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Growing concerns over greenhouse gas emissions and energy insecurity caused by the depletion of conventional fuels have led to a search for sustainable fuel alternatives. As an alternative energy carrier, hydrogen (H 2) is particularly attractive as only water is released during combustion. The process of H 2 production from genetically engineered phototrophic microorganisms through biophotolysis leads the way to solve energy shortages. Genetically engineered cyanobacteria species are potential candidates due to their superior properties for reducing greenhouse gases and using solar energy as an energy source. The review discusses the mechanisms and enzymes involved in H 2 production by cyanobacteria and applications of genetic engineering. A critical analysis of the fundamental issues attributed to the technical advancement of photobiological cyanobacteria-based H 2 production is provided, as well as the perspectives for future research to reduce carbon dioxide emissions through the creation of waste-free technology. • Genetic engineering findings of cyanobacterial nitrogenase enzyme are described. • Recent genetic engineering methods to obtain hydrogenase mutants are discussed. • Engineering photosynthetic H 2 production is shown as an efficient method. • Development of a non-waste H 2 production technology is explained. [ABSTRACT FROM AUTHOR]

Environmental and energy security has now become a serious global problem, requiring a lot of research to find and implement its cost-effective and environmentally friendly alternatives. The development and use of renewable energy sources is necessary and important in order to avoid the emergence of a global economic crisis. One of the solution to prevent a future crisis caused by energy shortages is to introduce biofuels into the fuel market. Despite the fact that various forms of renewable energy are currently used, the prospects for the production of biofuels from cyanobacteria are quite high due to their unique properties, such as a high lipid content and a suitable fatty acid (FA) composition for the production of biofuels, their suitability for growing open water and the ability to grow on wastewater. The purpose of this article is to provide a comprehensive overview of the potential of cyanobacteria in the conversion of wastewater into biofuels. The article covers comparative data on the accumulation of lipids and the content of fatty acids in various representatives of cyanobacteria and their possibilities in the remediation of wastewater. Various approaches to the extraction of lipids from phototrophic microorganisms that are currently available, their advantages and disadvantages, and the results of the monitoring of the main key points of the development of the technology for converting cyanobacterial biomass into biofuels, with an emphasis on the existing barriers, effects and solutions, are also considered. Further research in this field is required for the successful implementation of this technology on an industrial scale. [ABSTRACT FROM AUTHOR]

The energy of cyanobacterial hydrogen (H 2) produced via bio-photolysis is being investigated as a potential solution to early-century environmental challenges. The main limiting factors of cyanobacterial H 2 photoproduction are the availability of electrons for [NiFe]-hydrogenase (H 2 ase) and the suppression of bidirectional H 2 ase activity induced by O 2 acquired from water molecules splitting in photosystem II. The current study investigated how photosynthetic inhibitors (PIs) affected H 2 production in non-N 2 -fixing cyanobacteria. Study findings revealed a rather high H 2 yield in Synechocystis sp. PSU 1262, as well as a beneficial (14.2-fold) influence of 500 μmol KCN on the H 2 production by the aforesaid strain. A 12/6-h light/dark cycle increased H 2 production by 80.3% in cells supplemented with 500 μmol KCN. Under the optimised conditions, the photobiological H 2 production of Synechocystis sp. PSU 1262 increased from 49.6 to 1552 nmol H 2 mg−1 Chl a h−1. PIs suppressed chlorophyll a concentration under illumination, lowering the O 2 levels, which enhanced bidirectional H 2 ase activity in Synechocystis sp. PSU 1262 cells. Applying varied light modes, preceded by the incorporation of PIs at optimal concentrations in H 2 production by research cyanobacterial strains, improved the H 2 yield and contributed significantly to the research originality. [Display omitted] • Six species of cyanobacteria from different ecosystems were isolated and identified. • The H 2 -producing activity of the strains was studied in the dark and in the light. • The effect of four inhibitors of photosynthesis on H 2 production was studied. • The effect of light and dark modes was evaluated on H 2 production by cyanobacteria. [ABSTRACT FROM AUTHOR]

Over the last five decades, solar-based hydrogen (H 2) production has been intensively studied. Specifically, the study of biophotolysis by cyanobacteria has received great attention to produce H 2 , and promising research approaches have been established. To date, numerous photobioreactors (PBRs) have been built to collect cyanobacterial biomass and generate bioenergy. Additionally, different PBR parameters were adjusted to increase the product yield. PBR development holds great potential not only for cell biomass but also for biological H 2 production. This review aimed to examine the mechanisms involved in H 2 production by cyanobacteria, explore the factors influencing the process, and describe five distinct PBRs known for their high H 2 production. This article examines the pros and cons of the most efficient PBRs for H 2 production and offers insights into strategies for increasing their productivity. [Display omitted] • Photosynthetic H 2 production processes was discussed. • Physiochemical factors affecting H 2 production were explained. • Five PBRs for H 2 production were described. • Advantages/disadvantages of PBRs used for H 2 production were described. [ABSTRACT FROM AUTHOR]

