Sodium bicarbonate augmentation enhances lutein biosynthesis in green microalgae Chlorella pyrenoidosa

Selecting optimal algal strains for robust photosynthetic upgrading of biogas under temperate oceanic climates

Biogas generated from anaerobic digestion can be upgraded to biomethane by photosynthetic biogas upgrading, using CO2 as a bioresource for algal (cyanobacteria and microalgae) cultivation. This allows the upgrading technology to offer economic and environmental benefits to conventional physiochemical upgrading techniques (which can be energy-intensive and costly) by co-generating biomethane with high-value biomass. However, a critical challenge in implementing this technology in temperate oceanic climatic conditions (as found in Japan, and the northwest coasts of Europe and of North America, with average temperatures ranging between 5 and 20 °C) is the selection of algal strains that must be capable of sustained growth under lower ambient temperatures. Accordingly, this paper investigated the selection of algae that met seven key criteria: optimal growth at high pH (9-11); at alkalinity of 1.5-2.5 g inorganic carbon per litre; operation at low temperature (5-20 °C); tolerance to high CO2 concentrations (above 20 %); capability for mixotrophic cultivation; ability to accumulate high-value metabolites such as photosynthetic pigments and bioactive fatty acids; and ease of harvesting. Of the twenty-six algal species assessed and ranked using a Pugh Matrix, Anabaena sp. and Phormidium sp. were assessed as the most favourable species, followed by Oscillatoria sp., Spirulina subsalsa, and Leptolyngbya sp. Adaptive laboratory evolution together with manipulation of abiotic factors could be effectively utilised to increase the efficiency and economic feasibility of the use of the selected strain in a photosynthetic biogas upgrading system, through improvement of growth and yield of high-value compounds.

Enhancing Biomass and Lipid Production in Messastrum gracile Using Inorganic Carbon Substrates and Alternative Solvents for Lipid Extraction

Microalgae show promise as a biomass and bioproduct for applications in various industries. The cultivation of microalgae plays a crucial role in optimizing biomass yield and bioproduct accumulation. The provision of inorganic carbon substrates substantially enhances microalgal growth and lipid biosynthesis, resulting in marked increases in the production of biofuels and other bioproducts. This study examined biomass and lipid accumulation in Messastrum gracile IFRPD 1061 under inorganic stress conditions, previously unreported. M. gracile IFRPD 1061 was subjected to varying conditions of inorganic carbon substrates, 1-3 g·L-1 sodium carbonate and bicarbonate concentration, to enhance biomass and lipid accumulation. Optimal productivity levels were observed with sodium bicarbonate addition of 3 g·L-1 and 1 g·L-1 for biomass and lipids, resulting in productivities of 392.64 and 53.57 mg·L-1·d-1, respectively. Results underlined the effectiveness of sodium carbonate and bicarbonate as inorganic carbon sources for stimulating microalgal growth and enhancing the production of high-value products. The extraction of lipids from freeze-dried biomass of M. gracile IFRPD 1061 demonstrated optimal yield using methanol/hexane solvents compared with the control experiments. Lipid extraction yields using methanol/hexane were 42.18% and 46.81% from oven-dried and freeze-dried biomass, respectively. Lipids extracted from oven-dried M. gracile IFRPD 1061 using methanol/hexane/chloroform solvents indicated the potential of methanol/hexane as a solvent for lipid extraction from dry microalgal biomass using an ultrasonic-assisted technique. This study contributes valuable insights into maximizing biofuel and bioproduct production from microalgae, highlighting A. gracilis as a promising candidate for industrial applications.

