Unsaturated Products Research Articles

Visible-light Driven Unsaturated Dicarboxylate Production from Gaseous CO<sub>2</sub> and Pyruvate with the System of Water-soluble Zinc Porphyrin and Dual-biocatalysts

Visible-light Driven Unsaturated Dicarboxylate Production from Gaseous CO<sub>2</sub> and Pyruvate with the System of Water-soluble Zinc Porphyrin and Dual-biocatalysts

Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters.

The outer membrane of gram-negative bacteria is a barrier to chemical and physical stress. Phospholipid transport between the inner and outer membranes has been an area of intense investigation and, in E. coli K-12, it has recently been shown to be mediated by YhdP, TamB, and YdbH, which are suggested to provide hydrophobic channels for phospholipid diffusion, with YhdP and TamB playing the major roles. However, YhdP and TamB have different phenotypes suggesting distinct functions. It remains unclear whether these functions are related to phospholipid metabolism. We investigated a synthetic cold sensitivity caused by deletion of fadR, a transcriptional regulator controlling fatty acid degradation and unsaturated fatty acid production, and yhdP, but not by ΔtamB ΔfadR or ΔydbH ΔfadR. Deletion of tamB recuses the ΔyhdP ΔfadR cold sensitivity further demonstrating the phenotype is related to functional diversification between these genes. The ΔyhdP ΔfadR strain shows a greater increase in cardiolipin upon transfer to the non-permissive temperature and genetically lowering cardiolipin levels can suppress cold sensitivity. These data also reveal a qualitative difference between cardiolipin synthases in E. coli, as deletion of clsA and clsC suppresses cold sensitivity but deletion of clsB does not. Moreover, increased fatty acid saturation is necessary for cold sensitivity and lowering this level genetically or through supplementation of oleic acid suppresses the cold sensitivity of the ΔyhdP ΔfadR strain. Together, our data clearly demonstrate that the diversification of function between YhdP and TamB is related to phospholipid metabolism. Although indirect regulatory effects are possible, we favor the parsimonious hypothesis that YhdP and TamB have differential phospholipid-substrate transport preferences. Thus, our data provide a potential mechanism for independent control of the phospholipid composition of the inner and outer membranes in response to changing conditions based on regulation of abundance or activity of YhdP and TamB.

Genetic evidence for functional diversification of gram-negative intermembrane phospholipid transporters.

The outer membrane of Gram-negative bacteria is a barrier to chemical and physical stress. Phospholipid transport between the inner and outer membranes has been an area of intense investigation and, in E. coli K-12, it has recently been shown to be mediated by YhdP, TamB, and YdbH, which are suggested to provide hydrophobic channels for phospholipid diffusion, with YhdP and TamB playing the major roles. However, YhdP and TamB have different phenotypes suggesting distinct functions. We investigated these functions using synthetic cold sensitivity (at 30 °C) caused by deletion of yhdP and fadR, a transcriptional regulator controlling fatty acid degradation and unsaturated fatty acid production, but not by ΔtamB ΔfadR or ΔydbH ΔfadR,. Deletion of tamB suppresses the ΔyhdP ΔfadR cold sensitivity suggesting this phenotype is related to phospholipid transport. The ΔyhdP ΔfadR strain shows a greater increase in cardiolipin upon transfer to the non-permissive temperature and genetically lowering cardiolipin levels can suppress cold sensitivity. These data also reveal a qualitative difference between cardiolipin synthases in E. coli, as deletion of clsA and clsC suppresses cold sensitivity but deletion of clsB does not despite lower cardiolipin levels. In addition to increased cardiolipin, increased fatty acid saturation is necessary for cold sensitivity and lowering this level genetically or through supplementation of oleic acid suppresses the cold sensitivity of the ΔyhdP ΔfadR strain. Although indirect effects are possible, we favor the parsimonious hypothesis that YhdP and TamB have differential substrate transport preferences, most likely with YhdP preferentially transporting more saturated phospholipids and TamB preferentially transporting more unsaturated phospholipids. We envision cardiolipin contributing to this transport preference by sterically clogging TamB-mediated transport of saturated phospholipids. Thus, our data provide a potential mechanism for independent control of the phospholipid composition of the inner and outer membranes in response to changing conditions.

