Algal Research-Biomass Biofuels and Bioproducts最新文献

The growing emphasis on sustainability in environmental health, climate change, and water usability has driven the exploration of economically and environmentally friendly approaches to enhance wastewater quality. Algae-mediated natural precipitation of minerals in wastewater, driven by these organisms' carbon utilization in photosynthesis, has emerged as a promising wastewater treatment (WWT) method due to its sustainability and cost-efficiency benefits. This study examines the impact of varying carbon content in bicarbonate forms on algae activity in mediating CaCO₃ precipitation and how pH in algae-mediated solutions influences calcite precipitation. Solutions with different Ca²⁺ and HCO₃⁻ concentrations were prepared, and algae growth curves were established to ensure solution suitability. The experiments, conducted in two sets, employed ANOVA and t-test analyses for samples with common calcium concentration. Results indicated that increasing HCO3- concentration positively correlates with algae mediation and CaCO₃ precipitation, while elevating pH from 9.8 to 11.0 negatively correlates with calcite precipitation. In conclusion, HCO₃⁻ additions were effective in enhancing algae-mediated calcite precipitation in wastewater. Recommendations include ensuring proportionate HCO₃⁻ additions to calcium content to optimize mineral precipitation without detrimental effects on algae.

Marine diatom-infecting DNA/RNA viruses (DI DNA/RNAVs) are of broad interest in basic and applied research on diatoms. However, the mechanisms that underly viral gene expression and its regulation in host diatoms have not been fully elucidated. In silico analysis of DI DNAV genomes revealed the presence of four putative open reading frames (ORFs), including the replication-associated protein (VP3) gene, the structural protein (VP2) gene, and genes of unknown function (the VP1 gene and the VP4 gene). In this study, we analyzed the expression of the viral ORF genes in three combinations of DI DNAVs and host diatoms. RT–PCR analysis was performed to determine the temporal expression pattern of the viral ORF genes in infected host diatoms. Compared with the VP2 and VP3 genes, the VP1 and VP4 genes exhibited increased levels of expression after infection. Furthermore, we characterized the promoter activities of the putative promoter regions in the four ORF genes. The activity of the promoter derived from the VP4 gene might be the highest among these genes. The consensus sequences among the potential promoter regions of the ORF genes were analyzed using consensus motif-finding algorithms and multiple sequence alignment programs. Some consensus sequences were found among the potential promoter regions of the ORF genes. The expression of the VP4 gene induced by strong promoter activity in the early stage of infection may be important for the viral life cycle. These findings may help researchers determine the mechanism of DI DNA/RNAVs gene expression in host diatoms and during viral infection.

Ulva are green algae known for their biomass accumulation on the coast due to eutrophication. As these algae are able to bioremediate nitrate loadings, they are used as biofilters of enriched waters in aquaculture. Ulva form a holobiont by naturally hosting various microbes, also involved in nitrate metabolism. However, little is known about fluctuations of the Ulva holobiont in fertilized waters over time. We surveyed fluctuations of the bacterial community associated with Ulva lacinulata cultivation, with (enriched, ENR) and without (seawater only, SW) nitrate-based fertilization. Ulva biofilm and cultivation water were regularly collected and contextual parameters (nutrients, temperature, pH) were regularly measured over twelve weeks. Metabarcoding of the 16S rDNA in the biofilm and water compartments revealed that fertilization led to higher alpha-diversity. Diversity patterns indicated that samples clustered together for each compartment in SW or ENR. Fertilization led to a different genus composition in the water after 5 days, and it led to a more even community in the biofilm, from few very dominant genera at the beginning of the experiment to more less dominant genera at the end. The core microbiota in the biofilm common to SW and ENR was mainly composed of genera involved in the host fitness and physiology. Core genera common to SW and ENR in the water were likely beneficiating from the culture conditions. Microbiota's predicted metabolic pathways revealed a heightened capacity for nitrate reduction in ENR. These results may serve as a foundation to understand nitrate loadings impact on Ulva's microbiota in eutrophication conditions.

Soil salinization poses severe abiotic stress that adversely affects plant growth and development, ultimately threatening global food security by inducing physiological abnormalities. In response to escalating nutrient demands, with global requirements quantified at 76 % for nitrogen and 87 % for phosphorus, modern agriculture is increasingly adopting sustainable practices to enhance nutrient recycling and reduce reliance on external inputs. Emerging sources of plant phytostimulants, such as microalgal and cyanobacterial biomass, show promise in augmenting crop yields and bolstering plant resistance to various abiotic factors, including salt stress. The efficacy of these microorganisms stems from their simplistic cellular structure, superior photosynthetic efficiency, capacity for heterotrophic growth, adaptability to varying environmental conditions, potential for metabolic engineering, and the abundance of valuable biomolecules (such as soluble amino acids, micronutrients, polysaccharides, and phytohormones) within their biomass. This review provides an analysis of the current research landscape concerning microalgae- and cyanobacteria-derived phytostimulants, highlighting their promise as an innovative and sustainable alternative to synthetic fertilizers in the agricultural sector. Moreover, it identifies various adaptive responses of plants to salinity stress and assesses the potential and challenges associated with the use of microalgae and cyanobacteria-based metabolites for developing new sustainable strategies to enhance crop tolerance to salinity stress.

