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Cyanobacteria comprise a good natural resource of a potential variety of neuro-chemicals, including acetylcholinesterase inhibitors essential for Alzheimer's disease treatment. Accordingly, eight different cyanobacterial species were isolated, identified, and evaluated on their growth on different standard nutrient media. It was found that the modified Navicula medium supported the highest growth of the test cyanobacteria. The effects of methylene chloride/methanol crude extracts of the test cyanobacteria on acetylcholinesterase activity were examined and compared. Anabaena variabilis (KU696637.1) crude extract recorded the highest acetylcholinesterase inhibition (62 ± 1.3%). Navicula medium chemical components were optimized through a Plackett–Burman factorial design. The biomass of Anabaena variabilis increased significantly when grown on the optimized medium compared to that of control. The chemical analysis of the fractions derived from Anabaena variabilis showed the presence of two compounds in significant amounts: the flavonoid 5,7-dihydroxy-2-phenyl-4H-chrome-4-one and the alkaloid 4-phenyl-2-(pyridin-3-yl) quinazoline. Molecular docking studies revealed that both compounds interact with the allosteric binding site of acetylcholinesterase at the periphery with π-π stackings with Tyr341 and Trp286 with good, predicted partition coefficient. The compounds obtained from this study open the door for promising drug candidates to treat Alzheimer's disease for their better pharmacodynamics and pharmacokinetic properties. [ABSTRACT FROM AUTHOR]

Biofilms are microbial colonies that are encased in an organic polymeric matrix and are resistant to antimicrobial treatments. Biofilms can adhere to both biotic and abiotic surfaces, allowing them to colonize medical equipment such as urinary and intravenous catheters, mechanical heart valves, endotracheal tubes, and prosthetic joints. Candida albicans biofilm is the major etiological cause of the pathogenesis of candidiasis in which its unobstructed growth occurs in the oral cavity; trachea, and catheters that progress to systemic infections in the worst scenarios. There is an urgent need to discover novel biofilm preventive and curative agents. In the present investigation, an effort is made to observe the role of cyanobacteria-derived AgNPs as a new antibiofilm agent with special reference to candidiasis. AgNPs synthesized through the green route using Anabaena variabilis cell extract were characterized by UV–visible spectroscopy. The nanoparticles were spherical in shape with 11–15 nm size and were monodispersed. The minimum inhibitory concentration (MIC) of AgNPs was obtained at 12.5 μg/mL against C. albicans. AgNPs 25 μg/mL showed 79% fungal cell membrane permeability and 22.2% ROS production. AgNPs (25 μg/mL) also facilitated 62.5% of biofilm inhibition and degradation. Therefore, AgNPs could be considered as a promising antifungal agent to control biofilm produced by C. albicans. [ABSTRACT FROM AUTHOR]

Biofilms are microbial colonies that are encased in an organic polymeric matrix and are resistant to antimicrobial treatments. Biofilms can adhere to both biotic and abiotic surfaces, allowing them to colonize medical equipment such as urinary and intravenous catheters, mechanical heart valves, endotracheal tubes, and prosthetic joints. Candida albicans biofilm is the major etiological cause of the pathogenesis of candidiasis in which its unobstructed growth occurs in the oral cavity; trachea, and catheters that progress to systemic infections in the worst scenarios. There is an urgent need to discover novel biofilm preventive and curative agents. In the present investigation, an effort is made to observe the role of cyanobacteria-derived AgNPs as a new antibiofilm agent with special reference to candidiasis. AgNPs synthesized through the green route using Anabaena variabilis cell extract were characterized by UV–visible spectroscopy. The nanoparticles were spherical in shape with 11–15 nm size and were monodispersed. The minimum inhibitory concentration (MIC) of AgNPs was obtained at 12.5 μg/mL against C. albicans. AgNPs 25 μg/mL showed 79% fungal cell membrane permeability and 22.2% ROS production. AgNPs (25 μg/mL) also facilitated 62.5% of biofilm inhibition and degradation. Therefore, AgNPs could be considered as a promising antifungal agent to control biofilm produced by C. albicans.

Selenium nanoparticles (SeNPs) are gaining importance in the field of medicines due to their high surface area and unique properties than their other forms of selenium. In this study, biogenic selenium nanoparticles (B-SeNPs) were synthesized using cyanobacteria and their bioactivities (antioxidant, antimicrobial, anticancer and biocompatibility) were determined for comparison with commercially available chemically synthesized selenium nanoparticles (C-SeNPs). Color change of reaction mixture from sky blue to orange-red indicated the synthesis of biogenic SeNPs (B-SeNPs). UV–Vis spectra of the reaction mixture exhibited peak at 266 nm. During optimization, 30 °C of temperature, 24 h of time and 1:2 concentration ratio of sodium selenite and cell extract represented the best condition for SeNPs synthesis. Various functional groups and biochemical compounds present in the aqueous extract of Anabaena variabilis NCCU-441, which may have possibly influenced the reduction process of SeNPs were identified by FT-IR spectrum and GC–MS. The synthesized cyanobacterial SeNPs were orange red in color, spherical in shape, 10.8 nm in size and amorphous in nature. The B-SeNPs showed better anti-oxidant (DPPH, FRAP, SOR and ABTS assays), anti-microbial (antibacterial and antifungal) and anti-cancer activitities along with its biocompatibility in comparison to C-SeNPs suggesting higher probability of their biomedical application. [ABSTRACT FROM AUTHOR]

