A review on unit operations, challenges, opportunities, and strategies to improve algal based biodiesel and biorefinery

Globally, the demand for energy is increasing with an emphasis on green fuels for a sustainable future. As the urge for alternative fuels is accelerating, microalgae have emerged as a promising source that can not only produce high lipid but many other platform chemicals. Moreover, it is a better alternative in comparison to conventional feedstock due to yearlong easy and mass cultivation, carbon fixation, and value-added products extraction. To date, numerous studies have been done to elucidate these organisms for large-scale fuel production. However, enhancing the lipid synthesis rate and reducing the production cost still remain a major bottleneck for its economic viability. Therefore, this study compiles information on algae-based biodiesel production with an emphasis on its unit operations from strain selection to biofuel production. Additionally, strategies to enhance lipid accumulation by incorporating genetic, and metabolic engineering and the use of leftover biomass for harnessing bio-products have been discussed. Besides, implementing a biorefinery for extracting oil followed by utilizing leftover biomass to generate value-added products such as nanoparticles, biofertilizers, biochar, and biopharmaceuticals has also been discussed.

Obtention of biodiesel through an enzymatic two-step process. Study of its performance and characteristic emissions

We describe the enzymatic synthesis of biodiesel from waste cooking oil (WCO) in a two-step production process: hydrolysis of WCO, followed by acid-catalyzed esterification of free fatty acids (FFAs). Among the three commercial enzymes evaluated, the inexpensive lipase Lipex® 100L supported on Lewatit® VP OC 1600 produced the best overall biodiesel yield (96.3%). Finally, we assessed the combustion efficiency of the obtained biodiesel and its blends. All blends tested presented lower emissions of CO and HC compared to diesel. The NOx emissions were higher due to biodiesel's high volatility and viscosity. The cost of biodiesel production was calculated using the process described.

A convenient route to mono-trans polyunsaturated free fatty acids

Trans unsaturated fatty acids in humans may be originated both from dietary supplementation and from an endogenous free-radical-catalyzed cis−trans isomerization of fatty acid residues in naturally occurring cis lipids. The latter process affords geometrical isomers and the polyunsaturated fatty acid mono-trans isomers were demonstrated to be connected with stress conditions in living organisms. Synthesis of mono-trans polyunsaturated fatty acid is useful for analytical and biological research, and in this case, the availability of free fatty acids is needed as well as the possibility of mg scale of the synthetic protocol. Herein, we report a simple synthetic route to mono-trans isomers of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which includes thiyl radical-catalyzed isomerization reaction of polyunsaturated fatty acid methyl esters and fraction isolation of mono-trans mixture isomers followed by optimization of hydrolysis condition to free fatty acids and purification of each mono-trans polyunsaturated fatty acid. Our approach to mono-trans polyunsaturated fatty acids as free acids can reach the mg scale, thus fostering more applications to biochemical and biological studies.

Defining Blood Plasma and Serum Metabolome by GC-MS

Metabolomics uses advanced analytical chemistry methods to analyze metabolites in biological samples. The most intensively studied samples are blood and its liquid components: plasma and serum. Armed with advanced equipment and progressive software solutions, the scientific community has shown that small molecules’ roles in living systems are not limited to traditional “building blocks” or “just fuel” for cellular energy. As a result, the conclusions based on studying the metabolome are finding practical reflection in molecular medicine and a better understanding of fundamental biochemical processes in living systems. This review is not a detailed protocol of metabolomic analysis. However, it should support the reader with information about the achievements in the whole process of metabolic exploration of human plasma and serum using mass spectrometry combined with gas chromatography.

