Cyanobacteria as a Promising Alternative for Sustainable Environment: Synthesis of Biofuel and Biodegradable Plastics

Hepatic protective effects and oxidative stress modulation via gene expression in zebrafish (Danio rerio) fed with Synechococcus elongatus PCC 7942 as a functional feed additive

The inclusion of cyanobacteria in aquafeeds is a sustainable alternative to traditional fishmeal. This study evaluated the effects of Synechococcus elongatus PCC 7942 supplementation on intestinal morphology, liver histopathology, and antioxidant gene expression in zebrafish (Danio rerio). Fish were fed a commercial diet (CF) or the same diet supplemented with S. elongatus (EF) for 35 days. Liver histopathology revealed that 62 % of fish in the CF group exhibited generalized liver alteration, while fish in the EF group showed a lower frequency of generalized alteration (31 %) and a higher frequency of multifocal lesions (46 %), suggesting improved hepatic homeostasis. Intestinal morphometry showed no significant changes in villus length between groups. Gene expression analysis demonstrated a significant downregulation of xenobiotic metabolism genes (cyp1a, gst), antioxidant defense genes (sod1, sod2, cat), and steroid metabolism (cyp19a1a) in fish fed S. elongatus, except for gpx, which remained unchanged. The reduction in antioxidant gene expression, along with improved liver histology, suggests a lower oxidative stress in the EF group, likely due to synergistic effects of S. elongatus in mitigating oxidative damage. These findings indicate that S. elongatus supplementation does not impair intestinal morphology or liver function but supports hepatic homeostasis by reducing oxidative stress and modulating liver histopathology. This highlights its potential as a functional feed additive in aquaculture.

Cyanobacteria fouling in photobioreactors: current status and future perspectives for prevention

Cyanobacteria biomass sources have the potential to contribute to the replacement of fossil fuels and to the reduction in global warming by sustainable conversion of atmospheric CO2 into biofuels and high-value chemicals. Cyanobacteria cultivation in photobioreactors (PBRs) results in biofouling on their transparent inner walls, which reduces photosynthetic efficiency and productivity. While cyanobacteria biofouling in PBRs is recognized as a significant operating challenge, this review draws attention to the lack of studies on antifouling strategies for PBRs involving cyanobacteria and discusses several areas related to cyanobacteria fouling mechanisms on PBR materials, which require further investigation. These include an in-depth analysis of conditioning films, the role of pili and EPS in gliding and adhesion, potential revisions to existing theoretical models for predicting adhesion, and material properties that affect cyanobacteria adhesion. We use knowledge from marine, medical, and industrial biofouling management to help identify strategies to combat cyanobacteria fouling in PBRs, and we review the applicability of various bioinspired physical and chemical strategies, as well as genetic engineering approaches to prevent cyanobacteria biofilm formation in PBRs.

A responsive living material prepared by diffusion reveals extracellular enzyme activity of cyanobacteria

Stimuli-responsive engineered living materials (ELMs) can respond to environmental or biochemical cues and have broad utility in biological sensors and machines, but have traditionally been limited to biocompatible scaffolds. This is because they are typically made by mixing cells into a precursor solution before crosslinking. Here, we demonstrate a diffusion mechanism for incorporating cells of the cyanobacterium Synechococcus elongatus sp. PCC 7942 (S. elongatus) into nanoclay-poly-N-isopropylacrylamide (NC-PNIPAm), a hydrogel with a cytotoxic precursor, by exploiting its temperature-dependent shape-morphing behavior. Subsequent growth of S. elongatus caused a decrease in the bending curvature and stiffness (local Young's modulus) of NC-PNIPAm due to partial degradation by an unannotated enzyme. Creation and observation of this cyanobacteria-hydrogel ELM showcases a method for diffusing cells into a hydrogel as well as characterizing an extracellular enzyme.