Hydroconversion of lignin-derived platform compound guaiacol to fuel additives and value-added chemicals over alumina-supported Ni catalysts

Hydroconversion of guaiacol (GUA) over γ-Al2O3 and phosphatized-γ-Al2O3 (γ-Al2O3(P)) supported Ni catalysts was initiated by Lewis-sites and active Ni sites. Conversion proceeded via transmethylation and hydrodemethylation/hydrodemethoxylation as major and minor pathways, respectively, resulting in mainly catechol and methylcatechols, and via series of consecutive hydrodehydroxylation (HDHY) and ring hydrogenation (HYD) reactions leading to partially and fully deoxygenated, saturated, and unsaturated products. High Ni-loading and high H2 pressure promoted the formation of cyclohexane and methyl-substituted cyclohexanes; however, above 300 °C the hydrogenation–dehydrogenation equilibrium favored the formation of benzene and methyl-substituted benzenes. Ni/γ-Al2O3(P) showed suppressed HYD/HDHY activity resulting in pronounced formation of catechol and/or phenol and their methyl-substituted derivatives. Surface phenolate species were substantiated as surface intermediates of hydrodeoxygenation. Phosphatizing reduced the concentration of both basic OH and Lewis acid (Al+) – Lewis base (O–) pair surface sites of the γ-Al2O3 support and, thereby, suppressed phenolate formation and hydrodeoxgenation.

Competing Mechanisms in Palladium-Catalyzed Alkoxycarbonylation of Styrene.

Palladium-catalyzed carbonylation is a versatile method for the synthesis of various aldehydes, esters, lactones, or lactams. Alkoxycarbonylation of alkenes with carbon monoxide and alcohol produces either saturated or unsaturated esters as a result of two distinct catalytic cycles. The existing literature presents an inconsistent account of the procedures favoring oxidative carbonylation products. In this study, we have monitored the intermediates featured in both catalytic cycles of the methoxycarbonylation of styrene PhCH=CH2 as a model substrate, including all short-lived intermediates, using mass spectrometry. Comparing the reaction kinetics of the intermediates in both cycles in the same reaction mixture shows that the reaction proceeding via alkoxy intermediate [PdII]-OR, which gives rise to the unsaturated product PhCH=CHCO2Me, is faster. However, with an advancing reaction time, the gradually changing reaction conditions begin to favor the catalytic cycle dominated by palladium hydride [PdII]-H and alkyl intermediates, affording the saturated products PhCH2CH2CO2Me and PhCH(CO2Me)CH3 preferentially. The role of the oxidant proved to be crucial: using p-benzoquinone results in a gradual decrease of the pH during the reaction, swaying the system from oxidative conditions toward the palladium hydride cycle. By contrast, copper(II) acetate as an oxidant guards the pH within the 5-7 range and facilitates the formation of the alkoxy palladium complex [PdII]-OR, which favors the oxidative reaction producing PhCH=CHCO2Me with high selectivity. Hence, it is the oxidant, rather than the catalyst, that controls the reaction outcome by a mechanistic switch. Unraveling these principles broadens the scope for developing alkoxycarbonylation reactions and their application in organic synthesis.

Abstract 1711: Rearranged active enhancers and promoter-enhancer contacts promote lipid metabolic reprogramming during secondary trastuzumab adaptation of HER2 positive breast cancer

