Red macroalgae are being actively investigated as a renewable biomass source because of their advantageous characteristics such as abundant carbohydrate contents, low lignin contents, and the absence ...of conflicts with food production. With recent technological advances, the efficient utilization of red macroalgae for biofuel and chemical production is now possible.
The red alga Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira (Agarophyton chilense Gurgel, J.N. Norris & Fredericq) is one of the few algae commercially farmed in Chile, where this alga ...is commonly named “Pelillo”. G. chilensis main by-product is agar, a gelling agent used in the food and pharmaceutical industries. This alga is also a valuable feedstock for the biorefinery of phycobiliproteins (PBPs), colored and fluorescent water-soluble proteins with industrial applications. This work aimed to valorize G. chilensis by sequentially extracting PBPs and agar. After freeze-thaw treatment, we successfully extracted two PBPs from alga: R-phycoerythrin (R-PE) and R-phycocyanin (R-PC). After two purification steps, we recovered 45 % of both PBPs (R-PE = 0.20 mg g−1 DW and R-PC = 0.23 mg·g−1 DW). After PBPs extraction, we successfully recovered agar from the residual algal matter. There were no significant differences between the physical parameters of agars obtained after PBP extraction and those from agars directly extracted from G. chilensis (melting and gelling temperature, and agar deformation). The agar yield after PBPs extraction was 24.9 ± 1.0 % and showed a gel strength of 726 ± 182.9 g·cm−2, whereas agar directly extracted from alga yielded 23.1 ± 2.0 % with a gel strength of 730.5 ± 96.9 g·cm−2. The agar obtained after PBPs extraction showed no inhibitory effects on microbial growth and allowed the effective separation of nucleic acids without agarose purification. Thereby, the method proposed in this work allowed the simultaneous extraction of PBPs and agar from G. chilensis.
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•The red seaweed Gracilaria chilensis (Agarophyton chilense) is a good source of phycobiliproteins and agar.•Phycobiliproteins are purified by salting-out and anion-exchange chromatography.•Purified phycobiliproteins (R-PE and R-PC) may be used in the food industry.•High-quality agar was successfully recovered from the residual algal matter after phycobiliproteins' extraction.•Agar extracted after phycobiliproteins' purification was useful for microbial growth and nucleic acid separation.
Recently, bioactive peptides derived from algae sources have gained significant recognition as vital functional ingredients in the development of health-enhancing foods and nutraceuticals. In this ...study, protein hydrolysates (SCPH and GSPH) derived from two red macroalgae (Sphaerococcus coronopifolius and Gelidium spinosum) were fractionated using semi-preparative-reversed phase high-performance liquid chromatography (RP-HPLC). Then, the peptides contained in the obtained fractions were identified by RP-HPLC coupled with tandem mass spectrometry (MS/MS). In silico analyzes of hydrophobicity, potential bioactivity using PeptideRanker, and toxicity of identified peptides were performed. Moreover, the prediction of Angiotensin-converting enzyme (ACE)- and Dipeptidyl-peptidase (DPP-IV)-inhibitory peptides using a quantitative structure-activity relationship (QSAR) was also carried out. Furthermore, in vitro evaluation of antioxidant and antibacterial activities, as well as ACE-, and DPP-IV-inhibitory properties was conducted for all peptide fractions. Our results showed that SCPH and GSPH fractions contain a large percentage of highly hydrophobic peptides with low molecular weight, and they exhibit no toxic effect. Among all identified peptides, 61 and 39 peptides, respectively from SCPH and GSPH fractions, presented a PeptideRanker score superior to 0.8. These peptide sequences exhibited a high proportion of potent predicted ACE- and DPP-IV-inhibitory peptides. Additionally, most of the peptide fractions exerted antioxidant, antibacterial, anti-ACE, and anti-DPP-IV inhibitory activities at different levels. Among them, F2 to F6 were the most active fractions. Overall, the results suggest that the bioactive peptide fractions separated from two red macroalgae protein hydrolysates could be considered as a beneficial ingredient for nutraceutical and functional food industries.
•Fractionation of two non-exploited red macroalgae protein hydrolysates (SCPH and GSPH) using semi-preparative RP-HPLC.•Identification of 579 and 472 unique and non-toxic peptides using RP-HPLC-MS/MS.•In silico analysis of identified peptides revealed that almost showed a significant predicted ACE and DPP-IV IC50 values.•Obtained peptidic fractions presented a higher in vitro antioxidant, antibacterial, anti-ACE, and anti-DPP-IV-inhibitory activities.•Peptide sequences derived from SCPH and GSPH show promise for potential use as functional ingredients for in the nutraceutical and food sectors.
