Elisabeth Delbeke

Characterization of French Coriander Oil as Source of Petroselinic Acid

Coriander vegetable oil was extracted from fruits of French origin in a 23% yield. The oil was of good quality, with a low amount of free fatty acids (1.8%) and a concurrently high amount of triacylglycerols (98%). It is a rich source of petroselinic acid (C18:1n-12), an important renewable building block, making up 73% of all fatty acids, with also significant amounts of linoleic acid (14%), oleic acid (6%), and palmitic acid (3%). The oil was characterized by a high unsaponifiable fraction, comprising a substantial amount of phytosterols (6.70 g/kg). The main sterol markers were β-sitosterol (35% of total sterols), stigmasterol (24%), and Δ7-stigmastenol (18%). Squalene was detected at an amount of 0.2 g/kg. A considerable amount of tocols were identified (500 mg/kg) and consisted mainly of tocotrienols, with γ-tocotrienol as the major compound. The phospholipid content was low at 0.3%, of which the main phospholipid classes were phosphatidic acid (33%), phosphatidylcholine (25%), phosphatidylinositol (17%), and phosphatidylethanolamine (17%). About 50% of all phospholipids were non-hydratable. The β-carotene content was low at 10 mg/kg, while a significant amount of chlorophyll was detected at about 11 mg/kg. An iron content of 1.4 mg/kg was determined through element analysis of the vegetable oil. The influence of fruit origin on the vegetable oil composition was shown to be very important, particularly in terms of the phospholipids, sterols, and tocols composition.

Self-Assembly Mechanism of pH-Responsive Glycolipids: Micelles, Fibers, Vesicles, and Bilayers

A set of four structurally related glycolipids are described: two of them have one glucose unit connected to either stearic or oleic acid, and two other ones have a diglucose headgroup (sophorose) similarly connected to either stearic or oleic acid. The self-assembly properties of these compounds, poorly known, are important to know due to their use in various fields of application from cleaning to cosmetics to medical. At basic pH, they all form mainly small micellar aggregates. At acidic pH, the oleic and stearic derivatives of the monoglucose form, respectively, vesicles and bilayer, while the same derivatives of the sophorose headgroup form micelles and twisted ribbons. We use pH-resolved in situ small angle X-ray scattering (SAXS) under synchrotron radiation to characterize the pH-dependent mechanism of evolution from micelles to the more complex aggregates at acidic pH. By pointing out the importance of the COO-/COOH ratio, the melting temperature, Tm, of the lipid moieties, hydration of the glycosidic headgroup, the packing parameter, membrane rigidity, and edge stabilization, we are now able to draw a precise picture of the full self-assembly mechanism. This work is a didactical illustration of the complexity of the self-assembly process of a stimuli-responsive amphiphile during which many concomitant parameters play a key role at different stages of the process.

Chemical and enzymatic modification of sophorolipids

The significance of renewable resources within the chemical industry is constantly increasing. In the pursuit of sustainability, they serve as alternatives for fossil resources whose supply is limited and who have a major impact on the environment. Due to their complex structure and divergent biological activities, sophorolipids are interesting renewable resources. Unfortunately, industrial applications of natural sophorolipids are limited because of their high production cost. Therefore, chemical and enzymatic modifications provide an excellent tool to shift the application area of sophorolipids to high-added value sectors, in particular for the pharmaceutical sector. This review will give an overview of the modifications performed so far and their possible applications.

A new class of antimicrobial biosurfactants: quaternary ammonium sophorolipids

New synthetic pathways are proposed for the production of a broad range of innovative sophorolipid amines and sophorolipid quaternary ammonium salts starting from microbially produced sophorolipids. The selective formation of an intermediate sophorolipid aldehyde proved to be a key synthetic step of the new derivatives. The sophorolipid quaternary ammonium salts were evaluated for their antimicrobial activity against Gram-negative and Gram-positive test strains. Minimum inhibitory concentration (MIC) values were determined for the active compounds. Derivatives with an octadecyl group on the nitrogen atom proved to be more active than the antibiotic gentamicin sulfate against all tested Gram-positive strains. The results show great promise for modified sophorolipids in the medical sector.