Evolutionary conservation of acylplastoquinone species from cyanobacteria to eukaryotic photosynthetic organisms of green and red lineages

Plastoquinone plays a crucial role in the photosynthetic electron transport system as an electron carrier, transferring electrons from photosystem II to cytochrome b6f complexes. Certain cyanobacteria acylate plastoquinone derivatives, plastoquinol, the reduced form of plastoquinone, and/or plastoquinone-C, the hydroxylated form of plastoquinone to synthesize newly found cyanobacterial lipids, acylplastoquinol and acylplastoquinone-C, the latter of which is known as plastoquinone-B in seed plants. The cyanobacterial genes, slr2103 in Synechocystis sp. PCC 6803 and its ortholog in Synechococcus sp. PCC 7002, encode a bifunctional acyltransferase for the synthesis of both acylplastoquinol and plastoquinone-B. Despite conservation of slr2103 orthologs across a wide range of cyanobacteria, only four cyanobacterial strains, including the two mentioned above, have been identified as producing acylplastoquinol and/or plastoquinone-B. Moreover, the extent to which acylplastoquinone species are distributed in eukaryotic photosynthetic organisms that lack slr2103 orthologs remains largely unknown. Using LC-MS/MS2 analysis of total cellular lipids, this study demonstrates that acylplastoquinol and plastoquinone-B are conserved not only in cyanobacteria with slr2103 orthologs but also in eukaryotic photosynthetic organisms lacking these orthologs, including primary and secondary endosymbiotic algae, and a seed plant. Notably, in eukaryotic photosynthetic organisms as well as in cyanobacteria, these acylplastoquinone species are predominantly esterified with saturated fatty acids. The evolutionary conservation of these acylplastoquinone species suggests replacement of slr2103 orthologs by alternative gene(s) responsible for their synthesis at least once after the primary endosymbiotic event in the evolution of photosynthetic organisms. The persistent conservation of acylplastoquinone species throughout the evolution likely reflects their critical physiological roles.

Synthetic biology strategies for sustainable bioplastic production by yeasts

The increasing environmental concerns regarding conventional plastics have led to a growing demand for sustainable alternatives, such as biodegradable plastics. Yeast cell factories, specifically Saccharomyces cerevisiae and Yarrowia lipolytica, have emerged as promising platforms for bioplastic production due to their scalability, robustness, and ease of manipulation. This review highlights synthetic biology approaches aimed at developing yeast cell factories to produce key biodegradable plastics, including polylactic acid (PLA), polyhydroxyalkanoates (PHAs), and poly (butylene adipate-co-terephthalate) (PBAT). We explore recent advancements in engineered yeast strains that utilize various synthetic biology strategies, such as the incorporation of new genetic elements at the gene, pathway, and cellular system levels. The combined efforts of metabolic engineering, protein engineering, and adaptive evolution have enhanced strain efficiency and maximized product yields. Additionally, this review addresses the importance of integrating computational tools and machine learning into the Design-Build-Test-Learn cycle for strain development. This integration aims to facilitate strain development while minimizing effort and maximizing performance. However, challenges remain in improving strain robustness and scaling up industrial production processes. By combining advanced synthetic biology techniques with computational approaches, yeast cell factories hold significant potential for the sustainable and scalable production of bioplastics, thus contributing to a greener bioeconomy.

Current insights into molecular mechanisms of environmental stress tolerance in Cyanobacteria

The photoautotrophic nature of cyanobacteria, coupled with their fast growth and relative ease of genetic manipulation, makes these microorganisms very promising factories for the sustainable production of bio-products from atmospheric carbon dioxide. However, both in nature and in cultivation, cyanobacteria go through different abiotic stresses such as high light (HL) stress, heavy metal stress, nutrient limitation, heat stress, salt stress, oxidative stress, and alcohol stress. In recent years, significant improvement has been made in identifying the stress-responsive genes and the linked pathways in cyanobacteria and developing genome editing tools for their manipulation. Metabolic pathways play an important role in stress tolerance; their modification is also a very promising approach to adapting to stress conditions. Several synthetic as well as systems biology approaches have been developed to identify and manipulate genes regulating cellular responses under different stresses. In this review, we summarize the impact of different stresses on metabolic processes, the small RNAs, genes and heat shock proteins (HSPs) involved, changes in the metabolome and their adaptive mechanisms. The developing knowledge of the adaptive behaviour of cyanobacteria may also be utilised to develop better stress-responsive strains for various applications.

