Comparative study on growth, survival and pigmentation of Solea aegyptiaca larvae by using four different microalgal species with emphasize on water quality and nutritional value

Harmony in detoxification: Microalgae unleashing the potential of lignocellulosic pretreatment wastewater for resource utilization

Lignocellulosic biomass is a pivotal renewable resource in biorefinery process, requiring pretreatment, primarily chemical pretreatment, for effective depolymerization and subsequent transformation. This process yields solid residue for saccharification and lignocellulosic pretreatment wastewater (LPW), which comprises sugars and inhibitors such as phenols and furans. This study explored the microalgal capacity to treat LPW, focusing on two key hydrolysate inhibitors: furfural and vanillin, which impact the growth of six green microalgae. Chlorella sorokiniana exhibited higher tolerance to furfural and vanillin. However, both inhibitors hindered the growth of C. sorokiniana and disrupted algal photosynthetic system, with vanillin displaying superior inhibition. A synergistic inhibitory effect (Q < 0.85) was observed with furfural and vanillin on algal growth. Furfural transformation to low-toxic furfuryl alcohol was rapid, yet the addition of vanillin hindered this process. Vanillin stimulated carbohydrate accumulation, with 50.48 % observed in the 0.1 g/L furfural + 0.1 g/L vanillin group. Additionally, vanillin enhanced the accumulation of C16: 0 and C18: 2, reaching 21.71 % and 40.36 %, respectively, with 0.1 g/L vanillin. This study proposed a microalgae-based detoxification and resource utilization approach for LPW, enhancing the comprehensive utilization of lignocellulosic components. The observed biomass modifications also suggested potential applications for biofuel production, contributing to the evolving landscape of sustainable biorefinery processes.

Unlocking the potential of microalgae cultivated on wastewater combined with salinity stress to improve biodiesel production

Microalgae have the potential as a source of biofuels due to their high biomass productivity and ability to grow in a wide range of conditions, including wastewater. This study investigated cultivating two microalgae species, Oocystis pusilla and Chlorococcus infusionum, in wastewater for biodiesel production. Compared to Kühl medium, KC medium resulted in a significant fold increase in cellular dry weight production for both O. pusilla and C. infusionum, with an increase of 1.66 and 1.39, respectively. A concentration of 100% wastewater resulted in the highest growth for O. pusilla, with an increase in biomass and lipid content compared to the KC medium. C. infusionum could not survive in these conditions. For further increase in biomass and lipid yield of O. pusilla, different total dissolved solids (TDS) levels were used. Maximum biomass and lipid productivities were achieved at 3000 ppm TDS, resulting in a 28% increase in biomass (2.50 g/L) and a 158% increase in lipid yield (536.88 mg/g) compared to KC medium. The fatty acid profile of O. pusilla cultivated on aerated wastewater at 3000 ppm TDS showed a high proportion of desirable saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) for biodiesel production. Cultivating microalgae in wastewater for biodiesel production can be cost-effective, especially for microalgae adapted to harsh conditions. It could be concluded that O. pusilla is a promising candidate for biodiesel production using wastewater as a growth medium, as it has high biomass productivity and lipid yield, and its fatty acid profile meets the standard values of American and European biodiesel standards. This approach offers a sustainable and environmentally friendly solution for producing biofuels while reducing the environmental impact of wastewater disposal.

Unveiling the Potential of Algal Extracts as Promising Antibacterial and Antibiofilm Agents against Multidrug-Resistant Pseudomonas aeruginosa: In Vitro and In Silico Studies including Molecular Docking

Multidrug-resistant Pseudomonas aeruginosa poses a global challenge due to its virulence and biofilm-forming ability, leading to persistent infections. This study had a dual focus: first, it aimed to investigate the biofilm activity and antibiotic resistance profiles of Pseudomonas aeruginosa isolates obtained from a fish-rearing farm. Second, it explored the potential of algal extracts as effective antibacterial and antibiofilm agents. The study analyzed 23 isolates of P. aeruginosa from the farm, assessing antibiotic resistance and biofilm formation. The antimicrobial and antibiofilm activities of two algal extracts, Arthrospira platensis (cyanobacteria) acetone extract (AAE) and Polysiphonia scopulorum (Rhodophyta) methanol extract (PME), were tested individually and combined (COE). The effects on biofilm-related gene expression were examined. AAE, PME, and COE were evaluated for antimicrobial and antibiofilm properties. Biofilm-related gene expression was measured and the extracts were analyzed for physicochemical properties and toxicity. Most P. aeruginosa isolates (86.9%) were antibiotic-resistant and formed biofilms. AAE, PME, and COE displayed promising antibacterial and antibiofilm effects, with COE being particularly effective. COE reduced a key biofilm-related gene expression. The fatty acid content (56% in AAE and 34% in PME) correlated with the effects. Specific compounds, such as phytol, bromophenol, and dihydroxy benzaldehyde, contributed to the activities. The extracts showed favorable characteristics and interactions with FabZ protein amino acids. This study suggests the potential of algal extracts as antibacterial and antibiofilm agents against drug-resistant infections. Further exploration in clinical applications is warranted.

