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Escherichia coli is a common host for biotechnology and synthetic biology applications. During growth and fermentation, the microbes are often exposed to stress conditions, such as variations in pH or solvent concentrations. Bacterial membranes play a key role in response to abiotic stresses. Ornithine lipids (OLs) are a group of membrane lipids whose presence and synthesis have been related to stress resistance in bacteria. We wondered if this stress resistance could be transferred to bacteria not encoding the capacity to form OLs in their genome, such as E. coli. In this study, we engineered different E. coli strains to produce unmodified OLs and hydroxylated OLs by expressing the synthetic operon olsFC. Our results showed that OL formation improved pH resistance and increased biomass under phosphate limitation. Transcriptome analysis revealed that OL-forming strains differentially expressed stress- and membrane-related genes. OL-producing strains also showed better growth in the presence of the ionophore carbonyl cyanide 3-chlorophenylhydrazone (CCCP), suggesting reduced proton leakiness in OL-producing strains. Furthermore, our engineered strains showed improved heterologous violacein production at phosphate limitation and also at low pH. Overall, this study demonstrates the potential of engineering the E. coli membrane composition for constructing robust hosts with an increased abiotic stress resistance for biotechnology and synthetic biology applications. Key points: • Ornithine lipid production in E. coli increases biomass yield under phosphate limitation. • Engineered strains show an enhanced production phenotype under low pH stress. • Transcriptome analysis and CCCP experiments revealed reduced proton leakage. [ABSTRACT FROM AUTHOR]

As the problem of antimicrobial resistance is constantly increasing, there is a renewed interest in antimicrobial products derived from natural sources, particularly obtained from innovative and eco-friendly materials. Insect lipids, due to their fatty acid composition, can be classified as natural antimicrobial compounds. In order to assess the antibacterial efficacy of Hermetia illucens lipids, we extracted this component from the larval stage, fed on different substrates and we characterized it. Moreover, we analyzed the fatty acid composition of the feeding substrate, to determine if and how it could affect the antimicrobial activity of the lipid component. The antimicrobial activity was evaluated against Gram-positive Micrococcus flavus and Gram-negative bacteria Escherichia coli. Analyzing the fatty acid profiles of larval lipids that showed activity against the two bacterial strains, we detected significant differences for C4:0, C10:0, C16:1, C18:3 n3 (ALA), and C20:1. The strongest antimicrobial activity was verified against Micrococcus flavus by lipids extracted from larvae reared on strawberry, tangerine, and fresh manure substrates, with growth inhibition zones ranged from 1.38 to 1.51 mm, while only the rearing on manure showed the effect against Escherichia coli. Notably, the fatty acid profile of H. illucens seems to not be really influenced by the substrate fatty acid profile, except for C18:0 and C18:2 CIS n6 (LA). This implies that other factors, such as the rearing conditions, larval development stages, and other nutrients such as carbohydrates, affect the amount of fatty acids in insects. Key points: • Feeding substrates influence larval lipids and fatty acids (FA) • Generally, there is no direct correlation between substrate FAs and the same larvae FAs • Specific FAs influence more the antimicrobial effect of BSF lipids [ABSTRACT FROM AUTHOR]

Carotenoids are natural lipophilic pigments, which have been proven to provide significant health benefits to humans, relying on their capacity to efficiently scavenge singlet oxygen and peroxyl radicals as antioxidants. Strains belonging to the genus Rhodosporidium represent a heterogeneous group known for a number of phenotypic traits including accumulation of carotenoids and lipids and tolerance to heavy metals and oxidative stress. As a representative of these yeasts, Rhodosporidium toruloides naturally produces carotenoids with high antioxidant activity and grows on a wide variety of carbon sources. As a result, R. toruloides is a promising host for the efficient production of more value-added lipophilic compound carotenoids, e.g., torulene and torularhodin. This review provides a comprehensive summary of the research progress on carotenoid biosynthesis in R. toruloides, focusing on the understanding of biosynthetic pathways and the regulation of key enzymes and genes involved in the process. Moreover, the relationship between the accumulation of carotenoids and lipid biosynthesis, as well as the stress from diverse abiotic factors, has also been discussed for the first time. Finally, several feasible strategies have been proposed to promote carotenoid production by R. toruloides. It is possible that R. toruloides may become a critical strain in the production of carotenoids or high-value terpenoids by genetic technologies and optimal fermentation processes. Key points: • Biosynthetic pathway and its regulation of carotenoids in Rhodosporidium toruloides were concluded • Stimulation of abiotic factors for carotenoid biosynthesis in R. toruloides was summarized • Feasible strategies for increasing carotenoid production by R. toruloides were proposed [ABSTRACT FROM AUTHOR]

Insect cuticular lipids, especially epicuticular hydrocarbons (CHC), have a significant role in insect ecology and interactions with other organisms, including fungi. The CHC composition of a specific insect species may influence the outcome of the interaction with a specific fungal strain. Some insects, such as Piezodorus guildinii, have low susceptibility towards fungal infections seemingly due to their CHC composition. The entomopathogenic fungus Beauveria bassiana can assimilate CHC and incorporate them as building blocks via cytochrome P450 monooxygenases (CYPs). However, little is known about other enzymes that promote the degradation/assimilation of these cuticular components. In this study, we performed a transcriptomic analysis to evaluate the in vitro response of two virulence-contrasting B. bassiana strains when grown on three different P. guildinii CHC sources. We found a different expression profile of virulence-related genes, as well as different GO and KEGG parameters enriched at 4 days post-inoculation, which could help account for the intrinsic virulence and for an alkane-priming virulence enhancement effect. The hypovirulent strain predominantly showed higher expression of cuticle penetration genes, including chitinases, proteases, and CYPs, with GO term categories of "heme binding," "monooxygenase activity," and "peroxisome" pathways enriched. The hypervirulent strain showed higher expression of cell wall remodeling and cell cycle genes, and cuticle adhesion and a distinct set of CYPs, with GO categories of "DNA-binding transcription factor activity" and KEGG pathways corresponding to "meiosis-yeast" and "cell cycle" enriched. These results suggest a delay and alternate routes in pathogenicity-related metabolism in the hypovirulent strain in comparison with the hypervirulent strain. Key points: •Transcriptomics of two B. bassiana strains grown in P. guildinii cuticular components •Virulence-related genes correlated with virulence enhancement towards P. guildinii •Differentially expressed genes, GOs and KEGGs showed different metabolic timelines associated with virulence [ABSTRACT FROM AUTHOR]

The study focuses on the simultaneous improvement of biomass, lipid, and docosahexaenoic acid (DHA) productivities in a single reactor using modulator control strategies. The efficacy of three different biochemical modulators, sesamol (Ses), 6-benzylaminopurine (6-BAP), and ethylenediaminetetraacetic acid (EDTA), as potential stimulants in augmenting the biomass, lipid, and DHA production of Schizochytrium sp. MTCC 5890 was elucidated. After 48 h of cultivation, among tested modulators, the individual supplementation of 6-BAP and Ses showed improvement in biomass, lipid, and DHA accumulation by 28.2%, 56.1%, and 87.2% and 21.7%, 47.9%, and 91%, respectively, over the non-supplemented group. In addition, the cooperative effect of selected concentrations, i.e., 10 mgL−1 6-BAP and 200 mgL−1 Ses, further increased the productivities of biomass of 13.5 gL−1d−1 ± 0.66, lipid of 7.4 gL−1d−1 ± 0.69, and DHA of 3.2 gL−1d−1 ± 1.09 representing 8%, 39%, and 69% increase over the individual addition of 6-BAP or Ses, respectively, in batch culture. Supplementation with 6-BAP + Ses at 12 h of time point eventually increased the lipid yield to 15.6 ± 0.42 gL−1 from 7.88 ± 0.31 gL−1 (control) and DHA yield to 6.4 ± 0.11 gL−1 from 2.23 ± 0.09 gL−1 (control), respectively. Furthermore, the process was optimized in continuous culture supplemented with 6-BAP + Ses for enhanced productivities. Continuous culture resulted in maximum biomass (2.04 ± 1.12 gL−1 day−1), lipid (1.0 ± 0.73 gL−1 day−1), and DHA (0.386 ± 0.22 gL−1 day−1) productivities, which were higher as compared with the batch and fed-batch processes by 26 ± 1.21%, 22 ± 1.01%, and 21 ± 0.98% and 24 ± 0.45%, 16 ± 0.38%, and 14 ± 0.12%, respectively. This work represents the potential application of the combined effect of modulators for the simultaneous enhancement of biomass production and lipid and DHA productivities. Key points: • The cumulative study of 6-BAP and sesamol proved to be more efficient in the simultaneous production of biomass, lipid, and DHA in a single reactor. • Addition of a combination of 6-BAP + Ses remarkably increased the biomass, lipid, and DHA productivities in tandem in continuous culture. [ABSTRACT FROM AUTHOR]

