Study of the Polysaccharide Production by the Microalga Vischeria punctata in Relation to Cultivation Conditions.

Vischeria punctata is a unicellular microalga that has industrial potential, as it can produce substances with beneficial properties. Among them, endopolysaccharides (accumulated in cells) and exopolysaccharides (released by cells into the culture medium) are of particular interest. This study aimed to investigate the effect of nutrient medium composition on the growth of V. punctata biomass and the synthesis of polysaccharides by microalgae. The effect of modifying a standard nutrient medium and varying cultivation parameters (temperature, time, and extractant type) on the yield of exopolysaccharides produced by the microalgae V. punctate was investigated. The methods of spectrophotometry, ultrasonic extraction, and alcohol precipitation were used in the study. It was found that after 61 days of cultivation, the concentration of polysaccharides in the culture medium was statistically significantly higher (p <0.05) when using a Prat nutrient medium (984.9 mg/g d.w.) than BBM 3N (63.0 mg/g d.w.). It was found that the increase in the V. punctata biomass when cultivated on different nutrient media did not differ significantly. The maximum biomass values on Prat and BBM 3N media were 1.101 mg/g d.w. and 1.120 mg/g d.w., respectively. Neutral sugars and uronic acids were found in the culture media. It follows on from the obtained data that the modified PratM medium was more efficient for extracting polysaccharides from V. punctata. The potential of microalgae as new sources of valuable chemicals (polysaccharides), which can be widely used in technologies for developing novel functional foods, biologically active food supplements, and pharmaceutical substances, was studied.

Study of the Physicochemical and Biological Properties of the Lipid Complex of Marine Microalgae Isolated from the Coastal Areas of the Eastern Water Area of the Baltic Sea.

The Baltic Sea algae species composition includes marine euryhaline, freshwater euryhaline, and true brackish water forms. This study aimed to isolate a lipid-pigment complex from microalgae of the Baltic Sea (Kaliningrad region) and investigate its antimicrobial activity against Gram-positive and Gram-negative bacteria. Microalgae were sampled using a box-shaped bottom sampler. Sequencing was used for identification. Spectroscopy and chromatography with mass spectroscopy were used to study the properties of microalgae. Antibiotic activity was determined by the disc diffusion test. Lipids were extracted using the Folch method. Analysis of the results demonstrated the presence of antimicrobial activity of the lipid-pigment complex of microalgae against E. coli (the zone diameter was 17.0 ± 0.47 mm and 17.0 ± 0.21 mm in Chlorella vulgaris and Arthrospira platensis, respectively) and Bacillus pumilus (maximum inhibition diameter 16.0 ± 0.27 mm in C. vulgaris and 16.0 ± 0.22 mm in A. platensis). The cytotoxic and antioxidant activities of the lipid complexes of microalgae C. vulgaris and A. platensis were established and their physicochemical properties and fatty acid composition were studied. The results demonstrated that the lipid-pigment complex under experimental conditions was the most effective against P. pentosaceus among Gram-positive bacteria. Antimicrobial activity is directly related to the concentration of the lipid-pigment complex. The presence of antibacterial activity in microalgae lipid-pigment complexes opens the door to the development of alternative natural preparations for the prevention of microbial contamination of feed. Because of their biological activity, Baltic Sea microalgae can be used as an alternative to banned antibiotics in a variety of fields, including agriculture, medicine, cosmetology, and food preservation.

Isolation of Valuable Biological Substances from Microalgae Culture.

Methods for purifying, detecting, and characterizing protein concentrate, carbohydrates, lipids, and neutral fats from the microalgae were developed as a result of research. Microalgae were collected from natural sources (water, sand, soil of the Kaliningrad region, Russia). Microalgae were identified based on morphology and polymerase chain reaction as Chlorella vulgaris Beijer, Arthrospira platensis Gomont, Arthrospira platensis (Nordst.) Geitl., and Dunaliella salina Teod. The protein content in all microalgae samples was determined using a spectrophotometer. The extracts were dried by spray freeze drying. Pressure acid hydrolysis with 1% sulfuric acid was determined to be the most effective method for extracting carbohydrates from microalgae biomass samples. The highest yield of carbohydrates (more than 56%) was obtained from A. platensis samples. The addition of carbohydrates to the cultivation medium increased the accumulation of fatty acids in microalgae, especially in Chlorella. When carbohydrates were introduced to nutrient media, neutral lipids increased by 10.9%, triacylglycerides by 10.9%, fatty acids by 13.9%, polar lipids by 3.1%, unsaponifiable substances by 13.1%, chlorophyllides by 12.1%, other impurities by 8.9% on average for all microalgae. It was demonstrated that on average the content of myristic acid increased by 10.8%, palmitic acid by 10.4%, oleic acid by 10.0%, stearic acid by 10.1%, and linoleic acid by 5.7% in all microalgae samples with the addition of carbohydrates to nutrient media. It was established that microalgae samples contained valuable components (proteins, carbohydrates, lipids, fatty acids, minerals). Thereby the study of the composition of lipids and fatty acids in microalgae, as well as the influence of carbohydrates in the nutrient medium on lipid accumulation, is a promising direction for scientific research in the fields of physiology, biochemistry, biophysics, genetics, space biology and feed additive production.