• The optimal concentration of CO 2 for cultivation of cyanobacterial strains was determined. • The optimal concentration of wastewater for cultivation of cyanobacteria was determined. • The fatty acid composition of lipids was studied. • The yield of dry biomass and methyl esters of Cyanobacterium sp. IPPAS B-1200 strain was determined. Current fresh water and energy shortage determines the need to study the possibilities of using living objects in bioenergy and environmental purification technologies. The development of waste-free technologies allows waste recycling, which saves raw materials and energy, in turn, reducing waste generation. The effect of different carbon dioxide concentrations and wastewater from households on the growth of cyanobacteria was studied in order to determine their capabilities in the purification processes. It was found that the optimal CO 2 concentration for the cultivation of cyanobacteria Cyanobacterium sp. IPPAS B-1200 and Desertifilum sp. IPPAS B-1220 was 10 %, and for the Cyanobacterium aponinum IPPAS B-1201 – 5%. It was revealed that the cultivation of the cyanobacterium Cyanobacterium sp. IPPASB-1200 on wastewater from the water storage reduces the concentration of organic pollutants and, accordingly, improves the physicochemical properties of water. The cleaning percentage for selected pollutants was 68–100 %. It was shown that the most optimal ratio of wastewater to nutrient media for cyanobacteria cultivation were 25:75 and 50:50. The lipid content (%/dry weight) in the biomass of the studied strains of cyanobacteria ranges from 15 to 22% after cultivation in wastewater. It was determined that the strains of Cyanobacterium genus were the most suitable for the production of biodiesel according to their fatty acids composition. It was determined that lipids were composed of only saturated and monounsaturated fatty acids. As a result of the studies, the optimal conditions for the growth of Cyanobacterium sp. IPPAS B-1200 were determined. This microorganism has a good potential to produce biodiesel as a producer of saturated and monounsaturated middle-chain-length fatty acids. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) is a renewable, abundant, and nonpolluting source of energy. Photosynthetic organisms capture sunlight very efficiently and convert it into organic molecules. Cyanobacteria produce H 2 by breaking down organic compounds and water. In this study, biological H 2 was produced from various strains of cyanobacteria. Moreover, H 2 accumulation by Synechocystis sp. PCC 6803 was as high as 0.037 μmol/mg Chl/h within 120 h in the dark. The wild-type, filamentous, non-heterocystous cyanobacterium Desertifilum sp. IPPAS B-1220 was found to produce a maximum of 0.229 μmol/mg Chl/h in the gas phase within 166 h in the light, which was on par with the maximum yield reported in the literature. DCMU at 10 μM increased H 2 production by Desertifilum sp. IPPAS B-1220 by 1.5-fold to 0.348 μmol H 2 /mg Chl/h. This is the first report on the capability of Desertifilum cyanobacterium to produce H 2. Image 1 • Four non-heterocystous cyanobacterial strains were investigated for H 2 production. • Best H 2 accumulation was observed with Synechocystis sp. PCC 6803 in the dark. • Photoautotrophic H 2 production yield of Desertifilum sp. IPPAS B-1220 was 0.229 μmol/mg Chl/h. • H 2 yield was increased with the Desertifilum sp. IPPAS B-1220 by 1.5-fold in the presence of DCMU. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen is a promising alternative to fossil fuel for a source of clean energy due to its high energy content. Some strains of phototrophic microorganisms are known as important object of scientific research and they are being explored to raise biohydrogen (BioH 2) yield. BioH 2 is still not commonly used in industrial area because of the low biomass yield and valuable down streaming process. This article deals with the methods of the hydrogen production with the help of two large groups of phototrophic microorganisms – microalgae and cyanobacteria. Microalgal hydrogen is environmentally friendly alternative to conventional fossil fuels. Algal biomass has been considered as an attractive raw source for hydrogen production. Genetic modified strains of cyanobacteria are used as a perspective object for obtaining hydrogen. The modern photobioreactors and outdoor air systems have been used to obtain the biomass used for hydrogen production. At present time a variety of immobilization matrices and methods are being examined for their suitability to make immobilized H 2 producers. Graphical abstract Image 1 Highlights • Hydrogen production from microalgae and cyanobacteria. • Mechanisms of biohydrogen metabolism. • Bioreactors for biohydrogen production process. • Enzymes of biohydrogen production. [ABSTRACT FROM AUTHOR]