The biosynthesis and secretion of Monascus pigments are closely related to the integrity of the cell membrane, which determines the composition of lipids and its content in cell membrane. The present study aimed to thoroughly describe the changes of lipid profiling in Monascus purpureus BWY-5, which was screened by carbon ion beam irradiation (12C6+) to almost single yield extracellular Monascus yellow pigments (extra-MYPs), by absolute quantitative lipidomics and tandem mass tags (TMT) based quantitative proteomic. 12C6+ irradiation caused non-lipid oxidation damage to Monascus cell membrane, leading to an imbalance in cell membrane lipid homeostasis. This imbalance was attributed to significant changes not only in the composition but also in the content of lipids in Monascus, especially the inhibition of glycerophospholipid biosynthesis. Integrity of plasma membrane was maintained by the increased production of ergosterol, monogalactosylmonoacylglycerol (MGMG) and sulfoquinovosylmonoacylglycerol (SQMG), while mitochondrial membrane homeostasis was maintained by the increase of cardiolipin production. The growth and extra-MYPs production of Monascus BWY-5 have been regulated by the promotion of sphingolipids (ceramide and sulfatide) biosynthesis. Simultaneous, energy homeostasis may be achieved by increase of TG synthesis and Ca2+/Mg2+-ATPase activity. These finding suggest ergosterol, cardiolipin, sphingolipids, MGMG and SQMG play a key facilitating role in cytomembrane lipid homeostasis maintaining for Monascus purpureus BWY-5, and then it is closely related to cell growth and extra-MYPs production. Key points: 1. Energy homeostasis in Monascus purpureus BWY-5 was achieved by increase of TG synthesis and Ca2+/Mg2+-ATPase activity. 2. Integrity of plasma membrane in Monascus purpureus BWY-5 was maintained by the increased production of ergosterol. 3. Mitochondrial membrane homeostasis in Monascus purpureus BWY-5 was maintaed by the increase of cardiolipin synthesis. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMW) is a zero-cost substrate for numerous value-added compounds. Although several studies on the production of lipids and carotenoids by Rhodotorula glutinis in OMW exist, none of them has specifically focused on the conditions for a target lipid or carotenoid. This study presents cultivation conditions that selectively stimulate the cell biomass, individual carotenoids and lipids. It was found that supplemental carbon and nitrogen sources as well as illumination affected cell biomass the most. High temperature, low initial pH, illumination, lack of urea and presence of glycerol stimulated the lipid synthesis. The highest total lipid content obtained in undiluted OMW supplemented with urea was 11.08 ± 0.17% (w/w) whilst it was 41.40 ± 0.21% (w/w) when supplemented with glycerol. Moreover, the main fatty acid produced by R. glutinis in all media was oleic acid, whose fraction reached 63.94 ± 0.58%. Total carotenoid yield was significantly increased with low initial pH, high temperature, illumination, certain amounts of urea, glycerol and cultivation time. Up to 192.09 ± 0.16 μg/g cell carotenoid yield was achieved. Torularhodin could be selectively produced at high pH, low temperature and with urea and glycerol supplementation. To selectively induce torulene synthesis, cultivation conditions should have low pH, high temperature and illumination. In addition, low pH, high temperature and urea supplementation served high production of β-carotene. Up to 85.40 ± 0.76, 80.67 ± 1.40 and 39.45 ± 0.69% of torulene, torularhodin and β-carotene, respectively, were obtained under selected conditions. Key points: • Cultivation conditions selectively induced target carotenoids and lipids • 41.40 ± 0.21% (w/w) lipid content and 192.09 ± 0.16 μg/g cell carotenoid yield were achieved • Markedly high selectivity values for torularhodin and torulene were achieved [ABSTRACT FROM AUTHOR]

Enhancing the lipid production of oleaginous yeasts is conducive to cutting the cost of feedstock for biodiesel. To increase the lipid productivity of Rhodotorula sp. U13N3, genes involving lipid degradation were knocked out and fermentation conditions were investigated. Results of transcription analysis demonstrated that genes encoding the ATG15-like lipase (ATG15) and peroxisomal acyl-CoA oxidase (ACOX2) were upregulated significantly at the lipogenesis stage. When ATG15 and ACOX2 were knocked out separately from the genome by the CRISPR/Cas9 method, both ΔATG15 and ΔACOX2 mutants showed better lipid production ability than the parent strain. Flow cytometry and confocal microscopic analyses indicated that simultaneous the knockout of ATG15 and ACOX2 did not impact the cell viability, whereas the lipid production was enhanced markedly as the lipid yield increased by 67.03% in shake flasks. Afterward, the ΔATG15ΔACOX2 transformant (TO2) was cultivated in shake flasks in the fed-batch mode; the highest biomass and lipid yield reached 45.76 g/L and 27.14 g/L at 216 h, respectively. Better performance was achieved when TO2 was cultivated in the 1-L bioreactor. At the end of fermentation (180 h), lipid content, yield, yield coefficient, and productivity reached 65.53%, 27.35 g/L, 0.277 g/g glycerol, and 0.152 g/L/h, respectively. These values were at the high level in comparison with Rhodotorula strains cultivated in glycerol media. Besides, fermentation modes did not affect the fatty acid composition of TO2 significantly. In conclusion, blocking the lipid degradation was an applicable strategy to increase the lipid production of Rhodotorula strains without compromising their cell viability. Key points: • ATG15-like lipase and acyl-CoA oxidase (ACOX2) participated in lipid degradation. • Knockout of ATG15 and ACOX2 increased lipid productivity, and lipid yield coefficient. • Cell viability maintained at high level in the knockout mutants during fermentation. [ABSTRACT FROM AUTHOR]

Amino acids are the building blocks of protein, promoting the balance between growth and lipid synthesis. However, the accumulation of microbial lipids involves multiple pathways, which requires the analysis of the global cellular metabolic network in which amino acid metabolism is involved. This review illustrates the dependence patterns of intracellular amino acids and lipids of oleaginous eukaryotic microorganisms in different environments and points out the contribution of amino acid metabolic precursors to the de novo synthesis of fatty acids. We emphasized the key role of amino acid metabolism in lipid remodeling and autophagy behavior and highlighted the regulatory effects of amino acids and their secondary metabolites as signal factors for microbial lipid synthesis. The application prospects of omics technology and genetic engineering technology in the field of microbial lipids are described. Key points: • Overview of microbial lipid synthesis mediated by amino acid metabolism • Insight into metabolic mechanisms founding multiple regulatory networks is provided • Description of microbial lipid homeostasis mediated by amino acid excitation signal [ABSTRACT FROM AUTHOR]

Biorefinery employing fungi can be a strategy for valorizing low-cost rest materials, by-products and wastes into several valuable bioproducts through the fungal fermentation. Mucoromycota fungi are soil fungi with a highly versatile metabolic system that positions them as powerful microbial cell factories for biorefinery applications. Lipids, pigments, chitin/chitosan, polyphosphates, ethanol, organic acids and enzymes are main Mucoromycota products that can be refined from the fermentation process and applied in nutrition, chemical or biofuel industries. In addition, Mucoromycota biomass can be used as it is for specific purposes, such as feed. Mucoromycota fungi can be employed in developing co-production processes, whereby several intra- and extracellular products are simultaneously formed in a single fermentation process, and, thus, economic viability of the process can be improved. This mini review provides a comprehensive overview over the recent advances in the production of valuable metabolites by Mucoromycota fungi and fermentation strategies which could be potentially applied in the industrial biorefinery settings. Key points: • Biorefineries utilizing Mucoromycota fungi as production cell factories can provide a wide range of bioproducts. • Mucoromycota fungi are able to perform co-production of various metabolites in a single fermentation process. • Versatile metabolism of Mucoromycota allows valorization of a various low-cost substrates such as wastes and rest materials. [ABSTRACT FROM AUTHOR]

