Diverse Biosynthetic Pathways and Protective Functions against Environmental Stress of Antioxidants in Microalgae

Microalgae in the food-health nexus: Exploring species diversity, high-value bioproducts, health benefits, and sustainable market potential

Microalgae are valuable nutraceutical sources because of their nutrient-rich profiles and diverse bioactive compounds. This review provides a comprehensive analysis of marine and freshwater microalgae, emphasizing their species diversity, nutrient composition, and methods used for their extraction and processing. The health benefits of microalgal-based nutraceuticals have been explored, with evidence highlighting their role in managing diabetes, cancer, oxidative stress, inflammation, and obesity. Additionally, the sustainability and environmental benefits of marine and freshwater microalgal cultivation are discussed. The market potential for these nutraceuticals has been explored, underpinned by recent advancements in biotechnology, nanotechnology, and omics approaches. Despite their promising potential, challenges such as extraction efficiency, purification processes, and production scalability currently limit the widespread application of microalgae in nutraceuticals. However, recent advancements in biotechnology and omics approaches are driving innovations, addressing these limitations, and unlocking new possibilities. Furthermore, ongoing research and technological innovations suggest a bright future for the integration of marine microalgae into the nutraceutical industry, promoting both human health and environmental sustainability. This review also evaluates the growing market potential and economic viability of microalgal-based nutraceuticals, highlighting their growing demand and economic viability and providing a comprehensive understanding of the benefits, market potential, and technological advancements of marine and freshwater microalgae, fostering further innovation in this promising field.

Ozone oxidation of actual waste leachate coupled with culture of microalgae for efficient lipid production under different temperatures

The production of waste leachate (WL) has been increasing annually with the growth of population and the improvement of living standards, but it has become a difficult task to treat and resource it. Furthermore, the shortage of energy is becoming more serious, so the development of renewable energy instead of expensive fossil fuels is especially essential for productive life. This study constructed a system to oxidize WL by ozone at different temperatures and used it as a culture substrate for microalgae to produce biodiesel. It was shown that the biomass and lipid content of microalgae reached 420 ± 43.59 mg/L and 41 ± 2.2 % at a low temperature of 15 °C, respectively. Compared with the reaction system at 5 °C, the oxidation of WL by ozone at 25-45 °C was more effective in removing ammonia nitrogen, total phosphorus, and chromaticity. Three-dimension excitation emission matrix (3D-EEM) fluorescence spectroscopy results showed that the fluorescence intensity of dissolved organic matter in WL was reduced by 59.4 %-67.7 % after the ozone oxidation, which improved the bioavailability of WL and laid a nutrient foundation for the growth of microalgae. At 45 °C, 72.7 % of the chromaticity of WL was removed by ozone oxidation alone, and the ozone-coupled microalgae treatment system reduced ammonia nitrogen from 416.25 ± 1.05 to 214.6 ± 7.99 mg/L in WL. In addition, microalgae regulated the antioxidant system to mitigate oxidative damage induced by high concentrations of reactive oxygen species (ROS) caused by extreme temperatures by adjusting the levels of superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH). The lipids of microalgae cultured in WL were dominated by saturated and unsaturated fatty acids, and the saturated fatty acids content of lipids reached 60.8 % at 15 °C, which was favorable for the production of biodiesel with better lubricating and combustion properties. This study provides a valuable theoretical basis for the resource utilization of WL and the practical production of microalgae biodiesel in cold regions.

Current Approaches and Implications in Discovery of Novel Bioactive Products from Microbial Sources

Bioactive Natural Products (BNPs) are in high demand due to their disease-preventive capabilities and resistance to pathogens. However, our understanding of BNP-producing microbes is limited, because many microbial populations remain uncultivated. Various approaches have been employed to explore the potential of these hidden microbes for new bioactive therapeutic compounds. Nevertheless, the possibility of discovering BNPs from microbial communities is largely cryptic due to their unculturable nature and the absence of triggers to activate the dormant Biosynthetic Gene Clusters (BGCs). Metagenome sequencing, followed by mining and characterization, is an effective approach for discovering new therapeutic BNPs. The inactive state of BGCs can be activated through the combinatorial interaction of different microbial communities within a common niche, overcoming programmable co-evolutionary stress and producing new BNPs. The present review discusses and explores the potential of hidden, uncultivated microbes for discovering novel Bioactive Natural Products (BNPs). Moreover, it provides insights into optimizing microbial production systems and fostering sustainable drug discovery and development practices by integrating multidisciplinary strategies. This review also emphasizes the critical role of microbial sources in the ongoing search for new bioactive products that can meet the demands of modern healthcare and environmental sustainability.

Enhancing domestic wastewater treatment through four chlorophyta strains-based phycoremediation: nutrient removal efficiency and algal physiology

Phycoremediation is a promising solution for environmentally sustainable wastewater treatment. However, its effectiveness depends on the selection of suitable microalgae species. In this study, four algal species (Chlorella sorokiniana, Chlorella vulgaris, Scenedesmus ecornis, and Strombomonas sp.) were evaluated for their ability to remove pollutants from secondary treated domestic wastewater using multi-soil-layering (MSL) technology. Among the four strains tested, Chlorella sorokiniana exhibited the highest algal density (2.832 ± 0.187 × 107 cells/mL) and outperformed other species with phosphorus, nitrogen, and COD removal rates exceeding 82.01%, 63.64%, and 61.09% respectively. In addition, Chlorella sorokiniana had a higher total chlorophyll content of 31.11 µg. L-1 (Chl a: 15.47 ± 0.148 µg. L-1; Chl b: 15.642 ± 0.052 µg. L-1) than other species. Physiological analyses of proline and glycine betaine indicated that the two Chlorella strains experienced lower stress levels, which facilitated an accelerated bioremediation process compared to other Chlorophyta, namely Scenedesmus ecornis and Strombomonas sp. The efficiency of C. sorokiniana in the treatment of secondary treated wastewater from MSL, combined with its maximum biomass production, underlines its potential for industrial application. Consequently, there is a compelling interest in evaluating C. sorokiniana within a prototype as a prelude to industrial development.

