Electrochromic Properties and Electrochemical Behavior of Marennine, a Bioactive Blue-Green Pigment Produced by the Marine Diatom Haslea ostrearia

Marennine has long been known as the unique peculiar pigment responsible for the natural greening of oysters. It is specifically produced by the marine diatom Haslea ostrearia and it is a natural blue molecule indeed promising for food industry because of the rarity of such non-toxic, blue-colored pigments. In the search for its still not defined molecular structure, investigation of the color changes with the redox state has been carried out combining different approaches. Reducing and oxidizing chemicals have been added to purified marennine solutions and a stable blue-green color has been confirmed for the oxidized state, while a yellow color corresponded to the reduced unstable state. Raman spectroscopy has been used to monitor changes in the Raman spectra corresponding to the different colored states, and cyclic voltammetry has allowed the detection of a redox system in which protons and electrons are exchanged. These findings show that marennine is a suitable stable blue pigment for use in food applications and help in the elucidation of the chromophore structure.

Extraction Improvement of the Bioactive Blue-Green Pigment “Marennine” from Diatom Haslea ostrearia’s Blue Water: A Solid-Phase Method Based on Graphitic Matrices

The compound “marennine” is a blue–green pigment produced by the benthic microalgae Haslea ostrearia, with pathogenicity reduction activities against some bacteria and promising potential as a natural pigment in seafood industries. After decades of research, the chemical family of this compound still remains unclear, mainly because structural studies were impaired by the presence of co-extracted compounds in marennine isolates. To improve the purity of marennine extract, we developed a novel extraction method using a graphitic stationary phase, which provides various advantages over the previous procedure using tandem ultrafiltration. Our method is faster, more versatile, provides a better crude yield (66%, compared to 57% for ultrafiltration) and is amenable to upscaling with continuous photobioreactor cultivation. Our goal was to take advantage of the modulable surface properties of the graphitic matrix by optimizing its interactions with marennine. As such, the effects of organic modifiers, pH and reducing agents were studied. With this improvement on marennine purification, we achieved altogether the isolation of a fucoidan-related, sulfated polysaccharide from blue water. Characterization of the polysaccharides fraction suggests that roughly half of UV-absorbing compounds could be isolated from the marennine crude extracts. The identification of sulfated polysaccharides could be a major breakthrough for marennine purification, providing targeted isolation techniques. Likewise, the added value of Haslea ostrearia and the role of polysaccharides in previous marennine chemical characterization and bioactivity studies remain to be determined.

Typification of the first recognized blue pigmented diatom, Haslea ostrearia (Bacillariophyceae)

Background and aims – The blue pigmented diatom, Haslea ostrearia (Gaillon) Simonsen, which has been the material object for many physiological and ecological studies, was first described from oyster ponds in France as Vibrio ostrearius Gaillon; however, his study material seems not to be conserved. Methods – A thorough search to retrieve potential available historical collections has been conducted. Key results – It has been proven that no relevant historical material exists for H. ostrearia. Thus, an oyster pond at Bouin in Baie de Bourgneuf, France, was sampled in 2018 to obtain material allowing neotype designation. Conclusion – Slides and stubs have been deposited as neotype material of the species in the Muséum National d’Histoire Naturelle, Paris, France (PC). At the same time, this material is the generitype of the genus Haslea Simonsen. Furthermore, isoneotypes have been deposited at the British Museum (BM) and the Bremerhaven Hustedt collection (BRM).

Antibacterial Activity of Haslea ostrearia Supernatant Adapted in Indonesia against Pathogenic Bacteria Relevant to Mariculture (In-Vitro Study)

Haslea ostrearia has known as the only diatom which synthesizes a water-soluble blue pigment, marennine. It has some biological activities such as allelopathy, antioxidant, antibacterial, antiviral, and growth inhibitor. Marennine is available in two forms, intracellular which located in the apical of the cell and extracellular which released into the culture medium. This research aimed to test the bioactivity of Haslea ostrearia supernatant adapted in Indonesia as an antibacterial against pathogenic bacteria relevant to marine culture using in-vitro study. This research was using an explorative method, data analysed statistically and descriptive-comparatively observed. Observation parameters were the inhibitory zone of antibacterial activity, absorbance value of MIC test, and bacterial growth qualitatively from MBC test. Marennine concentration in the supernatant of Haslea ostrearia adapted in Indonesia is about 3.74 mg. L-1. The highest concentration supernatant of Haslea ostrearia that shown antibacterial activity is 3.5 mg. L-1 with inhibitory zone diameter is about 6.87 mm for Staphylococcus aureus and 7.14 mm for Vibrio harveyi, correspondingly. The minimum concentration that inhibits the growth of Staphylococcus aureus is 0.03 mg. L-1, while for Vibrio harveyi is 0.06 mg. L-1. Antibacterial activity of supernatant Haslea ostrearia originally adapted in Indonesia classified into bacteriostatic