Immunomodulatory properties of polysaccharide extract samples from Cyanobacterium sp. Rippka B-1200

Cyanobacteria are most abundant in aquatic systems and can grow in freshwater, saline or brackish water, and cold/hot springs. Cyanobacteria have attracted considerable research attention in the last decade as a potential source of numerous biological products in large quantities, such as biofuels, pigments, polyunsaturated fatty acids, nutraceuticals, enzymes, and polysaccharides. Unlike most plant and fungal polysaccharides, the chemical composition, immunomodulatory activity, and molecular mechanisms of action of Cyanobacterium sp. Rippka B-1200 polysaccharides have been studied much less. The complexity of their primary structure due to the high variability of monosaccharides, their diverse bonds, the presence of substituents and high viscosity made detailed structural studies of cyanobacterial polysaccharides rare, which determines the need for analysis of cyanobacteria biomass components to identify active metabolites with promising biological activity. The aim of this study was to investigate the immunomodulatory properties of polysaccharides from Cyanobacterium sp. Rippka B-1200. Pharmacological and nutraceutical value of Cyanobacterium sp. Rippka B-1200 has been set, defining our study's scientific novelty. As a result, the molecular weight of immunoactive polysaccharide (6.0-8.0 kDa) was determined. The analysis shows that endopolysaccharide samples at a concentration of 300 mg/kg showed no significant immunomodulatory effect (1.60 ± 0.15 mg/g), and the thymus mass index of animals in the experimental group was comparable to that of the control group in which animals were immunosuppressed with cyclophosphamide (1.15 ± 0.24 mg/g). When exopolysaccharide samples were used at a concentration of 600 mg/kg, the thymus mass index of animals in the experimental group (3.60 ± 0.32 mg/g) was statistically comparable to that of the control group (without polysaccharide) in which immunosuppression was not induced (thymus index was 3.70 ± 0.25 mg/g). It was found that endopolysaccharide samples at a concentration of 600 mg/kg also exhibited high immunomodulatory activity. When Cyanobacterium sp. Rippka B-1200 endopolysaccharide samples were used, no internal organ changes were observed in experimental animals after immunosuppression. The empirical results presented in the study may find application in the development of both pharmaceutical and cosmetic products.

Bio-Food Quality, Environmental Pollution, and the Role of Algae in Promoting Human Health and Sustainability

Healthcare resources have changed fundamentally compared to decades ago. Modern bio-food products and sustainable solutions for their production have increased the attention of researchers, taking into account the current level of pollution of the earth and atmosphere along with modern technologies applied to processed foods. Therefore, this review aims to highlight: (1) the impact and relationship between the physiological parameters of the atmosphere, solar radiation and soil, (in terms of their composition and stages of formation and organization) along with the evolution to modern life; (2) the environmental impacts on algae, living organisms, food, and human health and sustainability. In addition, we address the significant impact of algae as a sustainable resource in reducing environmental pollution contributing to a healthier life.

In Vivo Biocompatibility of Synechococcus sp. PCC 7002-Integrated Scaffolds for Skin Regeneration

Cyanobacteria, commonly known as blue-green algae, are prevalent in freshwater systems and have gained interest for their potential in medical applications, particularly in skin regeneration. Among these, Synechococcus sp. strain PCC 7002 stands out because of its rapid proliferation and capacity to be genetically modified to produce growth factors. This study investigates the safety of Synechococcus sp. PCC 7002 when used in scaffolds for skin regeneration, focusing on systemic inflammatory responses in a murine model. We evaluated the following three groups: scaffolds colonized with genetically engineered bacteria producing hyaluronic acid, scaffolds with wild-type bacteria, and control scaffolds without bacteria. After seven days, we assessed systemic inflammation by measuring changes in cytokine profiles and lymphatic organ sizes. The results showed no significant differences in spleen, thymus, and lymph node weights, indicating a lack of overt systemic toxicity. Blood cytokine analysis revealed elevated levels of IL-6 and IL-1β in scaffolds with bacteria, suggesting a systemic inflammatory response, while TNF-α levels remained unaffected. Proteome profiling identified distinct cytokine patterns associated with bacterial colonization, including elevated inflammatory proteins and products, indicative of acute inflammation. Conversely, control scaffolds exhibited protein profiles suggestive of a rejection response, characterized by increased levels of cytokines involved in T and B cell activation. Our findings suggest that Synechococcus sp. PCC 7002 does not appear to cause significant systemic toxicity, supporting its potential use in biomedical applications. Further research is necessary to explore the long-term effects and clinical implications of these responses.