The performance of immobilized microalgae-alginate beads on biohydrogen production and its stability across several dark fermentation cycles is influenced by the sodium alginate concentrations. Thus, it is vital to determine the optimal condition for immobilization to achieve maximum encapsulation efficiency, stability and biohydrogen production. In this work, different sodium alginate concentrations (2 to 8 w/v%) were used to immobilize microalgae in influencing the dark fermentative biohydrogen productions from municipal wastewater, and its reusability was also investigated. The immobilized microalgae-alginate beads with sodium alginate concentration of 2 % showed the lowest stability and biohydrogen production in all cycles. The highest biohydrogen production was achieved by immobilized microalgal-alginate beads prepared from 8 % sodium alginate, followed by 6 % and 4 % in the first and second cycles. However, 8 % of immobilized microalgae-alginate beads generated the lowest biohydrogen volume during the third cycle. Besides, a model was rederived from the modified Gompertz model and Fick's law of diffusion equation to describe the relationship between polymeric viscosity and biohydrogen production from immobilized microalgae-alginate beads with different sodium alginate concentrations. As the sodium alginate concentrations increased, the viscosity also increased which significantly affected the properties of immobilization matrix formed such as encapsulation efficiency, growth of microalgae, diffusion of substrate and biohydrogen yield. The rederived model managed to fit the experimental data with a coefficient of determination values of >0.95 for all the polymerization degrees of alginate. The kinetic parameters, namely, yield of biohydrogen and specific microalgae growth rate of sodium alginate concentration of 6 % were 129.80 L kg⁻¹ and 4.69 h⁻¹, respectively, which were considered as maximum results as compared with other sodium alginate concentrations. Besides, the difference in biohydrogen productions for all cycles and kinetic data of biohydrogen yields obtained from the rederived model between sodium alginate concentration of 6 % and 8 % only exhibited a slight variance (<3 %). Thus, sodium alginate concentration of 6 % was considered to be an optimal for immobilizing microalgae in performing the dark fermentation. Overall, the results revealed the significance of suitable sodium alginate concentration in maximizing the immobilization of microalgae for performing the dark fermentative biohydrogen production.

This study investigated the combined effects of mixed LED light wavelengths and varying concentrations of the strigolactone analog (GR24) on methane and antibiotic removal in swine wastewater using different microalgae co-culture techniques. Four treatments were implemented: Treatment 1 involved Chlorella vulgaris monocultures, Treatment 2 included C. vulgaris-activated sludge-Clonostachys rosea (C. rosea), Treatment 3 included C. vulgaris-Bacillus licheniformis-C. rosea, and Treatment 4 included C. vulgaris-S395-2-C. rosea. These treatments were designed to optimize conditions for antibiotic and CO₂ removal. Treatment 4 showed the highest growth rate (0.329 ± 0.030 d⁻¹), mean daily productivity (0.166 ± 0.015 g L⁻¹ d⁻¹), CA activity (66.25 ± 5.39), and photosynthesis under a red-to-blue light ratio of 5:5. Significant antibiotic removal rates were achieved: 98.77 ± 1.05 % for tetracycline hydrochloride, 93.74 ± 5.06 % for oxytetracycline hydrochloride, 62.44 ± 5.58 % for ciprofloxacin, 55.07 ± 4.97 % for norfloxacin, 70.39 ± 6.03 % for sulfadimethoxine, and 67.46 ± 6.25 % for sulfamethoxazole. A concentration of 10⁻⁹ M GR24 maximally enhanced antibiotic and CO₂ removal in Treatment 4. This study provided valuable insights into improving wastewater treatment practices and environmental management.

The demand for functional fermented plant-based milk products has intensively increased. Here, the physical, biochemical and microbial consortia of two different kefir samples which are soymilk kefir (S) and cows' milk kefir (M) was evaluated and examination of nutritional and microbial value of adding Haematococcus pluvialis microalgae to soymilk kefir at a ratio of 0.25 % (S1) and 0.50 % (S2) was done in order to fulfill deficiencies caused by the lack of animal-based milk. As part of a functional comparison between the two samples, besides physicochemical and biochemical analysis, the structure and functional diversity of the bacterial communities was also evaluated by metagenomic analysis. S1 and S2 kefir samples presented significantly increased pH, protein, fatty acid index and decreased fat content than the M sample. It was also observed a high bacterial diversity in S1 and S2 kefir samples including greater abundance of Leuconostoc lactis (31.98 %), Lactococcus lactis (23.68 %), Leuconostoc mesenteroides (19.72 %); Liquorilactobacillus nagelii (32.70 %). Moreover, the increased concentration of H. pluvialis in S1 and S2 kefirs resulted in reduction of the abundance of Bacillus cereus. It can be concluded that microalgae biomass can be used as an innovative natural ingredient to develop fermented, functional, vegan and lactose-free kefir with high nutritional and bio-diversified options.

