Effect of Iron Concentration on the Co-Production of Fucoxanthin and Fatty Acids in Conticribra weissflogii.

The production of fucoxanthin and fatty acids in Conticribra weissflogii has been examined, but there is still a lack of understanding regarding the impact of trace elements, including iron, on their co-production. To address this knowledge gap, this study investigated the effects of FeCl3·6H2O on the growth, fucoxanthin, and fatty acids of C. weissflogii. The findings revealed that the highest cell density (1.9 × 106 cells mL-1), cell dry weight (0.89 ± 0.15 g L-1), and total fatty acid concentration (83,318.13 µg g-1) were achieved at an iron concentration of 15.75 mg L-1, while the maximum carotenoid and fucoxanthin contents were obtained at an iron concentration of 3.15 mg L-1. The study demonstrated that the content of the active substance in C. weissflogii could be increased by adjusting the iron concentration, providing new information as to the more efficient co-production of fucoxanthin and fatty acids and offering experimental support for large-scale production.

Transcriptome Analysis Revealed the Advantages of Room Temperature Preservation of Concentrated Oocystis borgei Cultures for Use in Aquaculture.

Oocystis borgei, a microalgae species employed for regulating the quality of aquaculture water, demonstrates the capacity to adsorb noxious substances, curtail the growth of detrimental bacteria, and outcompete blooming cyanobacteria. It can be concentrated by natural sedimentation and stored at room temperature, making it costless and simple to transport and use. To study the mechanism of adaptation to room temperature preservation, O. borgei was concentrated (1.19 × 107-1.21 × 107 cell/mL) and stored for 50 days at low (5 °C, LT), normal (25 °C, NT), and high (35 °C, HT) temperatures, respectively. Polysaccharide content, lipid content, cell survival, and resuscitation were evaluated. RNA-Seq was also used to examine how concentrated O. borgei responded to temperature. During storage, there was an increase in polysaccharide content and a decrease in lipid content, with both being significantly upregulated in the LT and HT groups. Survival and cell density were highest in the NT group. The RNA-Seq analysis revealed extensive differences in transcript levels. ATP synthesis was inhibited in the LT group due to the reduced expression of PsaD, PsaE, PsaF, PsaK, and PsaL. Under HT, the formation of reactive oxygen species (ROS) was facilitated by low levels of redox-related genes (nirA) and high levels of oxidative genes (gdhA, glna, and glts). The findings suggest that storing concentrated O. borgei at room temperature is optimal for microalgae preservation, enhancing theoretical research in this field. Our study provides further theoretical and practical support for the development of O. borgei as a live ecological preparation for aquaculture microalgae ecology management.

Effects of Temperature, Light and Salt on the Production of Fucoxanthin from Conticribra weissflogii.

Fucoxanthin is a natural active substance derived from diatoms that is beneficial to the growth and immunity of humans and aquatic animals. Temperature, light and salinity are important environmental factors affecting the accumulation of diatom actives; however, their effects on the production of fucoxanthin in C. weissflogii are unclear. In this study, single-factor experiments are designed and followed by an orthogonal experiment to determine the optimal combination of fucoxanthin production conditions in C. weissflogii. The results showed that the optimum conditions for fucoxanthin production were a temperature of 30 °C, a light intensity of 30 umol m-2 s-1 and a salinity of 25. Under these conditions, the cell density, biomass, carotenoid content and fucoxanthin content of C. weissflogii reached 1.97 × 106 cell mL-1, 0.76 g L-1, 2.209 mg L-1 and 1.372 mg g-1, respectively, which were increased to 1.53, 1.71, 2.50 and 1.48 times higher than their initial content. The work sought to give useful information that will lead to an improved understanding of the effective method of cultivation of C. weissflogii for natural fucoxanthin production.

Effects of Different Nitrogen Concentrations on Co-Production of Fucoxanthin and Fatty Acids in Conticribra weissflogii.

Fucoxanthin and fatty acids are active substances that are beneficial to the growth and immunity of humans and aquatic animals. However, relatively few species have been exploited for fucoxanthin and fatty acids in the industry. At the same time, due to its low extract content, poor stability, high production cost, and serious seasonal and regional limitations, the industry cannot normally meet the greater demand of the international market. Therefore, this experiment seeks to improve the fucoxanthin and fatty acid content of C. weissflogii by adjusting the nitrogen concentration in the culture medium. It was found that when the nitrogen concentration was 150 mg L-1, the cell number was 1.5 × 106 cell mL-1, and the average biomass was 0.75 g L-1. The mean value of carotenoid concentration was 2.179 mg L-1. The average concentration of fucoxanthin was 1.547 mg g-1. When the nitrogen concentration was 75 mg L-1, the fatty acid content reached its highest. By adjusting the concentration of nitrogen, the contents of fucoxanthin and fatty acids were increased. The results provided a theoretical basis for commercial extraction of fucoxanthin and fatty acids and further promoted the industrialization of fucoxanthin and fatty acids.