Limiting factors in the operation of photosystems I and II in cyanobacteria

Cyanobacteria are important targets for biotechnological applications due to their ability to grow in a wide variety of environments, rapid growth rates, and tractable genetic systems. They and their bioproducts can be used as bioplastics, biofertilizers, and in carbon capture and produce important secondary metabolites that can be used as pharmaceuticals. However, the photosynthetic process in cyanobacteria can be limited by a wide variety of environmental factors such as light intensity and wavelength, exposure to UV light, nutrient limitation, temperature, and salinity. Carefully considering these limitations, modifying the environment, and/or selecting cyanobacterial species will allow cyanobacteria to be used in biotechnological applications.

Synechococcus sp. PCC7335 responses to far-red enriched spectra and anoxic/microoxic atmospheres: Potential for astrobiotechnological applications

Recently, cyanobacteria have gained attention in space exploration to support long-term crewed missions via Bioregenerative Life Support Systems. In this frame, cyanobacteria would provide biomass and profitable biomolecules through oxygenic photosynthesis, uptaking CO2, and releasing breathable O2. Their growth potential and organic matter production will depend on their ability to photoacclimate to different light intensities and spectra, maximizing incident light harvesting. Studying cyanobacteria responses to different light regimes will also benefit the broader field of astrobiology, providing data on the possibility of oxygenic photosynthetic life on planets orbiting stars with emission spectra different than the Sun. Here, we tested the acclimation and productivity of Synechococcus sp. PCC7335 (hereafter PCC7335), capable of Far-Red Light Photoacclimation (FaRLiP) and type III chromatic acclimation (CA3), in an anoxic, CO2-enriched atmosphere and under a spectrum simulating the low energetic light regime of an M-dwarf star, also comparable to a subsuperficial environment. When exposed to the light spectrum, with few photons in the visible (VIS) and rich in far-red (FR), PCC7335 did not activate FaRLiP but acclimated only via CA3, achieving a biomass productivity higher than expected, considering the low VIS light availability, and a higher production of phycocyanin, a valuable pigment, with respect to solar light. Its growth or physiological responses of PCC7335 were not affected by the anoxic atmosphere. In these conditions, PCC7335 efficiently produced O2 and scavenged CO2. Results highlight the photosynthetic plasticity of PCC7335, its suitability for astrobiotechnological applications, and the importance to investigate biodiversity of oxygenic photosynthesis for searching life beyond Earth.

Deciphering the genetic landscape of enhanced poly-3-hydroxybutyrate production in Synechocystis sp. B12

BACKGROUND

Microbial biopolymers such as poly-3-hydroxybutyrate (PHB) are emerging as promising alternatives for sustainable production of biodegradable bioplastics. Their promise is heightened by the potential utilisation of photosynthetic organisms, thus exploiting sunlight and carbon dioxide as source of energy and carbon, respectively. The cyanobacterium Synechocystis sp. B12 is an attractive candidate for its superior ability to accumulate high amounts of PHB as well as for its high-light tolerance, which makes it extremely suitable for large-scale cultivation. Beyond its practical applications, B12 serves as an intriguing model for unravelling the molecular mechanisms behind PHB accumulation.

RESULTS

Through a multifaceted approach, integrating physiological, genomic and transcriptomic analyses, this work identified genes involved in the upregulation of chlorophyll biosynthesis and phycobilisome degradation as the possible candidates providing Synechocystis sp. B12 an advantage in growth under high-light conditions. Gene expression differences in pentose phosphate pathway and acetyl-CoA metabolism were instead recognised as mainly responsible for the increased Synechocystis sp. B12 PHB production during nitrogen starvation. In both response to strong illumination and PHB accumulation, Synechocystis sp. B12 showed a metabolic modulation similar but more pronounced than the reference strain, yielding in better performances.

CONCLUSIONS

Our findings shed light on the molecular mechanisms of PHB biosynthesis, providing valuable insights for optimising the use of Synechocystis in economically viable and sustainable PHB production. In addition, this work supplies crucial knowledge about the metabolic processes involved in production and accumulation of these molecules, which can be seminal for the application to other microorganisms as well.