Soil Salinization and Ancient Hulled Wheat: A Study on Antioxidant Defense Mechanisms

Soil salinization, which is second only to soil erosion in terms of soil degradation, significantly hinders crop growth and development, leading to reduced yields. This study investigated the enzymatic and non-enzymatic antioxidant defense mechanisms of four ancient hulled wheat species under salt stress, with and without exogenous glycine betaine (0.5 mM). We aimed to assess the salt tolerance of these species and their potential for cultivation in saline/sodic soils. Our findings indicate that sodium and potassium chloride concentrations exceeding 100 mM induce significant stress in hulled wheat. However, combined salt stress (sodium and potassium chloride) reduced this stress by approximately 20-30%. Furthermore, exogenous glycine betaine supplementation almost completely alleviated the negative effects of salt stress, particularly in Triticum boeoticum. This species exhibited a remarkable ability to restore normal growth functions under these conditions. Our results suggest that ancient hulled wheat, especially T. boeoticum, may be a promising candidate for cultivation in sodium-saline soils. By supplementing with potassium fertilizers in addition to nitrogen, plants can effectively control salt influx into their cells and maintain intracellular K+/Na+ balance, thereby mitigating the adverse effects of salinity stress. This approach has the potential to increase crop yields and enhance food security in saline environments.

A Biorefinery Approach Integrating Lipid and EPS Augmentation Along with Cr (III) Mitigation by Chlorella minutissima

The quest for cleaner and sustainable energy sources is crucial, considering the current scenario of a steep rise in energy consumption and the fuel crisis, exacerbated by diminishing fossil fuel reserves and rising pollutants. In particular, the bioaccumulation of hazardous substances like trivalent chromium has not only disrupted the fragile equilibrium of the ecological system but also poses significant health hazards to humans. Microalgae emerged as a promising solution for achieving sustainability due to their ability to remediate contaminants and produce greener alternatives such as biofuels. This integrated approach provides an ambitious strategy to address global concerns pertaining to economic stability, environmental degradation, and the energy crisis. This study investigates the intricate defense mechanisms deployed by freshwater microalgae Chlorella minutissima in response to Cr (III) toxicity. The microalga achieved an impressive 92% removal efficiency with an IC50 value of 200 ppm, illustrating its extraordinary resilience towards chromium-induced stress. Furthermore, this research embarked on thorough explorations encompassing morphological, pigment-centric, and biochemical analyses, aimed at revealing the adaptive strategies associated with Cr (III) resilience, as well as the dynamics of carbon pool flow that contribute to enhanced lipid and extracellular polysaccharide (EPS) synthesis. The FAME profile of the biodiesel produced complies with the benchmark established by American and European fuel regulations, emphasizing its suitability as a high-quality vehicular fuel. Elevated levels of ROS, TBARS, and osmolytes (such as glycine-betaine), along with the increased activity of antioxidant enzymes (CAT, GR, and SOD), reveal the activation of robust defense mechanisms against oxidative stress caused by Cr (III). The finding of this investigation presents an effective framework for an algal-based biorefinery approach, integrating pollutant detoxification with the generation of vehicular-quality biodiesel and additional value-added compounds vital for achieving sustainability under the concept of a circular economy.

Hormetic and transcriptomic responses of the toxic alga Prymnesium parvum to glyphosate

Growth of the toxic alga Prymnesium parvum is hormetically stimulated with environmentally relevant concentrations of glyphosate. The mechanisms of glyphosate hormesis in this species, however, are unknown. We evaluated the transcriptomic response of P. parvum to glyphosate at concentrations that stimulate maximum growth and where growth is not different from control values, the zero-equivalent point (ZEP). Maximum growth occurred at 0.1 mg l-1 and the ZEP was 2 mg l-1. At 0.1 mg l-1, upregulated transcripts outnumbered downregulated transcripts by one order of magnitude. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that the upregulated transcriptome is primarily associated with metabolism and biosynthesis. Transcripts encoding heat shock proteins and co-chaperones were among the most strongly upregulated, and several others were associated with translation, Redox homeostasis, cell replication, and photosynthesis. Although most of the same transcripts were also upregulated at concentrations ≥ZEP, the proportion of downregulated transcripts greatly increased as glyphosate concentrations increased. At the ZEP, downregulated transcripts were associated with photosynthesis, cell replication, and anion transport, indicating that specific interference with these processes is responsible for the nullification of hormetic growth. Transcripts encoding the herbicidal target of glyphosate, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), were upregulated at concentrations ≥ZEP but not at 0.1 mg l-1, indicating that disruption of EPSPS activity occurred at high concentrations and that nullification of hormetic growth involves the direct interaction of glyphosate with this enzyme. Results of this study may contribute to a better understanding of glyphosate hormesis and of anthropogenic factors that influence P. parvum biogeography and bloom formation.

Genetic Engineering and Innovative Cultivation Strategies for Enhancing the Lutein Production in Microalgae

Carotenoids, with their diverse biological activities and potential pharmaceutical applications, have garnered significant attention as essential nutraceuticals. Microalgae, as natural producers of these bioactive compounds, offer a promising avenue for sustainable and cost-effective carotenoid production. Despite the ability to cultivate microalgae for its high-value carotenoids with health benefits, only astaxanthin and β-carotene are produced on a commercial scale by Haematococcus pluvialis and Dunaliella salina, respectively. This review explores recent advancements in genetic engineering and cultivation strategies to enhance the production of lutein by microalgae. Techniques such as random mutagenesis, genetic engineering, including CRISPR technology and multi-omics approaches, are discussed in detail for their impact on improving lutein production. Innovative cultivation strategies are compared, highlighting their advantages and challenges. The paper concludes by identifying future research directions, challenges, and proposing strategies for the continued advancement of cost-effective and genetically engineered microalgal carotenoids for pharmaceutical applications.

