red macroalgae, was first discovered in the marine bacterium
Vibrio
sp. EJY3.
l
-AHG is converted to ...2-keto-3-deoxy-galactonate (KDGal) in two metabolic steps. Here, we identified the enantiomeric nature of KDGal in the
l
-AHG catabolic pathway via stereospecific enzymatic reactions accompanying the biosynthesis of enantiopure
l
-KDGal and
d
-KDGal. Enantiopure
l
-KDGal and
d
-KDGal were synthesized by enzymatic reactions derived from the fungal galacturonate and bacterial oxidative galactose pathways, respectively. KDGal, which is involved in the
l
-AHG pathway, was also prepared. The results obtained from the reactions with an
l
-KDGal aldolase, specifically acting on
l
-KDGal, showed that KDGal in the
l
-AHG pathway exists in an
l
-enantiomeric form. Notably, we demonstrated the utilization of
l
-KDGal by
Escherichia coli
for the first time.
E. coli
cannot utilize
l
-KDGal as the sole carbon source. However, when a mixture of
l
-KDGal and
d
-galacturonate was used,
E. coli
utilized both. Our study suggests a stereoselective method to determine the absolute configuration of a compound. In addition, our results can be used to explore the novel
l
-KDGal catabolic pathway in
E. coli
and to construct an engineered microbial platform that assimilates
l
-AHG or
l
-KDGal as substrates.
Key points
•
Stereospecific enzyme reactions were used to identify enantiomeric nature of KDGal
• KDGal in the
l
-AHG catabolic pathway exists in an
l
-enantiomeric form
• E. coli can utilize
l
-KDGal as a carbon source when supplied with
d
-galacturonate
Antibacterial activities of the methanolic extracts of Stypopodium schimperi (Kützing) Verlaque and Boudouresque, Halopteris filicina (Grateloup) Kützing, Dictyota dichotoma (Hudson) J.V.Lamouroux, ...Gracilaria bursa-pastoris (S.G.Gmelin) P.C.Silva, Ulva intestinalis Linnaeus species from the Iskenderun Bay, Turkey against Escherichia coli, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium and Proteus vulgaris were evaluated by using the microdilution method. Results of the study showed that all of the extracts had an antimicrobial effect on the tested bacteria. A minimum inhibitor concentration and minimum bactericidal concentrations of the extracts ranged from >125 to <0.39 mg mL-1. Furthermore, this is the first report on antibacterial effects of the methanolic extracts of S. schimperi (Kützing) Verlaque and Boudouresque and G. bursa-pastoris (S.G.Gmelin) P.C.Silva species. The present findings revealed that all studied seaweed species could act as a natural source of bioactive compounds for the treatment of infectious diseases.
Antibacterial activities of the methanolic extracts of Stypopodium schimperi (Kützing) Verlaque and Boudouresque, Halopteris filicina (Grateloup) Kützing, Dictyota dichotoma (Hudson) J.V.Lamouroux, Gracilaria bursa-pastoris (S.G.Gmelin) P.C.Silva, Ulva intestinalis Linnaeus species from the Iskenderun Bay, Turkey against Escherichia coli, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium and Proteus vulgaris were evaluated by using the microdilution method. Results of the study showed that all of the extracts had an antimicrobial effect on the tested bacteria. A minimum inhibitor concentration and minimum bactericidal concentrations of the extracts ranged from >125 to <0.39 mg mL-1. Furthermore, this is the first report on antibacterial effects of the methanolic extracts of S. schimperi (Kützing) Verlaque and Boudouresque and G. bursa-pastoris (S.G.Gmelin) P.C.Silva species. The present findings revealed that all studied seaweed species could act as a natural source of bioactive compounds for the treatment of infectious diseases.
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
GH50A,
GH50B,
GH50C, and
GH50D and the α-neoagarooligosaccharide (NAOS) hydrolase
GH117, 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,
GH50A,
GH50B, and
GH50C 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
GH50D and the α-NAOS hydrolase
GH117. Second, via the newly found alternative agarolytic pathway, NeoDP4 was depolymerized into AHG and agarotriose (AgaDP3) by
GH117, and AgaDP3 then was completely depolymerized into monomeric sugars by sequential reactions of the agarolytic β-galactosidases (ABG)
ABG and
GH117. 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.
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,
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.
