microalgae

The harvesting microalgae from their dilute culture medium is a challenging and costly process that accounts for about 30-30% of total production costs. Therefore, finding the suitable technique for harvesting candidate strains of commercial production is very important. In the present study, the effect of using different amounts (0.1, 0.3, 0.5, 0.7 and 1 g / l) of aluminum chloride (AlCl₃) as a flocculant was investigated on harvesting efficiency and pigments of microalgae, Dunaliella salina. At first, the native microalgae D. salina isolated from back barrier Lipar, Chabahar was cultured in laboratory to reach maximum production in exponential growth phase, then different amounts of flocculant were added to the culture medium. Finally, the efficiency of AlCl3 in harvesting process and also its effect on the pigments composition of harvested biomass were investigated. The possibility of reusing the flocculated medium culture was also tested. The results of this study showed that with increasing the consumption of aluminum chloride from 0.1 g to 1 g / l flocculation efficiency increased significantly. However, the consumption more than 0.7 g / l of flocculant aluminum chloride caused a significant reduction in the content of chlorophyll, total carotenoid and beta-carotene pigments in the harvested biomass. Therefore, to maintain the quality of harvested biomass, it is recommended to use 0.7 g / l aluminum chloride with 75% efficiency for harvesting microalgae D. salina.

In this study, the effect of lack and phosphorus deficiency (dipotassium phosphate; K2HPO4) on the growth rate, biomass, biochemical content, and fatty acid profile of Desmodemus sp. was investigated for 14 days. Accordingly, Desmodesmus microalgae were grown in culture media containing no phosphorus (P0), 10 (P10), 20 (P20), 30 (P30), and 40 mg/liter (P40). The P40 treatment was considered as a control group that had the amount of phosphorus required in the standard culture medium BG11. Based on the results, the highest cell density, specific growth rate, and biomass production were simultaneously recorded in the P20, P30, and P40 treatments on the 14th day of culture, which showed a significant difference from the other two groups (P<0.05). In addition, the highest chlorophyll a was also recorded in these three groups, which showed a significant increase compared to the group without phosphorus (P<0.05). The lowest chlorophyll b was recorded in P0 (1.62 mg/L) compared to other experimental groups (P<0.05). The analysis of body composition showed the highest amount of lipid productivity (14.93 mg/liter per day) in P20 treatment, which has a significant difference with other experimental groups, except for P10 (13.17 mg/liter per day) (P<0.05). The highest protein productivity rate was measured in P30 and P40 groups (P<0.05) and the highest carbohydrate productivity rate (10.55 mg/L per day) was measured in P40 without significant difference with P30 (8.87 mg/l per day). The highest amount of saturated fatty acids was observed in P0 (47.66% of total fat) and the highest long-chain unsaturated fatty acids in P40 treatment (30.58% of total fat) without significant difference with P30 (29.33% of total fat). Based on the results, the concentration of 20 mg/liter of phosphorus is a suitable concentration for the cultivation of Desmodesmus sp. microalgae for the production of biofuel, while the concentration of 40 mg/liter of phosphorus is a suitable concentration for the cultivation of the microalgae for using in the food and aquafeed industries.

White spot disease (WSD) is one of the most important diseases in shrimp farming, which has caused a decrease in production and severe economic damage all over the world, including Iran. Mortality caused by this severe disease is very high and reaches 100% within 3 to 10 days from the onset of the disease. According to global statistics, about 300,000 tons of shrimp are lost due to this disease every year in the world. For example, within the years 2004, 2006, 2007, 2015, 2016 and 2019, the outbreak of this disease caused millions of dollar losses to the producers in Iran. Since the VP28 viral protein gene is one of the most important white spot disease virus envelope proteins and plays a role in sticking to and penetrating shrimp cells, and since microalgae is the most important source of food for shrimp in the larval stage, So it can be a suitable host for making  a vaccine. So in this study, samples of shrimp (Penaeus indicus) suspected of white spot disease from Abadan (Khuzestan province) breeding ponds were transferred to the laboratory of Razi Vaccine and Serum Institute of Arak branch and the genomic DNA of the virus was extracted using proteinase K and phenol/chloroform methods. The VP28 gene was proliferated by PCR method, inserted into pCAMBIA1304 vector and finally transferred to Chlorella vulgaris microalgae using electroporation method.