Abstract Background: The development of secondary trastuzumab resistance signifies an evolutionary adaptation within HER2-positive breast cancer during anti-HER2 treatment. Our research reveals a comprehensive metabolic reprogramming, with a particular emphasis on the synthesis of unsaturated fatty acids and the degradation of arachidonic acid, accompanying this adaptation. Non-mutational epigenetic variations, particularly alterations in active enhancers, coupled with the rearrangement of enhancer-promoter contacts, demonstrate robust correlations with lipid metabolic reprogramming. These findings suggest that non-mutational epigenetic variations play a crucial role in driving the adaptation to trastuzumab. Materials and Methods: In a prior investigation, we successfully generated secondary trastuzumab-resistant SKBR3_HR cells. In our current study, total RNA was extracted from both trastuzumab-resistant SKBR3_HR and trastuzumab-sensitive SKBR3 cells for transcriptome analysis. Additionally, mass spectrometry was employed to analyze cellular metabolism in both resistant and sensitive cell populations. Simultaneously, we utilized the CUT&Tag kit with an anti-H3K27ac antibody to create a sequencing library for active enhancer measurement. Furthermore, the Micro-C kit was applied to generate a sequencing library for genome contact measurement. Results: In our study, secondary trastuzumab-adaptive SKBR3_HR cells demonstrated a reduction in cellular unsaturated fatty acids, with more than 110 UFAs or UFA-containing lipids showing decreases, while only 36 exhibited increases. This phenomenon may be attributed to the downregulation of SCD, FADS2, and HACD2. Simultaneously, the upregulation of PTGS1 and PTGES may contribute to a higher conversion of arachidonic acid to prostaglandin E2 (PGE2), resulting in immune inhibition. In SKBR3 and SKBR3_HR cells, 10,955 and 10,889 non-promoter H3K27me3 peaks, respectively, were identified as active enhancer regions. Among them, 379 enhancers became silent, and 313 transitioned into an active state during the formation of trastuzumab adaptation. Trastuzumab adaptation led to an increase in intra-chromosomal interactions, particularly short-distance contacts (< 1MB). By employing the activity-by-contact (ABC) algorithm, we observed significant variant contacts between PTGES and SCD promoters and enhancers within 1MB genomic regions in SKBR3_HR cells compared to SKBR3 cells. Conclusion: The formation of secondary trastuzumab adaptation involves the rearrangement of active enhancers and promoter-enhancer contacts, serving as an effective force to drive lipid metabolic reprogramming, especially the synthesis of unsaturated fatty acids and PGE2 production, reshaping the cellular fatty acid composition and anti-tumor immunity. Citation Format: Ningjun Duan, Yijia Hua, Yongmei Yin. Rearranged active enhancers and promoter-enhancer contacts promote lipid metabolic reprogramming during secondary trastuzumab adaptation of HER2 positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1711.

Urea-N influences biomass yield, neutral lipids accumulation, and unsaturated fatty acid production in photoautotrophically grown microalga Chlorella sp

Microalgal cultivation using cost-effective nutrients is found to decrease the biodiesel production cost significantly. Therefore, in this study, various nitrogen sources namely sodium nitrate, ammonium nitrate, potassium nitrate, and fertilizer-grade urea, were tested to evaluate their impact on the biomass, lipids, and fatty acid content of microalga Chlorella sp. For biodiesel production. Onset of the study, the highest biomass yield, about 1.35g/L, was obtained in urea-N, potassium nitrate, and sodium nitrate. For lipid extraction, different methods such as sonication, stirring, Soxhlet, homogenization, and sonication + Soxhlet were compared, and the highest efficiency (19.86% lipid content) was noticed in the combined sonication + Soxhlet method with chloroform: methanol (2:1). Regarding the lipid content, 19.86, 19.91, 18.44, and 19.13% were extracted from sodium nitrate, ammonium nitrate, potassium nitrate, and fertilizer grade urea-grown cultures, respectively. Further optimization of urea-N revealed that, of the 0.0, 0.75, 1.5, 2.25, and 3.0 g/L urea-N concentrations, total lipid content and neutral lipid was decreased when increasing the urea-N level in the medium and maximum content of 23.6%, and 14.7 %, were observed, respectively in 0.0 g/L urea-N. Biodiesel yield with respect to urea-N concentration showed a maximum of 64.7% biodiesel from 0 g/L grown microalgal cells. The fatty acid fingerprinting of the biodiesel by gas chromatography showed higher levels of UFAs (57.18% w/w lipids) in nil urea-N concentration (0 g/L) and higher levels of SFAs (39.84% w/w lipids) in higher urea-N (3.0 g/L) grown culture.

