Extraction of carotenoids from Chlorella vulgaris using green solvents and syngas production from residual biomass

Sustainable extraction methods of carotenoids from mango (Mangifera indica L. 'Kent') pulp: Ultrasound assisted extraction and green solvents

Mango is a good source of carotenoids for use in food, cosmetic, and pharmaceutical products because of their organoleptic and health-promoting properties. Safe and sustainable methods for their extraction is required. The present investigation was aimed to study concentration and carotenoid profile of 'Kent' mango pulp through a conventional extraction (CE) and ultrasound-assisted extraction (UAE) using traditional solvents (tetrahydrofuran-THF and diethyl ether: petroleum ether-DE:PE) and green solvents (GS) (2-metiltetrahydrofuran, 2 m-THF; cyclopentyl methyl ether, CPME). Mango showed (μg/g d.w.) β-carotene (29.4), zeaxanthin (1.28), β-cryptoxanthin (2.8), phytoene (18.68) and phytofluene (7.45) in a CE using DE:PE. Similar results were obtained applying DE:PE in UAE and GS in a CE, so CPME and 2-mTHF seem suitable solvents to replace DE:PE in CE. The yield of total carotenes, xanthophylls and carotenoids using GS combined with UAE was lower than with CE, but important enough to be used as a sustainable procedure for obtaining carotenoids from mango pulp.

Optimization and Characterization of Spirulina and Chlorella Hydrolysates for Industrial Application

Chlorella and Spirulina are the most used microalgae mainly as powder, tablets, or capsules. However, the recent change in lifestyle of modern society encouraged the emergence of liquid food supplements. The current work evaluated the efficiency of several hydrolysis methods (ultrasound-assisted hydrolysis UAH, acid hydrolysis AH, autoclave-assisted hydrolysis AAH, and enzymatic hydrolysis EH) in order to develop liquid dietary supplements from Chlorella and Spirulina biomasses. Results showed that, EH gave the highest proteins content (78% and 31% for Spirulina and Chlorella, respectively) and also increased pigments content (4.5 mg/mL of phycocyanin and 12 µg/mL of carotenoids). Hydrolysates obtained with EH showed the highest scavenging activity (95-91%), allowing us, with the other above features, to propose this method as convenient for liquid food supplements development. Nevertheless, it has been shown that the choice of hydrolysis method depended on the vocation of the product to be prepared.

Hansen Solubility Parameters Applied to the Extraction of Phytochemicals

In many analytical chemical procedures, organic solvents are required to favour a better global yield upon the separation, extraction, or isolation of the target phytochemical analyte. The selection of extraction solvents is generally based on the solubility difference between target analytes and the undesired matrix components, as well as the overall extraction procedure cost and safety. Hansen Solubility Parameters are typically used for this purpose. They are based on the product of three coordinated forces (hydrogen bonds, dispersion, and dipolar forces) calculated for any substance to predict the miscibility of a compound in a pure solvent, in a mixture of solvents, or in non-solvent compounds, saving time and costs on method development based on a scientific understanding of chemical composition and intermolecular interactions. This review summarises how Hansen Solubility Parameters have been incorporated into the classical and emerging (or greener) extraction techniques of phytochemicals as an alternative to trial-and-error approaches, avoiding impractical experimental conditions and resulting in, for example, saving resources and avoiding unnecessary solvent wasting.

Microalgae, Seaweeds and Aquatic Bacteria, Archaea, and Yeasts: Sources of Carotenoids with Potential Antioxidant and Anti-Inflammatory Health-Promoting Actions in the Sustainability Era

Carotenoids are a large group of health-promoting compounds used in many industrial sectors, such as foods, feeds, pharmaceuticals, cosmetics, nutraceuticals, and colorants. Considering the global population growth and environmental challenges, it is essential to find new sustainable sources of carotenoids beyond those obtained from agriculture. This review focuses on the potential use of marine archaea, bacteria, algae, and yeast as biological factories of carotenoids. A wide variety of carotenoids, including novel ones, were identified in these organisms. The role of carotenoids in marine organisms and their potential health-promoting actions have also been discussed. Marine organisms have a great capacity to synthesize a wide variety of carotenoids, which can be obtained in a renewable manner without depleting natural resources. Thus, it is concluded that they represent a key sustainable source of carotenoids that could help Europe achieve its Green Deal and Recovery Plan. Additionally, the lack of standards, clinical studies, and toxicity analysis reduces the use of marine organisms as sources of traditional and novel carotenoids. Therefore, further research on the processing of marine organisms, the biosynthetic pathways, extraction procedures, and examination of their content is needed to increase carotenoid productivity, document their safety, and decrease costs for their industrial implementation.