Enhanced lutein and protein production with improved organoleptic properties in a novel yellow strain of Auxenochlorella pyrenoidosa mutant through atmospheric and room temperature plasma mutagenesis and norflurazon-based screening

To achieve the triple purpose of enhancing lutein and protein contents as well as improving organoleptic properties in biomass of Auxenochlorella pyrenoidosa mutant as raw material of future food, a novel yellow mutant, CX41 strain, was successfully selected through atmospheric and room temperature plasma (ARTP) mutagenesis and norflurazon-based screening. CX41 strain exhibited a significantly increased lutein (0.86 mg/g) and protein (49.00 % DW) contents simultaneously, while higher levels of total (33.47 % DW) and essential amino acids (14.78 % DW) were achieved with higher amino acid score (86.49) than that of the original A4-1 strain, a yellow and high protein mutant bred previously. Sensory evaluation showed that CX41 biomass has more comparable to A4-1, while in comparison to the wild type (WT), it has a more inclination towards roasted, with a fainter grassy, woody, rancid and fishy odor, and a significant improvement in taste is reflected by a decrease of 8.40 % in sweetness, a reduction of 14.86 % in bitterness, and an increase of 5.93 % in umami intensity. Metabolome analysis revealed that the superior sensory profile was due to the significantly reduced relative odor activity of β-ionone (herbaceous odor) and substances such as 1-octene, hexanal, 1-octen-3-ol, and heptanal (fishy and rancid odors). The extensive enhancements demonstrated CX41 biomass as a highly promising raw material with high nutrients of lutein and protein as well as excellent taste and flavor for future food application.

Integrating bicarbonate-based microalgal production with alkaline sewage for ocean negative carbon emissions

Using sewage (wastewater) for ocean alkalinity enhancement (OAE) has been considered as one promising ocean negative carbon emissions (ONCE) approach due to its high carbon sequestration efficiency and low environmental risk. To make this process more profitable and sustainable, this perspective proposes to integrate bicarbonate-based microalgal production and sewage alkalinity enhancement for ONCE. In this concept, the spent aqueous alkaline bicarbonate-based microalgal medium is cheap or even free for OAE, while the produced microalgae with high value-added compositions make this process more profitable. To make the proposed idea more efficient and sustainable, the prospects for its future development are also discussed in this opinion article. This perspective provides a novel and practical idea for achieving efficient carbon neutralization and high economic value simultaneously.

Recovery mechanism of a microalgal species, Chlorella sp. from toxicity of doxylamine: Physiological and biochemical changes, and transcriptomics

Ubiquitous distribution of pharmaceutical contaminants in environment has caused unexpected adverse effects on ecological organisms; however, how microorganisms recover from their toxicities remains largely unknown. In this study, we comprehensively investigated the effect of a representative pollutant, doxylamine (DOX) on a freshwater microalgal species, Chlorella sp. by analyzing the growth patterns, biochemical changes (total chlorophyll, carotenoid, carbohydrate, protein, and antioxidant enzymes), and transcriptomics. We found toxicity of DOX on Chlorella sp. was mainly caused by disrupting synthesis of ribosomes in nucleolus, and r/t RNA binding and processing. Intriguingly, additional bicarbonate enhanced the toxicity of DOX with decreasing the half-maximum effective concentrations from 15.34 mg L-1 to 4.63 mg L-1, which can be caused by inhibiting fatty acid oxidation and amino acid metabolism. Microalgal cells can recover from this stress via upregulating antioxidant enzymatic activities to neutralize oxidative stresses, and photosynthetic pathways and nitrogen metabolism to supply more energies and cellular signaling molecules. This study extended our understanding on how microalgae can recover from chemical toxicity, and also emphasized the effect of environmental factors on the toxicity of these contaminants on aquatic microorganisms.

Bioactive Exploration in Functional Foods: Unlocking Nature's Treasures

BACKGROUND

Functional foods offer an appealing way to improve health and prevent chronic diseases, and this subject has received much attention lately. They are effective in preventing chronic diseases like cancer, diabetes, heart disease, and obesity, according to research.

OBJECTIVE

This work presents an in-depth analysis of functional foods, covering key challenges from a scientific, legal, and commercial perspective.

METHODS

Multiple databases were searched to find studies on functional foods included in the systematic literature review. Various aspects of functional foods, from their classification, impact on human wellness, effectiveness in inhibiting chronic diseases, the regulatory environment, global market trends, and industry challenges, are all clarified in this thorough review.