Bioactivity and Bioavailability of Carotenoids Applied in Human Health: Technological Advances and Innovation

This article presents a groundbreaking perspective on carotenoids, focusing on their innovative applications and transformative potential in human health and medicine. Research jointly delves deeper into the bioactivity and bioavailability of carotenoids, revealing therapeutic uses and technological advances that have the potential to revolutionize medical treatments. We explore pioneering therapeutic applications in which carotenoids are used to treat chronic diseases such as cancer, cardiovascular disease, and age-related macular degeneration, offering novel protective mechanisms and innovative therapeutic benefits. Our study also shows cutting-edge technological innovations in carotenoid extraction and bioavailability, including the development of supramolecular carriers and advanced nanotechnology, which dramatically improve the absorption and efficacy of these compounds. These technological advances not only ensure consistent quality but also tailor carotenoid therapies to each patient's health needs, paving the way for personalized medicine. By integrating the latest scientific discoveries and innovative techniques, this research provides a prospective perspective on the clinical applications of carotenoids, establishing a new benchmark for future studies in this field. Our findings underscore the importance of optimizing carotenoid extraction, administration, bioactivity, and bioavailability methods to develop more effective, targeted, and personalized treatments, thus offering visionary insight into their potential in modern medical practices.

Evolving perspectives on lutein production from microalgae - A focus on productivity and heterotrophic culture

Increased consumer awareness for healthier and more sustainable products has driven the search for naturally sourced compounds as substitutes for chemically synthesized counterparts. Research on pigments of natural origin, such as carotenoids, particularly lutein, has been increasing for over three decades. Lutein is recognized for its antioxidant and photoprotective activity. Its ability to cross the blood-brain barrier allows it to act at the eye and brain level and has been linked to benefits for vision, cognitive function and other conditions. While marigold flower is positioned as the only crop from which lutein is extracted from and commercialized, microalgae are proposed as an alternative with several advantages over this terrestrial crop. The main barrier to scaling up lutein production from microalgae to the commercial level is the low productivity compared to the high costs. This review explores strategies to enhance lutein production in microalgae by emphasizing the overall productivity over lutein content alone. Evaluation of how culture parameters, such as light quality, nitrogen sufficiency, temperature and even stress factors, affect lutein content and biomass development in batch phototrophic cultures was performed. Overall, the total lutein production remains low under this metabolic regime due to the low biomass productivity of photosynthetic batch cultures. For this reason, we describe findings on microalgal cultures grown under different metabolic regimes and culture protocols (fed-batch, pulse-feed, semi-batch, semi-continuous, continuous). After a careful literature examination, two-step heterotrophic or mixotrophic cultivation strategies are suggested to surpass the lutein productivity achieved in single-step photosynthetic cultures. Furthermore, this review highlights the urgent need to develop technical feasibility studies at a pilot scale for these cultivation strategies, which will strengthen the necessary techno-economic analyses to drive their commercial production.

Metabolomic Profiling of Floccularia luteovirens from Different Geographical Regions Proposes a Novel Perspective on Their Antioxidative Activities

Floccularia luteovirens, an endemic resource of the Tibetan Plateau, possesses significant medicinal and ecological values. However, the understanding of antioxidant capacity and metabolic profiling of F. luteovirens from diverse regions remains elusive due to limited resources. Therefore, to comprehensively comprehend the antioxidant capacity and metabolite diversity of F. luteovirens, we conducted a rounded analysis of its antioxidant capacity from three distinct regions using both untargeted and targeted metabolomics. Determination of antioxidant indices, such as ferric ion-reducing antioxidant power (FRAP), total phenolic content (TPC), and flavonoid content (FC), revealed the robust antioxidant capacity of F. luteovirens. QL F. luteovirens (QLFL) exhibited no significant difference compared to ZD F. luteovirens (ZDFL); however, both were significantly distinct from XH F. luteovirens (XHFL) across multiple indices. Furthermore, a positive correlation was observed between FRAP and flavonoid content. A total of 5782 metabolites were identified and chemically classified. Metabolites of F. luteovirens varied significantly at different regions and eight key differential metabolites were screened. Phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism, and cyanoamino acid metabolism were the main different regulatory pathways. Consequently, the disparities in the antioxidant activity of F. luteovirens may primarily be ascribed to the biosynthesis and metabolism of phenylalanine, while vanillic acid could potentially serve as a pivotal metabolite influencing the antioxidative capacity of F. luteovirens by targeted metabolomics. These findings enhance our understanding of the composition of F. luteovirens and provide valuable resources for its comprehensive utilization and targeted development.

Transcriptomics aids in uncovering the metabolic shifts and molecular machinery of Schizochytrium limacinum during biotransformation of hydrophobic substrates to docosahexaenoic acid

BACKGROUND

Biotransformation of waste oil into value-added nutraceuticals provides a sustainable strategy. Thraustochytrids are heterotrophic marine protists and promising producers of omega (ω) fatty acids. Although the metabolic routes for the assimilation of hydrophilic carbon substrates such as glucose are known for these microbes, the mechanisms employed for the conversion of hydrophobic substrates are not well established. Here, thraustochytrid Schizochytrium limacinum SR21 was investigated for its ability to convert oils (commercial oils with varying fatty acid composition and waste cooking oil) into ω-3 fatty acid; docosahexaenoic acid (DHA).

RESULTS

Within 72 h SR21 consumed ~ 90% of the oils resulting in enhanced biomass (7.5 g L- 1) which was 2-fold higher as compared to glucose. Statistical analysis highlights C16 fatty acids as important precursors of DHA biosynthesis. Transcriptomic data indicated the upregulation of multiple lipases, predicted to possess signal peptides for secretory, membrane-anchored and cytoplasmic localization. Additionally, transcripts encoding for mitochondrial and peroxisomal β-oxidation along with acyl-carnitine transporters were abundant for oil substrates that allowed complete degradation of fatty acids to acetyl CoA. Further, low levels of oxidative biomarkers (H2O2, malondialdehyde) and antioxidants were determined for hydrophobic substrates, suggesting that SR21 efficiently mitigates the metabolic load and diverts the acetyl CoA towards energy generation and DHA accumulation.

CONCLUSIONS

The findings of this study contribute to uncovering the route of assimilation of oil substrates by SR21. The thraustochytrid employs an intricate crosstalk among the extracellular and intracellular molecular machinery favoring energy generation. The conversion of hydrophobic substrates to DHA can be further improved using synthetic biology tools, thereby providing a unique platform for the sustainable recycling of waste oil substrates.

