Evaluating oleaginous yeasts for enhanced microbial lipid production using sweetwater as a sustainable feedstock.

BACKGROUND: Yeasts exhibit promising potential for the microbial conversion of crude glycerol, owing to their versatility in delivering a wide range of value-added products, particularly lipids. Sweetwater, a methanol-free by-product of the fat splitting process, has emerged as a promising alternative feedstock for the microbial utilization of crude glycerol. To further optimize sweetwater utilization, we compared the growth and lipid production capabilities of 21 oleaginous yeast strains under different conditions with various glycerol concentrations, sweetwater types and pH. RESULTS: We found that nutrient limitation and the unique carbon composition of sweetwater boosted significant lipid accumulation in several strains, in particular Rhodosporidium toruloides NRRL Y-6987. Subsequently, to decipher the underlying mechanism, the transcriptomic changes of R. toruloides NRRL Y-6987 were further analyzed, indicating potential sugars and oligopeptides in sweetwater supporting growth and lipid accumulation as well as exogenous fatty acid uptake leading to the enhanced lipid accumulation. CONCLUSION: Our comparative study successfully demonstrated sweetwater as a cost-effective feedstock while identifying R. toluroides NRRL Y-6987 as a highly promising microbial oil producer. Furthermore, we also suggested potential sweetwater type and strain engineering targets that could potentially enhance microbial lipid production.

Adaptive Laboratory Evolution of Cupriavidus necator H16 for Carbon Co-Utilization with Glycerol.

Cupriavidus necator H16 is a non-pathogenic Gram-negative betaproteobacterium that can utilize a broad range of renewable heterotrophic resources to produce chemicals ranging from polyhydroxybutyrate (biopolymer) to alcohols, alkanes, and alkenes. However, C. necator H16 utilizes carbon sources to different efficiency, for example its growth in glycerol is 11.4 times slower than a favorable substrate like gluconate. This work used adaptive laboratory evolution to enhance the glycerol assimilation in C. necator H16 and identified a variant (v6C6) that can co-utilize gluconate and glycerol. The v6C6 variant has a specific growth rate in glycerol 9.5 times faster than the wild-type strain and grows faster in mixed gluconate-glycerol carbon sources compared to gluconate alone. It also accumulated more PHB when cultivated in glycerol medium compared to gluconate medium while the inverse is true for the wild-type strain. Through genome sequencing and expression studies, glycerol kinase was identified as the key enzyme for its improved glycerol utilization. The superior performance of v6C6 in assimilating pure glycerol was extended to crude glycerol (sweetwater) from an industrial fat splitting process. These results highlight the robustness of adaptive laboratory evolution for strain engineering and the versatility and potential of C. necator H16 for industrial waste glycerol valorization.

Physical adsorption of anisotropic titania nanoparticles onto poly(2-vinylpyridine) latex and characterisation of the resulting nanocomposite particles.

Four poly(2-vinylpyridine) latexes with intensity-average mean diameters ranging between 246 and 955nm were prepared by aqueous emulsion polymerisation. These latexes were characterised by transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, aqueous electrophoresis, disc centrifuge photosedimentometry and thermogravimetry. The adsorption of rice grain-shaped nano-sized titania particles onto the surface of these latex particles from aqueous solution was investigated. It was found that the titania particles adsorb strongly at pH 10 and the optimal loading and packing density of titania was investigated for each latex. The resulting core-shell P2VP-titania nanocomposite particles were characterised in terms of their titania contents, surface coverages and colloidal stabilities. UV-Vis spectra were recorded for the titania nanoparticles, the original P2VP latexes and the poly(2-vinylpyridine)-titania nanocomposite particles. It was found that, for the larger nanocomposite particles, UV-Vis absorption was dominated by the latex core, whereas the smaller P2VP-titania nanocomposite particles exhibited UV attenuation to longer wavelengths compared to both the bare latex and the titania particles. The poly(2-vinylpyridine) cores were selectively removed by calcination of the nanocomposite particles and the resulting hollow titania structures were investigated by transmission electron microscopy.

Versatile routes to selenoether functionalised tertiary phosphines.

New selenoether functionalised tertiary phosphines, based on aryl (2a, 2b) or alkyl (4) backbones, have been synthesised and characterised. P,Se-chelation has been achieved upon complexation to square-planar Pt(II) (3a) or Pd(II) (3b) metal centres. For 3a and 3b, weak non-covalent M...Se contacts were established using single crystal X-ray crystallography.

Sulfimidation of thioether groups--a versatile method for modifying and linking thia/oxa crowns.