RESULTS

This study aims to enhance understanding and establish a pathway for functional foods to be acknowledged as valid choices in the field of dietary supplements. It provides a thorough investigation of bioactive compounds present in functional foods, including but not limited to polyphenols, carotenoids, omega fatty acids, prebiotics, probiotics, and dietary fiber, along with an overview of their potential to mitigate chronic illnesses. We engage in an in-depth exploration of regulatory frameworks, shed light on groundbreaking research advancements, and meticulously examine strategies for commercialization and the variety of global challenges that accompany them. Establishing scientific consensus, navigating complex regulatory processes, dealing with skeptical consumers, and rising levels of competition are all problems that need to be solved in this field.

CONCLUSION

The field of functional foods can advance further, promoting better public health outcomes, by deeply comprehending and addressing these complex dimensions.

Microalgal lutein: Advancements in production, extraction, market potential, and applications

Lutein, a bioactive xanthophyll, has recently attracted significant attention for numerous health benefits, e.g., protection of eye health, macular degeneration, and acute and chronic syndromes etc. Microalgae have emerged as the best platform for high-value lutein production with high productivity, lutein content, and scale-up potential. Algal lutein possesses numerous bioactivities, hence widely used in pharmaceuticals, nutraceuticals, aquaculture, cosmetics, etc. This review highlights advances in upstream lutein production enhancement and feasible downstream extraction and cell disruption techniques for a large-scale lutein biorefinery. Besides bioprocess-related advances, possible solutions for existing production challenges in microalgae-based lutein biorefinery, market potential, and emerging commercial scopes of lutein and its potential health applications are also discussed. The key enzymes involved in the lutein biosynthesizing Methyl-Erythritol-phosphate (MEP) pathway have been briefly described. This review provides a comprehensive updates on lutein research advancements covering scalable upstream and downstream production strategies and potential applications for researchers and industrialists.

Recent Advances in the Carotenoids Added to Food Packaging Films: A Review

Food spoilage is one of the key concerns in the food industry. One approach is the improvement of the shelf life of the food by introducing active packaging, and another is intelligent packaging. Detecting packed food spoilage in real-time is key to stopping outbreaks caused by food-borne diseases. Using active materials in packaging can improve shelf life, while the nonharmful color indicator can be useful to trace the quality of the food through simple color detection. Recently, bio-derived active and intelligent packaging has gained a lot of interest from researchers and consumers. For this, the biopolymers and the bioactive natural ingredient are used as indicators to fabricate active packaging material and color-changing sensors that can improve the shelf life and detect the freshness of food in real-time, respectively. Among natural bioactive components, carotenoids are known for their good antimicrobial, antioxidant, and pH-responsive color-indicating properties. Carotenoids are rich in fruits and vegetables and fat-soluble pigments. Including carotenoids in the packaging system improves the film's physical and functional performance. The recent progress on carotenoid pigment-based packaging (active and intelligent) is discussed in this review. The sources and biological activity of the carotenoids are briefly discussed, and then the fabrication and application of carotenoid-activated packaging film are reviewed. The carotenoids-based packaging film can enhance packaged food's shelf life and indicate the freshness of meat and vegetables in real-time. Therefore, incorporating carotenoid-based pigment into the polymer matrix could be promising for developing novel packaging materials.

Lutein production from microalgae: A review

Lutein production from microalgae is a sustainable and economical strategy to offer the increasing global demands, but is still challenged with low lutein content at the high-cell density for commercial production. This review summarizes the suitable conditions for cell growth and lutein accumulation, and presents recent cultivation strategies to further improve lutein productivity. Light and nitrogen play critical roles in lutein biosynthesis that lead to the efficient multi-stage cultivation by increasing lutein content at the later stage. In addition, metabolic and genetic designs for carbon regulation and lutein biosynthesis are discussed at the molecule level. The in-situ lutein accumulation in fermenters by regulating carbon metabolism is considered as a cost-effective direction. Then, downstream processes are summarized for the efficient lutein recovery. Finally, challenges of current lutein production from microalgae are discussed. Meanwhile, potential solutions are proposed to improve lutein content and drive down costs of microalgal biomass.