Exploring Sustainable Agriculture with Nitrogen-Fixing Cyanobacteria and Nanotechnology

The symbiotic relationship between nitrogen-fixing cyanobacteria and plants offers a promising avenue for sustainable agricultural practices and environmental remediation. This review paper explores the molecular interactions between nitrogen-fixing cyanobacteria and nanoparticles, shedding light on their potential synergies in agricultural nanotechnology. Delving into the evolutionary history and specialized adaptations of cyanobacteria, this paper highlights their pivotal role in fixing atmospheric nitrogen, which is crucial for ecosystem productivity. The review discusses the unique characteristics of metal nanoparticles and their emerging applications in agriculture, including improved nutrient delivery, stress tolerance, and disease resistance. It delves into the complex mechanisms of nanoparticle entry into plant cells, intracellular transport, and localization, uncovering the impact on root-shoot translocation and systemic distribution. Furthermore, the paper elucidates cellular responses to nanoparticle exposure, emphasizing oxidative stress, signaling pathways, and enhanced nutrient uptake. The potential of metal nanoparticles as carriers of essential nutrients and their implications for nutrient-use efficiency and crop yield are also explored. Insights into the modulation of plant stress responses, disease resistance, and phytoremediation strategies demonstrate the multifaceted benefits of nanoparticles in agriculture. Current trends, prospects, and challenges in agricultural nanotechnology are discussed, underscoring the need for responsible and safe nanoparticle utilization. By harnessing the power of nitrogen-fixing cyanobacteria and leveraging the unique attributes of nanoparticles, this review paves the way for innovative, sustainable, and efficient agricultural practices.

Green Synthesis of Bioplastics from Microalgae: A State-of-the-Art Review

The synthesis of conventional plastics has increased tremendously in the last decades due to rapid industrialization, population growth, and advancement in the use of modern technologies. However, overuse of these fossil fuel-based plastics has resulted in serious environmental and health hazards by causing pollution, global warming, etc. Therefore, the use of microalgae as a feedstock is a promising, green, and sustainable approach for the production of biobased plastics. Various biopolymers, such as polyhydroxybutyrate, polyurethane, polylactic acid, cellulose-based polymers, starch-based polymers, and protein-based polymers, can be produced from different strains of microalgae under varying culture conditions. Different techniques, including genetic engineering, metabolic engineering, the use of photobioreactors, response surface methodology, and artificial intelligence, are used to alter and improve microalgae stocks for the commercial synthesis of bioplastics at lower costs. In comparison to conventional plastics, these biobased plastics are biodegradable, biocompatible, recyclable, non-toxic, eco-friendly, and sustainable, with robust mechanical and thermoplastic properties. In addition, the bioplastics are suitable for a plethora of applications in the agriculture, construction, healthcare, electrical and electronics, and packaging industries. Thus, this review focuses on techniques for the production of biopolymers and bioplastics from microalgae. In addition, it discusses innovative and efficient strategies for large-scale bioplastic production while also providing insights into the life cycle assessment, end-of-life, and applications of bioplastics. Furthermore, some challenges affecting industrial scale bioplastics production and recommendations for future research are provided.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

Harnessing recalcitrant lignocellulosic biomass for enhanced biohydrogen production: Recent advances, challenges, and future perspective

Biohydrogen (Bio-H2) is widely recognized as a sustainable and environmentally friendly energy source, devoid of any detrimental impact on the environment. Lignocellulosic biomass (LB) is a readily accessible and plentiful source material that can be effectively employed as a cost-effective and sustainable substrate for Bio-H2 production. Despite the numerous challenges, the ongoing progress in LB pretreatment technology, microbial fermentation, and the integration of molecular biology techniques have the potential to enhance Bio-H2 productivity and yield. Consequently, this technology exhibits efficiency and the capacity to meet the future energy demands associated with the valorization of recalcitrant biomass. To date, several pretreatment approaches have been investigated in order to improve the digestibility of feedstock. Nevertheless, there has been a lack of comprehensive systematic studies examining the effectiveness of pretreatment methods in enhancing Bio-H2 production through dark fermentation. Additionally, there is a dearth of economic feasibility evaluations pertaining to this area of research. Thus, this review has conducted comparative studies on the technological and economic viability of current pretreatment methods. It has also examined the potential of these pretreatments in terms of carbon neutrality and circular economy principles. This review paves the way for a new opportunity to enhance Bio-H2 production with technological approaches.

