C18 Fatty Acids Research Articles

Catalytic Hydrotreating of Crude Pongamia pinnata Oil to Bio-Hydrogenated Diesel over Sulfided NiMo Catalyst

This work studied the catalytic activity and stability of Ni-MoS2 supported on γ-Al2O3, SiO2, and TiO2 toward deoxygenation of different feedstocks, i.e., crude Pongamia pinnata oil (PPO) and refined palm olein (RPO). PPO was used as a renewable feedstock for bio-hydrogenated diesel production via catalytic hydrotreating under a temperature of 330 °C, H2 pressure of 50 bar, WHSV of 1.5 h−1, and H2/oil (v/v) of 1000 cm3/cm3 under continuous operation. The oil yield from a Soxhlet extraction of PPO was up to 26 wt.% on a dry basis, mainly consisting of C18 fatty acids. The catalytic activity in terms of conversion and diesel yield was in the same trend as increasing in the order of NiMo/γ-Al2O3 > NiMo/TiO2 > NiMo/SiO2. The hydrodeoxygenation (HDO) activity was more favorable over the sulfided NiMo supported on γ-Al2O3 and TiO2, while a high DCO was observed over the sulfided NiMo/SiO2 catalyst, which related to the properties of the support material and the intensity of metal–support interaction. The deactivation of NiMo/SiO2 and NiMo/TiO2 occurred in a short period, due to the phosphorus and alkali impurities in PPO which were not found in the case of RPO. NiMo/γ-Al2O3 exhibited the high resistance of impure feedstock with excellent stability. This indicates that the catalytic performance is influenced by the purity of the feedstock as well as the characteristics of the catalysts.

The Multifaceted Roles of Fungal Cutinases during Infection.

Cuticles cover the aerial epidermis cells of terrestrial plants and thus represent the first line of defence against invading pathogens, which must overcome this hydrophobic barrier to colonise the inner cells of the host plant. The cuticle is largely built from the cutin polymer, which consists of C16 and C18 fatty acids attached to a glycerol backbone that are further modified with terminal and mid-chain hydroxyl, epoxy, and carboxy groups, all cross-linked by ester bonds. To breach the cuticle barrier, pathogenic fungal species employ cutinases—extracellular secreted enzymes with the capacity to hydrolyse the ester linkages between cutin monomers. Herein, we explore the multifaceted roles that fungal cutinases play during the major four stages of infection: (i) spore landing and adhesion to the host plant cuticle; (ii) spore germination on the host plant cuticle; (iii) spore germ tube elongation and the formation of penetrating structures; and (iv) penetration of the host plant cuticle and inner tissue colonisation. Using previous evidence from the literature and a comprehensive molecular phylogenetic tree of cutinases, we discuss the notion whether the lifestyle of a given fungal species can predict the activity nature of its cutinases.

Biohydrogenation Pathway of α-Linolenic Acid in Rumen of Dairy Cow In Vitro.

Simple SummaryFew studies have investigated a relationship between t9,c12,c15-C18:3 and ALA, an α-Linolenic acid c9,c12,c15-C18:3 in the rumen. These results indicated that t9,c12,c15-C18:3 was an intermediate of the α-linolenic acid shifted rumen biohydrogenation pathway. This study hypothesized a pathway for α-linolenic acid biohydrogenation in rumen.The t9,c12,c15-C18:3 as an isomer of α-linolenic acid (c9,c12,c15-C18:3; ALA), has been recently detected in milk, but has not been found in the rumen. This study hypothesized that it may be a biohydrogenation product of ALA in rumen and aimed to explore whether it was present in the rumen and help to understand the rumen biohydrogenation mechanisms of ALA. The in vitro experiment included two treatments, a control check (CK group) with 50 µL ethanol added, and ALA group with 50 µL ethanol and 2.6 mg ALA (ALA addition calculated by 1.30% of dry matter base of diet); each sample of fermentation fluid had the composition of C18 fatty acids analyzed at 0, 0.5, 1, 2, 3, 4, 5, and 6 h. The results showed that no t9,c12,c15-C18:3 was detected in the CK group, but ALA addition increased the concentration of t9,c12,c15-C18:3 in fermentation fluid. The content of t9,c12,c15-C18:3 peaked 1 h after fermentation, then declined gradually. At 1 h, no t9c12c15-C18:3 was detected in the fermentation fluid of the CK treatment. The results suggested that ALA converted to the isomer t9,c12,c15-C18:3 through biohydrogenation in the rumen. The addition of ALA can also increase the concentration of t9,c12-C18:2, c9,t11-C18:2, c12-C18:1, t11-C18:1, t9-C18:1, and c6-C18:1 in fermentation fluid. It was concluded using an in vitro experiment that t9,c12,c15-C18:3 was a product of rumen biohydrogenation of ALA.