Comprehensive approach to the multigram, heavy-metal-free synthesis of 4-EWG-substituted quinoline derivatives

2-Nitrotoluenes activated by CN, SO2Tol, CO2R or COR groups condense under particular conditions with acetaldehyde in moderate to excellent yields. The unsaturated products are starting materials for cyclization furnishing quinoline oxides substituted with the above electron-withdrawing groups. Under relevant reaction conditions they can be reduced to the corresponding substituted quinolines. The protocol is suitable for multigram scale and extends the scope of the condensation step on non–CN–substituted 2-nitroarenes.

Decarboxylative - Dimerization of levulinic acid using spent Li-ion battery electrode material with lithium nickel cobalt manganese oxide as a catalyst

A low cost catalyst prepared by pyrolyzing electrode coating material from spent Li-ion battery cells was shown as an effective catalyst for the decarboxylative - dimerization of levulinic acid to a mixture of C6 and C9 fuel precursors. The highest levulinic acid conversion of 94% was observed with 10% (w/w) catalyst loading under 1.24 MPa H2 at 140 °C, 15 h. A reaction scheme was proposed to explain the novel transformation producing C9 lactone products and C6 unsaturated alcohol product through a decarboxylative pathway followed by the aldol dimerization of levulinic acid.

Understanding the influence of solvents on the Pt-catalyzed hydrodeoxygenation of guaiacol

Bio-oil derived from fast pyrolysis of lignocellulosic biomass needs to be deoxygenated to become a substitute for petroleum fuels. Here, we study the hydrodeoxygenation mechanism of guaiacol, a bio-oil model compound derived from the lignin fraction of biomass, on Pt(111) terrace sites in the presence of water, diethyl ether, 1-butanol, and n-hexane as solvent. Using first-principles periodic density functional theory (DFT) calculations and mean-field microkinetic reactor modeling, a detailed reaction mechanism is investigated targeting various products such as catechol, phenol, anisole, benzene, cyclohexanone, and cyclohexanol. Solvent phase DFT outcomes are mostly similar to that of the vapor phase; however, microkinetic modeling results suggest that rate controlling species and transition states differ somewhat in the various reaction environments. Catechol was found to be the major aromatic product across all reaction environments. Over Pt(111), unsaturated monooxygenate production from catechol is unlikely.

Composite material for a volume energy-intensive resistor

A three-fraction composition of the ceramic forming mass was developed for obtaining energy-intensive resistors based on powders of electrocorundum with grainism F 120, F 400 and a thin milk electrically conductive fraction from a colloidgraphite drug of the S-1 brand. To bind the grains when forming the workpiece, an aluminumchromophosphate bundle was used, which allows to receive clogging, unsaturated products. The components of the forming mass mixed and pressed semi-finished products. For comparison, an analysis of the structure and composition of the resistor of the company HVR International was carried out. The effect of pressing pressure developed by the amount of electrical resistance and the density of the material has been studied. Changing the content of colloidal nano-size graphite, they received a wide range of electrical tests. Based on colloidal graphite and aluminum-containing ligament, masses are obtained that reduce contact resistance. Ill. 3. Ref. 16. Tab. 4.

Structure Elucidation of Secondary Metabolites: Current Frontiers and Lingering Pitfalls.