Engineering strategies and applications of cyanobacterial exopolysaccharides: A review on past achievements and recent perspectives

Cyanobacteria are ideally suited for developing sustainable biological products but are underdeveloped due to a lack of genetic tools. Exopolysaccharide (EPS) is one of the essential bioproducts with widespread industrial applications. Despite their unique structural characteristics associated with distinct biological and physicochemical aspects, EPS from cyanobacteria has been underexplored. However, it is expected to accelerate in the near future due to the utilization of low-cost cyanobacterial platforms and readily available information on the structural data and specific features of these biopolymers. In recent years, cyanobacterial EPSs have attracted growing scientific attention due to their simple renewability, rheological characteristics, massive production, and potential uses in several biotechnology domains. This review focuses on the most recent research on potential new EPS producers and their distinct compositions responsible for novel biological activities. Additionally, nutritional and process parameters discovered recently for enhancing EPS production and engineering strategies applied currently to control the biosynthetic pathway for enhanced EPS production are critically highlighted. The process intensification of previously developed EPS extraction and purification processes from cyanobacterial biomass is also extensively explained. Furthermore, the newly reported biotechnological applications of cyanobacterial exopolysaccharides are also discussed.

Engineering RNA polymerase to construct biotechnological host strains of cyanobacteria

Application of cyanobacteria for bioproduction, bioremediation and biotransformation is being increasingly explored. Photoautotrophs are carbon-negative by default, offering a direct pathway to reducing emissions in production systems. More robust and versatile host strains are needed for constructing production strains that would function as efficient and carbon-neutral cyanofactories. We have tested if the engineering of sigma factors, regulatory units of the bacterial RNA polymerase, could be used to generate better host strains of the model cyanobacterium Synechocystis sp. PCC 6803. Overexpressing the stress-responsive sigB gene under the strong psbA2 promoter (SigB-oe) led to improved tolerance against heat, oxidative stress and toxic end-products. By targeting transcription initiation in the SigB-oe strain, we could simultaneously activate a wide spectrum of cellular protective mechanisms, including carotenoids, the HspA heat shock protein, and highly activated non-photochemical quenching. Yellow fluorescent protein was used to test the capacity of the SigB-oe strain to produce heterologous proteins. In standard conditions, the SigB-oe strain reached a similar production as the control strain, but when cultures were challenged with oxidative stress, the production capacity of SigB-oe surpassed the control strain. We also tested the production of growth-rate-controlled host strains via manipulation of RNA polymerase, but post-transcriptional regulation prevented excessive overexpression of the primary sigma factor SigA, and overproduction of the growth-restricting SigC factor was lethal. Thus, more research is needed before cyanobacteria growth can be manipulated by engineering RNA polymerase.

Recent advances in sustainable hydrogen production from microalgae: Mechanisms, challenges, and future perspectives

The depletion of fossil fuel reserves has resulted from their application in the industrial and energy sectors. As a result, substantial efforts have been dedicated to fostering the shift from fossil fuels to renewable energy sources via technological advancements in industrial processes. Microalgae can be used to produce biofuels such as biodiesel, hydrogen, and bioethanol. Microalgae are particularly suitable for hydrogen production due to their rapid growth rate, ability to thrive in diverse habitats, ability to resolve conflicts between fuel and food production, and capacity to capture and utilize atmospheric carbon dioxide. Therefore, microalgae-based biohydrogen production has attracted significant attention as a clean and sustainable fuel to achieve carbon neutrality and sustainability in nature. To this end, the review paper emphasizes recent information related to microalgae-based biohydrogen production, mechanisms of sustainable hydrogen production, factors affecting biohydrogen production by microalgae, bioreactor design and hydrogen production, advanced strategies to improve efficiency of biohydrogen production by microalgae, along with bottlenecks and perspectives to overcome the challenges. This review aims to collate advances and new knowledge emerged in recent years for microalgae-based biohydrogen production and promote the adoption of biohydrogen as an alternative to conventional hydrocarbon biofuels, thereby expediting the carbon neutrality target that is most advantageous to the environment.

TFP Bioeconomy Impact post Covid-19 on the agricultural economy

BACKGROUND

This research was focused on measuring the TFP bioeconomy post-Covid-19 in six regions of the world.