Three 4-monosubstituted butyrolactones from a regulatory gene mutant of Streptomyces rochei 7434AN4

Extensive metabolite analysis of Streptomyces rochei 7434AN4 was performed to discover uncharacterized secondary metabolites. A mutant strain of S. rochei, in which two regulatory genes srrC (a tetR-type repressor) and srrY (SARP-type activator) were inactivated, accumulated three 4-monosubstituted γ-butyrolactones YT02-A, YT02-B, and KH01-A, which were not detected in the parent strain. Their structures were identified as 4,10-dihydroxy-10-methyldodecan-4-olide, 4,10-dihydroxy-10-methylundecan-4-olide, and 4-hydroxy-11-oxo-10-methyldodecan-4-olide. A structural comparison indicated that the three butanolides and the signaling molecules, termed S.rochei butenolides (SRBs), could share common C12 or C13 fatty acids for their biosynthesis intermediates, however, these three butanolides did not induce antibiotic production even at 50μM concentration (1000-folds of the minimum antibiotic-inducing concentration of SRBs) in S.rochei.

Molecular and functional characterization of a SCD 1b from European sea bass (Dicentrarchus labrax L.)

Fatty acid desaturation is a highly complex and regulated process involving different molecular and genetic actors. Ultimally, the fatty acid desaturase enzymes are responsible for the introduction of double bonds at different positions of specific substrates, resulting in a wide variety of mono- and poly-unsaturated fatty acids. This substrate-specificity makes it possible to meet all the functional needs of the different tissues against a wide variety of internal and external conditions, giving rise to a varied profile of expression and functionality of the different desaturases in the body. Being our main interest to study and characterize at the molecular level the fatty acid desaturation process in fishes, we have focused our effort on characterizing SCD 1b from European sea bass (Dicentrarchus labrax, L.). In this work, we have characterized a tearoyl-CoA Desaturase cDNA that codes a protein of 334 amino acids, which shares the greatest homology to marine fish SCD 1b. Northern blot analysis showed two transcripts of 3.5kb and 1.4kb. Two putative cis-acting conserved motifs are localized in the cDNA 5'-end: a polypyrimidine CT dinucleotide repeat tract and two non-palindromic putative NRL-response elements (NREs). The deduced protein presents two Δ9 FADs like domain, three His-rich motifs, a total of nine His residues acting as di‑iron coordination ligands. The SCD 1b 3D protein modelling shows a structure made up primarily of α-helices, four of which could be transmembrane helices. The catalytic region is oriented to the cytosolic side of the Endoplasmic Reticulum membrane, where the 9-histidine residues are arranged coordinated to two non-heme Fe2+ ions. A new His-containing motif NX3H-like includes an Asn residue that participates in the coordination of Fe2+1 through a water molecule. The protein has a large pocket with a large opening to the outside. It includes a tunnel in which the substrate-binding site is located. The external shape is reminiscent of a boathook. It shows group specificity, although a greater preference for 18C substrates. The length of the tunnel, delimited by seven amino acids that forms a pocket at the end of the tunnel, the possibility that the substrates adopt different conformations inside the tunnel as well as and the movement of acyl chain inside the tunnel, could explain the high preference for 18C fatty acids and the group specificity of the enzyme. The cDNA encodes a functional SCD enzyme, whose subcellular localization is the Endoplasmic Reticulum, which complements the ole1Δ gene-disrupted gene in DTY-11A Saccharomyces cerevisiae strain and produces an increment of palmitoleic and oleic acids. The scd 1b gene is expressed in all tested tissues, showing the liver and adipose tissue a higher level of expression against the brain, heart, gonad and intestine. Scd 1b expression was always bigger than those of the Δ6 fad gene, being especially significant in adipose tissue and liver. From our data, we conclude that, in contrast to the functional significance of SCD 1b in adipose tissue, liver and heart, Δ6 FAD seems to play a more determining role in the biosynthesis of unsaturated fatty acids in the intestine, brain and gonad in fish.

