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The aim of the present investigation was to study the impact of foliar spraying with Chlorella vulgaris, Arthrospira platensis, and Tetradesmus dimorphus suspensions as biostimulants on growth and yield characteristics of common beans such as Phaseolus vulgaris. Seven treatments were tested during the study: T1 (soil amended with N-urea but no microalgae foliar application), T2 (foliar spraying with C. vulgaris but no N-urea added to the soil), T3 (foliar spraying with T. dimorphus but no N-urea added to the soil), T4 (foliar spraying with A. platensis but no N-urea added to the soil), T5 (foliar spraying with C. vulgaris and soil amended with N-urea), T6 (foliar spraying with T. dimorphus and soil amended with N-urea), T7 (foliar spraying with A. platensis and soil amended with N-urea) and control (untreated). Foliar spraying was applied after 7, 25, and 77 days from sowing using the test microalgae suspensions in concentration of 10 g 100 mL−1. Plant growth and biochemical parameters were measured at the end of both vegetative and fruiting growth stages. Compared with control, the treatments from T1 to T7 showed noticeable increase in all growth parameters and yield attribute. The foliar application with C. vulgaris and chemical fertilizer treated plants (T5) exhibited the maximum increase in total plant height (26.9%), dry weight (37.28%), protein content (48.06 ± 2.403 mg g−1 fresh wt.), and total carbohydrate (394 ± 19.7 mg g−1 dry wt.) during vegetative stage as well as number of pods per plant (5.2 ± 0.26), number of seed/pod (3.5 ± 0.18), pods dry weight (0.95 ± 0.05 g plant−1) during fruiting stage. Thus, it is advisable to use C. vulgaris as a biostimulant for enhancing P. vulgaris growth and crop production.

Anaerobic digestate of food waste as a waste product of anaerobic digestion contains a significant amount of nutrients making its direct disposal prohibitive due to environmental regulations. However, the nutrients in this waste are a valuable feedstock for waste-to-product endeavours such as microalgae cultivation coupled to the treatment of the digestate. A limitation to this path is the high toxic concentration of ammonia nitrogen in the digestate which limits microalgae growth, leading to the requirement for significant dilution before use. This study focused on the bioprospecting and sourcing of species capable of sustained growth in very high concentrations of ammonia nitrogen. Ten local strains of microalgae were isolated, comprising mainly of unicellular species, a colonial species, and a filamentous species. Three unicellular species were chosen (Chlorella sp., MUR 271; Scenedesmus obliquus (Tetradesmus obliquus), MUR 272; and Oocystis sp., MUR 273) and screened alongside previously isolated strains (Scenedesmus quadricauda, MUR 268; Chlorella sp., MUR 269; and Scenedesmus dimorphus (Tetradesmus dimorphus) MUR 270) which had undergone long-term acclimation in digestate. The most tolerant of the newly isolated strains was MUR 273 (Oocystis sp.), capable of proliferation in up to 600 mg L−1 NH3-N concentration in digestate. The maximum specific growth rate, μmax, of MUR 273 was 0.36 ± 0.01 day−1 at 150 mg L−1 NH3-N. The results indicate that MUR 273 displayed tolerance levels similar to that obtained with MUR 268 which had previously undergone long-term acclimation in digestate and could potentially be used in the treatment and valorization of the anaerobic digestate of food waste with significantly less dilution.

The enhanced lipid accumulation in microalgae is envisioned under special stress conditions with the cost of algal growth, which in turn affects the overall lipid productivity. The selection of suitable stress conditions facilitates better lipid productivity without any harmful effect on microalgae growth and algal biomass production. In the present study, we have attempted to select the best salinity conditions towards better growth, biomass accumulation, and lipid productivity of microalgae. The study also envisaged testing the feasibility of the stepwise salinity stress-induced cultivation approach to minimize the growth penalty effect of microalgae. The highest specific growth rate (0.129, 0.133, 0.113 µday−1) and doubling per day (0.185, 0.193, 0.163 per day) were obtained at salinity concentration of 40 mM NaCl in BG-11 medium for Scenedesmus quadricauda (Sq19), Scenedesmus dimorphus (Sd12), and Chlorella sp. (Chl16), respectively. Maximal lipid content of 18.28, 30.70, and 32.19%, and lipid productivity of 8.59, 13.81, and 10.27 mg l−1 day−1 were achieved at 160 mM of NaCl in BG-11 media with the Sq19, Sd12, and Chl16 algal isolates, respectively. The utilization of stepwise salinity stress (160 mM) induced cultivation of Sd12 algal isolate results in higher lipid content (39.42%) and slightly improved lipid productivity than the control (without any stress, 20.4% lipid content). The results indicate the feasibility of enhancing the lipid content and productivity through the salinity-induced stepwise cultivation strategy.