NH 3 is an important chemical fertilizer and expecting as H 2 carrier. Several methods have been investigated for eco-friendly NH 3 production under mild conditions instead of Haber-Bosch process using 400 °C, 20 MPa. Here, cyanobacterial Anabaena variabilis was utilized as a nitrogenase-producing biocatalyst that converts N 2 /H 2 O to NH 3 under ambient conditions. Biocatalytic reactions revealed that MV•+ can penetrate cell membrane and transfer electrons generated in inorganic photocatalyst. We first reported photobiocatalytic NH 3 production of cyanobacteria and TiO 2. Comparing with natural system, NH 3 formation rate of the hybrid system increased 81.3 times with an initial rate of 2031.7 nmol·h−1 and turnover number of 216.8. [Display omitted] • Cyanobacteria cultivated in Allen & Arnon medium possess active [MoFe]-nitrogenase. • Photocatalysis of TiO 2 can transfer electrons to both methyl and benzyl viologens. • Only reduce MV•+ can permeate cell envelope and transfer electrons to nitrogenase. • Photobiocatalysis of TiO 2 -cyanobacteria system produces NH 3 from N 2 fixation. [ABSTRACT FROM AUTHOR]

Biogenic silver nanoparticles (AgNPs) are of significant interest due to their widespread application. In order to make nontoxic cost-effective AgNPs, several microorganisms have been utilized. In the present study, emphasis was given to Anabaena variabilis–mediated AgNPs synthesis. Optimal conditions for extract preparation were heating of extraction mixture at 100 °C for 5 min, while for AgNPs synthesis, optimal conditions were 1:9 v/v (cell extract: AgNO3 (1 mM)), pH 7.4, and 30 °C reaction temperatures. The synthesized AgNPs were characterized initially by UV-Vis spectrophotometer and the maximum absorbance peak was obtained at 440 nm. XRD technique confirmed their crystalline nature. SEM with EDX showed 66% elemental silver by weight, which signified the purity of AgNPs. DLS study showed nearly monodispersed nature of AgNPs. TEM observation confirmed the synthesis of 11–15 nm spherical NPs. FTIR analysis of synthesized AgNPs showed the functional moieties responsible for their bioactivity. The biomolecules of AgNPs were confirmed by LCMS/MS. Anabaena variabilis–mediated AgNPs showed good antibacterial and antifungal activity. In combination with standard antibiotic (streptomycin) and antifungal agents (amphotericin B, fluconazole), AgNPs showed significant synergistic effect. The blend of antibacterial and antifungal properties, coupled with their intrinsic "green" and facile synthesis, made these biogenic nanoparticles attractive in nanomedicine. [ABSTRACT FROM AUTHOR]

Cyanobacteria comprise a good natural resource of a potential variety of neuro-chemicals, including acetylcholinesterase inhibitors essential for Alzheimer’s disease treatment. Accordingly, eight different cyanobacterial species were isolated, identified, and evaluated on their growth on different standard nutrient media. It was found that the modified Navicula medium supported the highest growth of the test cyanobacteria. The effects of methylene chloride/methanol crude extracts of the test cyanobacteria on acetylcholinesterase activity were examined and compared. Anabaena variabilis (KU696637.1) crude extract recorded the highest acetylcholinesterase inhibition (62 ± 1.3%). Navicula medium chemical components were optimized through a Plackett–Burman factorial design. The biomass of Anabaena variabilis increased significantly when grown on the optimized medium compared to that of control. The chemical analysis of the fractions derived from Anabaena variabilis showed the presence of two compounds in significant amounts: the flavonoid 5,7-dihydroxy-2-phenyl-4H-chrome-4-one and the alkaloid 4-phenyl-2-(pyridin-3-yl) quinazoline. Molecular docking studies revealed that both compounds interact with the allosteric binding site of acetylcholinesterase at the periphery with π-π stackings with Tyr341 and Trp286 with good, predicted partition coefficient. The compounds obtained from this study open the door for promising drug candidates to treat Alzheimer’s disease for their better pharmacodynamics and pharmacokinetic properties.