Extraction of astaxanthin from Haematococcus pluvialis with hydrophobic deep eutectic solvents based on oleic acid

Three novel hydrophobic deep eutectic solvents (DESs) based on oleic acid and terpenes (thymol, dl-menthol, and geraniol) were prepared, characterized, and used to extract astaxanthin from the microalga Haematococcus pluvialis without any pre-treatment of the cells. The three DES were composed of Generally Recognized As Safe (GRAS) and edible ingredients. All the tested DESs gave astaxanthin recovery values of about 60 and 30% in 6 h if applied on freeze-dried biomass or directly on algae culture, respectively. The carotenoid profile was qualitatively identical to what was obtained by using traditional organic solvents, regardless of the DES used; the monoesters of astaxanthin with C18-fatty acids were the main compounds found in all the carotenoid extracts. The thymol:oleic acid DES (TAO) could preserve astaxanthin content after prolonged oxidative stress (40% of the astaxanthin initially extracted was still present after 13.5 h of light exposure), thanks to the superior antioxidant properties of thymol. The capacity of improving astaxanthin stability combined with the intrinsic safety and edibility of the DES components makes the formulation astaxanthin-TAO appealing for the food ingredients/additives industry.

Physiological Response of an Oil-Producing Microalgal Strain to Salinity and Light Stress.

By separating and extracting algae from the collected water samples, an oil-producing diatom strain was obtained. Microscopic observation of the strain revealed that its morphological characteristics were highly similar to those of the genus Cyclotella. The cloning of 18S rDNA and phylogenetic analysis showed that the algae were clustered with Cyclotella menegheniana with a high support rate, indicating that the alga was C. menegheniana. The fatty acid content of the alga was determined and found to be mainly C14, C16, and C18 fatty acids, which were in accordance with the relevant standards for edible oil. In this study, different gradient levels of salinity and light were set to investigate the culture and bioactive substance production of C. menegheniana. The results showed that the best growth condition was achieved when the salinity was 15 g·L−1, and its biomass and oil content were the highest at 0.27 g·L−1 and 21%, respectively. The final biomass was the highest when the light intensity was 2000 Lux and the oil content was 18.7%. The results of the study provided a basis for the large-scale production of edible oils and biodiesel.