Flue gas not only contains carbon dioxide (CO 2 ) but also air pollutants (sulfur oxides (SO x ) and nitrogen oxides (NO x )). The effective utilization of flue gas could help us to reduce the cost of microalgal biomass production. This study assessed and explored the utilization of flue gas for the absorption characteristics of different components and their biological effect in microalgal culture systems. In abiotic absorption experiments, the absorptivity of CO 2 was reduced by a maximum of 3.1%, and the concentration of the available carbon source in the culture medium was decreased by 6.7% when sulfur dioxide (SO 2 , at 100 mg/m 3 ) was presented in the flue gas. Meanwhile, the presence of oxygen (O 2 , at 4%) in the flue gas improved the absorptivity of nitric oxide (NO). When Scenedesmus dimorphus was cultured using bisulfites and nitrites (at 10 mmol/L and 8 mmol/L, respectively) as the sulfur and nitrogen sources, SO x and NO x in the flue gas did not significantly affect growth of microalgal cells and the carbohydrate, lipid, and protein content. The consumption rates of nutrient elements were calculated, which could provide an adjustment strategy for the initial gas source when culturing microalgae with the flue gas. This study indicates that the flue gas used for microalgal culture should be partially desulfurized, so that the SO x and CO 2 concentrations can optimize growth of microalgal cells, while the denitrification might not be needed since the flue gas can be oxidized to utilize the NO. Key points • The concentration of the available carbon source in the culture medium was decreased when SO 2 was presented in the flue gas, and the presence of O 2 in the flue gas improved the absorptivity of NO. • An adjustment strategy for the initial gas source when culturing microalgae with the flue gas was firstly proposed. • For flue gas containing 10% CO 2 and 60 mg/m 3 of SO 2 , growth of Scenedesmus dimorphus showed no difference in cell growth in normal culture conditions.

Background: With the further development of anaerobic digestion, an increasing output of anaerobically digested wastewater (ADW ), which typically contained high concentrations of ammonium, phosphate, and suspended solids, was inevitable. Microalgae cultivation offered a potential waste-to-value strategy to reduce the high nutrient content in ADW and obtain high value-added microalgae. However, ADW generally contained a mass of pollutants (suspended solids, competitors, etc.), which could inhibit microalgae growth and even result in microalgae death by limiting light utilization. Thus, it is highly imperative to solve the problem by a novel modified photobioreactor for further practical applications.Results: Four microalgae species, Scenedesmus dimorphus, Scenedesmus quadricauda, Chlorella sorokiniana, and Chlorella vulgaris ESP-6, were cultivated in the membrane photobioreactor (MPBR) fed with ADW to investigate the efficiency of ammonia and phosphorus removal. The results showed that C. sorokiniana had the best performance for the removal of ammonia and phosphorus from ADW. The highest amount of C. sorokiniana biomass was 1.15 g/L, and the removal efficiency of phosphate (66.2%) peaked at an ammonia concentration of 128.5 mg/L after 9 days’ incubation. Moreover, the MPBR with 0.1 μm membrane pore size had the best ammonia and phosphate removal efficiencies (43.9 and 64.9%) at an ammonia concentration of 128.5 mg/L during 9 days’ incubation. Finally, the continuous multi-batch cultivation of C. sorokiniana was performed for 45 days in MPBR, and higher removal ammonia amount (18.1 mg/day) and proteins content (45.6%) were obtained than those (14.5 mg/day and 37.4%) in an normal photobioreactor.Conclusion: In this study, a novel MPBR not only eliminated the inhibitory effects of suspended solid and microorganisms, but also maintained a high microalgae concentration to obtain a high amount of ammonia and phosphate removal. The research provided a theoretical foundation for the practical application of MPBRs in various wastewater treatment schemes without pretreatment by algae, which could be used as biofuels or protein feed.

Biofilm cultivation is considered a promising method to achieve higher microalgae biomass productivity with less water consumption and easier harvest compared to conventional suspended cultivation. However, studies focusing on the selection of substratum material and optimization of the growth of certain microalgae species on specific substratum are limited. This study investigated the selection of membranous and fabric fiber substrata for the attachment of unicellular microalgae Scenedesmus dimorphus and filamentous microalgae Tribonema minus in biofilm cultivation. The results indicated that both algal species preferred hydrophilic membranous substrata and nitrate cellulose/cellulose acetate membrane (CN-CA) was selected as a suitable candidate on which the obtained biomass yields were up to 10.24 and 7.81 g m−2 day−1 for S. dimorphus and T. minus, respectively. Furthermore, high-thread cotton fiber (HCF) and low-thread polyester fiber (LPEF) were verified as the potential fabric fiber substrata for S. dimorphus (5.42 g m−2 day−1) and T. minus (5.49 g m−2 day−1) attachment, respectively. The regrowth of microalgae biofilm cultivation strategy was applied to optimize the algae growth on the fabric fiber substrata, with higher biomass density and shear resistibility achieved for both algal species. The present data highlight the importance to establish the standards for selection the suitable substratum materials in ensuring the high efficiency and sustainability of the attached microalgal biomass production.Key points• CN-CA was suitable membranous substratum candidate for algal biofilm cultivation.• HCF and LPEF were potential fabric fiber substrata for S. dimorphus and T. minus.• Regrowth biofilm cultivation was effective in improving algal biomass and attachment.

