Search Results (12)

The industrial cultivation of microalgae for high-value products faces significant challenges, particularly in maintaining long-term, cost-effective operations. Semi-continuous cultivation presents a promising solution to this problem. In this study, the green alga Chlorella sorokiniana IPPAS C-1 was cultivated in a flat-panel 5 L photobioreactor under optimized conditions, with three biological replicates. We evaluated batch mode against three semi-continuous dilution fractions (50%, 75%, and 87.5%). The 75% dilution fraction demonstrated superior performance, achieving the highest biomass productivity with an average specific productivity of 1.36 g DW L⁻¹ day⁻¹ over seven harvest cycles. Furthermore, this regime ensured stable biochemical composition—including proteins, lipids, carbohydrates, and pigments—as well as a consistent lipid profile and sustained photosynthetic activity throughout the cultivation. These findings are useful for the development of scalable and efficient technological protocols for the industrial production of Chlorella in flat-panel photobioreactors. Full article

The need to reduce anthropogenic greenhouse gas emissions drives the development of innovative carbon dioxide capture technologies. Microalgae-based biotechnologies represent a promising approach in this field. In this study, we evaluated the CO₂ assimilation efficiency of two novel microalgae strains, Desmodesmus armatus ARC-06 and Tribonema minus ARC-10, under low (0.04%) and high (1.5%) CO₂ conditions in a periodic cultivation system. The two strains exhibited distinct CO₂ adaptation strategies. D. armatus demonstrated higher tolerance to low CO₂ conditions, whereas T. minus showed superior performance under elevated CO₂. Although elevated CO₂ stimulated growth in both strains, their carbon dioxide sequestration efficiency (CDSE) differed markedly. The maximum CDSE was significantly higher in T. minus (30.0 ± 1.52%) compared to D. armatus (16.5 ± 1.12%). Similarly, the average CDSE over the cultivation period was greater in T. minus (19.1 ± 2.18%) than in D. armatus (11.8 ± 1.45%). These results underscore the importance of bioprospecting for novel microalgae strains, and the need for further research to develop efficient biological CO₂ sequestration methods. Full article

Microalgae biotechnology is increasingly applied across diverse fields, from food and medicine to energy and environmental protection, with strain selection being crucial for both target product accumulation and scalability potential. In this study, we for the first time assess the scalability of two new promising green microalgae strains, Neochlorella semenenkoi IPPAS C-1210 and Desmodesmus armatus ARC-06, in 5-L flat-panel photobioreactors. The growth characteristics of each culture, along with their biochemical composition and CO₂ utilization efficiency, were examined and compared to the well-studied model strain Chlorella sorokiniana IPPAS C-1. While C-1 achieved the highest biomass concentration (7.1 ± 0.4 g DW L⁻¹ by day 8) and demonstrated superior specific productivity (1.5 ± 0.1 g DW L⁻¹ d⁻¹) and CO₂ utilization efficiency (average 25.4%, peaking at 34% on day 3), ARC-06 accumulated the highest starch content (51% of DW), twice that of C-1. Strain C-1210 showed intermediate performance, reaching 6.8 ± 0.8 g DW L⁻¹ biomass with a CUE of 22.7%, whereas ARC-06 had the lowest CUE (12.8%). These results, combined with proposed cultivation optimization strategies, provide a foundation for scaling up N. semenenkoi and D. armatus production in industrial flat-panel PBR systems. Full article

Recent advances in research techniques have enabled rapid progress in the study of spirulina, an ancient edible cyanobacteria. Nowadays, spirulina species are classified into three genera: Spirulina, Arthrospira, and Limnospira. The latter now refers to industrially manufactured spirulina strains. Whole-genome sequencing revealed gene clusters involved in metabolite production, and the physiology of spirulina. Omics technologies demonstrated the absence of hazardous compounds in spirulina cells, confirming the safety of this biomass as a food product. Spirulina is a good source of different chemicals used in food manufacturing, food supplements, and pharmaceuticals. Spirulina’s enrichment with inherent biologically active substances makes it a potential supplier of natural products for dietary and pharmaceutical applications. Spirulina is also a prospective component of both terrestrial and space-based life support systems. Here, we review current breakthroughs in spirulina research and clarify fallacies that can be found in both professional literature and public media. Full article