Ribosomally derived lipopeptides containing distinct fatty acyl moieties

Lipopeptides represent a large group of microbial natural products that include important antibacterial and antifungal drugs and some of the most-powerful known biosurfactants. The vast majority of lipopeptides comprise cyclic peptide backbones N-terminally equipped with various fatty acyl moieties. The known compounds of this type are biosynthesized by nonribosomal peptide synthetases, giant enzyme complexes that assemble their products in a non-gene-encoded manner. Here, we report the genome-guided discovery of ribosomally derived, fatty-acylated lipopeptides, termed selidamides. Heterologous reconstitution of three pathways, two from cyanobacteria and one from an arctic, ocean-derived alphaproteobacterium, allowed structural characterization of the probable natural products and suggest that selidamides are widespread over various bacterial phyla. The identified representatives feature cyclic peptide moieties and fatty acyl units attached to (hydroxy)ornithine or lysine side chains by maturases of the GCN5-related N-acetyltransferase superfamily. In contrast to nonribosomal lipopeptides that are usually produced as congener mixtures, the three selidamides are selectively fatty acylated with C10, C12, or C16 fatty acids, respectively. These results highlight the ability of ribosomal pathways to emulate products with diverse, nonribosomal-like features and add to the biocatalytic toolbox for peptide drug improvement and targeted discovery.

Production of 11R‐hydroxyeicosatetraenoic acid from arachidonic acid by Escherichia coli cells expressing arachidonate 11R‐lipoxygenase from Nostoc sp.

AbstractLinoleate 9R‐lipoxygenase (9R‐LOX) from Nostoc sp. SAG 25.82 was identified as arachidonate (ARA) 11R‐LOX by the determination of the product obtained from the conversion of ARA. The specific activity and catalytic efficiency (kcat/Km) of the enzyme for C20 and C22 polyunsaturated fatty acids followed the order ARA > eicosapentaenoic acid > docosahexaenoic acid. The production of the lipid mediator 11R‐hydroxyeicosatetraenoic acid (11R‐HETE) was performed using Escherichia coli cells expressing ARA 11R‐LOX from Nostoc sp. The reaction conditions, such as pH, temperature, solvent and its concentration, and substrate and cell concentrations, were optimized using the recombinant cells, and the optimal conditions for the production of 11R‐HETE from ARA were pH 7.0, 25°C, 10 g L−1 cells, 5.0 mM ARA, 4% (v/v) ethanol, and 10 mM cysteine as a reducing agent. Under these optimized conditions, E. coli cells expressing 11R‐LOX converted 5.0 mM ARA into 4.74 mM 11R‐HETE in 60 min, with a molar conversion yield of 95% a volumetric productivity of 79 μM min−1 and a specific productivity of 7.9 μM min−1 g−1. To the best of our knowledge, this is the first report on the quantitative biotechnological production of 11R‐HETE.

Regioselectivity of an arachidonate 9S-lipoxygenase from Sphingopyxis macrogoltabida that biosynthesizes 9S,15S- and 11S,17S-dihydroxy fatty acids from C20 and C22 polyunsaturated fatty acids

Lipoxygenases (LOXs) biosynthesize lipid mediators (LMs) as human signaling molecules. Among LMs, specialized pro-resolving mediators (SPMs) are involved in the resolution of inflammation and infection in humans. Here, the putative LOX from the bacterium Sphingopyxis macrogoltabida was identified as arachidonate 9S-LOX. The enzyme catalyzed oxygenation at the n-12 position of C20 and C22 polyunsaturated fatty acids (PUFAs) to form 9S- and 11S-hydroperoxy fatty acids, which were reduced to 9S- and 11S-hydroxy fatty acids (HFAs) by cysteine, respectively, and it catalyzed again oxygenation at the n-6 position of HFAs to form 9S,15S- and 11S,17S-DiHFAs, respectively. The regioselective residues of 9S-LOX were determined as lle395 and Val569 based on the amino acid alignment and homology models. The regioselectivity of the I395F variant was changed from the n-12 position on C20 PUFA to the n-6 position to form 15S-HFAs. This may be due to the reduction of the substrate-binding pocket by replacing the smaller Ile with a larger Phe. The V569W variant had a significantly lower second‑oxygenating activity compared to wild-type 9S-LOX because the insertion of the hydroxyl group of the first‑oxygenating products at the active site was seemed to be hindered by substituting a larger Trp for a smaller Val. The compounds, 11S-hydroxydocosapentaenoic acid, 9S,15S-dihydroxyeicosatetraenoic acid, 9S,15S-dihydroxyeicosapentaenoic acid, 11S,17S-hydroxydocosapentaenoic acid, and 11S,17S-dihydroxydocosahexaenoic acid, were newly identified by polarimeter, LC-MS/MS, and NMR. 11S,17S-DiHFAs as SPM isomers biosynthesized from C22 PUFAs showed anti-inflammatory activities in mouse and human cells. Our study contributes may stimulate physiological studies by providing new LMs.

