Laurent Dufossé

Inhibition of marine bacteria by extracts of macroalgae: potential use for environmentally friendly antifouling paints

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. A search for new non-toxic antifoulants has been carried out among marine macroalgae. Antifouling activity of aqueous, ethanolic and dichloromethane extracts from 30 marine algae from Brittany coast (France) was examined in vitro against 35 isolates of marine bacteria. About 20% of the extracts were found to be active. The high levels of inhibitory activities against bacteria recorded in some extracts and the absence of toxicity on the development of oyster and sea urchin larvae and to mouse fibroblast growth suggests a potential for novel active ingredients in antifouling preparations.

Enzymatic hydrolysis of proteins from yellowfin tuna (Thunnus albacares) wastes using Alcalase

Enzymatic hydrolysis of tuna stomach proteins by Alcalase was investigated in a batch reactor. The influence of the process variables (enzyme/substrate ratio; effect of intermediate substrate and enzyme addition) was studied with regards to the extent of proteolytic degradation and to the molecular weight distribution of the peptides. A linear correlation was found between the degree of hydrolysis (DH) and the enzyme concentration. After addition of extra substrate during the course of hydrolysis, the final DH obtained was proportional to the substrate added, suggesting that the concentration of hydrolysable bonds was one of the main factors controlling the hydrolysis rate. Preliminary results showed that tuna protein hydrolysates performed effectively as nitrogenous source in microbial growth media.

Filamentous fungi are large-scale producers of pigments and colorants for the food industry

With globalization in the research trends, healthier life styles, and the growing market for the natural food colorants in the economically fast-growing countries all over the world, filamentous fungi are being investigated as readily available sources of chemically diverse colorants. With two selected examples, polyketide-Monascus-like pigments from the new fungal production strains, and the promising and yet unexplored hydroxy-anthraquinoid colorants, the present review highlights exciting recent findings, which may pave the way for alternative and/or additional biotechnological processes for the industrial production of natural food colorants of improved functionality. As an additional aspect, marine fungi are discussed as potential sources of novel pigments of numerous color hues and atypical chemical structures.

Evaluation of nitrogenous substrates such as peptones from fish:a new method based on Gompertz modeling of microbial growth.

Fish peptones from tuna, cod, salmon, and unspecified fish were compared with a casein one by using a new method based on Gompertz modeling of microbial growth. Cumulative results obtained from six species of bacteria, yeasts, and fungi showed that, in most cases, these fish peptones are very effective. Nevertheless, this study raised some questions about the standardization of fish raw material, the enzymatic hydrolysis of fish proteins, and the composition of the culture medium used for testing the peptones.

Natural hydroxyanthraquinoid pigments as potent food grade colorants: an overview

Natural pigments and colorants are widely used in the world in many industries such as textile dying, food processing or cosmetic manufacturing. Among the natural products of interest are various compounds belonging to carotenoids, anthocyanins, chlorophylls, melanins, betalains… The review emphasizes pigments with anthraquinoid skeleton and gives an overview on hydroxyanthraquinoids described in Nature, the first one ever published. Trends in consumption, production and regulation of natural food grade colorants are given, in the current global market. The second part focuses on the description of the chemical structures of the main anthraquinoid colouring compounds, their properties and their biosynthetic pathways. Main natural sources of such pigments are summarized, followed by discussion about toxicity and carcinogenicity observed in some cases. As a conclusion, current industrial applications of natural hydroxyanthraquinoids are described with two examples, carminic acid from an insect and Arpink red™ from a filamentous fungus.Graphical abstract

Antioxidant and Free Radical Scavenging Properties of Marennine, a Blue-Green Polyphenolic Pigment from the Diatom Haslea ostrearia (Gaillon/Bory) Simonsen Responsible for the Natural Greening of Cultured Oysters

Among microalgae, the marine diatom Haslea ostrearia has the distinctive feature of synthesizing and releasing, into the surrounding environment, a blue-green polyphenolic pigment called marennine. The oyster-breeding industry commonly makes use of this natural phenomenon for the greening of oysters grown in the ponds of the French Atlantic coast. This article reports the in vitro antioxidant properties of pure marennine. Two kinds of evaluation systems were adopted to test the antioxidative activity of marennine: antioxidant capacity assays (beta-carotene and thymidine protection assays and iron reducing power assay) and free radical scavenging assays (DPPH*, O2*-, and HO*). In almost all cases, marennine exhibited significantly higher antioxidative and free radical scavenging activities than natural and synthetic antioxidants commonly used in food, as shown by comparing median effective concentration (EC 50) values, for each test independently. This medium molecular weight polyphenol (around 10 kDa) from microalgae is thus a potentially useful natural antioxidant. Because of its blue-coloring property and water solubility, it could also be used as a natural food-coloring additive.