Red yeasts, mainly included in the genera Rhodotorula, Rhodosporidiobolus, and Sporobolomyces, are renowned biocatalysts for the production of a wide range of secondary metabolites of commercial interest, among which lipids, carotenoids, and other isoprenoids. The production of all these compounds is tightly interrelated as they share acetyl-CoA and the mevalonate pathway as common intermediates. Here, T-DNA insertional mutagenesis was applied to the wild type strain C2.5t1 of Rhodotorula mucilaginosa for the isolation of albino mutants with impaired carotenoids biosynthesis. The rationale behind this approach was that a blockage in carotenoid biosynthetic pathway could divert carbon flux toward the production of lipids and/or other molecules deriving from terpenoid precursors. One characterized albino mutant, namely, strain W4, carries a T-DNA insertion in the CAR1 gene coding for phytoene desaturase. When cultured in glycerol-containing medium, W4 strain showed significant decreases in cell density and fatty acids content in respect to the wild type strain. Conversely, it reached significantly higher productions of phytoene, CoQ10, and sterols. These were supported by an increased expression of CAR2 gene that codes for phytoene synthase/lycopene cyclase. Thus, in accordance with the starting hypothesis, the impairment of carotenoids biosynthesis can be explored to pursue the biotechnological exploitation of red yeasts for enhanced production of secondary metabolites with several commercial applications. Key points: • The production of lipids, carotenoids, and other isoprenoids is tightly interrelated. • CAR1 gene mutation results in the overproduction of phytoene, CoQ10, and sterols. • Albino mutants are promising tools for the production of secondary metabolites. [ABSTRACT FROM AUTHOR]

The oleaginous yeast Rhodotorula toruloides is a potential lipid producer for biodiesel production. However, this yeast shows growth inhibition due to harmful compounds when cultivated in hemicellulose hydrolysate. Here, we present a comparative analysis of colony selection and heterologous adaptive laboratory enhancement (ALE) strategies for obtaining robust strains. We implemented these ALE strategies for R. toruloides in a culture medium containing sugarcane hemicellulose hydrolysate. Our comparison study showed that the strain obtained with heterogeneous ALE strategy (Rth) reached a µmax of 55% higher than the parental strain. It also exhibited higher biomass production (6.51 g/l) and lipid content (60%). ALE with colony selection strategy (Rtc) had a fitness gain in terms of shortening of the lag phase (9 h) when compared to Rth and parental strain (11.67, 12.33 h, respectively). When cultivated in Eucalyptus urograndis hemicellulose hydrolysate, the Rth strain achieved a high lipid content, 64%. Kinetics studies showed a strong effect of acetic acid as a repressor of xylose consumption during R. toruloides cultivation. Key points • Distinct adaptive laboratory strategies resulted in strains with different physiologies. • Heterologous adaptive laboratory enhancement provided the best results (fitness gain of 55% in µmax). • The Rth strain achieved a lipid content of 64.3% during cultivation in eucalyptus hemicellulose hydrolysate. [ABSTRACT FROM AUTHOR]

In Cognac, the musts are rich in grape solids and fermentations are usually run with turbidities ranging between 500 and 1500 NTU (nephelometric turbidity unit). These conditions, considered favourable for generating the desired organoleptic profiles of the final Eaux-de-vies, are unusual in winemaking, and, consequently, their impact on yeast metabolism is poorly understood. This study aims to better describe and understand the synthesis of fermentative aromas in such lipid-excess conditions, while integrating the effect of two other very important parameters: the initial concentration of assimilable nitrogen and the temperature of fermentation. To reach this objective, a Box–Behnken design was implemented to describe and model the simple effects of these factors as well as their interactions. Although the lipid concentration was very high, impacts on the production of fermentative aromas were observed. Indeed, high lipid levels promoted the synthesis of higher alcohols. Observing this effect was surprising because there is no metabolic connection between the anabolic pathways of production of these alcohols and the lipid pathway. This effect may be partly explained by impairment in the activity of alcohol acetyl transferases in the presence of lipids, which catalyse the conversion of higher alcohols into the corresponding esters. Therefore, in this study, the negative impact of turbidity was very significant on acetate esters related to the production of acetyl-CoA, which was the main molecule disturbed by the strong presence of lipids. Finally, and more surprisingly, lipid intake did not impact the synthesis of ethyl esters, which depended on the concentration of exogenous lipids. Key points: • Innovative work on the fermentation of white wine musts with very high lipid contents. • Precise fermentation management and monitoring in Cognac-making conditions. • Experimental design to study the impact of lipids, assimilable nitrogen and temperature on fermentative aroma synthesis. [ABSTRACT FROM AUTHOR]

Adaptive laboratory evolution is a powerful tool for microorganism improvement likely to produce enhanced microalgae better tailored to their industrial uses. In this work, 12 wild-type strains of Tisochrysis lutea were co-cultivated under increasing thermal stress for 6 months. Indeed, temperature was oscillating daily between a high and a low temperature, with increasing amplitude along the experiment. The goal was to enhance the polyunsaturated fatty acid content of the polar lipids. Samples were taken throughout the evolution experiment and cultivated in standardized conditions to analyze the evolution of the lipid profile. Genomic analysis of the final population shows that two strains survived. The lipid content doubled, impacting all lipid classes. The fatty acid analyses show a decrease in SFAs correlated with an increase in monounsaturated fatty acids (MUFAs), while changes in polyunsaturated fatty acid (PUFAs) vary between both photobioreactors. Hence, the proportion of C18-MUFAs (18:1 n-9) and most C18-PUFAs (18:2 n-6, 18:3 n-3, and 18:4 n-3) increased, suggesting their potential role in adjusting membrane fluidity to temperature shifts. Of particular interest, DHA in polar lipids tripled in the final population while the growth rate was not affected. Key points: • Adaptive laboratory evolution on a mix of 12 T. lutea strains led to survival of 2 • Thermal stress impacted cell size, total lipid cell content, and all lipid classes • DHA cell content partitioned to polar lipids tripled throughout the experiment [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by various yeasts. Mmf1, a putative transporter of MELs, is conserved in the MEL biosynthesis gene clusters of diverse MEL producers, including the genera Ustilago, Pseudozyma, Moesziomyces, and Sporisorium. To clarify the function of Mmf1, we generated the gene-deleted strain of P. tsukubaensis ΔPtMMF1 and evaluated its MEL production. Using thin-layer chromatography analyses, we detected most MELs produced by ΔPtMMF1 in the culture supernatant. The spot size of diacylated MEL-B (the only product of the parental strain) was significantly smaller for strain ΔPtMMF1 than for the parental strain, and a mono-acylated MEL-D spot was detected. In addition, an unknown glycolipid was detected in the sample extracted from strain ΔPtMMF1. Liquid chromatography–mass spectrometry and nuclear magnetic resonance analyses revealed that the unknown glycolipid was a novel MEL homologue, mono-acylated MEL-B. Key points: • P. tsukubaensis is able to secrete MELs without PtMMF1p. • Strain ΔPtMMF1 mainly produced mono-acylated MELs. [ABSTRACT FROM AUTHOR]

The commercial reality of microalgal biotechnology for the production of individual bioactives is constrained by the high cost of production and requires a biorefinery approach. In this investigation, we examined the influence of different nutrient deprivation (nitrogen (N), phosphorus (P), sulphur (S) and manganese (Mn)) on growth, chlorophyll a (Chl a), biohydrogen (H2) and fatty acid profiles in Parachlorella kessleri EMCCN 3073 under both aerobic and anaerobic conditions. Anaerobic conditions combined with the nutrient deprivation resulted in cell division blockage, reduction in Chl a and remarkable changes in pH, whereas a significant increase in the H2 production was observed after 24 h. The highest cumulative H2 productivity was observed in N-deficient medium (300 μL/L, day 9) followed by Mn-deficient medium (250 μL/L, day 7). The highest H2 production rate (3.37 μL/L/h) was achieved by Mn-deficient medium after 24 h. In terms of fatty acid composition, P. kessleri exhibited a differential response to different nutrient stresses. Under aerobic conditions, N-deficient media resulted in the highest lipid content (119% compared to control, day 7), whereas earlier lipid induction at (1–3 days) was observed with Mn- and S-deficient media with 18–91% and 25–34% increase, respectively, compared with the replete control. Meanwhile, higher lipid content was observed under anaerobic conditions combined with Mn-, N-, P- and S-deprived media (day 1) with 20%, 13%, 8% and 7% increases respectively compared with the control. This investigation, for the first time clearly, highlights the potential of P. kessleri as a sustainable biorefinery platform, for H2 and fatty acid bio-production under anaerobic conditions. Key points: • Parachlorella kessleri could provide a future sustainable biorefinery platform. • Nutrient-deprived anaerobic conditions blocked cell growth but differentially induced H2production. • Nutrient status, under both aerobic/anaerobic conditions, alters lipids and fatty acids profile of P. kessleri. • Nutrient-deprived (N- and Mn-) anaerobic conditions: future biorefinery platform. [ABSTRACT FROM AUTHOR]