Algae: Study of Edible and Biologically Active Fractions, Their Properties and Applications.

The beneficial properties of algae make them perfect functional ingredients for food products. Algae have a high energy value and are a source of biologically active substances, proteins, fats, carbohydrates, vitamins, and macro- and microelements. They are also rich in polyunsaturated fatty acids, proteins, mycosporine-like amino acids, polysaccharides, polyphenols, carotenoids, sterols, steroids, lectins, halogenated compounds, polyketides, alkaloids, and carrageenans. Different extraction parameters are used depending on the purpose and the substances to be isolated. In this study, the following parameters were used: hydromodule 1:10 and an extraction duration of 1-2 h at the extraction temperature of 25-40 °C. A 30-50% solution of ethanol in water was used as an extractant. Algae extracts can be considered as potential natural sources of biologically active compounds with antimicrobial activity and antiviral properties. The content of crude protein, crude fat, and carbohydrates in U. Prolifera, C. racemosa var. peltata (Chlorophyta), S. oligocystum and S. fusiforme (SF-1) was studied. It was found that C. muelleri (Bacillariophyta), I. galbana (Haptophyta), and T. weissflogii (Bacillariophyta) contain about 1.9 times more omega-3 than omega-6 fatty acids. N. gaditana (Ochrophyta), D. salina (Chlorophyta), P. tricornutum (Bacillaryophyta) and I. galbana (Haptophyta) extracts showed inhibitory activity of varying intensities against E. coli or P. aeruginosa. In addition, algae and algae-derived compounds have been proposed to offer attractive possibilities in the food industry, especially in the meat sector, to evolve functional foods with myriad functionalities. Algae can increase the biological activity of food products, while the further study of the structure of compounds found in algae can broaden their future application possibilities.

Influence of Carbohydrate Additives on the Growth Rate of Microalgae Biomass with an Increased Carbohydrate Content.

Our study focused on investigating the possibilities of controlling the accumulation of carbohydrates in certain microalgae species (Arthrospira platensis Gomont, Chlorella vulgaris Beijer, and Dunaliella salina Teod) to determine their potential in biofuel production (biohydrogen). It was found that after the introduction of carbohydrates (0.05 g⋅L-1) into the nutrient medium, the growth rate of the microalgae biomass increased, and the accumulation of carbohydrates reached 41.1%, 47.9%, and 31.7% for Arthrospira platensis, Chlorella vulgaris, and Dunaliella salina, respectively. Chlorella vulgaris had the highest total carbohydrate content (a mixture of glucose, fructose, sucrose, and maltose, 16.97%) among the studied microalgae, while for Arthrospira platensis and Dunaliella salina, the accumulation of total carbohydrates was 9.59% and 8.68%, respectively. Thus, the introduction of carbohydrates into the nutrient medium can stimulate their accumulation in the microalgae biomass, an application of biofuel production (biohydrogen).

Evaluation of Biocompatibility and Antagonistic Properties of Microorganisms Isolated from Natural Sources for Obtaining Biofertilizers Using Microalgae Hydrolysate.