In Situ Detoxification of the Fermentation Medium during γ-Decalactone Production with the Yeast Sporidiobolus salmonicolor

γ‐Decalactone (γ‐C10) is known to be highly toxic for the microorganims used for its production. In this work, three techniques were studied in order to overcome this toxicity during a bioconversion process using ricinoleic acid as precursor of the lactone: in situ trapping in oily phases, in porous hydrophobic sorbents and in β‐cyclodextrins. Oily phases added to the media (olive, Miglyol, tributyrin, and paraffin) had a protective effect on Sp. salmonicolor, and they improved the lactone production. β‐cyclodextrins, which have a hydrophobic cavity that can trap molecules such as γ‐C10, have been used to protect the yeasts. The results showed insufficient preservation of cell viability. Some sorbents (activated carbon and polystyrene‐based sorbents) were successfully tested during bioconversion. In all cases viability exceeded the reference one. Nevertheless the aroma production was 30% lower than the reference. All of these solutions led to some enhancement of the cell viability during bioconversion of methyl ricinoleate to γ‐C10. For improvement of the lactone production, the oil trapping method seemed to be the best with the experimental conditions tested.

Production of γ-decalactone and 4-hydroxy-decanoic acid in the genus Sporidiobolus

Within the genus Sporidiobolus, S. odorus has been widely reported as having the ability to convert castor oil or its derivatives to γ-decalactone, but other species have also shown potential for lactone production. In this work, the bioconversion of ricinoleic acid methyl ester to γ-decalactone was studied with four species of Sporidiobolus: S. salmonicolor, S. ruinenii, S. johnsonii, and S. pararoseus. With 4.1 g/l of ricinoleic acid methyl ester, only S. salmonicolor and S. ruinenii were able to produce γ-decalactone (12 and 40 mg/l respectively). S. johnsonii and S. pararoseus did not produce any lactone in spite of consuming the precursor. The four strains showed different sensitivities to lactone. Between S. salmonicolor and S. ruinenii, the latter was the best biocatalyst. During four successive batch cultivations in a 7-l bioreactor, 5.5 g/l of γ-decalactone was produced with S. ruinenii in each 10-d run. This was essentially due to its ability to produce the open form of γ-decalactone (i.e., 4-hydroxy-decanoic acid), which is far less toxic than the lactone.

Water-soluble red pigments from Isaria farinosa and structural characterization of the main colored component

The present study describes the red pigment synthesized by the filamentous fungi Isaria farinosa under submerged culture conditions. The pigment production was optimal under the following conditions: pH 5, agitation speed 150 rpm, temperature 27 °C, incubation time 192 h, light source total darkness, sucrose and glucose as carbon source, yeast extract, meat peptone and monosodium glutamate at a fixed concentration of 3% as nitrogen source. The addition of 10 mM CaCl2 to the culture medium increased the biomass and pigment production. Structural elucidation of the pigment using gas chromatography‐mass spectrometry, Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy revealed that the red pigment contains an anthraquinone‐related compound. In addition, the isolated pigment was water soluble, and was stable when exposed to salt solution (96.1% of stability after treatment with sodium chloride), acid (72.1% with citric acid), heat (86.2% at 60 °C), and sunlight (99.4%). These results are promising to further exploit the fungal culture of Isaria farinosa for producing the red pigment and, subsequently, to considerably increase its yield. The study has commercial importance in the production of Isaria farinosa pigment for industrial application after considerable toxicological examination. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Anthraquinones and Derivatives from Marine-Derived Fungi: Structural Diversity and Selected Biological Activities.

Anthraquinones and their derivatives constitute a large group of quinoid compounds with about 700 molecules described. They are widespread in fungi and their chemical diversity and biological activities recently attracted attention of industries in such fields as pharmaceuticals, clothes dyeing, and food colorants. Their positive and/or negative effect(s) due to the 9,10-anthracenedione structure and its substituents are still not clearly understood and their potential roles or effects on human health are today strongly discussed among scientists. As marine microorganisms recently appeared as producers of an astonishing variety of structurally unique secondary metabolites, they may represent a promising resource for identifying new candidates for therapeutic drugs or daily additives. Within this review, we investigate the present knowledge about the anthraquinones and derivatives listed to date from marine-derived filamentous fungi′s productions. This overview highlights the molecules which have been identified in microorganisms for the first time. The structures and colors of the anthraquinoid compounds come along with the known roles of some molecules in the life of the organisms. Some specific biological activities are also described. This may help to open doors towards innovative natural substances.