Reaction of the mixed thioether/ether crowns [9]aneO2S , [12]aneO3S and [18]aneO4S2 with one mol. equivalent of the aminating agent MSH (o-mesitylsulfonylhydroxylamine) in Et2O results in the formation of the mono-sulfimidated systems {[9]aneO2(S=NH2)}+, {[12]aneO3(S=NH2)}+ and {[18]aneO4S(S=NH2)}+, while using two mol. equivalents of MSH with gives the disulfimidium cation {[18]aneO4(S=NH2)2}2+. All of these species have been isolated in good yields as the [mesSO3]- (mes=2,4,6-Me3C6H2) salts and can be readily converted to the [BPh4]- salts by metathesis with Na[BPh4]. Treatment of or with lithium diisopropylamide (LDA) and N-bromosuccinimide (NBS) at -78 degrees C, followed by addition of a further equivalent of the parent thia/oxa crown, gives monocationic N-bridged sulfimide bicyclic compounds ( and respectively), in which the crowns are linked by the sulfimidic nitrogen. Reaction of with LDA and NBS leads to formation of the {([18]aneO4S2)N}+ cation which exhibits an intramolecular S-N-S bridge. Crystallographic studies on representative examples of each compound type are described, together with their spectroscopic properties.

The first use of the free selenimide Ph2Se=NH as a synthon; the synthesis and X-ray crystal structure of [Ph2SeNSePh2][BPh4].

Reaction of o-mesitylsulfonylhydroxylamine (MSH) with Ph(2)Se results in the [Ph(2)SeNH(2)](+) cation; low temperature deprotonation (LDA), bromination (NBS) and then treatment with Ph(2)Se-Na[BPh(4)] generates [Ph(2)SeNSePh(2)][BPh(4)], via the selenimides Ph(2)Se=NH and Ph(2)Se=NBr.

Sulfimidation--a new and versatile strategy for the post ring-closure derivatisation of mixed thia/oxa crowns.

Reaction of [18]aneO(5)S with the aminating agent MSH results in the {[18]aneO(5)SNH(2)}+ cation which may be converted through to the linked crown system [({[18]aneO(5)S}(2)N)]+ via deprotonation, bromination and reaction with the parent crown; significantly, despite their positive charge, both systems can coordinate sodium cations to the ether linkages.

Neutral molecular Pd6 hexagons using kappa3-P2O-terdentate ligands.

The one-step synthesis of three new P2O-terdentate carboxylic acid ditertiary phosphines 2-{(Ph2PCH2)2N}-3-(X)C6H3CO2H (X = OCH3, L1; X = OH, L2) and 2-{(Ph2PCH2)2N}-5-(OH)C6H3CO2H (L3) by a phosphorus-based Mannich condensation reaction using Ph2PCH2OH and the appropriate amine in CH3OH is reported. Compounds L1-L3 function as typical kappa2-P2-didentate ligands upon complexation to Pd(CH3)Cl(cod) (cod = cycloocta-1,5-diene), affording the neutral, mononuclear complexes Pd(CH3)Cl(L1-L3) (1-3). Metathesis of 1 with NaX (X = Br, I) gave the corresponding (methyl)bromopalladium(II) (4) and (methyl)iodopalladium(II) (5) complexes, respectively. When chloroform or chloroform/methanol solutions of 1-3 (or 5) were allowed to stand, at ambient temperatures, yellow crystalline solids were isolated in very high yields (71-88%) and were analyzed for the novel hexameric palladium(II) compounds 6-9. All new compounds reported have been fully characterized by a combination of spectroscopic (multinuclear NMR, Fourier transform IR, electrospray mass spectrometry, matrix-assisted laser desorption ionization time-of-flight mass spectrometry) and analytical methods. The self-assembly reactions are remarkably clean as monitored by 31P{1H} and 1H NMR spectroscopy. Single-crystal X-ray structures have been determined for L1, 4, 7.17CDCl3.2Et2O, 8.6CHCl3.8CH3OH, and 9.17CDCl3. In hexamers 7-9, all six square-planar palladium(II) metal centers comprise a kappa2-P2-chelating diphosphine, a kappa1-O-monodentate carboxylate, and either a chloride or iodide ligand, leading to 48-membered metallomacrocycles (with outside diameters of ca. 2.5 nm). Whereas only intramolecular O-H...N hydrogen bonding between the hydroxy group and tertiary amine has been observed in 7, strong intermolecular O-H...O hydrogen bonding of the type CO...HO(CH3)...HO, involving a methanol solvate, has been found in 8, leading to an unprecedented three-dimensional network motif.