Under standard laboratory conditions, Synechococcus elongatus PCC 7942 lacks EcaA^Syn, a periplasmic carbonic anhydrase (CA). In this study, a S. elongatus transformant was created that expressed the homologous EcaA^Cya from Cyanothece sp. ATCC 51142. This additional external CA had no discernible effect on the adaptive responses and physiology of cells exposed to changes similar to those found in S. elongatus natural habitats, such as fluctuating CO₂ and HCO₃⁻ concentrations and ratios, oxidative or light stress, and high CO₂. The transformant had a disadvantage over wild-type cells under certain conditions (Na⁺ depletion, a reduction in CO₂). S. elongatus cells lacked their own EcaA^Syn in all experimental conditions. The results suggest the presence in S. elongatus of mechanisms that limit the appearance of EcaA^Syn in the periplasm. For the first time, we offer data on the expression pattern of CCM-associated genes during S. elongatus adaptation to CO₂ replacement with HCO₃⁻, as well as cell transfer to high CO₂ levels (up to 100%). An increase in CO₂ concentration coincides with the suppression of the NDH-1₄ system, which was previously thought to function constitutively. Full article

The microalgae Vischeria sp. IPPAS C-70 produces eicosapentaenoic acid. Several stresses cause the formation of fatty acid peaks that resemble hexadecadienoic acids. We used the integrated technique including TLC, HPLC, and GC–MS to search and determine these fatty acids. Double bond positioning in these fatty acids indicated that they were conjugated dienes and allenes. We identified and described natural nine isomers of C16 polyunsaturated fatty acids, including common methylene-interrupted dienes (Δ6,9-16:2, Δ7,10-16:2, Δ9,12-16:2), and unusual conjugated dienes (Δ6,8-, Δ7,9-, Δ8,10-, Δ9,11-, and Δ10,12-16:2), as well as allenic diene (Δ9,10-16:2). We hypothesize that the formation of conjugated dienes and allenes among fatty acids is the result of oxidative stress caused by H₂O₂. Hydrogen peroxide also caused an increase in saturated at the expense of unsaturated fatty acids, suggesting inhibition either fatty acid desaturases activities or the corresponding gene expression. Full article

Despite many publications about Chlorella-like algae, their reliable and accurate identification is still difficult due to their simplicity and high phenotypic plasticity. The molecular approach has revolutionized our understanding of the diversity of ’small green balls’, and a natural classification of this group is currently being developed. This work is aimed at providing a detailed study of the phylogenetic position, morphology, ultrastructure, and physiology of the biotechnologically remarkable Chlorella-like strain IPPAS C-1210. Based on the SSU–ITS1–5.8S–ITS2 phylogeny, genetic distances, and the presence of compensatory base changes (CBCs) in ITS1 and conserved regions of ITS2 secondary structures, we describe a new genus, Neochlorella, with IPPAS C-1210 as the authentic strain of the type species, N. semenenkoi gen. and sp. nov. In addition, we justify the reassignment of the strain C. thermophila ITBB HTA 1–65 into N. thermophila comb. nov. The distinctive ultrastructural and physiological traits of the new species are discussed. Full article

Microalgae are increasingly being used for capturing carbon dioxide and converting it into valuable metabolites and biologically active compounds on an industrial scale. The efficient production of microalgae biomass requires the optimization of resources, including CO₂. Here, we estimated the productivity of Chlorella sorokiniana IPPAS C-1 depending on CO₂ concentrations and the ventilation coefficient of the gas-air mixture (GAM) in flat-panel photobioreactors (FP-PBRs) at laboratory (5 L) and pilot (18 L) scales. For the laboratory scale, the PBRs operated at 900 µmol quanta m⁻² s⁻¹ and 35.5 ± 0.5 °C; the optimal CO₂ flow rate was estimated at 3 mL CO₂ per 1 L of suspension per minute, which corresponds to 1.5% CO₂ in the GAM and an aeration rate of 0.2 vvm. These parameters, being scaled up within the pilot PBRs, resulted in a high specific growth rate (µ ≈ 0.1 h⁻¹) and high specific productivity (P_sp ≈ 1 g dw L⁻¹ d⁻¹). The principles of increasing the efficiency of the intensive cultivation of C. sorokiniana IPPAS C-1 are discussed. These principles are relevant for the development of technological regimes for the industrial production of Chlorella in flat-panel PBRs of various sizes. Full article

Flat-panel photobioreactors are effective systems for microalgae cultivation. This paper presents the growth characteristics of the microalgae Chlorella sorokiniana IPPAS C-1 as a result of three-stage scale-up cultivation in a specially designed cultivation system. First, C. sorokiniana was grown aseptically in 250 mL glass vessels; then, it was diluted and inoculated into a 5-liter flat-panel horizontal photobioreactor; and, at the last stage, the culture was diluted and inoculated into a 70-liter flat-panel vertical photobioreactor. In the presented cycle, the cultured biomass increased by 326 times in 13 days (from 0.6 to 195.6 g dw), with a final biomass concentration of 2.8 g dw L⁻¹. The modes of semi-continuous cultivation were considered. The biomass harvest and dilution of the suspension were carried out either every day or every 3–4 days. For C. sorokiniana IPPAS C-1, a conversion coefficient of optical density values to dry biomass (g L⁻¹) was refined through a factor of 0.33. The key parameters of the photobioreactors tested in this work are discussed. Full article

