Biotechnological strategies overcoming limitations to H. pluvialis-derived astaxanthin production and Morocco's potential.

Haematococcus pluvialis is the richest source of natural astaxanthin, but the production of H. pluvialis-derived astaxanthin is usually limited by its slow cell proliferation and astaxanthin accumulation. Efforts to enhance biomass productivity, astaxanthin accumulation, and extraction are ongoing. This review highlights different approaches that have previously been studied in microalgal species for enhanced biomass productivity, as well as optimized methods for astaxanthin accumulation and extraction, and how these methods could be combined to bypass the challenges limiting natural astaxanthin production, particularly in H. pluvialis, at all stages (biomass production, and astaxanthin accumulation and extraction). Biotechnological approaches, such as overexpressing low CO2 inducible genes, utilizing complementary carbon sources, CRISPR-Cas9 bioengineering, and the use of active compounds, for biomass productivity are outlined. Direct astaxanthin extraction from H. pluvialis zoospores and Morocco's potential for microalgal-based astaxanthin production are equally discussed. This review emphasizes the need to engineer an optimized H. pluvialis-derived astaxanthin production system combining two or more of these strategies for increased growth, and astaxanthin productivity, to compete in the larger, lower-priced market in aquaculture and nutraceutical sectors.

Aphanothece sp. as promising biostimulant to alleviate heavy metals stress in Solanum lycopersicum L. by enhancing physiological, biochemical, and metabolic responses.

Heavy metals (H.M) are a major environmental concern around the world. They have harmful impact on plant productivity and pose a serious risk to humans and animals health. In the present study, we investigated the effect of Aphanothece crude extract (ACE) on physiological, biochemical, and metabolic responses of tomato plant exposed to 2 mM Pb and Cd. The results showed a significant reduction of tomato plant weights and perturbation in nutrients absorption under 2 mM Pb and Cd conditions. Moreover, ACE treatment showed a significant enhancement of plant biomass compared to plants under Pb and Cd. On the other hand, ACE application favoured H.M accumulation in root and inhibited their translocation to shoot. In addition, ACE treatment significantly enhanced several stress responses in plant under Pb and Cd stress such as scavenging enzymes and molecules: POD, CAT, SOD, proline, and polyphenols etc. Furthermore, ACE treatment showed remodulation of metabolic pathways related to plant tolerance such as wax construction mechanism, particularly SFA, UFA, VLFA, alkanes, alkenes, and sterols biosynthesis to enhance tolerance and resistance to H.M stress. In the present study, we emphasized that ACE alleviates H.M stress by minimizing metal translocation to above-part of plant and enhancing plant growth, nutrients absorption, and biochemical responses.

Investigation of bacterial diversity using 16S rRNA sequencing and prediction of its functionalities in Moroccan phosphate mine ecosystem.

Native plants in extreme environments may harbor some unique microbial communities with particular functions to sustain their growth and tolerance to harsh conditions. The aim of this study was to investigate the bacterial communities profiles in some native plants and samples of the Moroccan phosphate mine ecosystem by assessing the percentages of taxonomic identification using six hypervariable regions of the 16S rRNA. The rhizosphere of the three wild plants in the Moroccan phosphate mine is characterized by interesting bacterial diversity including Proteobacteria (62.24%, 71.15% and 65.61%), Actinobacteria (22.53%, 15.24%, 22.30%), Bacteroidetes (7.57%; 4.23%; 7.63%), and Firmicutes (5.82%; 1.17%; 2.83%). The bulk phosphate mine samples were dominated by Actinobacteria with average relative abundance of 97.73% that are different from those inferred in the rhizosphere samples of the native plants. The regions V3, V4 and V67 performed better in the taxonomic profiling at different taxonomic levels. Results indicated that both plant genotype and mainly soil conditions may be involved in the shaping of bacterial diversity. Such indication was also confirmed by the prediction of functional profiles that showed enrichment of many functions related to biological nitrogen fixation in the rhizosphere of native plants and the stress related functions in the bulk phosphate mine in comparison with the wheat rhizosphere samples.

Microalgae as promising source for integrated wastewater treatment and biodiesel production.

Microalgae have been studied for their potential of wastewater treatment as well as a promising source for biodiesel production. This study investigates the potential of microalgae to remove nutrients from domestic wastewater (DWW) while producing lipids-rich biomass for biodiesel production. Eight microalgae were cultivated in (DWW) to evaluate their nutrients removal capacity and biomass production. Total phosphorus (TP) of DWW reduced from 2 mg L-1 to 0.02 mg L-1 with the treatment efficiency of 99.15% and the highest performance was noted in Chlamydomonas reinhardtii (C. reinhardtii). For total nitrogen (TN), treatment efficiency climbed to 99.07%. It is reduced from 18.35 to 0.17 mg L-1 recorded in C. reinhardtii and Chlorella pyrenoidosa (C. pyrenoidosa). On the other hand, all microalgae showed a high lipids-rich biomass in wastewater compared to BG11. The highest lipid content was 36.93% noted in Chlorella sorokiniana (C. sorokiniana). Fatty acids methyl ester (FAME) profiles showed a high content of palmitic C16:0, oleic C18:1 and stearic acids C18:0 in studied microalgae strains. In summary, microalgae envisage its potential application in integrated wastewater treatment and biodiesel production. In perspective, the authors focus on the validation of this bioprocess in pilot scale. Furthermore, the use of microalgae for other applications such CO2 biosequestration and added value products. Novelty statement: The present study investigates the potential of Moroccan microalgae as candidates to wastewater remediation and high biomass production with high lipid rate for biodiesel production.