Type II metacaspase mediates light-dependent programmed cell death in Chlamydomonas reinhardtii

Among the crucial processes that preside over the destiny of cells from any type of organism are those involving their self-destruction. This process is well characterized and conceptually logical to understand in multicellular organisms; however, the levels of knowledge and comprehension of its existence are still quite enigmatic in unicellular organisms. We use Chlamydomonas (Chlamydomonas reinhardtii) to lay the foundation for understanding the mechanisms of programmed cell death (PCD) in a unicellular photosynthetic organism. In this paper, we show that while PCD induces the death of a proportion of cells, it allows the survival of the remaining population. A quantitative proteomic analysis aiming at unveiling the proteome of PCD in Chlamydomonas allowed us to identify key proteins that led to the discovery of essential mechanisms. We show that in Chlamydomonas, PCD relies on the light dependence of a photosynthetic organism to generate reactive oxygen species and induce cell death. Finally, we obtained and characterized mutants for the 2 metacaspase genes in Chlamydomonas and showed that a type II metacaspase is essential for PCD execution.

Reddening of the Unicellular Green Alga Euglena gracilis by Dried Bonito Stock and Intense Red Light Irradiation

This study confirms for the first time that the significant red coloration of Euglena gracilis is induced by bonito stock (BS), a traditional Japanese food, and intense red light exposure (605~660 nm, 1000~1300 µmol photons/m2/s). Under the condition, excessive photosynthetic activity destroyed many chloroplasts, while carotenoids were maintained, resulting in the formation of reddened cells. The HPLC analysis revealed that diadinoxanthin was the primary carotenoid present in reddened cells. Additionally, an undefined xanthophyll, not produced under normal culture conditions, was synthesized and suggested to contain a C=O bond. While it has been reported that strong light stress can increase the total carotenoid content of cells, this study did not verify this claim, and it should be investigated further in future research. Under white light irradiation conditions (90 μmol photons/m2/s) in BS medium, no reddening of cells was observed, and good growth was achieved (over four times the cell density in CM medium on the seventh day). This cell suspension is considered to have a high nutritional value because it is composed of functional food, BS and E. gracilis. The fact that this method does not involve genetic modification suggests the possibility of industrial applications, including food use, even in reddened cells.

Modification in the ascorbate-glutathione cycle leads to a better acclimation to high light in the rose Bengal resistant mutant of Nannochloropsis oceanica

Understanding how to adapt outdoor cultures of Nannochloropsis oceanica to high light (HL) is vital for boosting productivity. The N. oceanica RB2 mutant, obtained via ethyl methanesulfonate mutagenesis, was chosen for its tolerance to Rose Bengal (RB), a singlet oxygen (1O2) generator. Compared to the wild type (WT), the RB2 mutant showed higher resilience to excess light conditions. Analyzing the ascorbate-glutathione cycle (AGC), involving ascorbate peroxidases (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.8.1.7), in the RB2 mutant under HL stress provided valuable insights. At 250 μmol photon m-2 s-1 (HL), the WT strain displayed superoxide anion radicals (O2▪-) and hydrogen peroxide (H2O2) accumulation, increased lipid peroxidation, and cell death compared to normal light (NL) conditions (50 μmol photon m-2 s-1). The RB2 mutant didn't accumulate O2▪- and H2O2 after HL exposure, and exhibited increased APX, DHAR, and GR activities and transcript levels compared to WT and remained consistent after HL treatment. Although the RB2 mutant had a smaller ascorbate (AsA) pool than the WT, its ability to regenerate dehydroascorbate (DHA) increased post HL exposure, indicated by a higher AsA/DHA ratio. Additionally, under HL conditions, the RB2 mutant displayed an improved glutathione (GSH) regeneration rate (GSH/GSSG ratio) without changing the GSH pool size. Remarkably, H2O2 or menadione (a O2▪- donor) treatment induced cell death in the WT strain but not in the RB2 mutant. These findings emphasize the essential role of AGC in the RB2 mutant of Nannochloropsis in handling photo-oxidative stress.

Illuminating the diversity of carotenoids in microalgal eyespots and phototaxis

Photosynthetic organisms biosynthesize various carotenoids, a group of light-absorbing isoprenoid pigments that have key functions in photosynthesis, photoprotection, and phototaxis. Microalgae, in particular, contain diverse carotenoids and carotenoid biosynthetic pathways as a consequence of the various endosymbiotic events in their evolutionary history. Carotenoids such as astaxanthin, diadinoxanthin, and fucoxanthin are unique to algae. In microalgae, carotenoids are concentrated in the eyespot, a pigmented organelle that is important for phototaxis. A wide range of microalgae, including chlorophytes, euglenophytes, ochrophytes, and haptophytes, have an eyespot. In the chlorophyte Chlamydomonas reinhardtii, carotenoid layers in the eyespot reflect light to amplify the photosignal and shield photoreceptors from light, thereby enabling precise phototaxis. Our recent research revealed that, in contrast to the β-carotene-rich eyespot of C. reinhardtii, the euglenophyte Euglena gracilis relies on zeaxanthin for stable eyespot formation and phototaxis. In this review, we highlight recent advancements in the study of eyespot carotenoids and phototaxis in these microalgae, placing special emphasis on the diversity of carotenoid-dependent visual systems among microalgae.

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.

How Plants Tolerate Salt Stress

Soil salinization inhibits plant growth and seriously restricts food security and agricultural development. Excessive salt can cause ionic stress, osmotic stress, and ultimately oxidative stress in plants. Plants exclude excess salt from their cells to help maintain ionic homeostasis and stimulate phytohormone signaling pathways, thereby balancing growth and stress tolerance to enhance their survival. Continuous innovations in scientific research techniques have allowed great strides in understanding how plants actively resist salt stress. Here, we briefly summarize recent achievements in elucidating ionic homeostasis, osmotic stress regulation, oxidative stress regulation, and plant hormonal responses under salt stress. Such achievements lay the foundation for a comprehensive understanding of plant salt-tolerance mechanisms.