The role of hepatic lipid composition in obesity-related metabolic disease

Obesity is a primary antecedent to non-alcoholic fatty liver disease whose cardinal feature is excessive hepatic lipid accumulation. Although total hepatic lipid content closely associates with hepatic and systemic metabolic dysfunction, accumulating evidence suggests that the composition of hepatic lipids may be more discriminatory. This review summarises cross-sectional human studies using liver biopsy/lipidomics and proton magnetic resonance spectroscopy to characterise hepatic lipid composition in people with obesity and related metabolic disease. A comprehensive literature search identified 26 relevant studies published up to 31st March 2021 which were included in the review. The available evidence provides a consistent picture showing that people with hepatic steatosis possess elevated saturated and/or monounsaturated hepatic lipids and a reduced proportion of polyunsaturated hepatic lipids. This altered hepatic lipid profile associates more directly with metabolic derangements, such as insulin resistance, and may be exacerbated in non-alcoholic steatohepatitis. Further evidence from lipidomic studies suggests that these deleterious changes may be related to defects in lipid desaturation and elongation, and an augmentation of the de novo lipogenic pathway. These observations are consistent with mechanistic studies implicating saturated fatty acids and associated bioactive lipid intermediates (ceramides, lysophosphatidylcholines and diacylglycerol) in the development of hepatic lipotoxicity and wider metabolic dysfunction, whilst monounsaturated fatty acids and polyunsaturated fatty acids may exhibit a protective role. Future studies are needed to prospectively determine the relevance of hepatic lipid composition for hepatic and non-hepatic morbidity and mortality; and to further evaluate the impact of therapeutic interventions such as pharmacotherapy and lifestyle interventions.

Artificial Intelligence in Functional Food Ingredient Discovery and Characterisation: A Focus on Bioactive Plant and Food Peptides

Scientific research consistently demonstrates that diseases may be delayed, treated, or even prevented and, thereby, health may be maintained with health-promoting functional food ingredients (FFIs). Consumers are increasingly demanding sound information about food, nutrition, nutrients, and their associated health benefits. Consequently, a nutrition industry is being formed around natural foods and FFIs, the economic growth of which is increasingly driven by consumer decisions. Information technology, in particular artificial intelligence (AI), is primed to vastly expand the pool of characterised and annotated FFIs available to consumers, by systematically discovering and characterising natural, efficacious, and safe bioactive ingredients (bioactives) that address specific health needs. However, FFI-producing companies are lagging in adopting AI technology for their ingredient development pipelines for several reasons, resulting in a lack of efficient means for large-scale and high-throughput molecular and functional ingredient characterisation. The arrival of the AI-led technological revolution allows for the comprehensive characterisation and understanding of the universe of FFI molecules, enabling the mining of the food and natural product space in an unprecedented manner. In turn, this expansion of bioactives dramatically increases the repertoire of FFIs available to the consumer, ultimately resulting in bioactives being specifically developed to target unmet health needs.

Isolation and Identification of Non-Conjugated Linoleic Acid from Processed Panax ginseng Using LC-MS/MS and 1H-NMR

Black ginseng exhibits numerous pharmacological activities due to higher and more diverse ginsenosides than unprocessed white ginseng. The ginsenoside derivatives have been investigated in order to determine their chemical structures and pharmacological activities. We found a peak which was increased 10-fold but unidentified in the methanol extracts of a black ginseng product. The unknown peak was tracked and identified as linoleic acid rather than a ginsenoside derivative using liquid chromatography–tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. NMR analysis confirmed no presence of conjugated linoleic acids. Ginsenoside profiles and linoleic acid contents in black ginseng products were quantified using LC-MS/MS. Linoleic acid content was more directly proportional to the number of applied thermal cycles in the manufacturing process than any ginsenosides.

Silver (I)-dimercaptotriazine functionalized silica: A highly selective liquid chromatography stationary phase targeting unsaturated molecules

Silver(I)-mercaptopropyl (Ag-MP) functionalized silica gel has demonstrated its effectiveness in separating various unsaturated organic compounds including unsaturated fatty acid ethyl esters (FAEEs), triglycerols (TAGs) and long-chain alkyl ketones (alkenones). While Ag-MP stationary phase displays many advantages over the conventional silver ion-impregnated silica gel (e.g., stability, high recovery, etc.), potential drawbacks of Ag-MP include relatively low retentions for unsaturated molecules, which could limit chromatographic resolutions under certain circumstances. In this study, we evaluate a new silver-thiolate stationary phase: silver(I)-dimercaptotriazine (Ag-DMT) functionalized silica gel targeting the separation of unsaturated compounds. We show Ag-DMT affords substantially higher retention factors, peak resolutions and capacities for TAGs and FAEEs than Ag-MP does. Ag-DMT also yields higher purity eicosapentaenoic acid (EPA) from fish oil FAEE mixtures than Ag-MP. In addition, Ag-DMT resolves double bond positional and cis/trans-isomers of C_18:1 fatty acid methyl esters (FAMEs) as well as unsaturated methyl/ethyl alkenones with different number of double bonds. Based on van't Hoff plots, enthalpy changes during the adsorption of unsaturated FAEEs onto Ag-DMT are ~2 times higher than those on Ag-MP. Such difference may be attributed to the stronger electron-withdrawing effect of the thiol group on DMT, which results in more positively charged silver ions hence greater interactions with unsaturated molecules. The stronger interaction between double bonds and Ag-DMT is further corroborated by density-functional theory (DFT) calculations. Ag-DMT shows its high stability for repeated uses in the separation of TAGs over 319 runs, with peak resolutions decreasing by < 3%. Collectively, our data demonstrate the exceptionally high efficiency of Ag-DMT column for separating unsaturated molecules.

