Formation of Amphiphilic Molecules from the Most Common Marine Polysaccharides, toward a Sustainable Alternative?

Marine polysaccharides are part of the huge seaweeds resources and present many applications for several industries. In order to widen their potential as additives or bioactive compounds, some structural modifications have been studied. Among them, simple hydrophobization reactions have been developed in order to yield to grafted polysaccharides bearing acyl-, aryl-, alkyl-, and alkenyl-groups or fatty acid chains. The resulting polymers are able to present modified physicochemical and/or biological properties of interest in the current pharmaceutical, cosmetics, or food fields. This review covers the chemical structures of the main marine polysaccharides, and then focuses on their structural modifications, and especially on hydrophobization reactions mainly esterification, acylation, alkylation, amidation, or even cross-linking reaction on native hydroxyl-, amine, or carboxylic acid functions. Finally, the question of the necessary requirement for more sustainable processes around these structural modulations of marine polysaccharides is addressed, considering the development of greener technologies applied to traditional polysaccharides.

Measuring the Antimicrobial Activity of Lauric Acid against Various Bacteria in Human Gut Microbiota Using a New Method

Lauric acid (LA) has a broad spectrum of anti-microbiological activities against enveloped viruses and various bacteria, and might be useful to protect against microbial infection and control the balance and distribution of bacteria in human gut microbiota. It is not necessarily more difficult to measure antimicrobial activity the traditional way, but it is, however, more laborious. In the present study, we developed a new method to measure the antimicrobial activity of LA in multiple samples with a microplate reader. A "test complex" (TC) was produced consisting of 100 μL of agar medium with LA in the bottom layer and 300 μL of broth in the top layer in 96-well deep-well microplates. Afterward, analysis of the broth in the top layer showed that the antimicrobial activity was the same as that of the "control complex," (CC) which consisted of 100 μL of agar medium in the bottom layer and 300 μL of broth with LA in the top layer. Furthermore, evaluation of the antimicrobial effect of the TC when using a microplate reader was the same as that with the use of the colony counting method. The colony counting method has confirmed that the antimicrobial activity of LA when bacteria are inoculated into the broth was equivalent between CC and TC, and we validated this by correlating the number of bacteria with absorbance. In addition, the broth itself in TC was transparent enough that the turbidity of broth can be used as an index of the number of bacteria, which enabled the use of a microplate reader for multiple samples. For human gut microbes, LA was shown to have low antimicrobial activity against commensal lactic acid bacteria, but high antimicrobial activity against pathogenic Bacteroides and Clostridium, suggesting that LA might modulate intestinal health, as confirmed by the proposed method.

One-pot synthesis of fluorescent polysaccharides: adenine grafted agarose and carrageenan

New fluorescent polysaccharides were synthesized by grafting the nucleobase adenine on to the backbones of agarose and κ-carrageenan, which were characterized by FT-IR, (13)C NMR, TGA, XRD, UV, and fluorescence properties. The synthesis involved a rapid water based potassium persulfate (KPS) initiated method under microwave irradiation. The emission spectra of adenine grafted agarose and κ-carrageenan were recorded in aqueous (5×10(-5) M) solution, exhibiting λ(em,max) 347 nm by excitation at 261 nm, affording ca. 30% and 40% enhanced emission intensities, respectively compared to that of pure adenine solution in the same concentration. Similar emission intensity was recorded in the pure adenine solution at its molar equivalent concentrations present in the 5×10(-5) M solution of the agarose and carrageenan grafted products, that is, 3.28×10(-5) M and 4.5×10(-5) M respectively. These fluorescent adenine grafted products may have potential utility in various sensor applications.

Effect of genipin, a naturally occurring crosslinker on the properties of kappa-carrageenan

Genipin-fixed kappa-carrageenan was prepared in ambient conditions in aqueous solution using genipin, a naturally occurring crosslinker with kappa-carrageenan (kappaC). The crosslinked kappaC showed the greatest swelling capacity in acidic medium having pH 1.2 when compared to those in neutral and alkaline media. Enhanced stability of the crosslinked product with respect to the non-modified kappaC was confirmed by degradation studies in Ringer's solution, rheological and thermogravimetric measurements. Genipin fixation of kappaC was confirmed by measuring the bulk density, true density, pore volume, porosity, intrinsic viscosity, UV absorbance and optical rotation of the crosslinked kappaC, and as well as by optical microscopy, SEM, and MS/MS studies. The crosslinked product may be useful as super absorbent and sustained release formulation in biomedical applications.