Microalgae started receiving attention as producers of third generation of biofuel, but they are rich in many bioactive compounds. Indeed, they produce many molecules endowed with benefic effects on human health which are highly requested in the market. Thus, it would be important to fractionate algal biomass into its several high-value compounds: this represents the basis of the microalgal biorefinery approach. Usually, conventional extraction methods have been used to extract a single class of molecules, with many side effects on the environment and on human health. The development of a green downstream platform could help in obtaining different class of molecules with high purity along with low environmental impact. This review is focused on technical advances that have been performed, from classic methods to the newest and green ones. Indeed, it is fundamental to set up new procedures that do not affect the biological activity of the extracted molecules. A comparative analysis has been performed among the conventional methods and the new extraction techniques, i.e., switchable solvents and microwave-assisted and compressed fluid extractions. [ABSTRACT FROM AUTHOR]

Bacteria belonging to Rhodococcus genus represent ideal candidates for microbial biotechnology applications because of their metabolic versatility, ability to degrade a wide range of organic compounds, and resistance to various stress conditions, such as metal toxicity, desiccation, and high concentration of organic solvents. Rhodococcus spp. strains have also peculiar biosynthetic activities that contribute to their strong persistence in harsh and contaminated environments and provide them a competitive advantage over other microorganisms. This review is focused on the metabolic features of Rhodococcus genus and their potential use in biotechnology strategies for the production of compounds with environmental, industrial, and medical relevance such as biosurfactants, bioflocculants, carotenoids, triacylglycerols, polyhydroxyalkanoate, siderophores, antimicrobials, and metal-based nanostructures. These biosynthetic capacities can also be exploited to obtain high value-added products from low-cost substrates (industrial wastes and contaminants), offering the possibility to efficiently recover valuable resources and providing possible waste disposal solutions. Rhodococcus spp. strains have also recently been pointed out as a source of novel bioactive molecules highlighting the need to extend the knowledge on biosynthetic capacities of members of this genus and their potential utilization in the framework of bioeconomy. Key points: • Rhodococcus possesses promising biosynthetic and bioconversion capacities. • Rhodococcus bioconversion capacities can provide waste disposal solutions. • Rhodococcus bioproducts have environmental, industrial, and medical relevance. [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MEL) are glycolipids mainly produced by pseudo-yeasts. These molecules present remarkable biological activities widely explored in many fields, including medicine, pharmaceuticals, and cosmetics. This review presents the main biological activity of MEL on the HL60, K562, B16, PC12, and skin cells. There is strong evidence that MEL changes the levels of glycosphingolipids of HL-60 lineage, which induce differentiation into granulocytic cells. Regarding B16 cells, MEL can trigger both apoptosis (10 μM) and cell differentiation (5 μM), in which the MEL concentration is related to each metabolic pathway. MEL can also trigger differentiation in PC12 cells due to the increase in the GalCer content. In this specific case, the effects are transient, and the differentiated cells are unstable and tend to apoptosis. MEL-B can particularly maintain skin hydration and moisture due to their self-assembled structures that resemble the tissue cells. Moreover, MEL-B repair aquaporin expression in the HaCaT keratinocytes damaged with UVA irradiation, whereas MEL-C suppresses the expression of COX-2 protein in fibroblasts, indicating that these glycolipids activate the cellular antioxidant mechanism. Recent findings denoted the anti-melanogenic activity of MEL since they suppress tyrosinase enzyme at mRNA levels in B16 and NHMs cells. MEL act effectively on mammalian cells; however, there is no clear pattern of their metabolic effects. Also, gene expression levels seem to be related to two main factors: chemical structure and concentration. However, the specific signaling cascades that are induced by MEL remain inconclusive. Thus, further investigations are vital to understanding these mechanisms clearly. Key points: • The four MEL homologs promote different biological responses in mammalian cells. • MEL modifies the pattern of glycosphingolipids in the plasma membrane of tumor cells. • Activation/deactivation of phosphorylation of serine/threonine kinase proteins. [ABSTRACT FROM AUTHOR]

Candida tropicalis has recently emerged as a valuable yeast species with respect to lipid metabolism, not only for its oleaginous characteristics but also for its ability to utilize diverse range of substrates. Hence, it can be explored as an ideal host for lipid metabolic engineering, although inadequate genetic transformation system for developing the stable transformant has limited this scope. To resolve this existing constraint, we have come up with a novel strategy of a genomic integrating system in the oleaginous strain SY005 of C. tropicalis. Employing this system, comprising of host-specific regulatable promoter, transcription terminator, and integration locus, we have first examined the expression of a reporter gene, and then ectopically expressed a transcription factor CtRAP1 encoding the repressor activator protein 1 of C. tropicalis SY005. A maximum lipid content of 0.37 g/g dry cell weight was achieved in the engineered strain upon galactose induction, leading to 60% (w/w) increase relative to the wild type strain SY005. This work demonstrates the use of a markerless integrative transformation system to promote lipid accumulation in the diploid yeast without applying nutrient stress and hampering cell growth. The findings of this study will augment the research on lipid metabolic engineering and exploit the enormous potential of C. tropicalis as an industrial lipid feedstock. Key points •A transformation system was established in oleaginous yeast Candida tropicalis SY005 •Activity of host-specific molecular elements was verified by reporter gene expression •SY005 was engineered to ectopically express a transcriptional regulator gene CtRAP1 •The engineered strain exhibited 60% increase in lipid content on galactose induction •The increase in lipid content was correlated with the induced expression of CtRAP1 [ABSTRACT FROM AUTHOR]

Oleaginous filamentous fungi grown under the nitrogen limitation, accumulate high amounts of lipids in the form of triacylglycerides (TAGs) with fatty acid profiles similar to plant and fish oils. In this study, we investigate the effect of six phosphorus source concentrations combined with two types of nitrogen substrate (yeast extract and ammonium sulphate), on the biomass formation, lipid production, and fatty acid profile for nine oleaginous Mucoromycota fungi. The analysis of fatty acid profiles was performed by gas chromatography with flame ionization detector (GC-FID) and the lipid yield was estimated gravimetrically. Yeast extract could be used as both nitrogen and phosphorus source, without additional inorganic phosphorus supplementation. The use of inorganic nitrogen source (ammonium sulphate) requires strain-specific optimization of phosphorus source amount to obtain optimal lipid production regarding quantity and fatty acid profiles. Lipid production was decreased in ammonium sulphate-based media when phosphorus source was limited in all strains except for Rhizopus stolonifer. High phosphorus source concentration inhibited the growth of Mortierella fungi. The biomass (22 g/L) and lipid (14 g/L) yield of Umbelopsis vinacea was the highest among all the tested strains. Key points: • The strain specific P requirements of Mucoromycota depend on the nature of N source. • Yeast extract leads to consistent biomass and lipid yield and fatty acids profiles. • Umbelopsis vinacea showed the highest biomass (22 g/L) and lipid (14 g/L) yield. • High P source amounts inhibit the growth of Mortierella fungi. [ABSTRACT FROM AUTHOR]

High dietary concentration of vegetable oil, particularly those rich in n-6 polyunsaturated fatty acids (PUFAs), can induce negative physiological effects including excessive lipid deposition in teleost fish. Omega-3 desaturase (Fat-1) of Caenorhabditis elegans is able to convert n-6 PUFAs to n-3 PUFAs and thus induces a low n-6/n-3 PUFAs ratio alleviating lipid deposition. In this study, we investigated the effects of dietary n-6 PUFAs on lipid metabolism of fat-1 transgenic zebrafish (Tg:fat-1), to explore the role of fat-1 in fish lipid metabolism. We first generated Tg:fat-1 zebrafish and assayed the effects of a low-fat diet (LFD) and a high-fat diet (HFD) prepared from soybean oil. Wild type zebrafish (WT) fed with HFD (HFD-WT) exhibited increased obesity and lipid deposition, especially in the abdominal cavity and liver. These defects were absent from HFD-Tg:fat-1. For each diet group, Tg:fat-1 exhibited significantly decreased levels of almost all hepatic lipid classes compared with WT. Expression levels of lipid synthesis-related genes and lipid deposition-related genes were markedly lower in the liver of HFD-Tg:fat-1 compared with HFD-WT. In contrast, the steatolysis-related genes significantly upregulated in HFD-Tg:fat-1. Then expression profiles of mitochondrial energy metabolism-related genes and ATP contents in the livers from LFD-WT, LFD-Tg:fat-1, HFD-WT, and HFD-Tg:fat-1 were determined. Our findings suggest that fat-1 protects fish from abnormal lipid deposition induced by high-vegetable oil feeding, through endogenously converting n-6 PUFAs to n-3 PUFAs. Key points: • fat-1 transgenic zebrafish (Tg:fat-1) can endogenously convert n-6 PUFAs to n-3 PUFAs. • Tg:fat-1 avoid serious abnormal lipid deposition induced by high-vegetable oil feeding. • fat-1 transgenosis effectively improved lipid metabolism and mitochondrial energy metabolism in zebrafish. [ABSTRACT FROM AUTHOR]