PUFA synthase-independent DHA synthesis pathway in Parietichytrium sp. and its modification to produce EPA and n-3DPA

The demand for n-3 long-chain polyunsaturated fatty acids (n-3LC-PUFAs), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), will exceed their supply in the near future, and a sustainable source of n-3LC-PUFAs is needed. Thraustochytrids are marine protists characterized by anaerobic biosynthesis of DHA via polyunsaturated fatty acid synthase (PUFA-S). Analysis of a homemade draft genome database suggested that Parietichytrium sp. lacks PUFA-S but possesses all fatty acid elongase (ELO) and desaturase (DES) genes required for DHA synthesis. The reverse genetic approach and a tracing experiment using stable isotope-labeled fatty acids revealed that the ELO/DES pathway is the only DHA synthesis pathway in Parietichytrium sp. Disruption of the C20 fatty acid ELO (C20ELO) and ∆4 fatty acid DES (∆4DES) genes with expression of ω3 fatty acid DES in this thraustochytrid allowed the production of EPA and n-3docosapentaenoic acid (n-3DPA), respectively, at the highest level among known microbial sources using fed-batch culture.

Freeze-dried Nannochloropsis oceanica biomass protects eicosapentaenoic acid (EPA) from metabolization in the rumen of lambs

Eicosapentaenoic acid (EPA) from freeze-dried biomass of Nannochloropsis oceanica microalgae resists ruminal biohydrogenation in vitro, but in vivo demonstration is needed. Therefore, the present study was designed to test the rumen protective effects of N. oceanica in lambs. Twenty-eight lambs were assigned to one of four diets: Control (C); and C diets supplemented with: 1.2% Nannochloropsis sp. oil (O); 12.3% spray-dried N. oceanica (SD); or 9.2% N. oceanica (FD), to achieve 3 g EPA /kg dry matter. Lambs were slaughtered after 3 weeks and digestive contents and ruminal wall samples were collected. EPA concentration in the rumen of lambs fed FD was about 50% higher than lambs fed SD or O diets. Nevertheless, the high levels of EPA in cecum and faeces of animals fed N. oceanica biomass, independently of the drying method, suggests that EPA was not completely released and absorbed in the small intestine. Furthermore, supplementation with EPA sources also affected the ruminal biohydrogenation of C18 fatty acids, mitigating the shift from the t10 biohydrogenation pathways to the t11 pathways compared to the Control diet. Overall, our results demonstrate that FD N. oceanica biomass is a natural rumen-protected source of EPA to ruminants.

Insights into lipid accumulation features of Coccomyxa sp. IITRSTKM4 under nutrient limitation regimes