Status of food colorants in India: conflicts and prospects

Food colorants are imperative ingredients for attracting consumers and in deciding their preferences. Here we discuss the current status of natural colorants and synthetic food colorants on the Indian market by appraising the growth of the food colorant market both globally and nationally, based on published case studies on synthetic food colorants (SFCs), rules, and regulations implemented by Food Safety and Standards Authority of India on natural food colorants and SFCs. The substantial lacunae in the research on the impacts of SFCs in the Indian population identified through our literature survey signify the scope and need for appraisal of the issues prevailing in the Indian food colorant market as well as the necessity of renewing the food colorant policies. The illegal use of banned food colorants, the adulteration of natural food colorants, mislabelling of SFCs as natural colorants, and the permitted use of internationally banned food colorants, as well as the unawareness among consumers are serious issues recognized. Appropriate labelling to denote natural food colorants' presence, renewed standards of policy to determine the permitted use of food colorants, comprehensive regulations for the production and use of natural food colorants, stringent rules to constrain the production of toxic SFCs are obligatory to breakdown the dilemma on the Indian food market. Most importantly, awareness and responsiveness should be generated among consumers regarding the illegal use and adulteration of colorants and the need to use natural colorants. We also recommend a logo to designate the presence of natural colorants which will aid the consumers to make the right choice.

Toxicity Effects of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) on Two Green Microalgae Species

Amongst per- and polyfluoroalkyl substances (PFAS) compounds, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have a high persistence in physicochemical and biological degradation; therefore, the accumulation of PFOS and PFOA can negatively affect aquatic organisms and human health. In this study, two microalgae species (Chlorella vulgaris and Scenedesmus obliquus) were exposed to different concentrations of a PFOS and PFOA mixture (0 to 10 mg L^-1). With increases in the contact time (days) and the PFAS concentration (mg L^-1) from 1 to 7, and 0.5 to 10, respectively, the cell viability, total chlorophyll content, and protein content decreased, and the decrease in these parameters was significantly greater in Scenedesmus obliquus. As another step in the study, the response surface methodology (RSM) was used to optimize the toxicity effects of PFAS on microalgae in a logical way, as demonstrated by the high R² (>0.9). In another stage, a molecular docking study was performed to monitor the interaction of PFOS and PFOA with the microalgae, considering hydrolysis and the enzymes involved in oxidation-reduction reactions using individual enzymes. The analysis was conducted on carboxypeptidase in Chlorella vulgaris and on c-terminal processing protease and oxidized cytochrome c6 in Scenedesmus obliquus. For the enzyme activity, the affinity and dimensions of ligands-binding sites and ligand-binding energy were estimated in each case.

An overview on microalgae as renewable resources for meeting sustainable development goals

The increased demands and dependence on depleted oil reserves, accompanied by global warming and climate change have driven the world to explore and develop new strategies for global sustainable development. Among sustainable biomass sources, microalgae represent a promising alternative to fossil fuel and can contribute to the achievement of important Sustainable Development Goals (SDGs). This article has reviewed the various applications of microalgal biomass that includes (i) the use in aquaculture and its sustainability; (ii) commercial value and emerging extraction strategies of carotenoids; (iii) biofuels from microalgae and their application in internal combustion engines; (iv) the use and reuse of water in microalgae cultivation; and (v) microalgae biotechnology as a key factor to assist SDGs. The future prospects and challenges on the microalgae circular bio economy, issues with regard to the scale-up and water demand in microalgae cultivation are also highlighted.