Sterols attract increasing attention due to their important bioactivities. The oleaginous yeast Yarrowia lipolytica has large lipid droplets, which provide storage for the accumulated steroid compounds. In this study, we have successfully constructed a campesterol biosynthetic pathway by modifying the synthetic pathway of ergosterol in Y. lipolytica with different capacity of lipid synthesis. The results showed that the maximal campesterol production was produced in the engineered strain YL-D+M−E−, as the optimal lipid content. Furthermore, we found that campesterol mainly exists in the lipid droplets. The campesterol production was further accumulated through the overexpression of two copies of dhcr7. Finally, the maximal campesterol production of 837 mg/L was obtained using a 5-L bioreactor in the engineered YL-D+D+M−E−, exhibiting a 3.7-fold increase compared with the initial strain YL-D+E−. Our results demonstrate that the proper promotion of lipid content plays an important role in campesterol biosynthesis in Y. lipolytica, and what we found provides an effective strategy for the production of hydrophobic compounds. Key Points • Campesterol was biosynthesized by deleting erg5 and introducing heterologous dhcr7. • Campesterol production elevated via promotion of lipid content. • Campesterol was mainly found in lipid droplets. • Promotion of lipid content is an effective strategy to produce hydrophobic compounds. [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MELs) are novel biosurfactants performing excellent physical-chemical properties as well as bioactivities. This study is aimed to explore the antibacterial and antibiofilm activity of mannosylerythritol lipids against foodborne gram-positive Staphylococcus aureus. The results of growth curve and survival rate revealed the significant inhibitory effect of MELs against S. aureus. The visualized pictures by scanning electron microscope and transmission electron microscope exposed apparent morphological and ultrastructure changes of MEL-treated cells. Furthermore, flow cytometry confirmed that MELs have promoted cell apoptosis and damaged the cell membrane. Notably, MEL-A also exhibited outstanding antibiofilm activity against S. aureus biofilm on different material surfaces including polystyrene, glass, and stainless steel, verified by confocal laser scanning microscope. These findings suggest that the antimicrobial activity of MELs is related to inhibit planktonic cells and biofilm of S. aureus, indicating that it has potential to be an alternative to antibacterial agents and preservatives applied into food processing. Key Points • MELs have strong antibacterial activity against Staphylococcus aureus. • MELs mainly damage the cell membrane of Staphylococcus aureus. • Mannosylerythritol lipids inhibit the bacterial adhesion to remove biofilm. [ABSTRACT FROM AUTHOR]

Six local isolates of yeasts were screened for cell mass and lipid production in mixed glucose and xylose medium. Candida tropicalis SY005 and Trichosporon (Apiotrichum) loubieri SY006 showed significant lipid accumulation of 24.6% and 32% (dry cell weight), respectively when grown in medium containing equal mass of both the sugars. SY005 produced relatively higher cell mass of 9.66 gL−1 due to higher rate of sugar consumption, which raised the lipid productivity of the organism to 0.792 gL−1day−1 as compared to 0.446 gL−1day−1 in SY006. When grown with each sugar separately, the xylose consumption rate of SY005 was found to be 0.55 gL−1 h−1 after 4 days as compared to 0.52 gL−1 h−1 for SY006. Transcript expression of the high affinity xylose transporter (Cthaxt), xylose reductase (Ctxyl1), and xylitol dehydrogenase (Ctxyl2) of SY005 was monitored to unravel such high rate of sugar consumption. Expression of all the three genes was observed to vary in mixed sugars with Cthaxt exhibiting the highest expression in presence of only xylose. Expression levels of both Ctxyl1 and Ctxyl2, involved in xylose catabolism, were maximum during 24–48 h of growth, indicating that xylose utilization started in the presence of glucose, which was depleted in the medium after 96 h. Together, the present study documents that C. tropicalis SY005 consumes xylose concomitant to glucose during early period of growth, and it is a promising yeast strain for viable production of storage lipid or other high-value oleochemicals utilizing lignocellulose hydrolysate. [ABSTRACT FROM AUTHOR]

There are a large number of valuable substances in diatoms, such as neutral lipid and pigments. However, due to the lack of clear metabolic pathways, their applications are still limited. Recently, chemical modulators are found to be powerful tools to investigate the metabolic pathways of neutral lipids. Thus, in this study, to identify new neutral lipid accumulation effectors, we screened the natural products that we separated before in the model diatom Phaeodactylum tricornutum (P. tricornutum) by using Nile-red staining method. Two compounds, penicillide and verrucarin J which were isolated from two marine fungal strains, were identified to promote neutral lipid accumulation. However, penicillide and verrucarin J were also found to significantly inhibit the growth of P. tricornutum through specifically inhibiting the photosynthesis of P. tricornutum. Quantitative analysis results showed that penicillide and verrucarin J significantly increased total lipid and triacylglycerol (TAG) contents, which are consistent with previous Nile-red staining results. The expression of key genes such as DGAT2D, GPAT2, LPAT2, and PAP involved in TAG synthesis and unsaturated fatty acids also increased after penicillide and verrucarin J treatments. Besides, many TAG-rich plastoglobuli formed in plastids shown by increased lipid droplets in the cytosol. Finally, penicillide and verrucarin J were found to reduce the expression of synthetic genes of fucoxanthin, and consequently reduced the content of fucoxanthin, indicating that there might be crosstalk between lipid metabolism and fucoxanthin metabolism. Thus, our work exhibits two useful compounds that could be used to further study the metabolic pathways of neutral lipid and fucoxanthin, which will fulfill the promise of diatoms as low cost, high value, sustainable feedstock for high-value products such as neutral lipid and pigments. [ABSTRACT FROM AUTHOR]

Microbial oils are lipids produced by oleaginous microorganisms, which can be used as a potential feedstock for oleochemical production. The oleaginous yeast Rhodotorula toruloides can co-produce microbial oils and high-value compounds from low-cost substrates, such as xylose and acetic acid (from hemicellulosic hydrolysates) and raw glycerol (a byproduct of biodiesel production). One step towards economic viability is identifying the best conditions for lipid production, primarily the most suitable carbon-to-nitrogen ratio (C/N). Here, we aimed to identify the best conditions and cultivation mode for lipid production by R. toruloides using various low-cost substrates and a range of C/N ratios (60, 80, 100, and 120). Turbidostat mode was used to achieve a steady state at the maximal specific growth rate and to avoid continuously changing environmental conditions (i.e., C/N ratio) that inherently occur in batch mode. Regardless of the carbon source, higher C/N ratios increased lipid yields (up to 60% on xylose at a C/N of 120) but decreased the specific growth rate. Growth on glycerol resulted in the highest specific growth and lipid production (0.085 g lipids/gDW*h) rates at C/Ns between 60 and 100. We went on to study lipid production using glycerol in both batch and fed-batch modes, which resulted in lower specific lipid production rates compared with turbisdostat, however, fed batch is superior in terms of biomass production and lipid titers. By combining the data we obtained in these experiments with a genome-scale metabolic model of R. toruloides, we identified targets for improvements in lipid production that could be carried out either by metabolic engineering or process optimization. [ABSTRACT FROM AUTHOR]

Mannosylerythritol lipids (MELs) have attracted particular interest of medical, pharmaceutical, and cosmetic fields, due to their specific characteristics, including non-toxicity, easy biodegradability, and environmental compatibility. Therefore, this review aims to highlight recent findings on MEL biological properties, focusing on issues related to therapeutic applications. Among the main findings is that MELs can play a fundamental role due to their antimicrobial properties against several nosocomial pathogen microorganisms. Other remarkable biological properties of MELs are related to skincare, as antiaging (active agent), and in particular on recover of skin cells that were damaged by UV radiation. MEL is also related to the increased efficiency of DNA transfection in liposome systems. Regarding the health field, these glycolipids seem to be associated with disturbance in the membrane composition of cancerous cells, increasing expression of genes responsible for cytoplasmic stress and apoptosis. Moreover, MELs can be associated with nanoparticles, as a capping agent, also acting to increase the solubility and cytotoxicity of them. Furthermore, the differences in the chemical structure of MEL could improve and expand their biochemical diversity and applications. Such modifications could change their interfacial properties and, thus, reduce the surface tension value, enhance the solubility, lower critical micelle concentrations, and form unique self-assembly structures. The latest is closely related to molecular recognition and protein stabilization properties of MEL, that is, essential parameters for their effective cosmetical and pharmaceutical effects. Thus, this current research indicates the huge potential of MEL for use in biomedical formulations, either alone or in combination with other molecules. [ABSTRACT FROM AUTHOR]