The Potential of Genome Editing for Improving Seed Oil Content and Fatty Acid Composition in Oilseed Crops

A continuous rise in demand for vegetable oils, which comprise mainly the storage lipid triacylglycerol, is fueling a surge in research efforts to increase seed oil content and improve fatty acid composition in oilseed crops. Progress in this area has been achieved using both conventional breeding and transgenic approaches to date. However, further advancements using traditional breeding methods will be complicated by the polyploid nature of many oilseed crops and associated time constraints, while public perception and the prohibitive cost of regulatory processes hinders the commercialization of transgenic oilseed crops. As such, genome editing using CRISPR/Cas is emerging as a breakthrough breeding tool that could provide a platform to keep pace with escalating demand while potentially minimizing regulatory burden. In this review, we discuss the technology itself and progress that has been made thus far with respect to its use in oilseed crops to improve seed oil content and quality. Furthermore, we examine a number of genes that may provide ideal targets for genome editing in this context, as well as new CRISPR-related tools that have the potential to be applied to oilseed plants and may allow additional gains to be made in the future.

Review of recent developments in GC-MS approaches to metabolomics-based research

BACKGROUND

Metabolomics aims to identify the changes in endogenous metabolites of biological systems in response to intrinsic and extrinsic factors. This is accomplished through untargeted, semi-targeted and targeted based approaches. Untargeted and semi-targeted methods are typically applied in hypothesis-generating investigations (aimed at measuring as many metabolites as possible), while targeted approaches analyze a relatively smaller subset of biochemically important and relevant metabolites. Regardless of approach, it is well recognized amongst the metabolomics community that gas chromatography-mass spectrometry (GC-MS) is one of the most efficient, reproducible and well used analytical platforms for metabolomics research. This is due to the robust, reproducible and selective nature of the technique, as well as the large number of well-established libraries of both commercial and 'in house' metabolite databases available.

AIM OF REVIEW

This review provides an overview of developments in GC-MS based metabolomics applications, with a focus on sample preparation and preservation techniques. A number of chemical derivatization (in-time, in-liner, offline and microwave assisted) techniques are also discussed. Electron impact ionization and a summary of alternate mass analyzers are highlighted, along with a number of recently reported new GC columns suited for metabolomics. Lastly, multidimensional GC-MS and its application in environmental and biomedical research is presented, along with the importance of bioinformatics.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The purpose of this review is to both highlight and provide an update on GC-MS analytical techniques that are common in metabolomics studies. Specific emphasis is given to the key steps within the GC-MS workflow that those new to this field need to be aware of and the common pitfalls that should be looked out for when starting in this area.

GC-MS Analysis of Medium- and Long-Chain Fatty Acids in Blood Samples

Our body contains a wide variety of fatty acids that differ in chain length, the degree of unsaturation, and location of the double bonds. As the various fatty acids play distinct roles in health and disease, methods that can specifically determine the fatty acid profile are needed for fundamental and clinical studies. Here we describe a method for the separation and quantification of fatty acids ranging from 8 to 24 carbon chain lengths in blood samples using gas chromatography-mass spectrometry following derivatization using pentafluorobenzyl bromide. This method quantitatively monitors fatty acid composition in a manner that satisfies the requirements for comprehensiveness, sensitivity, and accuracy.