Analytical methods allow for the structure determination of submilligram quantities of complex secondary metabolites. This has been driven in large part by advances in NMR spectroscopic capabilities, including access to high-field magnets equipped with cryogenic probes. Experimental NMR spectroscopy may now be complemented by remarkably accurate carbon-13 NMR calculations using state-of-the-art DFT software packages. Additionally, microED analysis stands to have a profound effect on structure elucidation by providing X-ray-like images of microcrystalline samples of analytes. Nonetheless, lingering pitfalls in structure elucidation remain, particularly for isolates that are unstable or highly oxidized. In this Account, we discuss three projects from our laboratory that highlight nonoverlapping challenges to the field, with implications for chemical, synthetic, and mechanism of action studies. We first discuss the lomaiviticins, complex unsaturated polyketide natural products disclosed in 2001. The original structures were derived from NMR, HRMS, UV-vis, and IR analysis. Owing to the synthetic challenges presented by their structures and the absence of X-ray crystallographic data, the structure assignments remained untested for nearly two decades. In 2021, the Nelson group at Caltech carried out microED analysis of (-)-lomaiviticin C, leading to the startling discovery that the original structure assignment of the lomaiviticins was incorrect. Acquisition of higher-field (800 MHz 1H, cold probe) NMR data as well as DFT calculations provided insights into the basis for the original misassignment and lent further support to the new structure identified by microED. Reanalysis of the 2001 data set reveals that the two structure assignments are nearly indistinguishable, underscoring the limitations of NMR-based characterization. We then discuss the structure elucidation of colibactin, a complex, nonisolable microbiome metabolite implicated in colorectal cancer. The colibactin biosynthetic gene cluster was detected in 2006, but owing to colibactin's instability and low levels of production, it could not be isolated or characterized. We used a combination of chemical synthesis, mechanism of action studies, and biosynthetic analysis to identify the substructures in colibactin. These studies, coupled with isotope labeling and tandem MS analysis of colibactin-derived DNA interstrand cross-links, ultimately led to a structure assignment for the metabolite. We then discuss the ocimicides, plant secondary metabolites that were studied as agents against drug-resistant P. falciparum. We synthesized the core structure of the ocimicides and found significant discrepancies between our experimental NMR spectroscopic data and that reported for the natural products. We determined the theoretical carbon-13 NMR shifts for 32 diastereomers of the ocimicides. These studies indicated that a revision of the connectivity of the metabolites is likely needed. We end with some thoughts on the frontiers of secondary metabolite structure determination. As modern NMR computational methods are straightforward to execute, we advocate for their systematic use in validating the assignments of novel secondary metabolites.

Immobilization of lipase on hydrophobic MOF synthesized simultaneously with oleic acid and application in hydrolysis of natural oils for improving unsaturated fatty acid production

The hydrolysis of natural oils (vegetable oils and fats) by lipase has significant applications in food and medicine. However, free lipases are usually sensitive to temperature, pH and chemical reagents in aqueous solutions, which hinders their widespread industrial application. Excitingly, immobilized lipases have been widely reported to overcome these problems. Herein, inspired by lipase interface activation, a hydrophobic Zr-MOF (UiO-66-NH2-OA) with oleic acid was synthesized for the first time in an emulsion consisting of oleic acid and water, and the Aspergillus oryzae lipase (AOL) was immobilized onto the UiO-66-NH2-OA through hydrophobic interaction and electrostatic interaction to obtain immobilized lipase (AOL/UiO-66-NH2-OA). 1H NMR and FT-IR data indicated that oleic acid was conjugated with the 2-amino-1,4-benzene dicarboxylate (BDC-NH2) by amidation reaction. As a result, the Vmax and Kcat values of AOL/UiO-66-NH2-OA were 179.61 μM﹒min−1 and 8.27 s−1, which were 8.56 and 12.92 times higher than those of the free enzyme, respectively, due to the interfacial activation. After treated at 70 °C for 120 min, the immobilized lipase maintained 52 % of its original activity, but free AOL only retained 15 %. Significantly, the yield of fatty acids by the immobilized lipase reached 98.3 % and still exceeded 82 % after seven times of recycling.

Catalytic activity of Cu-BTC metal organic framework for borrowing hydrogen and tandem reactions of an alcohol under solvent and base free condition

The Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) metal–organic framework was found to be a potential, stable and reusable catalyst for the solvent- and base-free borrowing hydrogen and tandem reactions of an alcohol. The Cu-BTC exhibited borrowing hydrogen activity in N-alkylation of aniline with benzyl alcohol, a model reaction of borrowing hydrogen, giving the saturated product (N-alkylated aniline). However, the formation of unsaturated product (chalcone) in the reaction of acetophenone with benzyl alcohol for α-C-alkylation, another model reaction of borrowing hydrogen, showed potential of Cu-BTC for the catalysis of tandem reactions to synthesize unsaturated products utilizing alcohols as a reagent. The study shows that the Cu-O pair sites of Cu-BTC are involved in the catalysis of borrowing hydrogen and tandem reactions.