The role of bioprocess systems engineering in extracting chemicals and energy from microalgae

In this study, the role of process systems engineering in enhancing the algae economy is highlighted. First, basic characteristics of the various strains of microalgae are presented. In addition, the beneficial extracted bioproducts and their applications are reviewed. Then, an overview of the various technologies available in each step of biorefinery to produce added-value products and biofuels from microalgae is provided. These technologies are compared in terms of required energy and efficiency. Different perspectives of the algae industry, from molecule to enterprises scale where process systems engineering can have a role, are addressed. Subsequently, the roles of process systems engineering in process and product design, process control, and supply chain of the algae biorefinery are discussed. It is found that process systems engineering can play an important role in the biobased economy, especially by applying sustainability and economic concepts in the decision-making process for selecting the best feedstock, processing pathways, and desired products. Tools such as market analysis, techno-economic analysis, life cycle assessment (LCA), and supply chain (SC) analysis can be applied to design sustainable algae biorefinery. There are, however, several challenges such as the lack of data, the complexity of optimization, and validation that should be addressed before using these tools.

Obtaining Fat-Soluble Pigments—Carotenoids from the Biomass of Chlorella Microalgae

The aim of this study was to use a directed mode of cultivation of the microalgae Chlorella for biomass production, followed by the subsequent extraction of carotenoids. The effect of a stress inducer of carotenogenesis (hydrogen peroxide) and a growth stimulator (pyridoxine, vitamin B6) on the accumulation of photosynthetic pigments by the biomass of the microalga C. vulgarisBIN in the process of directed cultivation was studied. It was revealed that the combination of these additives in the culture medium increases the content of chlorophylls and carotenoids in the biomass twofold compared to the control sample. The preliminary activation of the biomass by high-speed ultra-homogenization (a rotor rotation range from 6000 to 12,000 rpm) was also investigated. Using ultrasound extraction, the pigment complex was isolated from the activated biomass. The saponification and subsequent neutralization of carotenoids were carried out in an inert medium. The resulting sample contained carotenoids in the amount of 52 ± 3 mg/mL. The chemical profile of the carotenoids in the biomass of the microalga Chlorella vulgaris BIN was also established. The major carotenoid was lutein (45%), followed by fucoxanthin (12%) and β-carotene (4.3%). The oil extract of the carotenoids may be used for the further production of a microencapsulated product with the aim of targeted delivery to the lower parts of the gastrointestinal tract.

Algal biomass valorisation to high-value chemicals and bioproducts: Recent advances, opportunities and challenges

Algae are considered promising biomass resources for biofuel production. However, some arguments doubt the economical and energetical feasibility of algal cultivation, harvesting, and conversion processes. Beyond biofuel, value-added bioproducts can be generated via algae conversion, which would enhance the economic feasibility of algal biorefineries. This review primarily focuses on valuable chemical and bioproduct production from algae. The methods for effective recovery of valuable algae components, and their applications are summarized. The potential routes for the conversion of lipids, carbohydrates, and proteins to valuable chemicals and bioproducts are assessed from recent studies. In addition, this review proposes the following challenges for future algal biorefineries: (1) utilization of naturally grown algae instead of cultivated algae; (2) fractionation of algae to individual components towards high-selectivity products; (3) avoidance of humin formation from algal carbohydrate conversion; (4) development of strategies for algal protein utilisation; and (5) development of efficient processes for commercialization and industrialization.

Integrated microalgal biorefinery for the production and application of biostimulants in circular bioeconomy

Adverse detrimental impacts of environmental pollution over the health regimen of people has driven a shift in lifestyle towards cleaner and natural resources, especially in the aspects of food production and consumption. Microalgae are considered a rich source of high value metabolites to be utilized as plant growth biostimulants. These organisms however, are underrated compared to other microbial counterparts, due to inappropriate knowledge on the technical, enviro-economical constrains leading to low market credibility. Thus, to avert these issues, the present review comprehensively discusses the biostimulatory potential of microalgae interactively combined with circular bio-economy perspectives. The biochemical content and intracellular action mechanism of microalgal biostimulants were described. Furthermore, detailed country-wise market trends along with the description of the existing regulatory policies are included. Enviro-techno-economic challenges are discussed, and the consensus need for shift to biorefinery and circular bio-economy concept are emphasized to achieve sustainable impacts during the commercialization of microalgal biostimulants.