Heavy metal copper (Cu) will inevitably impact the marine macroalgae
(
), which is a culture of economic importance along China's coastline. In this study, the detoxification mechanism of Cu stress ...on
was revealed by assessing physiological indicators in conjunction with transcriptome and metabolome analyses at 1 d after Cu stress. Our findings revealed that 25 μM Cu stimulated ROS synthesis and led to the enzymatic oxidation of arachidonic acid residues. This process subsequently impeded
growth by suppressing photosynthesis, nitrogen metabolism, protein synthesis, etc. The entry of Cu ions into the algae was facilitated by ZIPs and IRT transporters, presenting as Cu
. Furthermore, there was an up-regulation of Cu efflux transporters HMA5 and ABC family transporters to achieve compartmentation to mitigate the toxicity. The results revealed that
elevated the antioxidant enzyme superoxide dismutase and ascorbate-glutathione cycle to maintain ROS homeostasis. Additionally, metabolites such as flavonoids, 3-O-methylgallic acid, 3-hydroxy-4-keto-gama-carotene, and eicosapentaenoic acid were up-regulated compared with the control, indicating that they might play roles in response to Cu stress. In summary, this study offers a comprehensive insight into the detoxification mechanisms driving the responses of
to Cu exposure.
3,6-Anhydro-L-galactose (L-AHG) is a monomeric sugar in agarose derived from red macroalgae. Owing to its various physiological activities such as anti-inflammation, moisturizing, skin whitening, ...anti-colon cancer, and anti-cariogenicity, L-AHG is a potential functional ingredient. In our previous study, a simple and efficient two-step L-AHG production process was designed for high-titer L-AHG production, where a single enzyme was used after the liquefaction of agarose by acid prehydrolysis. However, the enzyme used did not completely hydrolyze agarobiose (AB). Therefore, in this study, for the efficient hydrolysis of AB and the high-titer production of L-AHG, various β-galactosidases belonging to glycoside hydrolase families 1, 2, 35, and 42 were compared by testing their substrate specificities and kinetic parameters. Among the five β-galactosidases, Bga42A, originating from
Bifidobacterium longum
ssp
. infantis
ATCC 15,697, showed the highest substrate specificity. Consequently, the two-step process utilizing Bga42A as a single enzyme resulted in a high-titer production of L-AHG at 85.9 g/L, demonstrating the feasibility of producing L-AHG from agarose.
Key points
• L-AHG derived from red macroalgae has various physiological activities.
• Various β-galactosidases were evaluated to efficiently hydrolyze agarobiose.
• Bga42A showed the highest substrate specificity against agarobiose.
• The highest amount of L-AHG with 85.9 g/L was simply produced.
Graphical Abstract
The macroalga
could be a sustainable and nutritional food resource. However, its composition may vary according to its environment and to processing methods used. To investigate these variations, ...wild
from Quebec were harvested in October 2019 and June 2020, and dried (40 °C, ≃5 h) or stored as frozen controls (-80 °C). The chemical (lipids, proteins, ash, carbohydrates, fibers), mineral (I, K, Na, Ca, Mg, Fe), potential bioactive compound (carotenoids, polyphenols, β-carotene, α-tocopherol) compositions, and the in vitro antioxidant activity and angiotensin-converting enzyme (ACE) inhibition potential of water-soluble extracts were determined. The results suggested a more favorable macroalgae composition in June with a higher content of most nutrients, minerals, and bioactive compounds. October specimens were richer only in carbohydrates and carotenoids. No significant differences in antioxidant or anti-ACE inhibitory activities were found between the two harvest months. The drying process did not significantly impact the chemical and mineral compositions, resulting in only small variations. However, drying had negative impacts on polyphenols and anti-ACE activities in June, and on carotenoids in October. In addition, a concentration effect was observed for carotenoids, β-carotene and α-tocopherol in June. To provide macroalgae of the highest nutritional quality, the drying process for June specimens should be selected.