Microalgal lipids are deemed to be the most promising alternative to petroleum fuels, enduring the pressure of fuel scarcity. Screening oleaginous microalgae from natural habitats are imperative, as novel strains producing enhanced biofuel components can make them economically viable. The present investigation involves the isolation and characterization of a novel microalga Coccomyxa sp. IITRSTKM4, under nitrogen (N)-, phosphorus (P)-, and sulfur (S)- limitation The reduction in biomass and chlorophyll content of nutrient-starved cells was compensated with stable PSII efficiency and enhanced cellular lipid content. The maximum lipid content ( ∼ 41 %) and lipid productivity (22 ± 2.2 mg/L/d) were achieved under N-deficiency and synergistic NPS-limitation, respectively. However, S-deficient cells resulted in increased carbohydrate content ( ∼ 33%). Further, analysis of biochemical components suggested that protein pools were diverted towards the synthesis of storage molecules (lipid/carbohydrate), aiding cell survival under nutrient starvation. FAME profiling of obtained lipid indicated that it majorly contains C16–C18 fatty acids. The estimated biodiesel quality index parameters have complied with the American (ASTM D6751) and European (EN 14214) standards, thus establishing Coccomyxa sp. IITRSTKM4 a suitable candidate for biodiesel production. Moreover, the production of lipid and carbohydrate under N- and S-deficiency evidences the versatility of the strain for producing biofuels. • Novel oleaginous microalgal strain isolated from water of Ganga Ghat, Haridwar. • Lipid accumulation under different nutrient regimes was investigated. • N/P deficiency improved lipid, whereas S-deficiency increased carbohydrate content. • Maximum lipid productivity was achieved in synergistic N/P/S-limitation. • Biodiesel properties complied with international fuel standards.

Preliminary evaluation of the green microalga Dunaliella salina as a potential feedstock for biodiesel: effect of molasses on growth and lipid profile

This research aims to evaluate the effect of molasses as a source of organic carbon on the growth and lipid profile of Dunaliella salina cultivated under different light regimes to determine its strategy and potential use to produce biodiesel. Two sources of nutrients (F/2 medium, F/2; molasses, M) and two light conditions (12 h light: 12 h darkness, 12L:12D) conformed four treatments (F/2 12L:12D, F/2 D, M 12L:12D, and MD) that were investigated with three replicates each. The concentration of microalgae produced by the groups under light conditions was more than double that of those grown in darkness. The highest biomass produced (46.91 ± 6.47 g L -1 ) was obtained in the F/2 medium with 12L:12D treatment, while the lowest (18.99 ± 0.78 g L -1 ) was in the M 12L:12D group. Regardless of the culture conditions, the lipids were mainly composed of the C16:0 and C18 fatty acids. The use of molasses as a culture medium produced the highest amount of C18:1, regardless of the light regime. Molasses promoted the highest production of fatty acids methyl esters. Depending on the culture medium, D. salina cells showed different percentages of saturated (SFA), monounsaturated (MFA), and polyunsaturated (PUFA) fatty acids. The highest amount of saturated fatty acids was obtained in F/2 12L:12D. The highest amount of polyunsaturated fatty acids was presented in the mixotrophic culture (molasses and light). The cultures grown with molasses were rich in monounsaturated fatty acids. An inexpensive industrial by-product, Cane molasses could be a low-cost feedstock for biodiesel in cultivating D. salina .

Comparative Assessment of Cooking Emission Contributions to Urban Organic Aerosol Using Online Molecular Tracers and Aerosol Mass Spectrometry Measurements

Cooking organic aerosol (COA) is an important source of particulate pollutants in urbanized regions. Yet, the diversity and complexity of COA components make direct identification and quantification of COA difficult. In this study, we conducted collocated OA measurements with an aerosol mass spectrometer (AMS) and a thermal desorption aerosol gas chromatography-mass spectrometer (TAG) in Shanghai. Cooking molecular tracers (e.g., C18 fatty acids, azelaic acid) measured by TAG provide unambiguous source information for evaluating the tracer ion (C6H10O+, m/z 98) used for identification and apportionment of COA in AMS analysis. Based on the collocated AMS and TAG measurements, two COA factors, namely, a primary COA (PCOA) and an oxygenated COA (OCOA) produced from rapid oxygenation of freshly emitted PCOA, were identified. Criteria for identifying COA factors from AMS analysis with different oxygenation levels are proposed, i.e., characteristic mass spectra, temporal variations, etc. Furthermore, two positive matrix factorization approaches, namely, AMS-PMF and the molecular marker (MM)-PMF, were compared for COA quantification, where high consistency was found with the contribution of COA to total PM2.5 mass estimated to be 9 ± 7% by AMS-PMF and 6 ± 5% by the MM-PMF. Our study highlights the important impacts of cooking activities on air quality in urban areas. We also demonstrate the advantage of conducting collocated measurements using multiple high time resolution mass spectrometric techniques in advancing our understanding of atmospheric OA chemistry and improving the accuracy of source apportionment.

