Titel Deelnemers "Korte inhoud" "Tuning the antimicrobial activity of microbial glycolipid biosurfactants through chemical modification" "Melike Pala, Martijn Castelein, Camille Dewaele, Sophie Roelants, Wim Soetaert, Christian Stevens" "Sophorolipids, glycolipid biosurfactants derived from microorganisms such as Starmerella bombicola, possess distinctive surface-active and bioactive properties, holding potential applications in cosmetics, pharmaceuticals and bioremediation. However, the limited structural variability in wild-type sophorolipids restricts their properties and applications. To address this, metabolic engineering efforts have allowed to create a portfolio of molecules. In this study, we went one step further by chemically modifying microbially produced sophorosides, produced by an engineered S. bombicola. Twenty-four new sophoroside derivatives were synthesized, including sophoroside amines with varying alkyl chain lengths (ethyl to octadecyl) on the nitrogen atom and their corresponding quaternary ammonium salts. Additionally, six different microbially produced glycolipid biosurfactants were hydrogenated to achieve fully saturated lipid tails. These derivatives, along with microbially produced glycolipids and three benchmark biosurfactants (di-rhamnolipids, alkyl polyglucosides, cocamidopropyl betaine), were assessed for antimicrobial activity against bacteria (Bacillus subtilis, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa) and yeast (Candida albicans). Results indicated that microbially produced glycolipids, such as bola sophorosides, acidic sophorolipids and acidic glucolipids exhibit selective antimicrobial activity against the test organisms. Conversely, lactonic sophorolipids, sophoroside amines and quaternary ammonium salts display a broad antimicrobial activity. N-octyl, N-dodecyl and N-octadecyl derivatives exhibit the lowest minimal inhibitory concentrations, ranging from 0.014 to 20.0 mg mL−1. This study demonstrates the potential synergy of thoughtful biotechnology and targeted chemistry to precisely tailor glycolipid biosurfactants to meet specific requirements across applications." "Astrobiology in space : a comprehensive look at the solar system" "Maarten De Mol" "The field of astrobiology aims to understand the origin of life on Earth and searches for evidence of life beyond our planet. Although there is agreement on some of the requirements for life on Earth, the exact process by which life emerged from prebiotic conditions is still uncertain, leading to various theories. In order to expand our knowledge of life and our place in the universe, scientists look for signs of life through the use of biosignatures, observations that suggest the presence of past or present life. These biosignatures often require up-close investigation by orbiters and landers, which have been employed in various space missions. Mars, because of its proximity and Earth-like environment, has received the most attention and has been explored using (sub)surface sampling and analysis. Despite its inhospitable surface conditions, Venus has also been the subject of space missions due to the presence of potentially habitable conditions in its atmosphere. In addition, the discovery of habitable environments on icy moons has sparked interest in further study. This article provides an overview of the origin of life on Earth and the astrobiology studies carried out by orbiters and landers." "MariClus : your one-stop platform for information on marine natural products, their gene clusters and producing organisms" "Cedric Hermans, Maarten De Mol, Marieke Mispelaere, Anne-Sofie De Rop, Jeltien Rombaut, Tesneem Nusayr, Rebecca Creamer, Sofie De Maeseneire, Paco Hulpiau" "Single-cell protein production from industrial off-gas through acetate : techno-economic analysis for a coupled fermentation approach" "Elodie Vlaeminck, Evelien Uitterhaegen, Koen Quataert, Stoilas-Stylianos Kontovas, Nikiforos Misailidis, Rafael G. Ferreira, Demetri Petrides, Karel De Winter, Wim Soetaert" "Third-generation (3G) biorefineries harnessing industrial off-gases have received significant attention in the transition towards a sustainable circular economy. However, uncertainties surrounding their techno-economic feasibility are hampering widespread commercialization to date. This study investigates the production of single-cell protein (SCP), a sustainable alternative food and feed protein, from steel mill off-gas through an efficient coupled fermentation approach utilizing acetate as an intermediate. A comprehensive model that comprises both the gas-to-acetate and the acetate-to-SCP fermentation processes, as well as gas pretreatment and downstream processing (DSP) operations, was developed and used to perform a techno-economic analysis (TEA). Sensitivity analyses demonstrated that significant cost reductions can be achieved by the process intensification of the gas-to-acetate fermentation. As such, an increase in the acetate concentration to 45 g/L and productivity to 4 g/L/h could lead to a potential cost reduction from 4.15 to 2.78 USD/kg. In addition, the influence of the production scale and other economic considerations towards the commercialization of off-gas-based SCPs are discussed. Conclusively, this research sheds light on the practical viability of a coupled fermentation process for SCP production by identifying key cost-influencing factors and providing targets for further optimization of the acetate platform, fostering sustainable and economically feasible bio-based innovations." "Acidic sophorolipid and antimicrobial peptide based formulation as antimicrobial and antibiofilm