Effect of sophorolipid quaternary ammonium salts on activated sludge system

Laccases (EC 1.10.3.2) are oxygen oxidoreductases, which catalyse widespread range of chemical reactions, mainly one-electron oxidation of mono-, diand polyphenols. These enzymes found widespread application in textile, food and medical industry. Besides using of this enzyme in the broadly defined industry, laccase can be use in environmental protection, degrading industrial pollution. Due to its low stability and poor reusability, in recent years, there has been an increasing interest in laccase immobilization, which facilitates possibility to use of laccase at various conditions. A wide range of materials of different origin might be use as supports for enzyme immobilization. Biopolymers are interesting and noteworthy materials, which found application in environmental protection thanks to biocompatibility and biodegradability. In presented work, spongin-based skeletons of Hippospongia communis, were used as a carrier for laccase immobilization. Obtained systems were used for degradation of bisphenol A, bisphenol F and bisphenol S in model solutions. Effective enzyme immobilization and degradation of those hazardous compounds were confirmed by using various methods. Moreover, effects of various initial process parameters, such as temperature, pH and concentration on the removal efficiency of bisphenols were evaluated in this study. In addition, obtained results show that reusability of the laccase was significantly improved after its immobilization. Acknowledgment: This work was supported by the Poznan University Technology Research grant no. 03/32/DSPB/0806/2018.

Sophorolipid Modification: The power of yeasts and enzymes

Abstract Sophorolipids are biosurfactants or biological detergents composed of a hydroxylated fatty acid and the glucose disaccharide sophorose. These commercially relevant molecules are produced by the yeast Starmerella bombicola and offer a green and renewable alternative for traditional surfactants. To further broaden up the application potential of sophorolipids, introduction of structural variation is essential as this influences their physicochemical and biological properties. However, creating molecular variants is not as straightforward as for petrochemically derived surfactants. This is, on the one hand, a consequence of the biological origin and restricting biochemistry behind it, and is, on the other hand, caused by the complexity of chemical processes regarding the necessity of protection and deprotection of the glucose units. In this chapter, several strategies to overcome these limitations will be discussed, such as the use of special substrates during yeast cultivation, design of engineered strains, and enzymatic modification.

Evaluation of biological properties and fate in the environment of a new class of biosurfactants

Selected sophorolipid quaternary ammonium salts (SQAS), being a new class of modified biosurfactants, were studied in this work for the first time with regard to their biodegradability and fate in the environment. It was made to find whether environment-friendly bioproducts like biosurfactants are still safe to the environment after their chemical modification. The susceptibility of these SQAS for biodegradation was estimated together with the evaluation of their influence on activated sludge microorganisms. Additionally, the mechanisms of removal of the SQAS from wastewater and from the aquatic environment, were analysed. The evaluated SQAS were potentially biodegradable, although none of them could be classified as readily biodegradable. The biodegradation degrees after 28 days ranged from 4 to 42%, dependent on the SQAS tested, i.e. below the required OECD 301D Closed Bottle Test level of 60%. Simultaneously, the analysis of the mass spectra revealed the presence of the breakdown products of each SQAS studied. Biodegradation was preceded by sorption of the SQAS on sludge particles, which occurred to be a main mechanism of the removal of these newly synthesized biosurfactants from wastewater. The mean degree of sorption calculated on the basis of SQAS determination was from 75 to 96%, dependent on the studied SQAS. The presence of SQAS in wastewater did not deteriorate the operation of the activated sludge system, although the products of the SQAS biodegradation remained in the liquid phase and might contribute to the increase of COD of the effluent to be introduced to the environment.

Beyond the Diketopiperazine Family with Alternatively Bridged Brevianamide F Analogues.

A method for the preparation of 3,5-bridged piperazin-2-ones from a tryptophan-proline-based diketopiperazine is described using diphosgene to induce the ring closure. Density functional theory calculations were conducted to study the mechanism of this C-C bond formation. Several derivatives of the thus obtained α-chloroamine were synthesized by substitution of the chlorine atom using a range of O-, N-, S-, and C-nucleophiles. This novel class of brevianamide F analogues possess interesting breast cancer resistance protein inhibitory activity.