Commercial Seaweed Liquid Extract as Strawberry Biostimulants and Bioethanol Production

Seaweeds are increasingly intriguing as a sustainable source of bioactive compounds. They have applications in agriculture, fuels, feed, and food products. To become a cost-competitive product with zero waste, a biorefinery approach is applied, where several products are valorized at the same time. True-Algae-Max (TAM^®) has been investigated for its ability to improve the yield and nutritional facts of a strawberry plant. Three concentrations of TAM (0, 50, and 100%) were examined by foliar spray in 2017 with 50% NPK chemical fertilizer. Results indicated that growth, yield, chlorophyll, and potassium content were significantly improved by TAM treatments. TAM50 % resulted in maximum root length, leaf area, plant fresh weight, fruit weight, and yield with an increase ranging from 10 to 110% compared to control. Compared to the NPK control, strawberries grown with TAM50% improved total soluble solids (TSS) from 7.58 to 10.12% and anthocyanin from 23.08 to 29.42 mg CGE 100 g^-1. Noteworthily, this reduced total sugar, and total phenolics were boosted by TAM applications, while non-reducing sugar was reduced compared to control. On the other hand, whole seaweed biomass and TAM residuals were used for bioethanol production by acid scarification. The maximum bioethanol yield was observed in residual biomass (0.34 g g^-1 dw), while the whole seaweed biomass showed only 0.20 g g^-1 dw. These results proved the biorefinery concept of using seaweed extract as a biostimulator and bioethanol production.

Chemical characterization and biological activities of ulvan extracted from Ulva fasciata (Chlorophyta)

Ulvan is a sulfated heteropolysaccharide present in the cell wall of Ulva species with a unique structure and biological potential used in various fields. Chemical characterization was carried out to determine the structure of ulvan from Ulva fasciata Delile collected from Eastern Harbor, Alexandria coast, Egypt. Ulva contains 31.5% carbohydrate with a total ulvan content of 43.66% of total carbohydrate (13.75 g/100 g DW) and sulfate content of 20.45% of ulvan. FTIR spectrum presented signals of the sulfate ester (C–O–S) and sulfate groups (S=O), typical for ulvan. GC–MS revealed that ulvan was mainly composed of rhamnose and fucose. 1H-NMR spectra of ulvan showed identical behavior of monosaccharides nature with peaks characteristic of sulfated polysaccharides at 3.2–5.3 ppm region. Scanning electron micrographs (SEM) demonstrated amorphous architecture, and the sulfated nature of polysaccharides was emphasized by EDX analysis. The extracted ulvan showed significant antimicrobial activity against human and fish pathogens as well as antifouling bacteria with minimum inhibitory concentrations (MIC) of 8 µg/mL. The extracted ulvan exhibited potent antioxidant activity with a scavenging effect of 84.93% for 2,2-diphenyl-1-picrylhydrazy free radical (DPPH). Moreover, it showed anti-arthritic properties for the first time with a maximum inhibition of 86.04% with IC50 of 43.21%, indicating their potential value for the health and food industry.

Enhancing biomass and lipid productivity of a green microalga Parachlorella kessleri for biodiesel production using rapid mutation of atmospheric and room temperature plasma

BACKGROUND

Microalgae, with their high adaptability to various stress conditions and rapid growth, are considered excellent biomass resources for lipid production and biodiesel feedstocks. However, lipid yield and productivity of the natural strains are common bottlenecks in their large-scale use for lipid production, which can be overcome by evolving new strains using conventional and advanced mutagenic techniques. It is challenging to generate microalgae strains capable of high lipid synthesis through natural selection. As a result, random mutagenesis is currently considered a viable option in many scenarios. The objective of this study was to explore atmospheric and room temperature plasma (ARTP) as a random mutagenesis technique to obtain high lipid-accumulating mutants of a green microalga for improved biodiesel production.