Transcriptome Analysis Reveals the Algicidal Mechanism of Brevibacillus laterosporus against Microcystis aeruginosa through Multiple Metabolic Pathways.

It is widely accepted that eutrophication has played an important role in the formation of harmful cyanobacterial blooms in recent decades, which impacts water quality and ecological environment and causes huge economic losses. Algicidal bacteria have a promising application prospect in controlling cyanobacterial blooms in aquaculture water. Here, the process of the algicidal bacterium Brevibacillus laterosporus strain Bl-zj acting on Microcystis aeruginosa was explored using transcriptome analysis to elucidate the algicidal mechanism. The results of the co-culture of bacterium and alga showed a strong alga-lysing effect of B. laterosporus against M. aeruginosa with an extreme morphology deformation of the algal cells. A total of 2744 differentially expressed genes of B. laterosporus were identified, which were mainly involved in the metabolism of amino acid, carbohydrate, and lipid. In the co-cultured group, the expression of genes mainly enriched in valine, leucine and isoleucine degradation, and fatty acid degradation were significantly increased. However, the expression of the genes related to ribosome were mainly inhibited. Transcriptome analysis showed that B. laterosporus obtained ATP and energy by the degradation of valine, leucine, isoleucine, and fatty acids, and destroyed algal cells by efflux pump transporters, secretion of hydrolytic enzymes, antibiotics, proteases, and other secondary metabolites, resulting in algal death and achieving the algicidal effect.

Allelopathic effect of Oocystis borgei culture on Microcystis aeruginosa.

This study evaluated the possibility of using Oocystis borgei to prevent and control harmful algae blooms. Firstly, Microcystis aeruginosa and O. borgei were co-cultured to assess the competition for nutrients between them. Different physiological and biochemical parameters, such as growth, cell membrane permeability and esterase activities were determined in exudate culture experiment to investigate allelopathic effects of O. borgei culture and mixed cultures (O. borgei and M. aeruginosa) at different growth phase on harmful microalgae (M. aeruginosa). Results showed that O. borgei could significantly inhibited M. aeruginosa when volume ratios were 4:1 and 1:1 (M. aeruginosa: O. borgei) in co-culture experiment. Further, it was found that the membrane system of M. aeruginosa was disintegrated by the culture filtrate of O. borgei at exponential phase. In addition, esterase activities and photorespiration were significantly inhibited. In conclusion, O. borgei exhibited different allelopathic effects at different growth phase. Its exponential phase showed a significant inhibitory effect, while no inhibitory effect was observed at the decline phase.

Transcriptional Analysis of Microcystis aeruginosa Co-Cultured with Algicidal Bacteria Brevibacillus laterosporus.

Harmful algal blooms caused huge ecological damage and economic losses around the world. Controlling algal blooms by algicidal bacteria is expected to be an effective biological control method. The current study investigated the molecular mechanism of harmful cyanobacteria disrupted by algicidal bacteria. Microcystis aeruginosa was co-cultured with Brevibacillus laterosporus Bl-zj, and RNA-seq based transcriptomic analysis was performed compared to M. aeruginosa, which was cultivated separately. A total of 1706 differentially expressed genes were identified, which were mainly involved in carbohydrate metabolism, energy metabolism and amino acid metabolism. In the co-cultured group, the expression of genes mainly enriched in photosynthesis and oxidative phosphorylation were significantly inhibited. However, the expression of the genes related to fatty acid synthesis increased. In addition, the expression of the antioxidant enzymes, such as 2-Cys peroxiredoxin, was increased. These results suggested that B. laterosporus could block the electron transport by attacking the PSI system and complex I of M. aeruginosa, affecting the energy acquisition and causing oxidative damage. This further led to the lipid peroxidation of the microalgal cell membrane, resulting in algal death. The transcriptional analysis of algicidal bacteria in the interaction process can be combined to explain the algicidal mechanism in the future.

NaCl Promotes the Efficient Formation of Haematococcus pluvialis Nonmotile Cells under Phosphorus Deficiency.

