Understanding taste is key for optimizing the palatability of seaweeds and other non-animal-based foods rich in protein. The lingual papillae in the mouth hold taste buds with taste receptors for the five gustatory taste qualities. Each taste bud contains three distinct cell types, of which Type II cells carry various G protein-coupled receptors that can detect sweet, bitter, or umami tastants, while type III cells detect sour, and likely salty stimuli. Upon ligand binding, receptor-linked intracellular heterotrimeric G proteins initiate a cascade of downstream events which activate the afferent nerve fibers for taste perception in the brain. The taste of amino acids depends on the hydrophobicity, size, charge, isoelectric point, chirality of the alpha carbon, and the functional groups on their side chains. The principal umami ingredient monosodium l-glutamate, broadly known as MSG, loses umami taste upon acetylation, esterification, or methylation, but is able to form flat configurations that bind well to the umami taste receptor. Ribonucleotides such as guanosine monophosphate and inosine monophosphate strongly enhance umami taste when l-glutamate is present. Ribonucleotides bind to the outer section of the venus flytrap domain of the receptor dimer and stabilize the closed conformation. Concentrations of glutamate, aspartate, arginate, and other compounds in food products may enhance saltiness and overall flavor. Umami ingredients may help to reduce the consumption of salts and fats in the general population and increase food consumption in the elderly.
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pH-sensitive gels: By using a cyclohexane-based scaffold to which various amino acid based substituents can be connected, low-molecular-weight compounds were obtained that can gelate water at very low concentrations. Their modular design (see picture: AA = amino acid(s), X = hydrophilic substituent, dark purple = hydrophobic region, light purple = hydrophilic region), allows tuning of the thermally and pH-induced reversible gel-to-sol transition of their gels.
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The transition to a biobased economy necessitates utilizing renewable resources as a sustainable alternative to traditional fossil fuels. Bioconversion is a way to produce many green chemicals from renewables, e.g., biopolymers like PHAs. However, fermentation and bioconversion processes mostly rely on expensive, and highly refined pure substrates. The utilization of crude fractions from biorefineries, especially herbaceous lignocellulosic feedstocks, could significantly reduce costs. This presentation shows the microbial production of PHA from such a crude stream by a wild-type thermophilic bacterium Schlegelella thermodepolymerans [1]. Specifically, it uses crude xylose-rich fractions derived from a newly developed biorefinery process for grassy biomasses (the ALACEN process). This new stepwise mild flow-through biorefinery approach for grassy lignocellulosic biomass allows the production of various fractions: a fraction containing esterified aromatics, a monomeric xylose-rich stream, a glucose fraction, and a native-like lignin residue [2]. The crude xylose-rich fraction was free of fermentation-inhibiting compounds meaning that the bacterium S.thermodepolymerans could effectively use it for the production of one type of PHA, polyhydroxybutyrate. Almost 90% of the xylose in the refined wheat straw fraction was metabolized with simultaneous production of PHA, matching 90% of the PHA production per gram of sugars, comparable to PHA yields from commercially available xylose. In addition to xylose, S. thermodepolymerans converted oligosaccharides with a xylose backbone (xylans) into fermentable xylose, and subsequently utilized the xylose as a source for PHA production. Since the xylose-rich hydrolysates from the ALACEN process also contain some oligomeric xylose and minor hemicellulose-derived sugars, optimal valorization of the C5-fractions derived from the refinery process can be obtained using S. thermodepolymerans. This opens the way for further exploration of PHA production from C5-fractions out of a variety of herbaceous lignocellulosic biomasses using the ALACEN process combined with S. thermodepolymerans. Overall, the innovative utilization of renewable resources in fermentation technology, as shown herein, makes a solid contribution to the transition to a biobased economy.[1] W. Zhou, D.I. Colpa, H. Permentier, R.A. Offringa, L. Rohrbach, G.J.W. Euverink, J. Krooneman. Insight into polyhydroxyalkanoate (PHA) production from xylose and extracellular PHA degradation by a thermophilic Schlegelella thermodepolymerans. Resources, Conservation and Recycling 194 (2023) 107006, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2023.107006. [2] S. Bertran-Llorens, W.Zhou. M.A.Palazzo, D.I.Colpa, G.J.W.Euverink, J.Krooneman, P.J.Deuss. ALACEN: a holistic herbaceous biomass fractionation process attaining a xylose-rich stream for direct microbial conversion to bioplastics. Submitted 2023.
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Structural and functional knowledge of proteins, which are essential in biological processes, is fundamental for our understanding of the Chemistry of Life. Structural biology - the field that studies the structure and function of proteins – has seen several revolutions over the last few years. Single particle analysis (SPA), where individual macromolecular assemblies are imaged under cryogenic conditions within highly automated electron microscopes, has been used to elucidate the structures of many novel and important proteins and complexes. Deep-learning–based computational techniques provided systematic predictions of an million three-dimensional protein structures. Cryo-electron tomography (ET) combined with sub-tomogram averaging (STA) enabled the investigation of conformational states of large macromolecular complexes. We expect in situ structural biology, where macromolecular assemblies are studied within the interior of focused-ion-beam milled frozen cells, to become the next revolution in our field. Such revolution would require well prepared vitreous samples (cells, tissue slices, organoids): the sample should be cooled fast enough to prevent the formation of crystalline ice. Previously, we developed the technology to prepare SPA samples using jets of cryogenic fluid directed onto the sample. This device, the VitroJet, has been further developed into a commercial product by CryoSol-World and has been sold worldwide. Here, we wish to advance the jetting technology such that it can vitrify cells. Crucial aspects are the speed of the jets and the timing and reproducibility of the fronts of the cryogens arriving onto the sample. We will design, build, characterise and refine a next generation of the ethane cup, a core component within the VitroJet. If successful, we should be able to increase its vitrification potential as well as its reproducibility by more than one order of magnitude. This technology will enable in situ structural biology studies necessary to understand the Chemistry of Life.