In recent years, research on natural products has gained considerable attention, particularly in the cosmetic industry, which is looking for new bio-active and biodegradable molecules. In this study, ...cosmetic properties of cyanobacteria and red macroalgae were analyzed. The extractions were conducted in different solvents (water, ethanol and two combinations of water:ethanol). The main molecules with antioxidant and photoprotective capacity were mycosporine-like amino acids (MAAs), scytonemin and phenolic compounds. The highest contents of scytonemin (only present in cyanobacteria) were observed in
sp. (BEA 1603B) and
sp. (BEA 1328B). The highest concentrations of MAAs were found in the red macroalgae
,
and
and in the cyanobacterium
sp.
sp. was the unique species that presented an MAA with maximum absorption in the UV-B band, being identified as mycosporine-glutaminol for the first time in this species. The highest content of polyphenols was observed in
sp. and
. Water was the best extraction solvent for MAAs and phenols, whereas scytonemin was better extracted in a less polar solvent such as ethanol:
H
O (4:1). Cyanobacterium extracts presented higher antioxidant activity than those of red macroalgae. Positive correlations of antioxidant activity with different molecules, especially polyphenols, biliproteins and MAAs, were observed. Hydroethanolic extracts of some species incorporated in creams showed an increase in the photoprotection capacity in comparison with the base cream. Extracts of these organisms could be used as natural photoprotectors improving the diversity of sunscreens. The combination of different extracts enriched in scytonemin and MAAs could be useful to design broad-band natural UV-screen cosmeceutical products.
Oxidative stress generated by UV exposition plays an important role on photoaging. Understanding the cell physiological responses due to the action of oxidative molecules process helps to develop ...approaches to reduce its impact on skin cells. In this context, algae can be source of biomolecules with antioxidant, inhibition of metalloproteinases and photoprotective capacities, such as mycosporine-like amino acids and phenolic compounds. This study focuses on the characterization of aqueous and hydroethanolic extracts of six red marine macroalgae: Phycocalidia acanthophora, Porphyra linearis, Condracanthus teedei, Gracilaria cornea, Osmundea pinnatifida and Plocamium cartilagineum (from two different sites). Besides their biochemical characterization, we also evaluated antioxidant capacity, potential to collagenase inhibition, and photoprotective capacity by different biological effective protection factors (BEPFs). Results evidenced a better correlation among the compounds of interest and bioactivity when using water as solvent rather than hydroethanolic solution. P. acanthophora and P. linearis aqueous extracts were highlighted in all analyses. Considering this fact, these two extracts were incorporate onto a cosmeceutical formulation. BEPFs evidenced that the incorporation of the extracts increased the photoprotection factors when compared to the control without physical filters. According to the findings herein described, the potential of red macroalgae as source of bioactive compounds with antiaging potential is reinforced.
•UV radiation triggers photoaging by increasing oxidative stress and changing compounds of the extracellular matrix.•Red macroalgae can be considered source of pigments, polysaccharides, mycosporine-like amino acids and antioxidant enzymes.•Porphyra linearis and Phycocalidia acanthophora were highlighted as potential sources of bioactive compounds.•Water has a higher potential on extraction of antioxidant compounds than hydroethanolic solution.•Polyphenols and mycosporine-like amino acids reduce collagenase activity.
Bioprocessing offers a sustainable and green approach to the production of chemicals. However, a bottleneck in introducing bioprocesses is cell factory development, which is costly and ...time-consuming. A systems biology approach can expedite cell factory design by using genome-wide analyses alongside mathematical modeling to characterize and predict cellular physiology. This approach can drive cycles of design, build, test, and learn implemented by metabolic engineers to optimize the cell factory performance. Streamlining of the design phase requires a clearer understanding of metabolism and its regulation, which can be achieved using quantitative and integrated omic characterization, alongside more advanced analytical methods. We discuss here the current impact of systems biology and challenges of closing the gap between bioprocessing and more traditional methods of chemical production.
Bioprocessing offers a green and sustainable alternative to fossil fuel-based chemical production. However, cell factory development is currently too inefficient to allow bioprocessing to become cost-competitive.
Systems biology can streamline factory design by combining genome-wide datasets with computational models to characterize metabolism.
To increase the contribution of systems biology, large-scale omic data analysis and interpretation need to occur faster and more accurately, and the predictive strength of in silico metabolic models needs to be improved.
This can be achieved by (i) developing new computational methods for data analysis, such as machine learning, and (ii) integrating into models regulatory structures that coordinate metabolism.
By increasing the predictive strength of models, the cost and time for cell factory development can be reduced.
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