RESULTS

A green microalgal species was isolated from the Chinese Yellow Sea and identified as Parachlorella kessleri (OM758328). The isolated microalga was subsequently mutated by ARTP to obtain high lipid-accumulating mutants. Based on the growth rate and lipid content, 5 mutants (named M1, M2, M4, M5, and M8) were selected from 15 pre-selected mutants. These five mutants varied in their growth rate from 0.33 to 0.68 day^-1, with the lipid content varying between 0.25 g/L in M2 to 0.30 g/L in M8 at 10th day of cultivation. Among the mutants, M8 showed the maximum biomass productivity (0.046 g/L/day) and lipid productivity (20.19 mg/L/day), which were 75% and 44% higher than the wild strain, respectively. The triglyceride (TAG) content of M8 was found to be 0.56 g/L at 16th day of cultivation, which was 1.77-fold higher than that of the wild strain. Furthermore, M8 had the highest saturated fatty acids (C16-18) with the lowermost polyunsaturated fatty acid content, which are favorable properties of a biodiesel feedstock according to international standards.

CONCLUSION

The mutant strain of P. kessleri developed by the ARTP technique exhibited significant improvements in biomass productivity, lipid content, and biodiesel quality. Therefore, the biomass of this mutant microalga could be a potential feedstock for biodiesel production.

The Potential of a New Commercial Seaweed Extract in Stimulating Morpho-Agronomic and Bioactive Properties of Eruca vesicaria (L.) Cav

This study aimed to understand the effect of commercial seaweed extract as a biofertilizer, named True-Algae-Max (TAM®), on the yield, nutritional, antioxidant, and cytotoxic activity of Eruca vesicaria. Three concentrations of TAM® (5, 10, and 15%) were studied by foliar spray over the two cultivation years (2016 and 2017) without any chemical fertilizer, along with a control consisting of synthetic nitrogen, phosphorus and potassium (NPK) fertilizers. The yield and composition of E. vesicaria were significantly improved in all treatments, particularly at 10% concentration of TAM®, which resulted in maximum yield (1.99 kg m−2) and significant amounts of chlorophyll, carotenoids, phenolic compounds, flavonoids and total nutrients. Compared to the NPK control, E. vesicaria grown with 10% of TAM® improved total antioxidant activity from 41.80 to 49.36 mg g−1 and cytotoxicity from 25.30 to 60.40% with an IC50 value 85.7 µg mL−1 against the hepatocellular carcinoma cell line (HepG2). These findings indicate that seaweed extract can generally be used as a safe potential multifunctional biofertilizer in the agricultural field. The use of seaweed as a biofertilizer could potentially help mitigate the adverse effects of main nutrient deficiencies, diminishing the use of chemical fertilizers.

Potential Applications of Native Cyanobacterium Isolate (Arthrospira platensis NIOF17/003) for Biodiesel Production and Utilization of Its Byproduct in Marine Rotifer (Brachionus plicatilis) Production

To achieve strong, successful and commercial aqua-biotechnological microalgae applications, screening, isolation, molecular identification, and physiological characterizations are needed. In the current study, a native cyanobacteria strain Arthrospira platensis NIOF17/003 was isolated from the surface water of El-Khadra Lake, a saline-alkaline lake located in Wadi El-Natrun, Egypt. The cyanobacterium was phylogenetically identified by 16S rRNA molecular marker and deposited in the GenBank database (accession number MW396472). The late exponential phase of A. platensis NIOF17/003 was reached at the 8th day of growth using Zarrouk medium, with a recorded dry weight (DW) of 0.845 g L−1. The isolated strain showed 52% of protein, 14% of carbohydrate, biomass productivity of 143.83 mg L−1 day−1, 8.5% of lipid, and lipid productivity of 14.37 mg L−1 day−1. In general, the values of cetane number, iodine value, cold filter plugging point (52.9, 85.5 g I2/100 g oil, and −2.2 °C, respectively) of the isolated fatty acid methyl esters are in accordance with those suggested by international standards. Besides, applying algal-free lipid (FL) as biodiesel byproduct in the production of rotifer (Brachionus plicatilis) revealed that a 0.6 g L−1 FL significantly increased the rotifer population females carrying eggs, confirming that FL can be used efficiently for B. plicatilis production. The current study concluded that the new isolate A. platensis NIOF17/003 is a promising strain for double sustainable use in biodiesel production and aquaculture feed.