Current approaches, and challenges on identification, remediation and potential risks of emerging plastic contaminants: A review

Plastics are widely employed in modern civilization because of their durability, mold ability, and light weight. In the recent decade, micro/nanoplastics research has steadily increased, highlighting its relevance. However, contaminating micro/nanoplastics in marine environments, terrestrial ecosystems, and biological organisms is considered a severe threat to the environmental system. Geographical distribution, migration patterns, etymologies of formation, and ecological ramifications of absorption are just a few topics covered in the scientific literature on environmental issues. Degradable solutions from material science and chemistry are needed to address the micro/nanoplastics problem, primarily to reduce the production of these pollutants and their potential effects. Removing micro/nanoplastics from their discharge points has been a central and effective way to mitigate the adverse pollution effects. In this review, we begin by discussing the hazardous effect on living beings and the identification-characterization of micro/nanoplastics. Then, we provide a summary of the existing degradation strategies, which include bio-degradation and advanced oxidation processes (AOPs), and a detailed discussion of their degradation mechanisms is also represented. Finally, a persuasive summary of the evaluated work and projections for the future of this topic is provided.

Emulsion-Based Delivery Systems to Enhance the Functionality of Bioactive Compounds: Towards the Use of Ingredients from Natural, Sustainable Sources

In recent years, the trend in the population towards consuming more natural and sustainable foods has increased significantly. This claim has led to the search for new sources of bioactive compounds and extraction methods that have less impact on the environment. Moreover, the formulation of systems to protect these compounds is also focusing on the use of ingredients of natural origin. This article reviews novel, natural alternative sources of bioactive compounds with a positive impact on sustainability. In addition, it also contains information on the most recent studies based on the use of natural (especially from plants) emulsifiers in the design of emulsion-based delivery systems to protect bioactive compounds. The properties of these natural-based emulsion-delivery systems, as well as their functionality, including in vitro and in vivo studies, are also discussed. This review provides relevant information on the latest advances in the development of emulsion delivery systems based on ingredients from sustainable natural sources.

Zeaxanthin is required for eyespot formation and phototaxis in Euglena gracilis

The eyespot apparatus is an organelle that forms carotenoid-rich globules in diverse flagellated microalgae and functions in phototaxis. The euglenophytes have structurally and functionally distinct eyespot apparatuses from chlorophytes. β-Carotene is the most abundant pigment detected in chlorophytes' eyespots, while xanthophylls such as zeaxanthin and diadinoxanthin have been suggested to function in euglenophytes' eyespots. Here, we investigated the association between carotenoid composition and eyespot formation via pathway-scale mutagenesis using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome editing in the euglenophyte Euglena gracilis. Lycopene cyclase (lcy) mutants exhibited sole lycopene accumulation, defective red eyespots, and phototactic insensitivity. Conversely, β-carotene hydroxylase (cytochrome P450 97h1, cyp97h1) mutants accumulated β-carotene and its hydroxylated products β-cryptoxanthin and zeaxanthin and formed phototactic eyespot apparatuses, while cyp97h1 cyp97f2 double mutants were deficient in β-carotene hydroxylation and mostly lacked functional eyespots. Thus, zeaxanthin is required for the stable formation of functional eyespots in E. gracilis, highlighting evolutionary differences between euglenophytes and chlorophytes in the metabolic regulation of photoreactive organelle formation.

Progress on microalgae cultivation in wastewater for bioremediation and circular bioeconomy

Water usage increased alongside its competitiveness due to its finite amount. Yet, many industries still rely on this finite resource thus recalling the need to recirculate their water for production. Circular bioeconomy is presently the new approach emphasizing on the 'end-of-life' concept with reusing, recycling, and recovering materials. Microalgae are the ideal source contributing to circular bioeconomy as it exhibits fast growth and adaptability supported by biological rigidity which in turn consumes nutrients, making it an ideal and capable bioremediating agent, therefore allowing water re-use as well as its biomass potential in biorefineries. Nevertheless, there are challenges that still need to be addressed with consideration of recent advances in cultivating microalgae in wastewater. This review aimed to investigate the potential of microalgae biomass cultivated in wastewater. More importantly, how it'll play a role in the circular bioeconomy. This includes an in-depth look at the production of goods coming from wastes tattered by emerging pollutants. These emerging pollutants include microplastics, antibiotics, ever-increasingly sewage water, and heavy metals which have not been comprehensively compared and explored. Therefore, this review is aiming to bring new insights to researchers and industrial stakeholders with interest in green alternatives to eventually contribute towards environmental sustainability.

Bioactive compounds by microalgae and potentials for the management of some human disease conditions

Microalgae biomasses are excellent sources of diverse bioactive compounds such as lipids, polysaccharides, carotenoids, vitamins, phenolics and phycobiliproteins. Large-scale production of these bioactive substances would require microalgae cultivation either in open-culture systems or closed-culture systems. Some of these bioactive compounds (such as polysaccharides, phycobiliproteins and lipids) are produced during their active growth phase. They appear to have antibacterial, antifungal, antiviral, antioxidative, anticancer, neuroprotective and chemo-preventive activities. These properties confer on microalgae the potential for use in the treatment and/or management of several neurologic and cell dysfunction-related disease conditions, including Alzheimer's disease (AD), AIDS and COVID-19, as shown in this review. Although several health benefits have been highlighted, there appears to be a consensus in the literature that the field of microalgae is still fledgling, and more research needs to be carried out to ascertain the mechanisms of action that underpin the effectiveness of microalgal compounds. In this review, two biosynthetic pathways were modeled to help elucidate the mode of action of the bioactive compounds from microalgae and their products. These are carotenoid and phycobilin proteins biosynthetic pathways. The education of the public on the importance of microalgae backed with empirical scientific evidence will go a long way to ensure that the benefits from research investigations are quickly rolled out. The potential application of these microalgae to some human disease conditions was highlighted.

α-Carotene: a valuable carotenoid in biological and medical research

α-Carotene, one of the C₄₀ carotenes, is a natural lipid-soluble terpene. The chemical structure of α-carotene is based on the unsaturated polyene chain skeleton, with an ε-ring and a β-ring on each side of the skeleton. α-Carotene is widely found in dietary fruits and vegetables, and the concentration depends on the plant species. In addition, processing methods and storage conditions used in the food and medical industries can alter the concentration of α-carotene in raw materials. This review of α-carotene summarizes the major studies on chemical structure, source, extraction, detection, biosynthesis, processing effect, bioactivity, medicine, and biotechnology. Whether α-carotene supplementation or a diet rich in fruits and vegetables has a positive effect on the prevention of cancer, cardiovascular disease, and other diseases is the focus of this study. © 2022 Society of Chemical Industry.