Progress in valorisation of agriculture, aquaculture and shellfish biomass into biochemicals and biomaterials towards sustainable bioeconomy.

The recurrent environmental and economic issues associated with the diminution of fossil fuels are the main impetus towards the conversion of agriculture, aquaculture and shellfish biomass and the wastes into alternative commodities in a sustainable approach. In this review, the recent progress on recovering and processing these biomass and waste feedstocks to produce a variety of value-added products via various valorisation technologies, including hydrolysis, extraction, pyrolysis, and chemical modifications are presented, analysed, and discussed. These technologies have gained widespread attention among researchers, industrialists and decision makers alike to provide markets with bio-based chemicals and materials at viable prices, leading to less emissions of CO2 and sustainable management of these resources. In order to echo the thriving research, development and innovation, bioresources and biomass from various origins were reviewed including agro-industrial, herbaceous, aquaculture, shellfish bioresources and microorganisms that possess a high content of starch, cellulose, lignin, lipid and chitin. Additionally, a variety of technologies and processes enabling the conversion of such highly available bioresources is thoroughly analysed, with a special focus on recent studies on designing, optimising and even innovating new processes to produce biochemicals and biomaterials. Despite all these efforts, there is still a need to determine the more cost-effective and efficient technologies to produce bio-based commodities.

Phycoremediation mechanisms of heavy metals using living green microalgae: physicochemical and molecular approaches for enhancing selectivity and removal capacity.

Heavy metal (HM) contamination of water bodies is a serious global environmental problem. Because they are not biodegradable, they can accumulate in food chains, causing various signs of toxicity to exposed organisms, including humans. Due to its effectiveness, low cost, and ecological aspect, phycoremediation, or the use of microalgae's ecological functions in the treatment of HMs contaminated wastewater, is one of the most recommended processes. This study aims to examine in depth the mechanisms involved in the phycoremediation of HMs by microalgae, it also provides an overview of the prospects for improving the productivity, selectivity, and cost-effectiveness of this bioprocess through physicochemical and genetic engineering applications. Firstly, this review proposes a detailed examination of the biosorption interactions between cell wall functional groups and HMs, and their complexation with extracellular polymeric substances released by microalgae in the extracellular environment under stress conditions. Subsequently, the metal transporters involved in the intracellular bioaccumulation of HMs as well as the main intracellular mechanisms including compartmentalization in cell organelles, enzymatic biotransformation, or photoreduction of HMs were also extensively reviewed. In the last section, future perspectives of physicochemical and genetic approaches that could be used to improve the phytoremediation process in terms of removal efficiency, selectivity for a targeted metal, or reduction of treatment time and cost are discussed, which paves the way for large-scale application of phytoremediation processes.

Microalgae polysaccharides bio-stimulating effect on tomato plants: Growth and metabolic distribution.

Microalgae polysaccharides represent a potentially bioressource for the enhancement and the protection of agricultural crops. We investigate the possibility to use microalgae polysaccharides as a plant biostimulant. The crude polysaccharides extract (PS) from three microalgae strains were applied to Solanum lycopersicum plants by irrigation and compared basing on their effects on shoot and root length, nodes number and shoot and root dry weight. The application of 1 mg mL-1 PS from A. platensis, D. salina and Porphorydium sp. on tomato plants improved significantly the nodes number (NN), shoot dry weight (SDW), and shoot length (SS) by75 %, 46,6 %, 25,26 % compared to control respectively. Furthermore, crude PS treatment showed an improvement of carotenoid, chlorophyll and proteins content, and Nitrate Reductase (NR), NAD-Glutamate Dehydrogenase (NAD-GDH) activities in plants leaves compared to control. 1 mg mL-1 of Porphorydium sp. enhanced significantly the carotenoid content and NAD-GDH activity by 400 %, 200 % compared to control respectively. In the same way, A. platensis PS improved chl a, chl b and NR activity by 90.1 %, 102.7 % and 88.34 compared to control respectively. In addition, it is found that a PS treatment has affected the protein content, which reaches 88.3 % under 0.5 mg mL-1 of D. salina PS treatment. GC-MS metabolomics analysis also showed a change in lipids, sterol and alkanes profiles. Some sterols precursors were increased such as Cholesta-6,22,24-triene, which may indicate an enhancement of the biosynthesis of sterols and/or steroidal glycoalkaloids in treated plants. Therefore, this is an evidence to use microalgae polysaccharides as a plant biostimulant.