Increasing awareness of the harmful effects of synthetic colorants has led consumers to favor the use of natural alternatives such as plant or microbial pigments in food and cosmetics. Cyanobacteria are a rich source of many natural biopigments that are of high commercial value. In the market, bio-based pigments are usually sold as extracts to reduce purification costs. Various cell disruption methods are used for pigment extraction, such as sonication, homogenization, high pressure, supercritical CO 2 extraction, enzymatic extraction, as well as other promising novel extraction methods that make the production of cyanobacterial pigments economically viable. In addition, a continuous cultivation system is considered the most suitable cultivation mode for large-scale biomass production. However, a major limitation in the large-scale production of cyanobacterial pigments is the installation and operation costs. Thus, basic and applied research is still needed to overcome such limitations and enable cyanobacteria to enter the global market. This review focuses on various cyanobacterial pigments, their applications, and current biotechnological approaches to increase the production of biopigments for their potential use in the pharmaceutical, food, and cosmetic industries. The current state of production technologies based on either open pond systems or closed photobioreactors was compared. The potential of scientific and technological advances to increase yield and reduce production costs of cyanobacteria biomass-based pigments was also discussed. [Display omitted] • Cyanobacterial pigments (CPs) are safe and eco-friendly in comparison to synthetic ones. • CPs have commercial value due to their brilliant colors, antioxidant property and health promoting factors. • Various biotechnological approaches for optimizing CPs are considered. • The main extraction methodologies for each pigment are discussed and evaluated. [ABSTRACT FROM AUTHOR]

Due to the side effects of greenhouse gases, interest in alternative energy sources is growing, and research into hydrogen (Н 2) production from cyanobacteria has become a promising direction for the industry. The article provides an overview of cyanobacterial hydrogen production strategies and their current economic efficiency. It also describes metabolic, genetic and technical methods for obtaining H 2 from cyanobacteria. Cyanobacteria are considered potential producers of hydrogen energy that will be economically viable shortly, as they only need cheap salts, water and solar energy to grow. However, producing hydrogen from cyanobacteria still requires extensive work, and the main problem is the small amount of hydrogen energy obtained. To produce large amounts of cyanobacterial hydrogen, the most active wild-type strains must be selected and technological, modular and genetic research must be carried out simultaneously. The low energy efficiency of hydrogen from cyanobacteria also shows the need for comprehensive research through international programs. [Display omitted] • This review shows hydrogen production mechanisms by cyanobacterial cells. • Importance of biohydrogen production strategies is discussed. • Cyanobacterial hydrogen production factors were analyzed. • Trends and problems for developing cyanobacterial hydrogen production is showed. [ABSTRACT FROM AUTHOR]

A limited supply of oil prompts the search for non-traditional energy sources to replace traditional ones. This makes hydrogen gas an appealing alternative source. Photosynthetic organisms capture sunlight very efficiently and convert it into organic molecules. A promising wild strain was isolated for the first time, from the rice paddies of Kazakhstan (Kyzylorda and Almaty regions), which can be considered as one of the most active hydrogen producers compared to the literature. The result showed that among the 13 isolated and collection cyanobacterial strains, Synechocystis sp. S-1 is the most active H 2 producer (2.35 μmol H 2 mg−1 Chl a h−1) in the light. In contrast, the wild-type cyanobacterium Anabaena variabilis A-1 had higher productivity, nitrogenase activity, and a stronger capacity to produce hydrogen in the dark (8.67 μmol H 2 mg−1 Chl a h−1), which matched the maximum yield obtained in the research. The metabolic modulation performed significantly increased hydrogen production. The highest photohydrogen production rate was observed in cells incubated with 25 μmol HEPES and 50 μmol sodium bicarbonate (NaHCO 3). [Display omitted] • Novel cyanobacterial strains were isolated from rice paddies and identified. • Сyanobacterial strains have been screened for productivity. • Hydrogen production by cyanobacterial strains was examined. • Strains were adapted to produce H2 optimizing their physiological properties. [ABSTRACT FROM AUTHOR]