METHODS

The panel data was organized with FAO Statistics data. Linear programming with an enveloping data analysis (DEA) approach was used to measure the Malmquist TFP indices to determine the inter-annual productivity and technical efficiency changes by region.

RESULTS

The results show that the effect of Covid-19 on the bioeconomy productivity during the period 2012-2021 on average decreased by 11.6%. This effect was explained by the decomposition of the productivity change into the changes in technical efficiency. The workers decreased their efficiency by 11.7%. In the Northern American region, it decreased by 21.6%, in the Southern European region by 10.1, and in Western Europe by 11.7%.

CONCLUSION

The results show a downward trend that was affected in the year 2019 by Covid-19, however, it was possible to recover in the following year. One of the conclusions of these results is the effect of the immediate strategies that the governments of the region implemented. This effect was a little slower in the North American, Southeastern, and Eastern European regions. Finally, it is concluded that the measures implemented by the governments in the studied regions had an increasing effect in conditions of variable scale returns. In other words, the companies that remained on a constant scale decreased.

Characterization and Homology Modeling of Catalytically Active Recombinant PhaCAp Protein from Arthrospira platensis

Polyhydroxybutyrate (PHB) is a biocompatible and biodegradable polymer that has the potential to replace fossil-derived polymers. The enzymes involved in the biosynthesis of PHB are β-ketothiolase (PhaA), acetoacetyl-CoA reductase (PhaB), and PHA synthase (PhaC). PhaC in Arthrospira platensis is the key enzyme for PHB production. In this study, the recombinant E. cloni^®10G cells harboring A. platensis phaC (rPhaC_Ap) was constructed. The overexpressed and purified rPhaC_Ap with a predicted molecular mass of 69 kDa exhibited V_max, K_m, and k_cat values of 24.5 ± 2 μmol/min/mg, 31.3 ± 2 µM and 412.7 ± 2 1/s, respectively. The catalytically active rPhaC_Ap was a homodimer. The three-dimensional structural model for the asymmetric PhaC_Ap homodimer was constructed based on Chromobacterium sp. USM2 PhaC (PhaC_Cs). The obtained model of PhaC_Ap revealed that the overall fold of one monomer was in the closed, catalytically inactive conformation whereas the other monomer was in the catalytically active, open conformation. In the active conformation, the catalytic triad residues (Cys151-Asp310-His339) were involved in the binding of substrate 3HB-CoA and the CAP domain of PhaC_Ap involved in the dimerization.

Cyanobacterial Harmful Algal Bloom Toxin Microcystin and Increased Vibrio Occurrence as Climate-Change-Induced Biological Co-Stressors: Exposure and Disease Outcomes via Their Interaction with Gut-Liver-Brain Axis

The effects of global warming are not limited to rising global temperatures and have set in motion a complex chain of events contributing to climate change. A consequence of global warming and the resultant climate change is the rise in cyanobacterial harmful algal blooms (cyano-HABs) across the world, which pose a threat to public health, aquatic biodiversity, and the livelihood of communities that depend on these water systems, such as farmers and fishers. An increase in cyano-HABs and their intensity is associated with an increase in the leakage of cyanotoxins. Microcystins (MCs) are hepatotoxins produced by some cyanobacterial species, and their organ toxicology has been extensively studied. Recent mouse studies suggest that MCs can induce gut resistome changes. Opportunistic pathogens such as Vibrios are abundantly found in the same habitat as phytoplankton, such as cyanobacteria. Further, MCs can complicate human disorders such as heat stress, cardiovascular diseases, type II diabetes, and non-alcoholic fatty liver disease. Firstly, this review describes how climate change mediates the rise in cyanobacterial harmful algal blooms in freshwater, causing increased levels of MCs. In the later sections, we aim to untangle the ways in which MCs can impact various public health concerns, either solely or in combination with other factors resulting from climate change. In conclusion, this review helps researchers understand the multiple challenges brought forth by a changing climate and the complex relationships between microcystin, Vibrios, and various environmental factors and their effect on human health and disease.