Nowadays, sea foods are considered to provide more than 50% of the nutritional demands of ‎human communities. Therefore, with the development of the seafood market, the aquaculture ‎industry continues to grow day by day. Currently, some aquaculture food ingredients are made ‎from low price fishes (in the form of fish powder) and plants. But, the production of fish powder ‎cannot be increased due to disruption of the stability of aquatic ecosystems; Therefore, alternative ‎and environmentally friendly sources should be developed for aquaculture food ingredients. ‎Microalgae biomass suggests as a natural source instead of fish powder because the cellular ‎metabolites of these microorganisms contain a combination of essential amino acids, unsaturated ‎fatty acids, vitamins, and pigments. In addition to these unique properties and bioactive compounds ‎that are a major component of aquatic nutrition, microalgae can increase the survival of farmed ‎species, and improve the color and quality of fillets. Microalgae have the highest biomass productivity ‎among photosynthetic organisms, including forage crops, and therefore have high commercial ‎potential. Also, the production of microalgae does not require special arable land and freshwater ‎resources, which makes the feed based on microalgae contribute to environmental sustainability. ‎This article is a review of studies on the potential and application of microalgae in aquatic nutrition ‎to increase the productivity of aquaculture products.‎

This study was conducted to evaluate the effects of different levels of Cyanothece sp. on growth indices, survival rate and feed conversion ratio of western white shrimp (Litopenaeus vannamei) for 60 days in Chabahar fisheries research center. 240 individual with an average weight of 3.03 ±0.017 g were distributed in 12 tanks with a density of 20 shrimp per liter of storage. Treatment were 0 (control), 100 (treatment 1), 200 (treatment 2) and 300 (treatment 3) mg/kg extract of Cyanothece sp. Growth indices were examined including mean weight, total length, specific growth rate, feed conversion ratio, feed conversion efficiency and survival as 3 meals per day and at the end of the period. The results showed 200 mg/kg of microalgae extract had a positive and significant effect on survival parameters (P<0.05). Mean weight, length and specific growth coefficient (SGR) of shrimp fed a diet containing 200 mg / kg of extract 13.88 g, 13.03 cm and 2.56% were significantly higher than the measured values in other treatments, respectively. While due to the significant increase in feed conversion ratio (FCE) in shrimp treated with 200 mg / kg, the rate of feed conversion ratio (FCR) was significantly lower than other shrimps. It is concluded the use of microalgae extract can have a positive effect on growth rate, survival rate and persistence of young western white shrimp.

One of the main prerequisites for success in the microalgae production industry and the extraction of natural pigments from them is the selection of a suitable microalgae strain for culture. In this study, for the first time, isolation, purification and identification of native strain of Cyanothece sp. Chabahar was taken from Lipar back barrier (salinity up to 400 part per thousand, ppt). In the next step, to find suitable conditions for growing, this microalga was cultured in five different salinity levels (37, 60, 90, 120, 180 ppt) and growth rate, biomass production, chlorophyll a and b pigment content, total carotenoids and phycocyanin were assayed. The growth performance was performed by cell counting and measuring pigments using a spectrophotometer method. The analysis of data showed that increasing salinity from 37 to 90 ppt increased the number of microalgae cells and biomass and the maximum number of cells was 5×106 cells per ml and biomass 1.4 g/L was obtained at a salinity of 90 ppt. The maximum contents of chlorophyll a, chlorophyll b and phycocyanin were obtained (32μg/ml), (17μg/ml) and (2.47 μg/ml) at 90 ppt salinity, respectively. By increasing the salinity from 37 to 120 ppt, the total carotenoids production and beta-carotene also increased significantly, so that the amount of carotenoids reached from 0.8 to 4.67 μg/ml. Beta-carotene also increased from 0.03 to 0.17 mg/ml. Based on this information, optimal growth and accumulation of economic pigments in microalgae Cyanothece sp. can be obtained at salinity 90 to 120 ppt.