Systemic analysis of stress-induced transcription in the cyanobacterium Synechocystis sp. strain PCC 6803 identifies a number of genes as being induced in response to most abiotic stressors (heat, osmotic, saline, acid stress, strong light, and ultraviolet radiation). Genes for heat-shock proteins (HSPs) are activated by all these stresses and form a group that universally responds to all environmental changes. The functions of universal triggers of stress responses in cyanobacteria can be performed by reactive oxygen species (ROS), in particular H₂O₂, as well as changes in the redox potential of the components of the photosynthetic electron transport chain. The double mutant of Synechocystis sp. PCC 6803 (katG/tpx, or sll1987/sll0755), which is defective in antioxidant enzymes catalase (KatG) and thioredoxin peroxidase (Tpx), cannot grow in the presence of exogenous hydrogen peroxide (H₂O₂); and it is extremely sensitive to low concentrations of H₂O₂, especially under conditions of cold stress. Experiments on this mutant demonstrate that H₂O₂ is involved in regulation of gene expression that responds to a decrease in ambient temperature, and affects both the perception and the signal transduction of cold stress. In addition, they suggest that formation of ROS largely depends on the physical state of the membranes such as fluidity or viscosity. In cyanobacteria, an increase in membrane turnover leads to a decrease in the formation of ROS and an increase in resistance to cold stress. Therefore: (1) H₂O₂ is the universal trigger of stress responses in cyanobacterial cells; (2) ROS formation (in particular, H₂O₂) depends on the physical properties of both cytoplasmic and thylakoid membranes; (3) The destructive effect of H₂O₂ is reduced by increasing of fluidity of biological membranes. Full article

Synechocystis sp. PCC 6803 is a widely used model cyanobacterium for studying responses and acclimation to different abiotic stresses. Changes in transcriptome, proteome, lipidome, and photosynthesis in response to short term heat stress are well studied in this organism, and histidine kinase 34 (Hik34) is shown to play an important role in mediating such response. Corresponding data on long term responses, however, are fragmentary and vary depending on parameters of experiments and methods of data collection, and thus are hard to compare. In order to elucidate how the early stress responses help cells to sustain long-term heat stress, as well as the role of Hik34 in prolonged acclimation, we examined the resistance to long-term heat stress of wild-type and ΔHik34 mutant of Synechocystis. In this work, we were able to precisely control the long term experimental conditions by cultivating Synechocystis in automated photobioreactors, measuring selected physiological parameters within a time range of minutes. In addition, morphological and ultrastructural changes in cells were analyzed and western blotting of individual proteins was used to study the heat stress-affected protein expression. We have shown that the majority of wild type cell population was able to recover after 24 h of cultivation at 44 °C. In contrast, while ΔHik34 mutant cells were resistant to heat stress within its first hours, they could not recover after 24 h long high temperature treatment. We demonstrated that the early induction of HspA expression and maintenance of high amount of other HSPs throughout the heat incubation is critical for successful adaptation to long-term stress. In addition, it appears that histidine kinase Hik34 is an essential component for the long term high temperature resistance. Full article

In living cells, the perception of environmental stress and the subsequent transduction of stress signals are primary events in the acclimation to changes in the environment. Some molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. Based on genomic information, a systematic approach has been applied to the solution of this problem in cyanobacteria, involving mutagenesis of potential sensors and signal transducers in combination with DNA microarray analyses for the genome-wide expression of genes. Forty-five genes for the histidine kinases (Hiks), 12 genes for serine-threonine protein kinases (Spks), 42 genes for response regulators (Rres), seven genes for RNA polymerase sigma factors, and nearly 70 genes for transcription factors have been successfully inactivated by targeted mutagenesis in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Screening of mutant libraries by genome-wide DNA microarray analysis under various stress and non-stress conditions has allowed identification of proteins that perceive and transduce signals of environmental stress. Here we summarize recent progress in the identification of sensory and regulatory systems, including Hiks, Rres, Spks, sigma factors, transcription factors, and the role of genomic DNA supercoiling in the regulation of the responses of cyanobacterial cells to various types of stress. Full article