Determination of the biocompatibility of microorganisms isolated from natural sources (Kemerovo Oblast-Kuzbass) resulted in the creation of three microbial consortia based on the isolated strains: consortium I (Bacillus pumilus, Pediococcus damnosus, and Pediococcus pentosaceus), consortium II (Acetobacter aceti, Pseudomonas chlororaphis, and Streptomyces parvus), and consortium III (Amycolatopsis sacchari, Bacillus stearothermophilus; Streptomyces thermocarboxydus; and Streptomyces thermospinisporus). The nutrient media composition for the cultivation of each of the three studied microbial consortia, providing the maximum increase in biomass, was selected: consortium I, nutrient medium 11; consortium II, nutrient medium 13; for consortium III, nutrient medium 16. Consortia I and II microorganisms were cultured at 5-25 °C, and consortium III at 50-70 °C. Six types of psychrophilic microorganisms (P. pentosaceus, P. chlororaphis, P. damnosus, B. pumilus, A. aceti, and S. parvus) and four types of thermophilic microorganisms (B. stearothermophilus, S. thermocarboxydus, S. thermospinisporus, and A. sacchari) were found to have high antagonistic activity against the tested pathogenic strains (A. faecalis, B. cinerea, E. carotovora, P. aeruginosa, P. fluorescens, R. stolonifera, X. vesicatoria. pv. Vesicatoria, and E. aphidicola). The introduction of microalgae hydrolyzate increased the concentration of microorganisms by 5.23 times in consortium I, by 4.66 times in consortium II, by 6.6 times in consortium III. These data confirmed the efficiency (feasibility) of introducing microalgae hydrolyzate into the biofertilizer composition.

Production, Purification, and Study of the Amino Acid Composition of Microalgae Proteins.

Microalgae are known to be rich in protein. In this study, we aim to investigate methods of producing and purifying proteins of 98 microalgae including Chlorella vulgaris, Arthrospira platensis, Nostoc sp., Dunaliella salina, and Pleurochrysis carterae (Baltic Sea). Therefore, we studied their amino acid composition and developed a two-stage protein concentrate purification method from the microalgae biomass. After an additional stage of purification, the mass fraction of protein substances with a molecular weight greater than 50 kDa in the protein concentrate isolated from the biomass of the microalga Dunaliella salina increased by 2.58 times as compared with the mass fraction before filtration. In the protein concentrate isolated from the biomass of the microalga Pleurochrysis cartera, the relative content of the fraction with a molecular weight greater than 50.0 kDa reached 82.4%, which was 2.43 times higher than the relative content of the same fractions in the protein concentrate isolated from this culture before the two-stage purification. The possibilities of large-scale industrial production of microalgae biomass and an expanded range of uses determine the need to search for highly productive protein strains of microalgae and to optimize the conditions for isolating amino acids from them.

Study of Morphological Features and Determination of the Fatty Acid Composition of the Microalgae Lipid Complex.

Microalgae are rich in nutrients and biologically active substances such as proteins, carbohydrates, lipids, vitamins, pigments, phycobiliproteins, among others. The lipid composition of the microalgae Chlorella vulgaris, Arthrospira platensis, and Dunaliella salina was screened for the first time. The proposed method for purifying the lipid complex isolated from microalgae's biomass involved dissolving the lipid-pigment complex in n-hexane for 4 h and stirring at 500 rpm. We found that the largest number of neutral lipids is contained in the biomass of microalgae Arthrospira platensis, fatty acids, polar lipids (glycerophospholipids), and unsaponifiable substances-in the biomass of microalgae Dunaliella salina, chlorophyll, and other impurities-in the biomass of microalgae Chlorella vulgaris. The developed method of purification of the fatty acid composition of the microalgae lipid complex confirmed the content of fatty acids in microalgae, which are of interest for practical use in the production of biologically active components. We also determined the potential of its use in the development of affordable technology for processing microalgae into valuable food and feed additives.

Microalgae: A Promising Source of Valuable Bioproducts.

Microalgae are a group of autotrophic microorganisms that live in marine, freshwater and soil ecosystems and produce organic substances in the process of photosynthesis. Due to their high metabolic flexibility, adaptation to various cultivation conditions as well as the possibility of rapid growth, the number of studies on their use as a source of biologically valuable products is growing rapidly. Currently, integrated technologies for the cultivation of microalgae aiming to isolate various biologically active substances from biomass to increase the profitability of algae production are being sought. To implement this kind of development, the high productivity of industrial cultivation systems must be accompanied by the ability to control the biosynthesis of biologically valuable compounds in conditions of intensive culture growth. The review considers the main factors (temperature, pH, component composition, etc.) that affect the biomass growth process and the biologically active substance synthesis in microalgae. The advantages and disadvantages of existing cultivation methods are outlined. An analysis of various methods for the isolation and overproduction of the main biologically active substances of microalgae (proteins, lipids, polysaccharides, pigments and vitamins) is presented and new technologies and approaches aimed at using microalgae as promising ingredients in value-added products are considered.