Natural astaxanthin helps reduce the negative effects caused by oxidative stress and other related factors, thereby minimizing oxidative damage. Therefore, it has considerable potential and broad application prospects in human health and animal nutrition. Haematococcus pluvialis is considered to be the most promising cell factory for the production of natural astaxanthin. Previous studies have confirmed that nonmotile cells of H. pluvialis are more tolerant to high intensity of light than motile cells. Cultivating nonmotile cells as the dominant cell type in the red stage can significantly increase the overall astaxanthin productivity. However, we know very little about how to induce nonmotile cell formation. In this work, we first investigated the effect of phosphorus deficiency on the formation of nonmotile cells of H. pluvialis, and then investigated the effect of NaCl on the formation of nonmotile cells under the conditions of phosphorus deficiency. The results showed that, after three days of treatment with 0.1% NaCl under phosphorus deficiency, more than 80% of motile cells had been transformed into nonmotile cells. The work provides the most efficient method for the cultivation of H. pluvialis nonmotile cells so far, and it significantly improves the production of H. pluvialis astaxanthin.

Complete Genome Sequence Analysis of Brevibacillus laterosporus Bl-zj Reflects its Potential Algicidal Response.

We analyzed the complete genome of the bacteria Brevibacillus laterosporus Bl-zj. Its genome has a total length of 5,202,546 bp with 4594 annotated genes. The functional groups included transporters, pathogen-host interaction factors, antibiotic resistance genes, virulence factor, and secreted proteins were predicted, and carbon and nitrogen metabolism and transporters were mapped. A total of 34 genes possibly involved in algae-lysing processes were further screened, including 8 virulence factors, 18 secreted proteases, and 8 antibiotic-resistant genes, which could be playing important roles in host identification, invasion, and the destruction of algal cells. This study will provide a theoretical framework for the algicidal mechanism of algae-lysing bacteria and possible application to algal control.

Enhanced Biomass and Astaxanthin Production of Haematococcus pluvialis by a Cell Transformation Strategy with Optimized Initial Biomass Density.

: Astaxanthin from H. pluvialis is an antioxidant and presents a promising application in medicine for human health. The two-stage strategy has been widely adopted to produce astaxanthin by the Haematococcus industry and research community. However, cell death and low astaxanthin productivity have seriously affected the stability of astaxanthin production. This study aims to test the effect of cell transformation strategies on the production of astaxanthin from H. pluvialis and determine the optimal initial biomass density (IBD) in the red stage. The experimental design is divided into two parts, one is the vegetative growth experiment and the other is the stress experiment. The results indicated that: (1) the cell transformation strategy of H. pluvialis can effectively reduce cell death occurred in the red stage and significantly increase the biomass and astaxanthin production. (2) Compared with the control group, the cell mortality rate of the red stage in the treatment group was reduced by up to 81.6%, and the biomass and astaxanthin production was increased by 1.63 times and 2.1 times, respectively. (3) The optimal IBD was determined to be 0.5, and the highest astaxanthin content can reach 38.02 ± 2.40 mg·g-1. Thus, this work sought to give useful information that will lead to an improved understanding of the cost-effective method of cultivation of H. pluvialis for natural astaxanthin. This will be profitable for algal and medicine industry players.

Complete Genome Sequence of Brevibacillus laterosporus Bl-zj, an Algicidal Bacterium Isolated from Soil.

Brevibacillus laterosporus can be used as a biocontrol agent for varieties of plants, as it is a pathogen of invertebrates and can also inhibit many bacteria and fungi. Here, we describe the complete genome sequence of B. laterosporus strain Bl-zj, an algicidal bacterium on cyanobacteria isolated from the soil in China.

Microalgae Brewery Wastewater Treatment: Potentials, Benefits and the Challenges.

Concerns about environmental safety have led to strict regulations on the discharge of final brewery effluents into water bodies. Brewery wastewater contains huge amounts of organic compounds that can cause environmental pollution. The microalgae wastewater treatment method is an emerging environmentally friendly biotechnological process. Microalgae grow well in nutrient-rich wastewater by absorbing organic nutrients and converting them into useful biomass. The harvested biomass can be used as animal feed, as an alternative energy source for biodiesel production and as biofertilizer. This review discusses conventional and current brewery wastewater treatment methods, and the application and potential of microalgae in brewery wastewater treatment. This study also discusses the benefits as well as challenges associated with microalgae brewery and other industrial wastewater treatments.