Citral Hydrogenation over Dilute Alloy Catalysts

AbstractDilute alloy CuPt and NiPt catalysts are studied in the hydrogenation of citral, a model α,β‐unsaturated aldehyde. In situ and ex situ characterization is used to demonstrate that the Pt species within these nanoparticles are well dispersed and approach a single atom alloy structure. The distribution of Pt varies between the two host metal systems; under a hydrogen environment, the nanoparticle surface and near‐surface region of the NiPt nanoparticles is Pt rich, while the Pt is more uniformly distributed throughout the CuPt nanoparticles. When used for citral hydrogenation reactions, a rate enhancement is observed upon the addition of Pt to the Cu or Ni host catalysts, however this enhancement is determined to be due to the presence of additional metal and not a synergistic effect of the two metals. The Pt structure does, nonetheless, influence the observed selectivity trends. NiPt/SiO2 catalysts have high selectivity to the unsaturated aldehyde citronellal while the CuPt/SiO2 catalysts have increased selectivity to unsaturated alcohol products. This increased selectivity is attributed to a combination of hydrogen dissociation over Pt sites and a decrease in size of Cu ensembles due to the presence of Pt, which favors binding and hydrogenation of C=O rather than C=C bonds.

Post-irradiation degradation of radio-oxidized natural rubber latex films induced by 60Co gamma rays

The present work involves the post-irradiation aging of radio-oxidized natural rubber latex (NRL) films irradiated by 60Co gamma rays. The NRL films underwent the two consecutive processes: irradiation oxidation in air with a dose of 0.1 kGy h−1 (pre-irradiation phase) and radiolysis in argon with a dose of 10 kGy h−1 (post-irradiation phase). The changes of oxygen-containing groups in radio-oxidized NRL films were subsequently analyzed by FTIR (ATR method), XPS, and Raman spectroscopy. Analysis of the EPR spectra of free radicals and macroscope properties (including mechanical and thermodynamic properties) were also carried out. Pre-irradiation of NRL films in air resulted in the rapid formation of various carbonyl and unsaturated carbonyl products related to aliphatic esters, ketones, and carboxylic acids. These were followed by the decomposition of the oxygen-containing functional groups in the post-irradiation phase. In particular, the formation of an enol tautomer of a β-diketone functionality was observed. The increase and decrease of free radicals by EPR analysis were closely related to the crosslinking and degradation of the NRL network structures induced by irradiation. Further analysis indicated that the variations in macroscopic properties of NRL films were attributed to the secondary reactions of free radicals. Mechanistic routes for these irradiation aging processes are proposed and discussed.

Nitro-oleic acid regulates T cell activation through post-translational modification of calcineurin

Nitro-fatty acids (NO2-FAs) are unsaturated fatty acid nitration products that exhibit anti-inflammatory actions in experimental mouse models of autoimmune and allergic diseases. These electrophilic molecules interfere with intracellular signaling pathways by reversible post-translational modification of nucleophilic amino-acid residues. Several regulatory proteins have been identified as targets of NO2-FAs, modifying their activity and promoting gene expression changes that result in anti-inflammatory effects. Herein, we report the effects of nitro-oleic acid (NO2-OA) on pro-inflammatory T cell functions, showing that 9- and 10-NOA, but not their oleic acid precursor, decrease T cell proliferation, expression of activation markers CD25 and CD71 on the plasma membrane, and IL-2, IL-4, and IFN-γ cytokine gene expressions. Moreover, we have found that NO2-OA inhibits the transcriptional activity of nuclear factor of activated T cells (NFAT) and that this inhibition takes place through the regulation of the phosphatase activity of calcineurin (CaN), hindering NFAT dephosphorylation, and nuclear translocation in activated T cells. Finally, using mass spectrometry-based approaches, we have found that NO2-OA nitroalkylates CaNA on four Cys (Cys129, 228, 266, and 372), of which only nitroalkylation on Cys372 was of importance for the regulation of CaN phosphatase activity in cells, disturbing functional CaNA/CaNB heterodimer formation. These results provide evidence for an additional mechanism by which NO2-FAs exert their anti-inflammatory actions, pointing to their potential as therapeutic bioactive lipids for the modulation of harmful T cell-mediated immune responses.