Microencapsulation of carotenoid-rich materials: A review

Carotenoids are natural pigments that present several bioactive properties, including antioxidant, anticarcinogenic and provitamin A activities. However, these compounds are susceptible to degradation when exposed to a number of conditions (e.g. light, heat, oxygen), leading to loss of benefits and hampering their application in food products. Their hydrophobicity also makes incorporation into water-based foods more difficult. Microencapsulation techniques have been applied for decades to provide stability to carotenoid-rich extracts under typical conditions of processing and storage of foods, besides offering several other advantages to the use and application of these materials. This work reviews the recent advances in the microencapsulation of carotenoid-rich extracts, oils and oleoresins from varying sources, evidencing the technologies applied to encapsulate these materials, the effects of encapsulation on the obtained particles, and the impact of such processes on the bioaccessibility and release profile of carotenoids from microparticles. Moreover, recent applications of carotenoid-rich microparticles in food products are discussed. Most of the applied processes were effective in improving different aspects of the encapsulated materials, especially the stability of carotenoids during storage, resulting in microparticles with promising properties for future applications in food products. However, the lack of information about the effects of microencapsulation on carotenoids during processing of model foods, the sensory acceptance of enriched food products and the bioaccessibility and bioavailability of microencapsulated carotenoids reveals gaps that should be explored in the future.

Medicinal Prospects of Antioxidants From Algal Sources in Cancer Therapy

Though cancer therapeutics can successfully eradicate cancerous cells, the effectiveness of these medications is mostly restricted to several deleterious side effects. Therefore, to alleviate these side effects, antioxidant supplementation is often warranted, reducing reactive species levels and mitigating persistent oxidative damage. Thus, it can impede the growth of cancer cells while protecting the normal cells simultaneously. Moreover, antioxidant supplementation alone or in combination with chemotherapeutics hinders further tumor development, prevents chemoresistance by improving the response to chemotherapy drugs, and enhances cancer patients' quality of life by alleviating side effects. Preclinical and clinical studies have been revealed the efficacy of using phytochemical and dietary antioxidants from different sources in treating chemo and radiation therapy-induced toxicities and enhancing treatment effectiveness. In this context, algae, both micro and macro, can be considered as alternative natural sources of antioxidants. Algae possess antioxidants from diverse groups, which can be exploited in the pharmaceutical industry. Despite having nutritional benefits, investigation and utilization of algal antioxidants are still in their infancy. This review article summarizes the prospective anticancer effect of twenty-three antioxidants from microalgae and their potential mechanism of action in cancer cells, as well as usage in cancer therapy. In addition, antioxidants from seaweeds, especially from edible species, are outlined, as well.

2-Methyloxolane (2-MeOx) as Sustainable Lipophilic Solvent to Substitute Hexane for Green Extraction of Natural Products. Properties, Applications, and Perspectives

This review presents a complete picture of current knowledge on 2-methyloxolane (2-MeOx), a bio-based solvent for the extraction of natural products and food ingredients. It provides the necessary background about the properties of 2-MeOx, not only its solvent power and extraction efficiency, but its detailed toxicological profile and environmental impacts are discussed. We compared 2-MeOx with hexane which is the most used petroleum-based solvent for extraction of lipophilic natural products. The final part focuses on successful industrial transfer, including technologic, economic, and safety impacts. The replacement of petroleum-based solvents is a hot research topic, which affects several fields of modern plant-based chemistry. All the reported applications have shown that 2-MeOx is an environmentally and economically viable alternative to conventional petroleum-based solvents for extraction of lipophilic foodstuff and natural products.