Putative Protein Discovery from Microalgal Genomes as a Synthetic Biology Protein Library for Heavy Metal Bio-Removal

Simple Summary

Nowadays, heavy metal polluted wastewater is one of the global challenges that leads to an insufficient supply of clean water. Taking advantage of what nature has to offer, several organisms, including microalgae, can natively bioremediate these heavy metals. However, the effectiveness of such processes does not meet expectations, especially with the increasing amount of pollution in today’s world. Therefore, with the goal of creating effective strains, synthetic biology via bioengineering is widely used as a strategy to enhance the heavy metal bio-removing capability, either by directly engineering the native ability of organisms or by transferring the ability to a more suitable host. In order to do so, a list of genes or proteins involved in the processes is crucial for stepwise engineering. Yet, a large amount of information remains to be discovered. In this work, a comprehensive library of putative proteins that are involved in heavy metal bio-removal from microalgae was constructed. Moreover, with the development of machine learning, the 3D structures of these proteins are also predicted, using machine learning-based methods, to aid the use of synthetic biology further.

Abstract

Synthetic biology is a principle that aims to create new biological systems with particular functions or to redesign the existing ones through bioengineering. Therefore, this principle is often utilized as a tool to put the knowledge learned to practical use in actual fields. However, there is still a great deal of information remaining to be found, and this limits the possible utilization of synthetic biology, particularly on the topic that is the focus of the present work—heavy metal bio-removal. In this work, we aim to construct a comprehensive library of putative proteins that might support heavy metal bio-removal. Hypothetical proteins were discovered from Chlorella and Scenedesmus genomes and extensively annotated. The protein structures of these putative proteins were also modeled through Alphafold2. Although a portion of this workflow has previously been demonstrated to annotate hypothetical proteins from whole genome sequences, the adaptation of such steps is yet to be done for library construction purposes. We also demonstrated further downstream steps that allow a more accurate function prediction of the hypothetical proteins by subjecting the models generated to structure-based annotation. In conclusion, a total of 72 newly discovered putative proteins were annotated with ready-to-use predicted structures available for further investigation.

Carotenoids Biosynthesis, Accumulation, and Applications of a Model Microalga Euglenagracilis

The carotenoids, including lycopene, lutein, astaxanthin, and zeaxanthin belong to the isoprenoids, whose basic structure is made up of eight isoprene units, resulting in a C40 backbone, though some of them are only trace components in Euglena. They are essential to all photosynthetic organisms due to their superior photoprotective and antioxidant properties. Their dietary functions decrease the risk of breast, cervical, vaginal, and colorectal cancers and cardiovascular and eye diseases. Antioxidant functions of carotenoids are based on mechanisms such as quenching free radicals, mitigating damage from reactive oxidant species, and hindering lipid peroxidation. With the development of carotenoid studies, their distribution, functions, and composition have been identified in microalgae and higher plants. Although bleached or achlorophyllous mutants of Euglena were among the earliest carotenoid-related microalgae under investigation, current knowledge on the composition and biosynthesis of these compounds in Euglena is still elusive. This review aims to overview what is known about carotenoid metabolism in Euglena, focusing on the carotenoid distribution and structure, biosynthesis pathway, and accumulation in Euglena strains and mutants under environmental stresses and different culture conditions. Moreover, we also summarize the potential applications in therapy preventing carcinogenesis, cosmetic industries, food industries, and animal feed.

Inferred Subcellular Localization of Peroxisomal Matrix Proteins of Guillardia theta Suggests an Important Role of Peroxisomes in Cryptophytes

Peroxisomes participate in several important metabolic processes in eukaryotic cells, such as the detoxification of reactive oxygen species (ROS) or the degradation of fatty acids by β-oxidation. Recently, the presence of peroxisomes in the cryptophyte Guillardia theta and other "chromalveolates" was revealed by identifying proteins for peroxisomal biogenesis. Here, we investigated the subcellular localization of candidate proteins of G. theta in the diatom Phaeodactylum tricornutum, either possessing a putative peroxisomal targeting signal type 1 (PTS1) sequence or factors lacking a peroxisomal targeting signal but known to be involved in β-oxidation. Our results indicate important contributions of the peroxisomes of G. theta to the carbohydrate, ether phospholipid, nucleotide, vitamin K, ROS, amino acid, and amine metabolisms. Moreover, our results suggest that in contrast to many other organisms, the peroxisomes of G. theta are not involved in the β-oxidation of fatty acids, which exclusively seems to occur in the cryptophyte's mitochondria.

Developing a bioinformatics pipeline for comparative protein classification analysis

BACKGROUND

Protein classification is a task of paramount importance in various fields of biology. Despite the great momentum of modern implementation of protein classification, machine learning techniques such as Random Forest and Neural Network could not always be used for several reasons: data collection, unbalanced classification or labelling of the data.As an alternative, I propose the use of a bioinformatics pipeline to search for and classify information from protein databases. Hence, to evaluate the efficiency and accuracy of the pipeline, I focused on the carotenoid biosynthetic genes and developed a filtering approach to retrieve orthologs clusters in two well-studied plants that belong to the Brassicaceae family: Arabidopsis thaliana and Brassica rapa Pekinensis group. The result obtained has been compared with previous studies on carotenoid biosynthetic genes in B. rapa where phylogenetic analysis was conducted.

RESULTS

The developed bioinformatics pipeline relies on commercial software and multiple databeses including the use of phylogeny, Gene Ontology terms (GOs) and Protein Families (Pfams) at a protein level. Furthermore, the phylogeny is coupled with "population analysis" to evaluate the potential orthologs. All the steps taken together give a final table of potential orthologs. The phylogenetic tree gives a result of 43 putative orthologs conserved in B. rapa Pekinensis group. Different A. thaliana proteins have more than one syntenic ortholog as also shown in a previous finding (Li et al., BMC Genomics 16(1):1-11, 2015).