Synechocystis: A model system for expanding the study of cyanobacterial circadian rhythms

The study of circadian rhythms in bacteria was transformed by studies of the cyanobacterium Synechococcus elongatus. However, in a number of respects S. elongatus is atypical, and while those unusual characteristics were helpful for rapid progress in the past, another commonly used cyanobacterial species, Synechocystis sp. PCC 6803, may be more representative and therefore more productive for future insights into bacterial clock mechanisms. In the past, circadian studies of Synechocystis have suffered from not having an excellent reporter of circadian gene expression, but we introduce here a new luminescence reporter that rivals the reporters that have been used so successfully in S. elongatus. Using this new system, we generate for the first time in Synechocystis circadian period mutants resulting from point mutations. The temperature compensation and dark-pulse resetting that mediates entrainment to the environment is characterized. Moreover, we analyse the complex organization of clock genes in Synechocystis and identify which genes are essential for circadian rhythmicity and adaptive fitness for entrainment and optimal phase alignment to environmental cycles (and which genes are not). These developments will provide impetus for new approaches towards understanding daily timekeeping mechanisms in bacteria.

slr2103, a homolog of type-2 diacylglycerol acyltransferase genes, for plastoquinone-related neutral lipid synthesis and NaCl-stress acclimatization in a cyanobacterium, Synechocystis sp. PCC 6803

A cyanobacterium, Synechocystis sp. PCC 6803, contains a lipid with triacylglycerol-like TLC mobility but its identity and physiological roles remain unknown. Here, on ESI-positive LC-MS² analysis, it is shown that the triacylglycerol-like lipid (lipid X) is related to plastoquinone and can be grouped into two subclasses, X_a and X_b, the latter of which is esterified by 16:0 and 18:0. This study further shows that a Synechocystis homolog of type-2 diacylglycerol acyltransferase genes, slr2103, is essential for lipid X synthesis: lipid X disappears in a Synechocystis slr2103-disruptant whereas it appears in an slr2103-overexpressing transformant (OE) of Synechococcus elongatus PCC 7942 that intrinsically lacks lipid X. The slr2103 disruption causes Synechocystis cells to accumulate plastoquinone-C at an abnormally high level whereas slr2103 overexpression in Synechococcus causes the cells to almost completely lose it. It is thus deduced that slr2103 encodes a novel acyltransferase that esterifies 16:0 or 18:0 with plastoquinone-C for the synthesis of lipid X_b. Characterization of the slr2103-disruptant in Synechocystis shows that slr2103 contributes to sedimented-cell growth in a static culture, and to bloom-like structure formation and its expansion by promoting cell aggregation and floatation upon imposition of saline stress (0.3-0.6 M NaCl). These observations provide a basis for elucidation of the molecular mechanism of a novel cyanobacterial strategy to acclimatize to saline stress, and one for development of a system of seawater-utilization and economical harvesting of cyanobacterial cells with high-value added compounds, or blooming control of toxic cyanobacteria.

Versatile Applications of Cyanobacteria in Biotechnology

Cyanobacteria are blue-green Gram-negative and photosynthetic bacteria which are seen as one of the most morphologically numerous groups of prokaryotes. Because of their ability to fix gaseous nitrogen and carbon dioxide to organic materials, they are known to play important roles in the universal nutrient cycle. Cyanobacteria has emerged as one of the promising resources to combat the issues of global warming, disease outbreaks, nutrition insecurity, energy crises as well as persistent daily human population increases. Cyanobacteria possess significant levels of macro and micronutrient substances which facilitate the versatile popularity to be utilized as human food and protein supplements in many countries such as Asia. Cyanobacteria has been employed as a complementary dietary constituent of feed for poultry and as vitamin and protein supplement in aquatic lives. They are effectively used to deal with numerous tasks in various fields of biotechnology, such as agricultural (including aquaculture), industrial (food and dairy products), environmental (pollution control), biofuel (bioenergy) and pharmaceutical biotechnology (such as antimicrobial, anti-inflammatory, immunosuppressant, anticoagulant and antitumor); recently, the growing interest of applying them as biocatalysts has been observed as well. Cyanobacteria are known to generate a numerous variety of bioactive compounds. However, the versatile potential applications of cyanobacteria in biotechnology could be their significant growth rate and survival in severe environmental conditions due to their distinct and unique metabolic pathways as well as active defensive mechanisms. In this review, we elaborated on the versatile cyanobacteria applications in different areas of biotechnology. We also emphasized the factors that could impede the implementation to cyanobacteria applications in biotechnology and the execution of strategies to enhance their effective applications.