Accumulation of Astaxanthin Was Improved by the Nonmotile Cells of Haematococcus pluvialis.

The current commercial production of natural astaxanthin is mainly carried out using Haematococcus pluvialis vegetative cells in the "two-stage" batch mode. The motile vegetative cells are more sensitive to stress than nonmotile vegetative cells, thereby affecting the overall astaxanthin productivity in H. pluvialis cultures. In this study, we compared the differences between motile cells and nonmotile cells in astaxanthin productivity, morphological changes, the mortality rate, and the diameter of the formed cysts. The experimental design was achieved by two different types H. pluvialis cell under continuous light of 80 µmol photons m-2 s-1 for a 9-day induction period. The highest astaxanthin concentration of 48.42 ± 3.13 mg L-1 was obtained in the nonmotile cell cultures with the highest the productivity of 5.04 ± 0.15 mg L-1 day-1, which was significantly higher than that in the motile cell cultures. The microscopic examination of cell morphological showed a large number of photooxidative damaged cells occurring in the motile cell cultures, resulting in higher cell mortality rate (22.2 ± 3.97%) than nonmotile cell cultures (9.6 ± 0.63%). In addition, the analysis results of cell diameter statistics indicated that nonmotile cells were more conducive to the formation of large astaxanthin-rich cysts than motile cells. In conclusion, the works presented here suggest that the accumulation of astaxanthin was significantly improved by nonmotile cells of H. pluvialis, which provided a possibility of optimizing the existing H. pluvialis cultivation strategy for the industrial production.

Differences between Motile and Nonmotile Cells of Haematococcus pluvialis in the Production of Astaxanthin at Different Light Intensities.

Haematococcus pluvialis, as the best natural resource of astaxanthin, is widely used in nutraceuticals, aquaculture, and cosmetic industries. The purpose of this work was to compare the differences in astaxanthin accumulation between motile and nonmotile cells of H. pluvialis and to determine the relationship between the two cells and astaxanthin production. The experiment design was achieved by two different types of H. pluvialis cell and three different light intensities for an eight day induction period. The astaxanthin concentrations in nonmotile cell cultures were significantly increased compared to motile cell cultures. The increase of astaxanthin was closely associated with the enlargement of cell size, and the nonmotile cells were more conducive to the formation of large astaxanthin-rich cysts than motile cells. The cyst enlargement and astaxanthin accumulation of H. pluvialis were both affected by light intensity, and a general trend was that the higher the light intensity, the larger the cysts formed, and the larger the quantity of astaxanthin accumulated. In addition, the relatively low cell mortality rate in the nonmotile cell cultures indicated that the nonmotile cells have a stronger tolerance to photooxidative stress. We suggest that applying nonmotile cells as the major cell type of H. pluvialis to the induction period may help to enhance the content of astaxanthin and the stability of astaxanthin production.

Uptake of Urea Nitrogen by Oocystis borgei in Prawn (Litopenaeus vannamei) Aquaculture Ponds.

The goal of this study was to assess the rate of urea nitrogen uptake (ρ) by Oocystis borgei and the relationship between environmental factors and ρ. Light intensity, temperature, pH, salinity, and algal concentration, were used to construct an empirical model. The results showed that light intensity, algal concentration, pH and salinity had significant effects on ρ, and the optimal combination of environmental conditions for ρ was a temperature of 25°C, pH of 7.0, light intensity of 81 µmol m-2 s-1, salinity of 15‰, and algal concentration of 4.5 × 108 cell L-1-5.5 × 108 cell L-1. The model equation was ρ = 2 × 10-5 × (A0.363B0.783C0.045D-0.503E) + 0.0017, with a coefficient of determination (R2) of 0.83. No significant difference in variance was observed between the model-predicted values and the measured values (F = 0.238, p > 0.05), which demonstrated the high fitting degree of the simulation equation. This study provided valuable insight into the reduction of urea nitrogen levels in aquaculture water by O. borgei.

Effect of pure microcystin-LR on activity and transcript level of immune-related enzymes in the white shrimp (Litopenaeus vannamei).