Aerial microalgae Coccomyxa simplex isolated from a low-temperature, low-light environment, and its biofilm growth and lipid accumulation

Biofuels produced from renewable resources could be an effective and sustainable alternative to fossil fuels. However, biodiesel production from microalgae is slow during cold periods, which are unfavorable for the growth of conventional microalgae, especially in outdoor mass cultivation. We screened and isolated aerial microalgae that are able to grow at lower temperatures and light intensity than conventional algae. Seven aerial microalgae were isolated from the surface of rocks in a mountainous district in Japan. These microalgae were identified as Coccomyxa simplex (KGU-H002–008 strains), class Trebouxiophyceae, based on 18S rRNA gene analysis. These algal strains were cultured at 15 °C and 15 μmol photons m−2 s−1 until nitrogen was depleted in the liquid culture medium. Their biomass reached 0.7–1.5 g (dry cell weight) per L culture medium. The fatty acid contents of KGU-H002, -H004, and -H005 were approximately 150 mg g−1 dry cell weight (dcw), and these strains produced abundant C16 and C18 fatty acids. We prepared biofilms of C. simplex KGU-H002, -H004, and -H005, and examined their biomass and fatty acid accumulation in the aerial phase at 15 or 25 °C under low light intensity. Under both temperature conditions, the three strains showed a similar increase (~2.2-fold) in biomass. In KGU-H002 and -H004, the fatty acid content was higher at 15 °C than at 25 °C. These results indicate that aerial cultures of C. simplex KGU-H002 and -H004 have potential applications in biodiesel production under low temperature and low light intensity.

Comparative Response of Marine Microalgae to H2O2-Induced Oxidative Stress.

There have been growing interests in the biorefining of bioactive compounds from marine microalgae, including pigments, omega-3 fatty acids or antioxidants for use in the nutraceutical and cosmetic sectors. This study focused on the comparative responses of five marine microalgal species from different lineages, including the dinoflagellate Amphidinium carterae, chlorophyte Brachiomonas submarina, diatom Stauroneis sp., haptophyte Diacronema sp. and rhodophyte Rhodella violacea, to exposure during their batch growth to hydrogen peroxide (H2O2). A. carterae returned an enhanced signal with the DPPH assay (8.8µmol Trolox eq/g DW) when exposed to H2O2, which was associated with reduced pigment yields and increased proportions in saturated C16 and C18 fatty acids. B. submarina showed enhanced antioxidant response upon exposure to H2O2 with the DPPH assay (10µmol Trolox eq/g DW), a threefold decrease in lutein (from 2.3 to 0.8mg/g) but a twofold increase in chlorophyll b (up to 30.0mg/g). Stauroneis sp. showed a downward response for the antioxidant assays, but its pigment yields did not vary significantly from the control. Diacronema sp. showed reduced antioxidant response and fucoxanthin content (from 4.0 to 0.2mg/g) when exposed to 0.5mM H2O2. R. violacea exposed to H2O2 returned enhanced antioxidant activity and proportions of EPA but was not significantly impacted in terms of pigment content. Results indicate that H2O2 can be used to induce stress and initiate metabolic changes in microalgae. The responses were however species-specific, which would require further dosage optimisation to modulate the yields of specific metabolites in individual species.

A Novel Lipase from Lasiodiplodia theobromae Efficiently Hydrolyses C8-C10 Methyl Esters for the Preparation of Medium-Chain Triglycerides' Precursors.