GC-MS Analysis of Short-Chain Fatty Acids in Feces, Cecum Content, and Blood Samples

Short-chain fatty acids, the end products of fermentation of dietary fibers by the gut microbiota, have been shown to exert multiple effects on mammalian metabolism. For the analysis of short-chain fatty acids, gas chromatography-mass spectrometry is a very powerful and reliable method. Here, we describe a fast, reliable, and reproducible method for the separation and quantification of short-chain fatty acids in mouse feces, cecum content, and blood samples (i.e., plasma or serum) using gas chromatography-mass spectrometry. The short-chain fatty acids analyzed include acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, and heptanoic acid.

Carbon streaming in microalgae: extraction and analysis methods for high value compounds

There is a growing recognition that carbon-neutral biofuels and microalgae are eco-friendly options because of their high CO₂ sequestering capability and ability to grow in wastewater/sea water and non-arable land. Also the intrinsic properties of microalgal systems can be exploited for high value compounds such as carbohydrates, lipids, pigments and proteins. This article provides a comprehensive review of various microalgae cultivation practices utilizing organic and inorganic carbon sources. The merits and demerits of the various extraction and analytical procedures have also been discussed in detail.

A novel liquid chromatography/tandem mass spectrometry (LC-MS/MS) based bioanalytical method for quantification of ethyl esters of Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) and its application in pharmacokinetic study

Omega-3 fatty acids are clinically useful and the two marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are prevalent in fish and fish oils. Omega-3 fatty acid formulations should undergo a rigorous regulatory step in order to obtain United States Food and Drug Administration (USFDA) approval as prescription drug. In connection with that, despite quantifying EPA and DHA fatty acids, there is a need for quantifying the level of ethyl esters of them in biological samples. In this study, we make use of reverse phase high performance liquid chromatography coupled with mass spectrometry (RP-HPLC-MS)technique for the method development. Here, we have developed a novel multiple reaction monitoring method along with optimized parameters for quantification of EPA and DHA as ethyl esters. Additionally, we attempted to validate the bio-analytical method by conducting the sensitivity, selectivity, precision accuracy batch, carryover test and matrix stability experiments. Furthermore, we also implemented our validated method for evaluation of pharmacokinetics of omega fatty acid ethyl ester formulations.

Detection and qualitative analysis of fatty acid amides in the urine of alcoholics using HPLC-QTOF-MS

Fatty acid amides (FAAs) in alcoholism lead to liver diseases. These amides have been reported in plasma and in other organs of the body, while their detection or presence in the urine is still unknown. Therefore, the focus of the current study was to detect and analyze FAAs qualitatively in urine samples of alcoholics. Furthermore, the effects of Tinospora cordifolia (hepatoprotective medicinal plant) intervention on FAA levels in moderate alcoholics were also analyzed. In the study, asymptomatic chronic alcoholics (n = 22) without chronic liver disease and nonalcoholic healthy volunteers (n = 24) with a mean age of 39 ± 2.0 years were selected. The first-pass urine and fasting blood samples were collected in the morning on day 0 and day 14 after T. cordifolia water extract (TCE) treatment and analyzed using automated biochemistry analyzer and HPLC-QTOF-MS. Results indicated the increased levels of serum triglycerides, cholesterol, and liver function enzymes in alcoholic subjects, which were significantly down-regulated by TCE intervention. Multivariate discrimination analysis of QTOF-MS data showed increased urinary levels of oleoamide (2.55-fold), palmitamide (5.6-fold), and erucamide (1.6-fold) in alcoholics as compared to control subjects. Levels of oleamide (1.8-fold), palmitamide (1.7-fold), and linoleamide (1.5-fold) were found to be increased in plasma. Treatment with TCE in alcoholics (3.0 g lyophilized water extract/day) significantly decreased the plasma and urinary levels of all FAAs except linoleamide. The HPLC-QTOF-MS approach for FAAs analysis in both urinary and plasma samples of alcoholics worked very well. Moreover, findings (i.e., increased levels of FAAs in urine and in plasma) further support other findings that these amides play a very important role in alcoholism. Further, like our previous findings, TCE proved its hepatoprotective effect against alcoholism not only by lowering the levels of these detected FAAs, but also by decreasing the level of liver-specific enzymes and lipids.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.