agents" "Sahadevan Seena, Rafaela Ferrão, Melike Pala, Sophie Roelants, Wim Soetaert, Christian Stevens, Lino Ferreira, Akhilesh Rai" "Antimicrobial peptides (AMPs) are considered promising candidates to treat various infections in soft tissues and skin. However, no effective treatment based on AMPs has been reached to clinics due to their instability in serum and wounds. Biosurfactants such as acidic sophorolipids (ASLs) of very high concentrations (equal or above 5 mg/mL) have been demonstrated to be antimicrobial agents, however these concentrations might induce cytotoxic effects to human cells. Here, we have demonstrated the synergistic antimicrobial effect of ASL nanoparticles (NPs) and LL37 peptides (below their minimum inhibitory concentrations; MICs) to eradicate Gram-positive and Gram-negative bacteria in human serum (HS) and in the presence of trypsin. The formulations containing ASL NPs (500 mu g/mL) and LL37 peptides (15-25 mu g/mL) effectively kill wide strains of bacteria in 5 % HS and the presence of trypsin. Moreover, the combination of ASL NPs (500 mu g/mL) and LL37 peptides (15 mu g/mL) prevents the formation of S. aureus biofilm and eradicates the one-day old biofilm. Importantly, the combination of ASL NPs and LL37 peptides severely damages the cell membrane of Escherichia coli (E. coli) as shown by atomic force microscopy (AFM). The combination of ASL NPs and LL37 peptides rapidly damages the outer (OM) and inner membrane (IM) of E. coli, while ASL NPs (1000 mu g/mL) alone slowly compromise the integrity of the bacterial membrane. Importantly, the combination of ASL NPs and LL37 peptides is biocompatible to human keratinocyte cells (HaCaTs) and human umbilical vein endothelial cells (HUVECs), and induces the expression of antiinflammatory cytokine in macrophages. Overall, ASL NPs in combination with LL37 peptides might be developed as an effective topical formulation to prevent bacterial infections in the skin." "Improved production of novel (bola) glycolipid biosurfactants with the yeast Starmerella bombicola through an integrative approach combining genetic engineering and multiomics analyses" "Martijn Castelein, Nicolas de Fooz, Goedele Luyten, Lisa Van Renterghem, Sven Dierickx, Stijn Bovijn, Sophie Roelants, Lynn Vanhaecke, Wim Soetaert" "Starmerella bombicola is well known for its natural efficient capacity to produce glycolipids sophorolipids (SLs) at high titers (> 200 g/L) and high-volumetric productivities (> 2 g/L h). These traits make this nonpathogenic yeast industrially relevant, resulting in valorization of SLs as microbial biosurfactants by several companies. The efficient glycolipid machinery of S. bombicola has, on the other hand, been employed toward the biosynthesis of novel types of glycolipid biosurfactants. This has resulted in the generation of a battery of novel S. bombicola strains, producing a range of (novel) glycolipids of which an overview is given in the first part of this chapter. The novel glycolipids have varying properties resulting in a diverse valorization potential, which is very promising toward the further development of the bio-based economy. However, some of the novel S. bombicola strains suffer(ed) from decreased glycolipid productivity levels, while the molecular regulation of glycolipid biosynthesis with S. bombicola is yet to be fully elucidated. Our lab has applied several (integrated) -omic strategies to overcome these hurdles, and in some cases, this strategy allowed us to acquire the information required to resolve the productivity decrease, giving rise to efficient production of novel glycolipids. Further determination and integration of -omic datasets and even in-line/in-process determination of specific -omic data is expected to positively impact further developments and follow-up of glycolipid biosurfactant production processes with S. bombicola." "An exploratory in silico comparison of open-source codon harmonization tools" "Thomas Willems, Wim Hectors, Jeltien Rombaut, Anne-Sofie De Rop, Stijn Goegebeur, Tom Delmulle, Maarten De Mol, Sofie De Maeseneire, Wim Soetaert" "Background: Not changing the native constitution of genes prior to their expression by a heterologous host can affect the amount of proteins synthesized as well as their folding, hampering their activity and even cell viability. Over the past decades, several strategies have been developed to optimize the translation of heterologous genes by accommodating the difference in codon usage between species. While there have been a handful of studies assessing various codon optimization strategies, to the best of our knowledge, no research has been performed towards the evaluation and comparison of codon harmonization algorithms. To highlight their importance and encourage meaningful discussion, we compared different open-source codon harmonization tools pertaining to their in silico performance, and we investigated the influence of different gene-specific factors. Results: In total, 27 genes were harmonized with four tools toward two different heterologous hosts. The difference in %MinMax values between the harmonized and the original sequences was calculated (ΔMinMax), and statistical analysis of the obtained results was carried out. It became clear that not all tools perform similarly, and the choice of tool should depend on the intended application. Almost all biological factors under investigation (GC content, RNA secondary structures and choice of heterologous host) had a significant influence on the harmonization results and thus must be taken into account. These findings were substantiated using a validation dataset consisting of 