On the basis of determining isoelectric point of algae residue protein obtained from Scenedesmus dimorphus, this study investigated the effects of pH values, ratio of liquid to solid, extraction temperature and time on protein extraction rates, and assessed the nutritional value of protein extracted from microalgae residues. The results from orthogonal experiments revealed the optimum conditions for extracting proteins from algal residues (pH: 12; liquid-to-solid ratio: 40 mL/g; extraction temperature: 45 ℃; extraction time: 140 min). It was observed that under the optimal conditions, the protein extraction rate was 40.13%. Essential amino acids account for 44.3% of the proteins obtained from algal residues. The content of anti-nutritional factors in algal residues was significantly reduced, and the digestibility of algal residue proteins was higher than the digestibility of algal powder. This indicated that algal residues could be an ideal source of proteins for humans.

By mimicking the info-chemicals emitted by grazers, the common anionic surfactant sodium dodecyl sulfate (SDS) can induce colony formation in the green algal genus Scenedesmus at environmentally relevant concentrations. The morphometric effects can hinder the feeding efficiency of grazers, reducing energy flow along the pelagic food chain from Scenedesmus to consumers. Despite this potential ecological risk, few studies exist on whether the SDS-triggered induction of colonies is common in other species of the family Scenedesmaceae. Here, we investigated the effects of SDS on the growth and morphology of three species of Scenedesmaceae (Desmodesmus subspicatus, Scenedesmus acutus, and Tetradesmus dimorphus) and on the clearance rates of Daphnia galeata grazing on the SDS-induced colonies. SDS triggered colony formation in all algal species at concentrations nonlethal to them (0.1–10 mg L−1) in 72 h; however, the induction levels of colony formation were generally lower than for those in the Daphnia culture medium. We also found that the SDS-induced colonial algae reduced D. galeata clearance rates. Our results highlight the potential effect of SDS on the Daphnia–Scenedesmaceae system by triggering the morphological response of Scenedesmaceae at concentrations below those that exert toxicity. Such disruptive effects of pollutants on predator–prey interactions should be considered within the framework of ecological risk assessments.

Microalgae show great potential as a biodiesel feedstock, primarily attributed to their rapid growth rates and higher lipid content. Biomass pretreatment is a critical step in biodiesel production, as it is essential for providing unsaturated and saturated fatty acids to produce fatty acid methyl ester (FAME). The present study investigates the effect of two-stage cultivation of nutrient starvation and ultrasonic-assisted solvent extraction technique from Scenedesmus dimorphus on lipid content and productivity. Preliminary studies facilitated the identification of an appropriate range to which the variables must be optimized. Scenedesmus dimorphus was obtained from the National Repository for Microalgae and Cyanobacteria [NRMC-F]. The medium optimization resulted in a higher lipid content (38.45%) in the M4N medium under starved conditions. The generated model (R2 = 0.998) forecasted the lipid content of 0.317 g/L after 87.19 min of sonication under the sonication power (65.77 W) with a molar ratio [chloroform:methanol] (1.3:1), which was experimentally validated. Under optimized conditions, the efficiency of extraction has been improved from 64.6 to 72.5% with a maximum biodiesel yield of 25.4 wt.%. In summary, this research successfully identified the optimal growth medium and pretreatment conditions, ultimately maximizing the production of biodiesel.

Microalgae are an evolutionarily ancient and morphologically diverse group of photosynthetic eukaryotes, with taxonomic resolution complicated by environmentally driven phenotypic plasticity. This study merges deep learning and explainable artificial intelligence (XAI) to establish a transparent, reliable, and biologically meaningful framework for green microalgae (Chlorophyta) classification. Microscope images from three morphologically distinct algal species—Desmodesmus flavescens, Desmodesmus subspicatus, and Tetradesmus dimorphus representing the genera Desmodesmus and Tetradesmus within Chlorophyta—were analyzed using twelve convolutional neural networks, including EfficientNet-B0–B7, DenseNet201, NASNetLarge, Xception, and ResNet152V2. A curated dataset comprising 3624 microscopic images from three Chlorophyta species was used, split into training, validation, and test subsets. All models were trained using standardized preprocessing and data augmentation procedures, including grayscale conversion, CLAHE-based contrast enhancement, rotation, flipping, and brightness normalization. The model’s performance was assessed using accuracy and loss metrics on independent test datasets, while interpretability was evaluated through saliency maps and Gradient-weighted Class Activation Mapping (Grad-CAM) visualizations. ResNet152V2 achieved the highest overall performance among all evaluated architectures, outperforming EfficientNet variants, NASNetLarge, and Xception in terms of macro F1-score. Visualization analysis showed that both Grad-CAM and saliency mapping consistently highlighted biologically relevant regions—including cell walls, surface ornamentation, and colony structures—confirming that the models relied on taxonomically meaningful features rather than background artifacts. The findings indicate that the integration of deep learning and XAI can attain consistently high test accuracy for microalgal species, even with constrained datasets. This approach enables automated taxonomy and supports biodiversity monitoring, ecological assessment, biomass optimization, and biodiesel production by integrating interpretability with high predictive accuracy.