CONCLUSIONS

This study demonstrates that, when the biological features of proteins of interest are not specific, I can rely on a computational approach in filtering steps for classification purposes. The comparison of the results obtained here for the carotenoid biosynthetic genes with previous research confirmed the accuracy of the developed pipeline which can therefore be applied for filtering different types of datasets.

The responses of Scrippsiella acuminata to the stresses of darkness: antioxidant activities and formation of pellicle cysts

In order to understand the strategy of Scrippsiella acuminata to cold dark environment, the antioxidant responses and the formation of pellicle cysts of S. acuminata to darkness at 8°C and 20°C were investigated. Cell densities decreased significantly after 96 h dark treatment, and no live cells were observed after 9-days dark treatments. The darkness stress generally resulted in an increase of antioxidant defenses, including soluble protein, superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA). Cellular soluble protein and SOD activity increased sharply under 20°C darkness, which protected algal cells against the oxidative stress from darkness, and resulted in relatively lower MDA levels. Soluble protein and SOD activity were enhanced under 8°C darkness as well however not in a sharp rise, and higher levels of MDA and GSH were recorded. The results suggested high SOD and protein levels protected cells against harsh darkness stress, while high GSH not only helped algae cells resist dark stress, but also played an important role in low temperature stress. Darkness promoted the formation of pellicle cysts of S. acuminata, and the maximum formation rates were 16.06% to 21.74% at 8°C and 20°C, respectively. Germination of pellicle cysts occurred within 24 h after light exposure, however pellicle cysts could not withstand long-time darkness stress, and all pellicle cysts died after 9-days darkness exposure. The results of this study suggest that S. acuminata is able to overcome temporary cold darkness through forming pellicle cysts.

Antioxidant Activity and Carotenoid Content Responses of Three Haematococcus sp. (Chlorophyta) Strains Exposed to Multiple Stressors

There has been increasing demands worldwide for bioactive compounds of natural origins, especially for the nutraceutical and food-supplement sectors. In this context, microalgae are viewed as sustainable sources of molecules with an array of health benefits. For instance, astaxanthin is a xanthophyll pigment with powerful antioxidant capacity produced by microalgae such as the chlorophyte Haematococcus sp., which is regarded as the most suitable organism for the mass production of this pigment. In this study, three Haematococcus sp. strains were cultivated using a batch mode under favourable conditions to promote vegetative growth. Their environment was altered in a second phase using a higher and constant illumination regime combined with either exposure to blue LED light, an osmotic shock (with NaCl addition) or supplementation with a phytohormone (gibberellic acid, GA3), a plant extract (ginger), an herbicide (molinate) or an oxidant reagent (hydrogen peroxide). The effects of these stressors were evaluated in terms of antioxidant response and astaxanthin and β-carotene accumulation. Overall, strain CCAP 34/7 returned the highest Trolox Equivalent Antioxidant Capacity (TEAC) response (14.1-49.1 µmoL Trolox eq. g^- 1 of DW), while the highest antioxidant response with the Folin-Ciocalteu (FC) was obtained for strain RPFW01 (62.5-155 µmoL Trolox eq. g^- 1 of DW). The highest β-β-carotene content was found in strain LAFW15 when supplemented with the ginger extract (4.8 mg. g^- 1). Strain RPFW01 exposed to blue light returned the highest astaxanthin yield (2.8 mg. g^- 1), 5-fold that of strain CCAP 34/7 on average. This study documents the importance of screening several strains when prospecting for species with potential to produce high-value metabolites. It highlights that strain-specific responses can ensue from exposure of cells to a variety of stressors, which is important for the adequate tailoring of a biorefinery pipeline.

Improved Productivity of Astaxanthin from Photosensitive Haematococcus pluvialis Using Phototaxis Technology

Haematococcus pluvialis is a microalgae actively studied for the production of natural astaxanthin, which is a powerful antioxidant for human application. However, it is economically disadvantageous for commercialization owing to the low productivity of astaxanthin. This study reports an effective screening strategy using the negative phototaxis of the H. pluvialis to attain the mutants having high astaxanthin production. A polydimethylsiloxane (PDMS)-based microfluidic device irradiated with a specific light was developed to efficiently figure out the phototactic response of H. pluvialis. The partial photosynthesis deficient (PP) mutant (negative control) showed a 0.78-fold decreased cellular response to blue light compared to the wild type, demonstrating the positive relationship between the photosynthetic efficiency and the phototaxis. Based on this relationship, the Haematococcus mutants showing photosensitivity to blue light were selected from the 10,000 random mutant libraries. The M1 strain attained from the phototaxis-based screening showed 1.17-fold improved growth rate and 1.26-fold increases in astaxanthin production (55.12 ± 4.12 mg g⁻¹) in the 100 L photo-bioreactor compared to the wild type. This study provides an effective selection tool for industrial application of the H. pluvialis with improved astaxanthin productivity.

Heavy metal-induced stress in eukaryotic algae-mechanisms of heavy metal toxicity and tolerance with particular emphasis on oxidative stress in exposed cells and the role of antioxidant response

Heavy metals is a collective term describing metals and metalloids with a density higher than 5 g/cm3. Some of them are essential micronutrients; others do not play a positive role in living organisms. Increased anthropogenic emissions of heavy metal ions pose a serious threat to water and land ecosystems. The mechanism of heavy metal toxicity predominantly depends on (1) their high affinity to thiol groups, (2) spatial similarity to biochemical functional groups, (3) competition with essential metal cations, (4) and induction of oxidative stress. The antioxidant response is therefore crucial for providing tolerance to heavy metal-induced stress. This review aims to summarize the knowledge of heavy metal toxicity, oxidative stress and antioxidant response in eukaryotic algae. Types of ROS, their formation sites in photosynthetic cells, and the damage they cause to the cellular components are described at the beginning. Furthermore, heavy metals are characterized in more detail, including their chemical properties, roles they play in living cells, sources of contamination, biochemical mechanisms of toxicity, and stress symptoms. The following subchapters contain the description of low-molecular-weight antioxidants and ROS-detoxifying enzymes, their properties, cellular localization, and the occurrence in algae belonging to different clades, as well as the summary of the results of the experiments concerning antioxidant response in heavy metal-treated eukaryotic algae. Other mechanisms providing tolerance to metal ions are briefly outlined at the end.