Microcystins (MCs) in freshwater and marine waters released by toxin-producing cyanobacteria have negative impacts to the aquatic environment. This study aimed to investigate the effect of pure microcystin-LR on activity and transcript level of immune-related enzymes in the white shrimp Litopenaeus vannamei. After exposed to varying concentrations of pure microcystin-LR (MC-LR) for 30 days, the activity of superoxide dismutase (SOD), lysozyme (LZM), glutathione peroxidase (GPx), peroxidase (POD), acid phosphatase (ACP), alkaline phosphatase (AKP) and transcript level of cMn-sod, lzm, gpx were investigated in the hepatopancreas of white shrimp (L. vannamei). Immune-related enzyme activities responded differently to MC-LR exposure. SOD, GPx, and POD activity in the hepatopancreas were activated in a concentration-dependent manner while LZM activity was significantly inhibited in the treatment groups. ACP and AKP activity showed an increase, followed by a decrease. The transcript levels of cMn-sod, lzm, and gpx were consistent with changes in their encoding enzyme activity. These results demonstrated that sub-chronical exposure to MC-LR induced the alteration of immune-related enzymes and corresponding genes in the hepatopancreas, which may help explain the presence of detoxification mechanisms in crustaceans and how they were protected from MC-LR stress for a long period of time.

A preliminary study of the algicidal mechanism of bioactive metabolites of Brevibacillus laterosporus on Oscillatoria in prawn ponds.

The algae, Oscillatoria, is commonly found in prawn ponds and can lead to reduced productivity. We examined metabolites of the bacteria Brevibacillus laterosporus for algicidal qualities. To determine the possible algicidal mechanisms of these bioactive metabolites, different amounts of sterile filtrate of bacterial suspensions were added to cultures containing Oscillatoria. The dry weight, the concentrations of chlorophyll-a (chl-a), phycobiliprotein (PC, phycocyanin; APC, allophycocyanin; PE, phycoerythrin), and MDA (malondialdehyde) and the activities of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) of algae were measured during the algicidal application. The results showed that lower concentrations of the sterile filtrate (addition ≤ 4 mL) accelerated the growth rate of Oscillatoria, but significant inhibition and lysis were observed with higher concentrations (addition ≥ 8 mL). In two trials (the additions were 8 mL and 10 mL, respectively), the algal dry weights were reduced by 26.02% and 45.30%, and the chl-a concentrations were decreased by 46.88% and 63.73%, respectively, after seven days. During the algicidal treatment, the concentrations of PC, APC, PE, and MDA and the activities of SOD, POD, and CAT were significantly increased in the early cultivation and declined quickly at later stages. Finally, the algae-lysing mechanism of the bioactive metabolites of the bacteria Brevibacillus laterosporus on Oscillatoria had been proposed.

Effects of environmental factors on the uptake rates of dissolved nitrogen by a salt-water green alga (Oocystis borgei Snow).

Uptake rates for dissolved nitrogen (DN) by a marine alga (Oocystis borgei) were examined in a (15)N tracer experiment. Maximal uptake rates for all forms of DN were observed at temperatures between 25 and 30°C and at algal concentrations between 3.22 × 10(8) and 4.78 × 10(8 )cell L(-1). Light intensity required to achieve the maximal uptake rate was 45 µmol m(-2) s(-1) for dissolved inorganic nitrogen (DIN = NO(3) (-), NO(2) (-), NH(4) (+)) and methionine, and 126 µmol m(-2) s(-1) for urea. Salinity required to achieve the maximal uptake rate was 12.85 ppt for DIN, 19.89 ppt for urea and 26.2 ppt for methionine.

Influences of temperature on development and survival, reproduction and growth of a calanoid copepod (Pseudodiaptomus dubia).

Pseudodiaptomus dubia is a calanoid copepod that is distributed widely in the estuarine-coastal waters of Asia and is a dominant copepod in the shrimp grow-out ponds in southern China. A laboratory culture experiment was conducted to evaluate the influences of water temperature on larval development, survival, and reproduction. Results indicate that within a temperature range from 15 to 35 C degrees, larval development increases as the temperature increases. The water temperature for optimal larval survival rate ranges from 20 to 35 C degrees. Longevity and egg hatching time decrease as the temperature increases from 20 to 35 C degrees. Total fecundity and reproduction frequency increase as the water temperature increases, with the maximum at 30 C degrees. Fecundity and reproduction frequency decrease when the temperature exceeds 30 C degrees. Intrinsic growth rate [r(m)] ranges from 0.168 to 0.195 at 25 to 30 C degrees; net reproduction rate [R(0)] and finite growth rate (lambda) are 163 to 264 and 1.183 to 1.215, respectively, when the temperature is greater than 20 and 35 C degrees; population doubling time (t) varies from 3.556 to 4.128 days at temperatures less than 20 and 35 C degrees. Population generation time (T) is negatively correlated with temperature, with the optimal population growth rate at 25 to 30 C degrees.