In this study, combined genome, transcriptome, and metabolome analysis was performed for eight Saccharomyces cerevisiae mitochondrial respiration-deficient mutants. Each mutant exhibited a unique nuclear genome mutation pattern; the nuclear genome mutations, and thus potentially affected genes and metabolic pathways, showed a co-occurrence frequency of ≤ 3 among the eight mutants. For example, only a lipid metabolism-related pathway was likely to be affected by the nuclear genome mutations in one of the mutants. However, large deletions in the mitochondrial genome were the shared characteristic among the eight mutants. At the transcriptomic level, lipid metabolism was the most significantly enriched Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway for differentially expressed genes (DEGs) co-occurring in both ≥ 4 and ≥ 5 mutants. Any identified DEG enriched in lipid metabolism showed the same up-/down-regulated pattern among nearly all eight mutants. Further, 126 differentially expressed lipid species (DELS) were identified, which also showed the same up-/down-regulated pattern among nearly all investigated mutants. It was conservatively demonstrated that the similar change pattern of lipid metabolism in the entire investigated mutant population was attributed to mitochondrial dysfunction. The change spectrum of lipid species was presented, suggesting that the number and change degree of up-regulated lipid species were higher than those of down-regulated lipid species. Additionally, energy storage lipids increased in content and plasma-membrane phospholipid compositions varied in the relative proposition. The results for the genome, transcriptome, and lipidome were mutually validated, which provides quantitative data revealing the roles of mitochondria from a global cellular perspective. [ABSTRACT FROM AUTHOR]

The setup of an economic and sustainable method to increase the production and commercialization of products from microalgae, beyond niche markets, is a challenge. Here, a cascade approach has been designed to optimize the recovery of high valuable bioproducts starting from the wet biomass of Galdieria phlegrea. This unicellular thermo-acidophilic red alga can accumulate high-value compounds and can live under conditions considered hostile to most other species. Extractions were performed in two sequential steps: a conventional high-pressure procedure to recover phycocyanins and a solvent extraction to obtain fatty acids. Phycocyanins were purified to the highest purification grade reported so far and were active as antioxidants on a cell-based model. Fatty acids isolated from the residual biomass contained high amount of PUFAs, more than those recovered from the raw biomass. Thus, a simple, economic, and high effective procedure was set up to isolate phycocyanin at high purity levels and PUFAs. [ABSTRACT FROM AUTHOR]

Oleaginous microorganisms are of high biotechnological interest being considered as alternative sources of oil (single cell oil—SCO). Current research for increasing productivity of oleaginous microorganisms is focused on the overexpression of genes implicated in lipid synthesis, the inactivation of genes implicated in storage lipid turnover, and on the suppression of competitive to lipid biosynthesis pathways. An alternative strategy, described here, relies on evolution of Yarrowia lipolytica under alternating environments that promote growth, encourage storage lipid synthesis, and reward high energy-containing cells. Derived populations were characterized biochemically, especially on their ability to accumulate lipids, and compared with the starting strain. Interestingly, lipid-accumulating ability early in the evolution was decreased compared with the starting strain. Subsequently, oleaginous lineages dominated, leading to populations able to accumulate lipids in high amounts. A population obtained after 77 generations was able to accumulate 44% w/w of lipid, which was 30% higher than that of the starting strain. We conclude that evolution-based strategies can be utilized as a robust tool for improving lipid accumulation capacity in oleaginous microorganisms. [ABSTRACT FROM AUTHOR]

This review summarizes the current knowledge on the importance and role of lipids in wine yeast fermentation. Lipids play an important role in membrane structure, adaptation to stress, or as signaling molecules. They are also essential nutrients whose availability can vary depending on winemaking technology, with major effects on yeast alcoholic fermentation. Moreover, lipid supplementation can greatly stimulate the formation of yeast volatile metabolites. [ABSTRACT FROM AUTHOR]

Acinetobacter baylyi ADP1 is a microorganism with the potential to produce storage lipids. Here, a systematic study was carried out to evaluate growth performance and accumulation of wax esters and triacylglycerols using glycerol, xylose, glucose, acetate, ethanol, and pyruvate as carbon sources. High specific growth rates (μ) were found in gluconeogenic carbon sources (ethanol, acetate, and pyruvate: 0.94 ± 0.18, 0.93 ± 0.06, and 0.61 ± 0.01 h−1, respectively), and low in glucose (0.25 ± 0.01 h−1). Interestingly, these μ values were sustained in a broad range of concentrations of glucose (0.5–50 g L−1), pyruvate (3–10 g L−1), and acetate (0.3–2 g L−1), suggesting a high tolerance to glucose and pyruvate. It was observed that ADP1 is not able to use glycerol or xylose as unique carbon sources. On the other hand, ADP1 showed sensitivity to osmotic upshifts, noted by the lysis at the beginning of cultivations on different carbon sources. However, ADP1 is adapted to relatively high substrate concentrations as indicated by the minimal inhibitory concentrations (MICs) determined at 24 h of cultivations: 350, 50, 80, and 15 g L−1 for glucose, ethanol, pyruvate, and acetate, respectively. Remarkably, ADP1 co-utilized glucose, acetate, ethanol, and pyruvate. Finally, the accumulation of storage lipids, wax esters (WEs), and triacylglycerols (TAGs) showed to be substrate dependent. Under nitrogen-limiting conditions, the TAGs:WEs (mol:mol) accumulation ratios were 1:4.9 in pyruvate and 1:1.6 in glucose, the WEs were mainly accumulated in acetate. In ethanol, no accumulation of lipids was detected. [ABSTRACT FROM AUTHOR]

A growing world population and a growing number of applications for vegetable oils are generating an increasing demand for these oils, causing serious environmental problems. A sustainable lipid production is then fundamental to address these problems. Oleaginous yeasts are a promising solution for sustainable lipid production, but, with the current knowledge and technology, they are still not a serious alternative in the market. In this review, the potential of these yeasts is highlighted and a discussion is made mainly focused on the economics of the oleaginous yeast oil production and identification of the key points to be improved to achieve lower production costs and higher income. Three main stages of the production process, where costs are higher, were identified. To render economically feasible the production of oils using oleaginous yeasts, a reduction in production costs must occur in all stages, lipid yields and productivities must be improved, and production must be targeted to high-value product applications. [ABSTRACT FROM AUTHOR]

Commercial production of biofuel from oleaginous microalgae is often impeded by their slow growth rate than other fast-growing algal species. A promising strategy is to genetically engineer the fast-growing algae to accumulate lipids by expressing key lipogenic genes from oleaginous microalgae. However, lacking of strong expression cassette to transform most of the algal species and potential metabolic target to engineer lipid metabolism has hindered its biotechnological applications. In this study, we engineered the oxidative pentose phosphate pathway (PPP) of green microalga Chlorella pyrenoidosa for lipid enhancement by expressing a glucose-6-phosphate dehydrogenase (G6PD) from oleaginous diatom Phaeodactylum tricornutum. Molecular characterization of transformed lines revealed that heterologous PtG6PD was transcribed and expressed successfully. Interestingly, subcellular localization analyses revealed that PtG6PD was targeted to chloroplasts of C. pyrenoidosa. PtG6PD expression remarkably elevated NADPH content and consequently enhanced the lipid content without affecting growth rate. Collectively, this report represents a promising candidate to engineer lipid biosynthesis in heterologous hosts with notable commercial significance, and it highlights the potential role of plastidial PPP in supplying lipogenic NADPH in microalgae. [ABSTRACT FROM AUTHOR]

α-Linolenic acid (ALA) is an essential ω-3 fatty with reported health benefits. However, this molecule is naturally found in plants such as flaxseed and canola which currently limits production. Here, we demonstrate the potential to sustainably produce ALA using the oleaginous yeast Yarrowia lipolytica. Through the use of a recently identified Δ12-15 desaturase (Rk Δ12-15), we were able to enable production in Y. lipolytica. When combined with a previously engineered lipid-overproducing strain with high precursor availability, further improvements of ALA production were achieved. Finally, the cultivation of this strain at lower temperatures significantly increased ALA content, with cells fermented at 20 °C accumulating nearly 30% ALA of the total lipids in this cell. This low-temperature fermentation represents improved ALA titer up to 3.2-fold compared to standard growth conditions. Scale-up into a fed-batch bioreactor produced ALA at 1.4 g/L, representing the highest published titer of this ω-3 fatty acid in a yeast host. [ABSTRACT FROM AUTHOR]

Steroid phosphate esters are very rare natural lipids that have been comparatively recently isolated from fractions of polar lipids of marine sponges and starfish. These steroids exhibit interesting biological activities. When using the PASS computer program, we showed that many of steroid phosphate esters showed antifungal, antihypercholesterolemic, anesthetic, and other activities with a confidence of 73 to 93%. In addition, some of them can be used as inhibitors of cholesterol synthesis and show hepatoprotection properties. Phosphonosteroids demonstrate antineoplastic and antihypercholesterolemic activities with a certainty of 85 to 90%. And also, they can be used as ovulation inhibitors or female steroid contraceptives with confidence from 86 to 98%. [ABSTRACT FROM AUTHOR]