Mitigation of Environmental Stress-Impacts in Plants: Role of Sole and Combinatory Exogenous Application of Glutathione

Glutathione (GSH; γ-glutamyl-cysteinyl-glycine), a low-molecular-weight thiol, is the most pivotal metabolite involved in the antioxidative defense system of plants. The modulation of GSH on the plant in response to environmental stresses could be illustrated through key pathways such as reactive oxygen species (ROS) scavenging and signaling, methylglyoxal (MG) detoxification and signaling, upregulation of gene expression for antioxidant enzymes, and metal chelation and xenobiotic detoxification. However, under extreme stresses, the biosynthesis of GSH may get inhibited, causing an excess accumulation of ROS that induces oxidative damage on plants. Hence, this gives rise to the idea of exploring the use of exogenous GSH in mitigating various abiotic stresses. Extensive studies conducted borne positive results in plant growth with the integration of exogenous GSH. The same is being observed in terms of crop yield index and correlated intrinsic properties. Though, the improvement in plant growth and yield contributed by exogenous GSH is limited and subjected to the glutathione pool [GSH/GSSG; the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG)] homeostasis. Therefore, recent studies focused on the sequenced application of GSH was performed in order to complement the existing limitation. Along with various innovative approaches in combinatory use with different bioactive compounds (proline, citric acid, ascorbic acid, melatonin), biostimulants (putrescine, Moringa leaf extract, selenium, humic acid), and microorganisms (cyanobacteria) have resulted in significant improvements when compared to the individual application of GSH. In this review, we reinforced our understanding of biosynthesis, metabolism and consolidated different roles of exogenous GSH in response to environmental stresses. Strategy was also taken by focusing on the recent progress of research in this niche area by covering on its individualized and combinatory applications of GSH prominently in response to the abiotic stresses. In short, the review provides a holistic overview of GSH and may shed light on future studies and its uses.

Suppression of the Lycopene Cyclase Gene Causes Downregulation of Ascorbate Peroxidase Activity and Decreased Glutathione Pool Size, Leading to H2O2 Accumulation in Euglena gracilis

Carotenoids are photosynthetic pigments and hydrophobic antioxidants that are necessary for the survival of photosynthetic organisms, including the microalga Euglena gracilis. In the present study, we identified an uncharacterized gene encoding the E. gracilis β-carotene synthetic enzyme lycopene cyclase (EgLCY) and discovered a relationship between EgLCY-mediated carotenoid synthesis and the reactive oxygen species (ROS) scavenging system ascorbate-glutathione cycle. The EgLCY cDNA sequence was obtained via homology searching E. gracilis transcriptome data. An enzyme assay using Escherichia coli demonstrated that EgLCY converts lycopene to β-carotene. E. gracilis treated with EgLCY double-stranded RNA (dsRNA) produced colorless cells with hypertrophic appearance, inhibited growth, and marked decrease in carotenoid and chlorophyll content, suggesting that EgLCY is essential for the synthesis of β-carotene and downstream carotenoids, which are abundant and physiologically functional. In EgLCY dsRNA-treated cells, the ascorbate-glutathione cycle, composed of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR), was unusually modulated; APX and GR activities significantly decreased, whereas DHAR and MDAR activities increased. Ascorbate content was significantly increased and glutathione content significantly decreased in EgLCY dsRNA-treated cells and was correlated with their recycling enzyme activities. Fluorescent imaging demonstrated that EgLCY dsRNA-treated cells accumulated higher levels of H2O2 compared to wild-type cells. Taken together, this study revealed that EgLCY-mediated synthesis of β-carotene and downstream carotenoid species upregulates APX activity and increases glutathione pool size for H2O2 scavenging. Our study suggests a possible relationship between carotenoid synthesis and the ascorbate-glutathione cycle for ROS scavenging in E. gracilis.

Microalgae biofilm formation and antioxidant responses to stress induce by Lemna minor L., Chlorella vulgaris, and Aphanizomenon flos-aquae

The study shows how microalgae biofilm formation and antioxidant responses to the production of reactive oxygen species (ROS) is alter by the presences of Lemna minor L., Chlorella vulgaris, and Aphanizomenon flos-aquae. The study involves the cultivation of the biofilm of Chlorella vulgaris and Aphanizomenon flos-aquae in three bioreactors. The condition of growth for the biofilm formation was varied across the three bioreactors to enable the dominance Chlorella vulgaris and Aphanizomenon flos-aquae in one of the bioreactors. Lemna minor L. was also introduce into one of the bioreactors to determine its effect on the biofilm formation. The result obtained shows that C. vulgaris and A. flos-aquae dominate the biofilm, resulting in a high level of H₂O₂ and O₂^- (H₂O₂ was 0.122 ± 0.052 and 0.183 ± 0.108 mmol/L in C. vulgaris and A. flos-aquae, respectively, and O₂^- was 0.261 ± 0.039 and 0.251 ± 0.148 mmol/L in C. vulgaris and A. flos-aquae, respectively). The study also revealed that the presence of L. minor L. tend to reduce the oxidative stress to the biofilm leading to low production of ROS (H₂O₂ was 0.086 ± 0.027 and 0.089 ± 0.045 mmol/L in C. vulgaris and A. flos-aquae respectively, and O₂^- was 0.185 ± 0.044 and 0.161 ± 0.065 mmol/L in C. vulgaris and A. flos-aquae respectively). The variation in the ability of the biofilm of C. vulgaris and A. flos-aquae to respond via chlorophyll, carotenoid, flavonoid, anthocyanin, superoxide dismutase, peroxidase, catalase, glutathione reductase activities, antioxidant reducing power, phosphomolybdate activity, DPPH reduction activity, H₂O₂ scavenging activity, lipid content and organic carbon also supports the fact that the presence of biomass of microalgae and aquatic macrophytes tend to affect the process of microalgae biofilm formation and the ability of the biofilm to produce antioxidant. This high nutrient utilization leads to the production of biomass which can be used for biofuel production and other biotechnological products.