There is currently an escalating global demand for the utilization of plant and natural extracts as pesticides due to their minimal health risks. Cyanobacteria are highly valuable organisms with significant potential in agriculture and are of great interest for the development of agrochemical agents as biopesticides. The flexibility and adaptability of Cyanobacteria to various environmental conditions are facilitated by the presence of specialized enzymes involved in the production of biologically active diverse secondary metabolites, including alkaloids, lipopolysaccharides, non-protein amino acids, non-ribosomal peptides, polyketides, terpenoids, and others. This review focuses on the metabolites synthesized from cyanobacteria that have demonstrated effectiveness as antibacterial, antiviral, antifungal agents, insecticides, herbicides, and more. The potential role of cyanobacteria as an alternative to chemical pesticides for environmental conservation is discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of unregulated pesticides and chemical fertilizers can have detrimental effects on biodiversity and human health. This problem is exacerbated by the growing demand for agricultural products. To address these global challenges and promote food and biological security, a new form of agriculture is needed that aligns with the principles of sustainable development and the circular economy. This entails developing the biotechnology market and maximizing the use of renewable and eco-friendly resources, including organic fertilizers and biofertilizers. Phototrophic microorganisms capable of oxygenic photosynthesis and assimilation of molecular nitrogen play a crucial role in soil microbiota, interacting with diverse microflora. This suggests the potential for creating artificial consortia based on them. Microbial consortia offer advantages over individual organisms as they can perform complex functions and adapt to variable conditions, making them a frontier in synthetic biology. Multifunctional consortia overcome the limitations of monocultures and produce biological products with a wide range of enzymatic activities. Biofertilizers based on such consortia present a viable alternative to chemical fertilizers, addressing the issues associated with their usage. The described capabilities of phototrophic and heterotrophic microbial consortia enable effective and environmentally safe restoration and preservation of soil properties, fertility of disturbed lands, and promotion of plant growth. Hence, the utilization of algo-cyano-bacterial consortia biomass can serve as a sustainable and practical substitute for chemical fertilizers, pesticides, and growth promoters. Furthermore, employing these bio-based organisms is a significant stride towards enhancing agricultural productivity, which is an essential requirement to meet the escalating food demands of the growing global population. Utilizing domestic and livestock wastewater, as well as CO 2 flue gases, for cultivating this consortium not only helps reduce agricultural waste but also enables the creation of a novel bioproduct within a closed production cycle. [Display omitted] [ABSTRACT FROM AUTHOR]

A cyanobacterial strain from Lake Shar-Nuur, a freshwater lake in Mongolia, was isolated and characterized by a polyphasic approach. According to the 16S ribosomal RNA gene sequence, this strain (IPPAS B-1220) belongs to a newly described genus Desertifilum. In general, strains of Desertifilum maintain their genetic stability, as seen from the analysis of the 16S rRNA gene and 16S-23S rRNA internal transcribed spacer sequences from strains collected at distant locations. The newly discovered strain is characterized by an unusual fatty acid composition (16:1Δ7 and 16:2Δ7,10). Analysis of its draft genomic sequence reveals the presence of six genes for the acyl-lipid desaturases: two Δ9-desaturases, desC1 and desC2; two Δ12-desaturases, desA1 and desA2; one desaturase of unknown specificity, desX; and one gene for the bacillary-type desaturase, desG, which supposedly encodes an ω9-desaturase. A scheme for a fatty acid desaturation pathway that describes the biosynthesis of 16:1Δ7 and 16:2Δ7,10 fatty acids in Desertifilum is proposed. [ABSTRACT FROM AUTHOR]

The potential of cyanobacteria to perform a variety of distinct roles vital for the biosphere, including nutrient cycling and environmental detoxification, drives interest in studying their biodiversity. Increasing soil erosion and the overuse of chemical fertilizers are global problems in developed countries. The option might be to switch to organic farming, which entails largely the use of biofertilisers. Cyanobacteria are prokaryotic, photosynthetic organisms with considerable potential, within agrobiotechnology, to produce biofertilisers. They contribute significantly to plant drought resistance and nitrogen enrichment in the soil. This study sought, isolated, and investigated nitrogen-fixing cyanobacterial strains in rice fields, and evaluated the effect of Mo and Fe on photosynthetic and nitrogenase activities under nitrogen starvation. Cyanobacterial isolates, isolated from rice paddies in Kazakhstan, were identified as Trichormus variabilis K-31 (MZ079356), Cylindrospermum badium J-8 (MZ079357), Nostoc sp. J-14 (MZ079360), Oscillatoria brevis SH-12 (MZ090011), and Tolypothrix tenuis J-1 (MZ079361). The study of the influence of various concentrations of Mo and Fe on photosynthetic and nitrogenase activities under conditions of nitrogen starvation revealed the optimal concentrations of metals that have a stimulating effect on the studied parameters. [ABSTRACT FROM AUTHOR]