8 strategically chosen genes. Conclusions: Due to the size of the dataset, no complex models could be developed. However, this initial study showcases significant differences between the results of various codon harmonization tools. Although more elaborate investigation is needed, it is clear that biological factors such as GC content, RNA secondary structures and heterologous hosts must be taken into account when selecting the codon harmonization tool." "Aqueous self-assembly of a wide range of sophorolipid and glucolipid microbial bioamphiphiles (biosurfactants) : considerations on the structure-properties relationship" "Niki Baccile, Alexandre Poirier, Patrick Le Griel, Petra Pernot, Melike Pala, Sophie Roelants, Wim Soetaert, Christian Stevens" "Sophorolipids are well-known scaled-up microbial glycolipid biosurfactants with a strong potential for commercialization due to their biological origin and mildness in contact with the skin and the environment compared to classical surfactants. However, their association properties in water are still poorly understood, they cannot be predicted and their behavior in solution challenges half a century of knowledge generated in the field of surfactant science. By studying forty different types of sophorolipids and sophorosides in water using small angle X-ray scattering, and optical and cryogenic transmission electron microscopy, this work provides better understanding of their structure-property relationship and identifies which chemical groups in their molecular structure have a critical influence on their self-assembly properties. Structural features like the number of sugar headgroups, acetylation, end-chain functional group, (un)saturation, lactonization and length of chain are adjusted to both rationalize their impact and understand their effect on self-assembly. The number of sugar groups, pH, (un)saturation and lactonization were found to have a critical impact on sophorolipid self-assembly. The chemical nature of the end-chain functional group and chain length were also found to have a possibly critical impact, depending on the specific type of chemical function (COOH and long chains are critical). Mono-and diacetylation, as well as the position of sophorose in the fatty acid (0), 0)-1), are not critical, i.e., they did not significantly influence sophorolipid self-assembly." "'Unlocking the potential of a glycolipid platform through chemical modification'" "Melike Pala, Sophie Roelants, Wim Soetaert, Christian Stevens" "Sophorolipids are an important class of glycolipid microbial biosurfactants because of their attractive surface-active and biological properties recently resulting in industrial production. However, their commercialization has been mainly limited to household detergent applications due to the minimal structural variation that can be produced via fermentation. The amphiphilic structure and the availability of the reactive sites on the sophorolipids make them suitable candidates for chemical modification which enables the generation of sophorolipid derivatives in a fast and systematic way. The latter is crucial to obtain a fundamental understanding of the structure–activity relationship, in particular for high added-value applications. This review provides an overview of the recent developments in the chemical modification of sophorolipids and novel types of related microbial glycolipids and their targeted applications." "Engineering Comamonas testosteroni for the production of 2-pyrone-4,6-dicarboxylic acid as a promising building block" "Tom Delmulle, Stijn Bovijn, Sari Deketelaere, Martijn Castelein, Tom Erauw, Matthias D'hooghe, Wim Soetaert" "Background: Plastics are an indispensable part of our daily life. However, mismanagement at their end-of-life results in severe environmental consequences. The microbial conversion of these polymers into new value-added products offers a promising alternative. In this study, we engineered the soil-bacterium Comamonas testosteroni KF-1, a natural degrader of terephthalic acid, for the conversion of the latter to the high-value product 2-pyrone-4,6-dicarboxylic acid. Results: In order to convert terephthalic acid to 2-pyrone-4,6-dicarboxylic acid, we deleted the native PDC hydrolase and observed only a limited amount of product formation. To test whether this was the result of an inhibition of terephthalic acid uptake by the carbon source for growth (i.e. glycolic acid), the consumption of both carbon sources was monitored in the wild-type strain. Both carbon sources were consumed at the same time, indicating that catabolite repression was not the case. Next, we investigated if the activity of pathway enzymes remained the same in the wild-type and mutant strain. Here again, no statistical differences could be observed. Finally, we hypothesized that the presence of a pmdK variant in the degradation operon could be responsible for the observed phenotype and created a double deletion mutant strain. This newly created strain accumulated PDC to a larger extent and again consumed both carbon sources. The double deletion strain was then used in a bioreactor experiment, leading to the accumulation of 6.5 g/L of product in 24 h with an overall productivity of 0.27 g/L/h. Conclusions: This study shows the production of the chemical building block 2-pyrone-4,6-dicarboxylic acid from terephthalic acid through an engineered C. testosteroni KF-1 strain. It was observed that both a deletion of the native PDC hydrolase as well as a pmdK variant is needed to achieve high conversion yields. A product titer of 6.5 g/L in 24 h with an overall productivity of 0.27 g/L/h was achieved."