The selected acyclic halogenated monoterpenes derived from red macroalgae are investigated in terms of their isolation, their reactions with oxidants (ozone, OH radical) and the impacts of the ...first-generation oxidation products on the atmosphere. The yields of these monoterpenes from marine algae are small and highly variable (0.01-6.7%), the fractions can then enter the atmosphere through different meteorologically driven processes. The loss of the monoterpenes is mostly driven by OH radical, however, 1,6-dibromo-2,7-dichloro-3,7-dimethyl-oct-3-ene and 4-bromo-8-chloro-3,7-dimethyl-octa-2,6-dienal undergo significant loss via reaction with ozone (>50%). The atmospheric lifetimes of the compounds investigated range from ca. 1.5-10 h. Given their short lifetimes, these compounds can be rapidly oxidised to form a range of stable compounds. The investigation of first-generation products from the OH-initiated oxidation of 5,6-dichloro-2-dichloromethyl-6-methyl-octa-1,3,7-triene, 1,6-dibromo-2,7-dichloro-3,7-dimethyl-oct-3-ene and 4-bromo-8-chloro-3,7-dimethyl-octa-2,6-dienal showed the formation of stable organic hydroperoxides, alcohols and carbonyl compounds which can have significant impact on cloud condensation nuclei as contributors of secondary organic aerosols. Release of free halogen can occur from subsequent product oxidation, notably photolysis of carbonyl type species and these are briefly considered.
•3,6-Anhydro-l-galactose (AHG) is a rare sugar from agar of red macroalgae.•AHG inhibited the cell growth and acid production by Streptococcus mutans.•Inhibitory effect of AHG on S. mutans was ...significantly higher than xylitol.•AHG is considered as a new anticariogenic sugar to prevent dental caries.
The significance for anticariogenic sugar substitutes is growing due to increasing demands for dietary sugars and rising concerns of dental caries. Xylitol is widely used as an anticariogenic sugar substitute, but the inhibitory effects of xylitol on Streptococcus mutans, the main cause of tooth decay, are exhibited only at high concentrations. Here, the inhibitory effects of 3,6-anhydro-l-galactose (AHG), a rare sugar from red macroalgae, were evaluated on S. mutans, in comparison with those of xylitol. In the presence of 5g/l of AHG, the growth of S. mutans was retarded. At 10g/l of AHG, the growth and acid production by S. mutans were completely inhibited. However, in the presence of xylitol, at a much higher concentration (i.e., 40g/l), the growth of S. mutans still occurred. These results suggest that AHG can be used as a new anticariogenic sugar substitute for preventing dental caries.
3,6-Anhydro-l-galactose (l-AHG), a major component of agarose derived from red macroalgae, has excellent potential for industrial applications based on its physiological activities such as skin ...whitening, moisturizing, anticariogenicity, and anti-inflammation. However, l-AHG is not yet commercially available due to the complexity, inefficiency, and high cost of the current processes for producing l-AHG. Currently, l-AHG production depends on a multistep process requiring several enzymes. Here, we designed and tested a novel two-step process for obtaining high-titer l-AHG by using a single enzyme. First, to depolymerize agarose preferentially into agarobiose (AB) at a high titer, the agarose prehydrolysis using phosphoric acid as a catalyst was optimized at a 30.7% (w/v) agarose loading, which is the highest agarose or agar loading reported so far. Then AB produced by the prehydrolysis was hydrolyzed into l-AHG and d-galactose (d-Gal) by using a recently discovered enzyme, Bgl1B. We suggest that this simple and efficient process could be a feasible solution for the commercialization and mass production of l-AHG.
► Biomass dosage, pH, and contact time affect the biosorption of heavy metals. ► The red algal biomasses have high capacity for treating industrial effluents. ► The maximum biosorption capacity of ...heavy metals was 105.2
mg/g.
Biosorption is an effective process for the removal and recovery of heavy metal ions from aqueous solutions. The biomass of marine algae has been reported to have high biosorption capacities for a number of heavy metal ions. In this study, four species of red seaweeds
Corallina mediterranea,
Galaxaura oblongata,
Jania rubens and
Pterocladia capillacea were examined to remove Co(II), Cd(II), Cr(III) and Pb(II) ions from aqueous solution. The experimental parameters that affect the biosorption process such as pH, contact time and biomass dosage were studied. The maximum biosorption capacity of metal ions was 105.2
mg/g at biomass dosage 10
g/L, pH 5 and contact time 60
min. The biosorption efficiency of algal biomass for the removal of heavy metal ions from industrial wastewater was evaluated for two successive cycles.
Galaxaura oblongata biomass was relatively more efficient to remove metal ions with mean biosorption efficiency of 84%. This study demonstrated that these seaweeds constitute a promising, efficient, cheap and biodegradable sorbent biomaterial for lowering the heavy metal pollution in the environment.