Natural Carotenoids: Recent Advances on Separation from Microbial Biomass and Methods of Analysis

Biotechnologically produced carotenoids occupy an important place in the scientific research. Owing to their role as natural pigments and their high antioxidant properties, microbial carotenoids have been proposed as alternatives to their synthetic counterparts. To this end, many studies are focusing on their efficient and sustainable production from renewable substrates. Besides the development of an efficient upstream process, their separation and purification as well as their analysis from the microbial biomass confers another important aspect. Currently, the use of organic solvents constitutes the main extraction process; however, environmental concerns along with potential toxicity towards human health necessitate the employment of "greener" techniques. Hence, many research groups are focusing on applying emerging technologies such as ultrasounds, microwaves, ionic liquids or eutectic solvents for the separation of carotenoids from microbial cells. This review aims to summarize the progress on both the biotechnological production of carotenoids and the methods for their effective extraction. In the framework of circular economy and sustainability, the focus is given on green recovery methods targeting high-value applications such as novel functional foods and pharmaceuticals. Finally, methods for carotenoids identification and quantification are also discussed in order to create a roadmap for successful carotenoids analysis.

Roles of microalgae-based biofertilizer in sustainability of green agriculture and food-water-energy security nexus

For years, agrochemical fertilizers have been used in agriculture for crop production. However, intensive utilization of chemical fertilizers is not an ecological and environmental choice since they are destroying soil health and causing an emerging threat to agricultural production on a global scale. Under the circumstances of the increasing utilization of chemical fertilizers, cultivating microalgae to produce biofertilizers would be a wise solution since desired environmental targets will be obtained including (1) replacing chemical fertilizer while improving crop yields and soil health; (2) reducing the harvest of non-renewable elements from limited natural resources for chemical fertilizers production, and (3) mitigating negative influences of climate change through CO₂ capture through microalgae cultivation. Recent improvements in microalgae-derived-biofertilizer-applied agriculture will be summarized in this review article. At last, the recent challenges of applying biofertilizers will be discussed as well as the perspective regarding the concept of circular bio-economy and sustainable development goals (SDGs).

Promoting lutein production from the novel alga Acutodesmus sp. by melatonin induction

In the current research, a novel microalgae strain was isolated from Yajiageng Red Rock Beach and identified as Acutodesmus sp. HLGY. To obtain high-efficiency production of lutein from algae, the feasibility of using melatonin (MT) to increase lutein yield of Acutodesmus sp. HLGY was evaluated. Under the 7.5 μM MT treatment, the lutein content and lutein productivity were 17.44 mg g^-1 and 46.50 mg L^-1 d^-1, which were 1.53 times those of the control. Furthermore, exogenous MT increased the transcripts of key lutein synthesis- and antioxidant enzyme-related genes. Simultaneously, the carbohydrate, protein, and cellular reactive oxygen species (ROS) levels and lipid content were suppressed. More importantly, the ethylene and γ-aminobutyric acid contents were markedly increased by MT, which may be linked to the increase in lutein biosynthesis. This study proposes a valuable biotechnological approach for lutein production via a novel Acutodesmus sp. strain using MT induction and provides insights into the role of MT in promoting lutein biosynthesis.