Microalgae polysaccharides: the new sustainable bioactive products for the development of plant bio-stimulants?

Plant biostimulants are defined as materials containing microorganisms or substances whose function when applied to plants or the rhizosphere is to stimulate natural mechanisms to enhance plant growth, nutrient use efficiency, tolerance to abiotic stressors and crop quality, independent of their nutrient content. In agriculture, seaweeds (Macroalgae) have been used in the production of plant biostimulants while microalgae still remain unexploited. Microalgae are single cell microscopic organisms (prokaryotic or eukaryotic) that grow in a range of aquatic habitats, including, wastewaters, pounds, lakes, rivers, oceans, and even humid soils. These photosynthetic microorganisms are widely described as renewable sources of biofuels, bioingredients and biologically active compounds, such as polyunsaturated fatty acids (PUFAs), carotenoids, phycobiliproteins, sterols, vitamins and polysaccharides, which attract considerable interest in both scientific and industrial communities. Microalgae polysaccharides have so far proved to have several important biological activities, making them biomaterials and bioactive products of increasing importance for a wide range of applications. The present review describes microalgae polysaccharides, their biological activities and their possible application in agriculture as a potential sustainable alternative for enhanced crop performance, nutrient uptake and resilience to environmental stress. This review does not only present a comprehensive and systematic study of Microalgae polysaccharides as plant biostimulants but considers the fundamental and innovative principles underlying this technology.

Highly efficient catalytic/sonocatalytic reduction of 4-nitrophenol and antibacterial activity through a bifunctional Ag/ZnO nanohybrid material prepared via a sodium alginate method.

In this work, a bifunctional nanohybrid silver/zinc oxide material (Ag/ZnO) has been synthesized by a rapid route using sodium alginate simultaneously as a sacrificial template and silver reducing agent. The obtained samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid diffuse reflectance and liquid state UV-visible spectroscopy (DRS, UV-visible), and nitrogen adsorption-desorption analysis (BET-BJH). The XRD patterns showed that the Ag/ZnO sample is composed of a hexagonal zinc oxide structure with cubic metallic silver (Ag°). SEM micrographs exhibited a porous structure which was confirmed by BET-BJH methods to be mesoporous. The Ag/ZnO material was used as a nanocatalyst in the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as well as an antibacterial agent against Escherichia coli and Staphylococcus aureus. It was found that an efficient 4-NP reduction to 4-AP in the presence of NaBH4 shows a rate constant of 0.418 min-1 under ultrasonic energy and 0.316 min-1 without ultrasonic energy. Both the catalysis reaction and antibacterial activity analysis were conducted in water solution and showed a synergetic effect of metallic silver loading.

Nitrate Reductase Inhibition Induces Lipid Enhancement of Dunaliella Tertiolecta for Biodiesel Production.

Nitrogen stress increases lipids content in microalgae, the main feedstock for algal biodiesel. Sodium tungstate was used in this study to implement nitrogen stress by inhibiting nitrate reductase (NR) in Dunaliella tertiolecta. The reduction of NR activity was accompanied by reduction of chlorophyll and accumulation of lipids. One-stage and two-stage culture strategies were compared. One-stage culture raised total lipids from 18% (control) to 39% (w: w); however, two-stage culture raised lipids to 50% in which neutral lipids were enhanced 2.14 times. To assess the quality of biodiesel produced, fatty acid methyl esters (FAME) composition was studied. It showed a slight variation of unsaturation. In addition, some physical proprieties of biodiesel were estimated and showed that higher heating values were improved by tungstate treatment. In this study, we tried to shed light on some biological impact of NR inhibition in microalgae cells using sodium tungstate which could be exploited in the improvement of biodiesel production.

Antioxidant activity of some Moroccan marine microalgae: Pufa profiles, carotenoids and phenolic content.

In order to promote Moroccan natural resources, this study aims to evaluate the potential of microalgae isolated from Moroccan coastlines, as new source of natural antioxidants. Different extracts (ethanolic, ethanol/water and aqueous) obtained from 9 microalgae strains were screened for their in vitro antioxidant activity using DPPH free radical-scavenging assay. The highest antioxidant potentials were obtained in Dunalliela sp., Tetraselmis sp. and Nannochloropsis gaditana extracts. The obtained results indicate that ethanol extract of all microalgae strains exhibit higher antioxidant activity, when compared to water and ethanol/water extracts. Therefore, total phenolic and carotenoid content measurement were performed in active ethanol extracts. The PUFA profiles of ethanol extracts were also determined by GC/MS analysis. The studied microalgae strains displayed high PUFA content ranging from 12.9 to 76.9 %, total carotenoids content varied from 1.9 and 10.8mg/g of extract and total polyphenol content varied from 8.1 to 32.0mg Gallic acid Equivalent/g of extract weight. The correlation between the antioxidant capacities and the phenolic content and the carotenoids content were found to be insignificant, indicating that these compounds might not be major contributor to the antioxidant activity of these microalgae. The microalgae extracts exerting the high antioxidant activity are potential new source of natural antioxidants.