Investigation of Growth, Lipid Productivity, and Fatty Acid Profiles in Marine Bloom-Forming Dinoflagellates as Potential Feedstock for Biodiesel

Microalgae-based biodiesel is increasingly recognized as an alternative to crop-based biodiesel. In this study, 10 local strains of dinoflagellates collected from Hong Kong waters, including a monoculture and field sample of Scrippsiella sp. isolated from an algal bloom, were evaluated against the performance of green alga Tetraselmis suecica. The specific growth rate, biomass production, lipid productivity, and fatty acid profile were investigated. The total lipid content of isolated strains ranged from 16.2% to 32.2% of the total dry biomass, whereas palmitic acid (C16:0) and docosahexaenoic acid (DHA, C22:6n3) were dominant in the fatty acid profile. Scrippsiella sp. has a high lipid productivity (47.3 mg/L/day) and fatty acid methyl esters (FAME) content (55.2–73 mg/g dry weight (dw)), which were comparable to that in green alga T. suecica. Further, monoculture and field sampled blooming Scrippsiella sp. showed no significant difference in most parameters, suggesting the possibility of harvesting a natural algal bloom population as a mitigation strategy to harmful algal bloom and to use as biodiesel feedstock. Overall, dinoflagellate species showed a slower growth rate (0.04–0.57 day−1) than most compared species (0.07–1.34 day−1), likely due to a large genome size and low chlorophyll to carbon ratio. Notably, most investigated dinoflagellates were not ideal for mass biodiesel production due to the low growth rate and lipid productivity. However, a high level of polyunsaturated fatty acids (PUFA) in dinoflagellates are prospective for further studies in other biotechnological applications. Though effectively harvesting algal blooming biomass can be complex, it can be further explored as a strategy for algal bloom mitigation and potentially creating values at the advantage of natural bloom when applying harvested biomass for biodiesel and bioactive compounds extraction.

2-Methyloxolane as a Bio-Based Solvent for Green Extraction of Aromas from Hops (Humulus lupulus L.)

The potential of using the bio-based solvent 2-methyloxolane, also known as 2-methyltetrahydrofuran or 2-MeTHF, as an alternative to petroleum solvents such as hexane, was investigated for the extraction of volatile compounds from hop cones (Humulus lupulus L.). Lab scale extractions were coupled with in silico prediction of solutes solubility to assess the technical potential of this bio-based solvent. The predictive approach was performed using the simulation software COSMO-RS (conductor like screening model for real solvants) and showed that the 2-methyloxolane is as good as or better than hexane to solubilize the majority of aromas from hop cones. The experimental results indicated that the highest aroma yield was obtained with 2-methyloxolane with 20.2% while n-hexane was only able to extract 17.9%. The characterization of aromas extracted by the two solvents showed a similar composition, where lupulone was the main component followed by humulone. No selectivity of the solvents was observed for any of the major analytes. Finally, a sensory analysis was performed on the extracts, showing that both concretes using 2-methyloxolane and hexane have similar olfactory profiles. The results indicate that 2-methyloxolane could be a promising bio-based extraction solvent for hexane substitution.

An integrated approach for the valorization of mango seed kernel: Efficient extraction solvent selection, phytochemical profiling and antiproliferative activity assessment

A novel valorization strategy is proposed in this work for the sustainable utilization of a major mango processing waste (i.e. mango seed kernel, MSK), integrating green pressurized-liquid extraction (PLE), bioactive assays and comprehensive HRMS-based phytochemical characterization to obtain bioactive-rich fractions with high antioxidant capacity and antiproliferative activity against human colon cancer cells. Thus, a two steps PLE procedure was proposed to recover first the non-polar fraction (fatty acids and lipids) and second the polar fraction (polyphenols). Efficient selection of the most suitable solvent for the second PLE step (ethanol/ethyl acetate mixture) was based on the Hansen solubility parameters (HSP) approach. A comprehensive GC- and LC-Q-TOF-MS/MS profiling analysis allowed the complete characterization of the lipidic and phenolic fractions obtained under optimal condition (100% EtOH at 150 °C), demonstrating the abundance of oleic and stearic acids, as well as bioactive xanthones, phenolic acids, flavonoids, gallate derivatives and gallotannins. The obtained MSK-extract exhibited higher antiproliferative activity against human colon adenocarcinoma cell line HT-29 compared to traditional extraction procedures described in literature for MSK utilization (e.g. Soxhlet), demonstrating the great potential of the proposed valorization strategy as a valuable opportunity for mango processing industry to deliver a value-added product to the market with health promoting properties.