Treatment and resource utilization of dairy liquid digestate by nitrification of biological aerated filter coupled with assimilation of Chlorella pyrenoidosa

Ammonia inhibition is considered a key issue when using liquid digestate for microalgae cultivation. To study the effect of pretreatment with a biological aerated filter (BAF) on microalgae culture with dairy liquid digestate, nitrification characteristics of BAFs under different hydraulic retention time (HRT) and the growth characteristics of Chlorella pyrenoidosa in effluents of BAFs were investigated. Results showed that the BAFs can rapidly nitrify ammonia nitrogen and significantly improve the light transmittance of liquid digestate (the maximum promotion rate was ~260%), and the effect improved as the HRT increased. Pretreatment of liquid digestate with BAFs can eliminate ammonia inhibition for C. pyrenoidosa. Furthermore, lipid, crude protein, and higher heating value (HHV) output were also not affected by HRT. The similar removal of nitrate nitrogen in microalgae culture systems using effluents with 6-h and 12-h HRT (21.59% and 21.07%, respectively) were recorded. The results suggested that BAF coupled with microalgae culture is a novel option on the resource utilization of dairy liquid digestate.

Utilisation of CO2 from Sodium Bicarbonate to Produce Chlorella vulgaris Biomass in Tubular Photobioreactors for Biofuel Purposes

Microalgae are one of the most promising sources of renewable substrates used for energy purposes. Biomass and components accumulated in their cells can be used to produce a wide range of biofuels, but the profitability of their production is still not at a sufficient level. Significant costs are generated, i.a., during the cultivation of microalgae, and are connected with providing suitable culture conditions. This study aims to evaluate the possibility of using sodium bicarbonate as an inexpensive alternative CO2 source in the culture of Chlorella vulgaris, promoting not only the increase of microalgae biomass production but also lipid accumulation. The study was carried out at technical scale using 100 L photobioreactors. Gravimetric and spectrophotometric methods were used to evaluate biomass growth. Lipid content was determined using a mixture of chloroform and methanol according to the Blight and Dyer method, while the carbon content and CO2 fixation rate were measured according to the Walkley and Black method. In batch culture, even a small addition of bicarbonate resulted in a significant (p ≤ 0.05) increase in the amount of biomass, productivity and optical density compared to non-bicarbonate cultures. At 2.0 g∙L–1, biomass content was 572 ± 4 mg·L−1, the maximum productivity was 7.0 ± 1.0 mg·L–1·d–1, and the optical density was 0.181 ± 0.00. There was also an increase in the lipid content (26 ± 4%) and the carbon content in the biomass (1322 ± 0.062 g∙dw–1), as well as a higher rate of carbon dioxide fixation (0.925 ± 0.073 g·L–1·d–1). The cultivation of microalgae in enlarged scale photobioreactors provides a significant technological challenge. The obtained results can be useful to evaluate the efficiency of biomass and valuable cellular components production in closed systems realized at industrial scale.

Channeling of Carbon Flux Towards Carotenogenesis in Botryococcus braunii: A Media Engineering Perspective

Microalgae, due to their unique properties, gained attention for producing promising feedstocks having high contents of proteins, antioxidants, carotenoids, and terpenoids for applications in nutraceutical and pharmaceutical industries. Optimizing production of the high-value renewables (HVRs) in microalgae requires an in-depth understanding of their functional relationship of the genes involved in these metabolic pathways. In the present study, bioinformatic tools were employed for characterization of the protein-encoding genes of methyl erythritol phosphate (MEP) pathway involved in carotenoid and squalene biosynthesis based upon their conserved motif/domain organization. Our analysis demonstrates nearly 200 putative genes showing a conservation pattern within divergent microalgal lineages. Furthermore, phylogenomic studies confirm the close evolutionary proximity among these microalgal strains in the carotenoid and squalene biosynthetic pathways. Further analysis employing STRING predicts interactions among two rate-limiting genes, i.e., phytoene synthase (PSY) and farnesyl diphosphate farnesyl synthase (FPPS), which are specifically involved in the synthesis of carotenoids and squalene. Experimentally, to understand the carbon flux of these rate-limiting genes involved in carotenogenesis, an industrial potential strain, namely, Botryococcus braunii, was selected in this study for improved biomass productivity (i.e., 100 mg L^-1 D^-1) along with enhanced carotenoid content [0.18% dry cell weight (DCW)] when subjected to carbon supplementation. In conclusion, our approach of media engineering demonstrates that the channeling of carbon flux favors carotenogenesis rather than squalene synthesis. Henceforth, employing omics perspectives will further provide us with new insights for engineering regulatory networks for enhanced production of high-value carbon biorenewables without compromising growth.