Enhancement production of lipid and unsaturation of fatty acids in Cryptococcus humicola via addition of calcium ion.

Lipids synthesized by oleaginous yeasts are considered to be the best candidates for biodiesel production. Cryptococcus humicola as an oleaginous yeast accumulated lipid in cells. In order to optimize the conditions for lipid production, different carbon and nitrogen sources were used and metals were added into the medium. Ca2+ addition increased the lipid production greatly. Xylose and peptone were optimal carbon source and nitrogen source, respectively for lipid accumulation. Response surface experiment results revealed that the accumulation of lipid could be maximized when the xylose, peptone and Ca2+ concentration was 61g/L, 4.31g/L, 0.67 mmol/L. C16 and C18 fatty acid account for about 91% of the total fatty acids. The most abundant fatty acid was oleic acid (42.68%), followed by palmitic acid (29.7%) and stearic acid (13.87%). The addition of Ca2+ increased the content of unsaturated fatty acids (such as C16:1 and C18:1) and improved the unsaturation of fatty acids. Quantitative real time PCR analysis revealed that expression of genes related to lipid biosynthesis showed up-regulated by Ca2+ treatment. This study provided a strategy for increase in lipid production and content of unsaturated fatty acids.

Maximizing unsaturated fatty acids production by using sugarcane agroindustry wastes in cultivation of Desmodesmus sp. in a flat plate photobioreactor

Microalgae lipid accumulation can be accomplished by different strategies rather than naturally reaching the stationary phase. Many studies employ nitrogen (N) depletion to improve lipid production; however, this approach might not be a suitable alternative when growth in wastewater is attempted. Agro-industry effluents in particular can have high concentrations of N, so nutrient removal is also required. This study evaluated two possibilities of achieving stress conditions in Desmodesmus sp. cultivation: light intensity and CO2 concentration. The culture medium also included liquid and solid residues from the sugarcane agro-industry: vinasse and a biofertilizer produced from bagasse biochar. Optimization of growth in a flat plate photobioreactor was conducted by combining a two-level factorial design and simplex methodology. Both the highest biomass and polyunsaturated fatty acid productivities (150.2 and 21.4 mg L−1 day−1, respectively) were achieved near the central points (5% CO2 in air and 1000 μmol m−2 s−1 light intensity). These results show the possibility of microalgae growth in a sustainable medium coupled with high-value lipid production, e.g., omegas-3, − 6, and − 9.

Efficient rapid fractionation of fatty acid methyl esters (FAMEs) through evaporative urea inclusion

FAMEs work as an alternative to petroleum-based diesel fuels for its low carbon footprint. However, FAMEs' qualities are constrained by the sources' fatty acid profiles. Fractionation of FAMEs can significantly change biodiesel's qualities. Compared to other fractionation methods, evaporative urea inclusion fractionation can rapidly and effectively separate the saturated FAMEs. In addition, FTIR analysis indicated the possible conjugation of host structures by unstable hydrogen bonding and oxygen bonding. Crystallite sizes and strain of urea inclusion compounds (UICs) were calculated from the XRD spectrum, influenced by FAMEs' structures and operation processes. Only the ratios of urea to FAMEs can significantly affect compositions in evaporative urea inclusion fractionation. However, UICs formation rates were influenced by all operation conditions, such as temperatures, pressures, and ratios of urea to FAMEs to solvent. The products were evaluated by the low-temperature performance, cetane number, oxidation stability, energy density, and emissions. Urea inclusion fractionation can significantly improve the low-temperature performance, the major constraint for enlarging the utilization. However, the decreased cetane number and oxidation stability indicated the possible need for antioxidants and cetane improvers after urea inclusion fractionation. Moreover, the unsaturated enriched products from urea inclusion fractionation can provide the feedstock to synthesize biochemical or biomaterials, such as carboxylic acids, polyesters, and biolubricants.