The present review describes the distribution and biological activities of natural mono-, di-, and triaromatic steroids. It is shown that the producers of aromatic steroids are microorganisms, fungi, and marine invertebrates, and also they were found in plants, animals, marine sediments, and karst deposits. Eighty biologically active aromatic steroids likely have an anti-tumor, anti-inflammatory, and neuroprotection activity with a confidence of 78 to 92%. The structures and predicted biological activities of aromatic steroids are available. This review emphasizes the role of aromatic steroids as an important source and potential leads for drug discovery and they are of great interest to chemists, physicians, biologists, pharmacologists, and the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

The marine diatom Thalassiosira pseudonana grown under air (0.04% CO2) and 1 and 5% CO2 concentrations was evaluated to determine its potential for CO2 mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO2 showed higher growth rates (1.14 and 1.29 div day−1, respectively) and biomass productivities (44 and 48 mgAFDWL−1 day−1) than air grown cultures (with 1.13 div day−1 and 26 mgAFDWL−1 day−1). The increase of CO2 resulted in higher cell volume and pigment content per cell of T. pseudonana. Interestingly, lipid content doubled when air was enriched with 1–5% CO2. Moreover, the analysis of the fatty acid composition of T. pseudonana revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO2 levels. These results suggested that T. pseudonana seems to be an ideal candidate for biodiesel production using flue gases. [ABSTRACT FROM AUTHOR]

The basidiomycetous yeast genus Pseudozyma produce large amounts of mannosylerythritol lipids (MELs), which are biosurfactants. A few Pseudozyma strains produce mono-acylated MEL as a minor compound using excess glucose as the sole carbon source. Mono-acylated MEL shows higher hydrophilicity than di-acylated MEL and has great potential for aqueous applications. Recently, the gene cluster involved in the MEL biosynthesis pathway was identified in yeast. Here, we generated an acyltransferase (PtMAC2) deletion strain of P. tsukubaensis 1E5 with uracil auxotrophy as a selectable marker. A PtURA5-mutant with a frameshift mutation in PtURA5 was generated as a uracil auxotroph of strain 1E5 by ultraviolet irradiation on plate medium containing 5-fluoro-orotic acid (5-FOA). In the mutant, PtMAC2 was replaced with a PtURA5 cassette containing the 5′ untranslated region (UTR) (2000 bp) and 3′ UTR (2000 bp) of PtMAC2 by homologous recombination, yielding strain ΔPtMAC2. Based on TLC and NMR analysis, we found that ΔPtMAC2 accumulates MEL acylated at the C-2′ position of the mannose moiety. These results indicate that PtMAC2p catalyzes acylation at the C-3′ position of the mannose of MEL. [ABSTRACT FROM AUTHOR]

Complex biochemical mechanisms are being involved in oleaginous microorganisms during storage lipid and polysaccharide metabolism. Detailed biochemical analyses and monitoring of key enzymes involved in carbon metabolism were performed in Yarrowia lipolytica and Umbelopsis isabellina, which are often used as model oleaginous microorganisms. It was found that during the early oleaginous phase, the carbon source (glucose) was channeled to lipid accumulation, but also to polysaccharide biosynthesis. However, during transition from the early to the late oleaginous phase, glucose was exclusively converted to lipids, while in U. isabellina, but not in Y. lipolytica, an additional conversion of cellular polysaccharides into lipids was observed. After glucose depletion in the growth medium, cellular storage material was degraded either for generating maintenance energy or for supporting further microbial growth, depending on the availability of essential nutrients in the growth medium. We demonstrated that in both microorganisms, reserve lipids were exclusively used as an intra-cellular carbon source in order to generate energy for maintenance purpose. When cellular storage material degradation was related to new cell mass production, a bioconversion of lipids into new lipid-free material, consisting of polysaccharides and proteins, was observed in Y. lipolytica, while new lipid-free material in U. isabellina was richer in proteins. Lipid and polysaccharide remodeling may occur in some cases in both microorganisms. This study revealed some new biochemical features of oleaginous microorganisms that may be crucial for the design of new biotechnological processes, such as the production of bio-molecules of industrial, technological, and medical interest. [ABSTRACT FROM AUTHOR]

The heterotrophic microalga Crypthecodinium cohnii is well known for its lipid accumulation, with a high proportion of docosahexaenoic acid (DHA). In this study, we report a novel screening approach to obtain mutants of C. cohnii with high growth and lipid content using the acetyl-CoA carboxylase (ACCase) inhibitor sethoxydim. C. cohnii mutants were generated using atmospheric and room-temperature plasma (ARTP) and then screened for two rounds in media supplemented with sethoxydim. These efforts led to the identification of mutant M-1-2, which had 24.32% higher growth and 7.05% higher lipid content than the wild type, demonstrating the effectiveness of the sethoxydim-based screening. Consistently, the M-1-2 mutant displayed a 16.15% increase in ACCase enzymatic activity and 1.53-fold upregulation of its ACCase-encoding gene based on comparative ACCase activity analysis and transcriptomic analysis, respectively. In addition, transcriptomic analysis showed that transcripts involved in fatty acid biosynthesis, energy, central carbohydrate, and amino acid metabolism were upregulated in the mutant compared to the wild type. [ABSTRACT FROM AUTHOR]

Photosynthesis and lipid allocation were investigated in Rubisco small subunit mutants of the microalga Chlamydomonas reinhardtii. Comparative analyses were undertaken with cells grown photoheterotrophically under sulphur-replete or sulphur-depleted conditions. The Y67A Rubisco mutant, which has previously demonstrated a pronounced reduction in Rubisco levels and higher hydrogen production rates than the wild type, also shows the following divergences in photosynthetic phenotype and lipid allocation: (i) low Fv/Fm (maximum photochemical efficiency), (ii) low effective quantum yield of photosystem II (ΦPSII), (iii) low effectiveness at protection against high light intensities, (iv) a higher level of total lipids per pigment and (v) changes in the relative proportions of different fatty acids, with a marked decrease in unsaturated fatty acids (FAs). The most abundant thylakoid membrane lipid, monogalactosyldiacylglycerol, decreased in amount, while the neutral lipid/polar lipid ratio increased in the mutant. The low amount and activity of the mutated Rubisco Y67A enzyme seems to have an adverse effect on photosynthesis and causes changes in carbon allocation in terms of membrane fatty acid composition and storage lipid accumulation. Our results suggest that Rubisco mutants of Chlamydomonas might be useful in biodiesel production. [ABSTRACT FROM AUTHOR]

This review shall provide support for the suitability of arid environments as preferred location to search for unknown lipid-accumulative bacteria. Bacterial lipids are attracting more and more attention as sustainable replacement for mineral oil in fuel and plastic production. The development of prokaryotic microorganisms in arid desert habitats is affected by its harsh living conditions. Drought, nutrient limitation, strong radiation, and extreme temperatures necessitate effective adaption mechanisms. Accumulation of storage lipids as energy reserve and source of metabolic water represents a common adaption in desert animals and presumably in desert bacteria and archaea as well. Comparison of corresponding literature resulted in several bacterial species from desert habitats, which had already been described as lipid-accumulative elsewhere. Based on the gathered information, literature on microbial communities in hot desert, cold desert, and humid soil were analyzed on its content of lipid-accumulative bacteria. With more than 50% of the total community size in single studies, hot deserts appear to be more favorable for lipid-accumulative species then humid soil (≤20%) and cold deserts (≤17%). Low bacterial lipid accumulation in cold deserts is assumed to result from the influence of low temperatures on fatty acids and the increased necessity of permanent adaption methods. [ABSTRACT FROM AUTHOR]

Natural lipids can be used to make biodiesel and many other value-added compounds. In this work, we explored a number of different metabolic engineering strategies for increasing lipid production in the oleaginous yeast Rhodosporidium toruloides IFO0880. These included increasing the expression of enzymes involved in different aspects of lipid biosynthesis-malic enzyme ( ME), pyruvate carboxylase ( PYC1), glycerol-3-P dehydrogenase ( GPD), and stearoyl-CoA desaturase ( SCD)-and deleting the gene PEX10, required for peroxisome biogenesis. Only malic enzyme and stearoyl-CoA desaturase, when overexpressed, were found to significantly increase lipid production. Only stearoyl-CoA desaturase, when overexpressed, further increased lipid production in a strain previously engineered to overexpress acetyl-CoA carboxylase ( ACC1) and diacylglycerol acyltransferase ( DGA1). Our best strain produced 27.4 g/L lipid with an average productivity of 0.31 g/L/h during batch growth on glucose and 89.4 g/L lipid with an average productivity of 0.61 g/L/h during fed-batch growth on glucose. These results further establish R. toruloides as a platform organism for the production of lipids and potentially other lipid-derived compounds from sugars. [ABSTRACT FROM AUTHOR]