Combined Production of Astaxanthin and β-Carotene in a New Strain of the Microalga Bracteacoccus aggregatus BM5/15 (IPPAS C-2045) Cultivated in Photobioreactor

Carotenoids astaxanthin and β-carotene are widely used natural antioxidants. They are key components of functional food, cosmetics, drugs and animal feeding. They hold leader positions on the world carotenoid market. In current work, we characterize the new strain of the green microalga Bracteacoccus aggregatus BM5/15 and propose the method of its culturing in a bubble-column photobioreactor for simultaneous production of astaxanthin and β-carotene. Culture was monitored by light microscopy and pigment kinetics. Fatty acid profile was evaluated by tandem gas-chromatography-mass spectrometry. Pigments were obtained by the classical two-stage scheme of autotrophic cultivation. At the first, vegetative, stage biomass accumulation occurred. Maximum specific growth rate and culture productivity at this stage were 100-200 mg∙L^-1∙day^-1, and 0.33 day^-1, respectively. At the second, inductive, stage carotenoid synthesis was promoted. Maximal carotenoid fraction in the biomass was 2.2-2.4%. Based on chromatography data, astaxanthin and β-carotene constituted 48 and 13% of total carotenoid mass, respectively. Possible pathways of astaxanthin synthesis are proposed based on carotenoid composition. Collectively, a new strain B. aggregatus BM5/15 is a potential biotechnological source of two natural antioxidants, astaxanthin and β-carotene. The results give the rise for further works on optimization of B. aggregatus cultivation on an industrial scale.

Biodegradation of Doxylamine From Wastewater by a Green Microalga, Scenedesmus obliquus

Pharmaceutical contaminants (PCs) have been recognized as emerging contaminants causing unexpected consequences to environment and humans. There is an urgent need for development of efficient technologies to treat these PCs from water. The current study has investigated the removal capacity of a green microalgal species, Scenedesmus obliquus, for doxylamine, chemical oxygen demand (COD), and nutrients from real wastewater. Results have indicated that S. obliquus can grow well in the doxylamine-polluted wastewater with the achievement of 56, 78.5, 100, and 89% removal of doxylamine, COD, total nitrogen (TN), and total phosphorus (TP). Addition of 2 g L^-1 bicarbonate enhanced the removal of doxylamine up to 63% and slightly inhibited the removal of COD. Decreased carbohydrate (28-26%) and increased protein content (30-33%) of the harvested biomass have been observed after cultivation in the wastewater. The current study has shown the feasibility of using microalgae-based biotechnologies for PC-contaminated wastewater.

Rapid and Positive Effect of Bicarbonate Addition on Growth and Photosynthetic Efficiency of the Green Microalgae Chlorella Sorokiniana (Chlorophyta, Trebouxiophyceae)

Bicarbonate ions are the primary source of inorganic carbon for autotrophic organisms living in aquatic environments. In the present study, we evaluated the short-term (hours) effects of sodium bicarbonate (NaHCO3) addition on the growth and photosynthetic efficiency of the green algae Chlorella sorokiniana (211/8k). Bicarbonate was added to nonaxenic cultures at concentrations of 1, 2, and 3 g L−1 leading to a significant increase in biomass especially at the highest salt concentration (3 g L−1) and also showing a bactericidal and bacteriostatic effect that helped to keep a reduced microbial load in the algal culture. Furthermore, bicarbonate stimulated the increase in cellular content of chlorophyll a, improving the photosynthetic performance of cells. Since microalgae of genus Chlorella spp. show great industrial potential for the production of biofuels, nutraceuticals, cosmetics, health, and dietary supplements and the use of bicarbonate as a source of inorganic carbon led to short-term responses in Chlorella sorokiniana, this method represents a valid alternative not only to the insufflation of carbon dioxide for the intensive cultures but also for the production of potentially bioactive compounds in a short period.