Global warming due to the excessive use of fossil fuels, environmental pollution, and rising greenhouse gases has led researchers to develop renewable energy sources such as the sun, wind, water, and biofuels. Microalgae, which are high in fatty acids, are suitable candidates for biofuel production.This study was designed to investigate the effect of different light intensities on the growth and accumulation of lipid in freshwater microalgae Chlamydomonas reinhardtii. For this purpose, microalgae were cultured at five light intensities of 50, 100, 200, 300, and 400 µmol m-2 s-1 for 20 days. The highest lipid content was (45.72±1.06%), and the lipid yield was (105.21±1.63 mg L−1 d−1), according to the growth curves in microalgae exposed to 300 µmol m-2 s-1. The amount of saturated fatty acids increased significantly with increasing light intensity, while monounsaturated and polyunsaturated fatty acids decreased. Among the fatty acids, methyl ester, palmitic acid, stearic acid, and alpha-linolenic acid showed the highest values at a light intensity of 300 µmol m-2 s-1. To evaluate the quality of biofuels, parameters such as saponification rate (SV), iodine value (IV), Cetane number (CN), degree of unsaturation (DU), long chain saturated factors (LCSF), and cold flow plugging properties (CFPP) was also estimated. The findings of this study showed that light intensity could improve the fat efficiency and biofuel properties obtained from the microalgae C. reinhardtii as a raw material in biofuel production.

Optimal aquaculture requires various criteria, among which the choice of food with the necessary potential is of particular importance. The aim of this study was to determine the effect of different levels of Spirulina platensis algae powder in shrimp diet on growth indices and survival percentage of Palaemon elegans shrimp larvae during a four week- culture period. The mean initial weight and length of post larvae were 0.0132 (g) and 6.88 (mm). Four diets consisting of the spirulina algae powder were prepared and substituted at 3, 5, 8 and 10 percent in a base shrimp diet as treatments and a control diet was without spirulina algae powder. Growth indices in the control treatment (without algae) had the lowest rate and was significantly different from treatments of 5, 3, 8 and 10 percent of spirulina algae (P<0/05). There was a significant difference between control and treatment fed with pure algae only in increasing total biomass (P<0/05). There was no significant difference between the group fed with pure algae and 3 percent treatment in the final length and increase of length (P<0/05), but the differences were significant in other growth indices with other treatments (P<0/05). The best growth indices were observed when shrimps were fed by 5 percent algae powder (P<0/05). in comparison between treatments of 3, 8 and 10 percent algae powder, the only significant difference observed in the final length, and an increase in length was detected in treatments 3 and 10 percent algae powder (P<0/05). Also, the survival rate in control treatment was significantly lower than other treatments (P<0/05). In general, based on the results of this study, the diet containing the 5 percent of spirulina algae powder showed the best results in the growth and survival of P. elegans shrimp post larvae.

Microalgae are a very diverse group of aquatic plants that have numerous applications in biotechnology today. These microscopic photosynthesizers, have an extensive role in producing oxygen on Earth, they are found in almost all water sources on Earth due to their high dispersion and abundance. In this study, to investigate the effect of carbon sources on biochemical compounds such as proteins, carbohydrates and antioxidants, sources of organic carbon like glucose and glycerol were used. The results showed that most carbohydrates production was in a sample with 3 g / liter of glucose plus 5 g / Liters of glycerol in Monoraphidium and the lowest amount in the control sample of Scenedesmus. The lowest amount of protein was in the sample contains 1 g / liter of glucose in Scenedesmus and the highest amount in the control sample of Monoraphidium. The amount of antioxidants calculated by FRAP, and it was the highest in the control sample of Monoraphidium and the lowest recorded in the sample containing 3 g / liter of glucose in Monoraphidium. The results of this study indicated that the use organic carbon sources such as a combination of glucose and glycerol stimulates the production of carbohydrates but reduces the production of proteins and antioxidants.