Medium-chain triglycerides (MCTs) are an emerging choice to treat neurodegenerative disorders such as Alzheimer’s disease. They are triesters of glycerol and three medium-chain fatty acids, such as capric (C8) and caprylic (C10) acids. The availability of C8–C10 methyl esters (C8–C10 ME) from vegetable oil processes has presented an opportunity to use methyl esters as raw materials for the synthesis of MCTs. However, there are few reports on enzymes that can efficiently hydrolyse C8–C10 ME to industrial specifications. Here, we report the discovery and identification of a novel lipase from Lasiodiplodia theobromae fungus (LTL1), which hydrolyses C8–C10 ME efficiently. LTL1 can perform hydrolysis over pH ranges from 3.0 to 9.0 and maintain thermotolerance up to 70 °C. It has high selectivity for monoesters over triesters and displays higher activity over commercially available lipases for C8–C10 ME to achieve 96.17% hydrolysis within 31 h. Structural analysis by protein X-ray crystallography revealed LTL1’s well-conserved lipase core domain, together with a partially resolved N-terminal subdomain and an inserted loop, which may suggest its hydrolytic preference for monoesters. In conclusion, our results suggest that LTL1 provides a tractable route towards to production of C8–C10 fatty acids from methyl esters for the synthesis of MCTs.

Complexation ability and physicochemical properties of starch inclusion complexes with C18 fatty acids

Starch, especially its amylose component, is well-known to form inclusion complexes with a variety of small molecules such as fatty acids. The structure of the lipid guest could affect its complexation ability and other properties such as thermal stability. The present study aimed to investigate the complexation ability and the physicochemical properties of high amylose maize starch (HAMS) inclusion complexes with C18 fatty acids of various numbers and positions of double bonds, including octadecanoic (stearic, SA), (Z)-octadec-9-enoic (oleic, OA), (E)-octadec-9-enoic (elaidic, EA), (9Z,12Z)-octadeca-9,12-dienoic (linoleic, LA), (9Z,12Z,15Z)-octadeca-9,12,15-trienoic (α-linolenic, ALA), and conjugated linoleic acids (CLA). Two complexation methods were used, which are the DMSO method and the “empty” V-type method. The formation, structural characteristics, and thermal properties of inclusion complexes formed were examined by complementary techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. As the guest fatty acid became more unsaturated and as the number of double bonds increased, the dissociation temperatures of HAMS-fatty acid inclusion complexes formed decreased with either complexation method. The DMSO method resulted in the formation of Form I inclusion complexes only, whereas the “empty” V-type method promoted the formation of Form II inclusion complexes with higher thermal stability. In addition, ethanol concentration was found to influence the formation of inclusion complexes when using the “empty” V-type method, and intermediate concentrations were more favorable to maintain a stable and flexible amylose helical structure to form inclusion complexes with higher crystallinity and thermal stability.

Effects of fish oil on growth kinetics and lipid accumulation in black soldier fly larvae

The main purpose of this study is to characterise how substrate lipid content affects growth kinetics of black soldier fly (BSF) larvae. Growth curves of larvae were characterised in substrates composed of chicken feed supplemented by 0-30% fish oil, and lipid content and fatty acid composition of the prepupae were quantified to examine up-take and assimilation of fish oil by the larvae. Increasing contents of fish oil resulted in reduced specific growth rates, reduced weight of the prepupae, and increased mortality. The prepupae had similar lipid contents at 0-20% fish oil, while 30% fish oil increased the lipid content of prepupae. In contrast, the fatty acid composition of the prepupae showed a strong dependency on substrate fish oil content, indicating that the larvae increased their uptake of fish oil with increasing fish oil content. C16-C22 fatty acids were bioaccumulated from the fish oil, but particularly C20 and C22 fatty acids were apparently also shortened or further metabolised. Microbial fermentation products rapidly accumulated in the substrates, and substrate lipids and carbohydrates were preserved and remained available for the larvae throughout their growth period. These results point out that although BSF larvae can utilise high contents of substrate lipids, it may be at the expense of reduced growth performance, and with limited effects on the composition of their biomass.