The development of an effective, realistic, and sustainable microbial biorefinery depends on several factors, including as one of the key aspects an adequate selection of microbial strain. The oleaginous red yeast Rhodotorula sp. has been studied as one powerful source for a plethora of high added-value biomolecules, such as carotenoids, lipids, and enzymes. Although known for over a century, the use of Rhodotorula sp. as resource for valuable products has not yet commercialized. Current interests for Rhodotorula sp. yeast have sparked from its high nutritional versatility and ability to convert agro-food residues into added-value biomolecules, two attractive characteristics for designing new biorefineries. In addition, as for other yeast-based bioprocesses, the overall process sustainability can be maximized by a proper integration with subsequent downstream processing stages, for example, by using eco-friendly solvents for the recovery of intracellular products from yeast biomass. This review intends to reflect on the current state of the art of microbial bioprocesses using Rhodotorula species. Therefore, we will provide an analysis of bioproduction performance with some insights regarding downstream separation steps for the extraction of high added-value biomolecules (specifically using efficient and sustainable platforms), providing information regarding the potential applications of biomolecules produced by Rhodotorula sp, as well as detailing the strengths and limitations of yeast-based biorefinery approaches. Novel genetic engineering technologies are further discussed, indicating some directions on their possible use for maximizing the potential of Rhodotorula sp. as cell factories.• Rhodotorula sp. are valuable source of high value-added compounds.• Potential of employing Rhodotorula sp. in a multiple product biorefinery.• Future perspectives in the biorefining of Rhodotorula sp. were discussed.Key points: The development of an effective, realistic, and sustainable microbial biorefinery depends on several factors, including as one of the key aspects an adequate selection of microbial strain. The oleaginous red yeast Rhodotorula sp. has been studied as one powerful source for a plethora of high added-value biomolecules, such as carotenoids, lipids, and enzymes. Although known for over a century, the use of Rhodotorula sp. as resource for valuable products has not yet commercialized. Current interests for Rhodotorula sp. yeast have sparked from its high nutritional versatility and ability to convert agro-food residues into added-value biomolecules, two attractive characteristics for designing new biorefineries. In addition, as for other yeast-based bioprocesses, the overall process sustainability can be maximized by a proper integration with subsequent downstream processing stages, for example, by using eco-friendly solvents for the recovery of intracellular products from yeast biomass. This review intends to reflect on the current state of the art of microbial bioprocesses using Rhodotorula species. Therefore, we will provide an analysis of bioproduction performance with some insights regarding downstream separation steps for the extraction of high added-value biomolecules (specifically using efficient and sustainable platforms), providing information regarding the potential applications of biomolecules produced by Rhodotorula sp, as well as detailing the strengths and limitations of yeast-based biorefinery approaches. Novel genetic engineering technologies are further discussed, indicating some directions on their possible use for maximizing the potential of Rhodotorula sp. as cell factories.• Rhodotorula sp. are valuable source of high value-added compounds.• Potential of employing Rhodotorula sp. in a multiple product biorefinery.• Future perspectives in the biorefining of Rhodotorula sp. were discussed. [ABSTRACT FROM AUTHOR]

Reprogramming of host metabolism is a common strategy for improving desired compounds in host cells and is essential to generate overproducing strains in biotechnology. As a promising feedstock converter, Yarrowia lipolytica has been engineered to extend its bioproduction ability related to the synthesis of new value-added molecules relevant to human food and disease treatment. New synthetic tools have been reported and new enzymes with biotechnological importance are recovered. Additionally, metabolic events occurring during substrate utilization and recombinant protein production have been elucidated. Its contributions as feed and in controlling disease in the food industry have also been provided. Likewise, the recent abilities of Yarrowia lipolytica in the bioconversion of food waste into single-cell protein have been reported. These aforementioned events made the novelty of this review compared to the existing ones on this oleaginous yeast.• The production of biolipids by the heterotrophic yeast Yarrowia lipolytica is examined.• A Summary of information concerning new value-added molecules has been highlighted.• Special focus on the importance of Yarrowia lipolytica in regulating the immune system has been provided.Key points: Reprogramming of host metabolism is a common strategy for improving desired compounds in host cells and is essential to generate overproducing strains in biotechnology. As a promising feedstock converter, Yarrowia lipolytica has been engineered to extend its bioproduction ability related to the synthesis of new value-added molecules relevant to human food and disease treatment. New synthetic tools have been reported and new enzymes with biotechnological importance are recovered. Additionally, metabolic events occurring during substrate utilization and recombinant protein production have been elucidated. Its contributions as feed and in controlling disease in the food industry have also been provided. Likewise, the recent abilities of Yarrowia lipolytica in the bioconversion of food waste into single-cell protein have been reported. These aforementioned events made the novelty of this review compared to the existing ones on this oleaginous yeast.• The production of biolipids by the heterotrophic yeast Yarrowia lipolytica is examined.• A Summary of information concerning new value-added molecules has been highlighted.• Special focus on the importance of Yarrowia lipolytica in regulating the immune system has been provided. [ABSTRACT FROM AUTHOR]

Targeting the bactoprenol-coupled cell wall precursor lipid II is a validated antibacterial strategy. In this review, selected prototype lipid II-binding antibiotics of different chemical classes are discussed. Although these compounds attack the same molecular target, they trigger nuanced and diverse cellular effects. Consequently, the mechanisms of antibacterial resistance and the likelihood of resistance development may vary substantially. [ABSTRACT FROM AUTHOR]

The sophorolipid-producing strain Starmerella bombicola CGMCC 1576 has a remarkable ability to produce sophorolipids (SLs) under the acidic and lactonic forms with almost equal proportion. In this study, we found the gene encoding for the long-chain acyl-CoA synthetase (ALCS). This enzyme was putatively identified as a membrane-bound long-chain fatty acid transport protein and contributed to the uptake of long-chain fatty acids. Disruption of the alcs gene resulted in an impaired growth of the alcs-deleted mutant in minimal media containing different fatty acids (C12:0, C14:0, C16:0, C18:0, C22:0, and C24:0) as the sole carbon source and led to a dramatic decrease in the uptake of the fluorescent-tagged long-chain fatty acid analogue-boron dipyrromethene difluoride dodecanoic acid (BODIPY-3823). The absence of this alcs gene caused obvious phenotype changes. Compared with the wild-type strain, the yield and compositions of the SLs produced by the gene-deleted mutant of ∆ alcs:: six showed almost no lactonic form of SLs, and the acidic SLs were composed of medium-chain. The ALCS enzyme was heterologously expressed in Escherichia coli JM109 (DE3) with pMAL-c2x-alcs. The enzyme was purified through a maltose-binding protein (MBP) affinity chromatography column and was confirmed to be homogeneous by SDS-PAGE. The recombinant enzyme could catalyze the formation of the long-chain acyl-CoA when the long-chain fatty acids and the coenzyme A were used as substrates. [ABSTRACT FROM AUTHOR]

Acyl-CoAs are crucial compounds involved in essential metabolic pathways such as the Krebs cycle and lipid, carbohydrate, and amino acid metabolisms, and they are also key signal molecules involved in the transcriptional regulation of lipid biosynthesis in many organisms. In this study, we took advantage of the high selectivity of mass spectrometry and developed an ion-pairing reverse-phase high-pressure liquid chromatography electrospray ionization high-resolution mass spectrometry (IP-RP-HPLC/ESI-HRMS) method to carry on a comprehensive analytical determination of the wide range of fatty acyl-CoAs present in actinomycetes. The advantage of using a QTOF spectrometer resides in the excellent mass accuracy over a wide dynamic range and measurements of the true isotope pattern that can be used for molecular formula elucidation of unknown analytes. As a proof of concept, we used this assay to determine the composition of the fatty acyl-CoA pools in Mycobacterium, Streptomyces, and Corynebacterium species, revealing an extraordinary difference in fatty acyl-CoA amounts and species distribution between the three genera and between the two species of mycobacteria analyzed, including the presence of different chain-length carboxy-acyl-CoAs, key substrates of mycolic acid biosynthesis. The method was also used to analyze the impact of two fatty acid synthase inhibitors on the acyl-CoA profile of Mycobacterium smegmatis, which showed some unexpected low levels of C acyl-CoAs in the isoniazid-treated cells. This robust, sensitive, and reliable method should be broadly applicable in the studies of the wide range of bacteria metabolisms in which acyl-CoA molecules participate. [ABSTRACT FROM AUTHOR]