Chlorella sorokiniana is a microalgae with high amounts of carotenoids, but the extraction methods need to be improved. This work hypothesized that the combination of ionic liquids (ILs) and ultrasound would provide a fast and efficient process for carotenoid extraction, allowing for the reuse of ILs in several extractive cycles. This study aimed to develop an improved ILs/ultrasound-based method for extracting carotenoids from C. sorokiniana. The potential reuse of ILs in five consecutive extraction cycles and the recovery of carotenoids was also examined. Moreover, the antioxidant activity of the carotenoid extracts and their effects on metabolic cell viability and cell death were investigated using HT22 neuronal cells. Initial tests with four ILs and acetone as a control were carried out in an ultrasonic probe. The ILs (1-butyl-3-methylimidazolium chloride [BMIM][Cl]; 1-hexyl-3-methylimidazolium chloride [HMIM][Cl]) were selected for the 2⁵⁻¹ fractional experimental design. The maximized parameters obtained in the experimental design were the following: IL ([HMIM][Cl]), a 1:10 solid-liquid ratio, a 1:4 IL-cosolvent ratio, and two repetitions of extraction with 7.5 min (with an extraction yield of 1.29 mg·g^‐1 of dry matter). A total of 11 carotenoids were separated, and nine were identified, the major ones being lutein and β-carotene. [HMIM][Cl] recyclability using resin Amberlite XAD-7HP was efficient for at least five cycles. On average, 91 % of the IL was recovered, and the pigment yield increased by 40 %. The antioxidant activities of the extracts obtained using [HMIM][Cl] and acetone were 1.65 μmol and 2.32 μmol of α-tocopherol, respectively. Both extracts (≤ 4.0 μg·mL^‐1) exhibited no significant toxicity to HT22 cells. The proposed method is an innovative and improved approach for carotenoid extraction from C. sorokiniana due to its short extraction times and high process yield. [HMIM][Cl] demonstrated stability in reuse cycles and proved to have the potential for obtaining carotenoids from C. sorokiniana.

In recent years, the proliferation of industrial effluents has posed significant challenges. In comparison to traditional physical and chemical methods, biological approaches have gained prominence among researchers due to their cost-effectiveness, abundant sources, ease of operation, and minimal secondary pollution. Moreover, employing microalgae for bioremediation offers the added advantage of concurrent production of diverse sustainable resources and biofuels. Nevertheless, challenges pertaining to recovery and reaction conditions continue to impede its large-scale implementation. Thus, exploration of improved solutions, such as enhanced reaction conditions, is imperative to maximize efficiency. In this review, we elucidate the mechanisms and pivotal factors involved in the removal of heavy metals by microalgae. Notably, we highlight innovative bioreactor technologies, including immobilization carriers, modified microalgae, and symbiotic systems, as focal points of this discussion. This comprehensive overview underscores the potential of microalgae-based bioremediation and paves the way for future advancements in this critical field.

This study investigates the phycoremediation potential of microalgae Chlorella vulgaris in the degradation of Direct green 6 (DG6), a synthetic azo dye commonly used in the textile industry, which poses significant environmental and health risks due to its toxic and carcinogenic properties. Over 50 days of treatment, we analyzed the effects of varying concentrations of DG6 on the biodegradation capabilities of C. vulgaris with the characterization of growth and antioxidant parameters. The findings demonstrate that C. vulgaris reduced DG6 levels significantly (p < 0.05) at higher temperatures (40 °C) compared to other environmental ambient temperatures. Within the acidic range pH < 7 progressive removal efficiency was observed within 25 days in consistency with the enhanced growth indices of biomass concentration (X_m), productivity (P_x), specific growth rate (μ_m), and doubling time (t_d) at the higher concentration of 60 mg L⁻¹. Induction of both enzymatic and non-enzymatic antioxidant activities were quantified for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), azoreductase, and laccase, as well as changes in the total ascorbate pool (AsA + DHA) and ferric reducing antioxidant power (FRAP). Furthermore, the underlying biodegradation mechanisms were elucidated by identifying the reductive cleavage of azo bonds by azoreductase and breakdown by peroxidases and laccase. These molecular by-products were identified using gas chromatography–mass spectrometry (GC–MS), which shed light on the metabolic pathways involved in DG6 biodegradation. This study underscores the effectiveness of C. vulgaris as a sustainable, low-cost solution for the bioremediation of azo-dye-polluted water. This study lays the groundwork for further exploration into the genetic and metabolic adaptations of algae under complex organic pollutant stress, with potential implications for ecophysiology, biotic interactions, and evolutionary biology.