The present investigation aims towards simultaneous increase in biomass and carbohydrate accumulation of Anabaena variabilis by formulating an optimal growth condition. Based on the individual factor studies, concentrations of three variables were optimized. An initial pH 8.9, 168.8 mg L−1 MgSO 4 , and 64.3 mg L−1 NaHCO 3 were the best combination resulting in respective ∼1.5 and ∼2.4-fold higher biomass and total carbohydrate yield compared to BG-11-grown control. Carbohydrate profiling indicated ∼2.6-fold rise in the yield of reducing sugar and glycogen. The bioethanol yield was, therefore, enhanced by ∼2.5-fold, reflecting almost two-times higher the value obtained earlier using the biphasic approach. The optimized condition also heightened the yield of the co-products C-phycocyanin and sodium copper chlorophyllin by ∼3-fold, and poly-β-hydroxybutyrate and exopolysaccharides by ∼2.6 and ∼1.8-fold. A ∼60% greater earning was projected from both bioethanol and co-products using the optimal medium under the large-scale set-up compared to control. Thus the present work engineered a robust way to maximize bioethanol production within a shortened time spell, ruling out the constraints of nutrient starvation under biphasic strategies alongside economizing the production process incorporating cyanobacterial refinery approach. Additionally, the details on photobioreactor prospects and sustainability assessment using 'Water footprint' would be beneficial for future research. Image 1 • Novel strategy was designed for enhancing bioethanol production from A. variabilis. • Optimizing the medium showed ∼2.4-fold higher carbohydrate production. • Rise in the fermentable carbohydrate components increased bioethanol by ∼2.5 fold. • Significantly higher production of C-PC, SCC, PHB and EPS was achieved. • Large scale projection showed ∼60% higher return from commercializing the products. [ABSTRACT FROM AUTHOR]

High nutritional content of Microalgae and many others advantages make it an important source for immunomodulating studies. Anabaena variabilis is a filamentous microalga with a heterocyst and it is capable of both photoautotrophic and heterotrophic growth. This study was done to investigate the activity of A. variabilis aqueous extract on some immunological, cytological and haematological parameters. Mice were divided into four groups, the control and the rest were received different doses from algal extract (40, 1200, 2400 mg/kg). ELISA (Enzyme-Linked Immunosorbent Assay) kit was used to measure interleukins (2, 4, 12) and gamma interferon. The results revealed that the aqueous extract increased the production of interleukins (2, 12) and gamma interferon while the production of interleukin 4 was decreased. The significant differences were not observed in each mitotic and haematological parametres, except in lymphocytes percentage. This aqueous extract this could be used as a therapeutic way for prevention of (Th2) cytokine-dominant disease. [ABSTRACT FROM AUTHOR]

There is a growing interest in photosynthetic microorganisms for converting solar energy to electricity aiming at practical application. Despite extensive research, existing methods are suffered from limited photocurrent. Here we report that appreciable photocurrent can be generated in a photo‐bioelectrochemical cell (PBEC) where reduced graphene oxide‐coated ITO electrode is used as an anode and wild type cyanobacterium Anabaena variabilis as photo‐biocatalyst that oxidizes water by solar light. With A. variabilis dispersed in buffer and 1,4‐benzoquinone as a redox mediator, our PBEC produced photocurrent of 223 μA cm−2 at an applied voltage of 0.4 V vs. Ag/AgCl. Incident photon to current efficiencies of 0.50 % and 5.2 % were obtained with white and monochromatic light at 660 nm, respectively. A complete PBEC with Pt/C cathode produced Pmax of 13 μW cm−2 at 115 μA cm−2. Methodology in this study can be extended to cover other cyanobacteria, electrode materials, and mediators to further enhance photocurrent and power density. Our results demonstrate the possibility of utilizing cyanobacteria that are ubiquitous in the environment as alternative energy sources. [ABSTRACT FROM AUTHOR]

In this study, five macroalgae and four microalgae in addition to seven Cyanophycean, blue-green algae, were isolated from different environmental habitats. The ability of these species for bioethanol and biodiesel production was assessed. Five techniques were examined for cell wall disruption, namely thermic shock, manual grinding, acid, base, and enzymatic digestion. Among these methods, sulfuric acid (3%) achieved the highest reducing sugar yield (%) followed by the enzymatic then the base hydrolysis methods. For each species, the resulted yield of reducing sugars (%) was dependent on the hydrolysis method rather than on the quantity of the total sugars (as mg/100 mg dr weight). After 48 hours of fermentation, Arthrospira platensis, Chlorella marina, and Ulva linza proved to be promising for bioethanol production estimating 45.49%, 23.24%, and 12.01% as ethanol yield, respectively. For all the tested species, grinding followed by enzymatic hydrolysis methods recovered maximum protein amounts (as mg/100 mg dry weight). On the other hand, Caulerpa prolifera, Anabaena variabilis, and Scenedesmus obliquus produced elevated biodiesel quantities of 13.55%, 21.63%, and 28.44% of dry weight, respectively. For each tested species, the quantity of the obtained biodiesel (%) was proportional to the extracted amount of lipids. Gas chromatography–mass spectroscopy (GC-MS) analysis of the produced oil showed dominant composition of saturated fatty acids implying a suitable oil quality. The results of this study recommended large-scale cultivation of A. platensis, C. marina, and U. linza as costless candidates for bioethanol production. The study also validated S. obliquus, A. variabilis, and Caulerpa prolifera as reliable biodiesel producers with an encouraging oil composition ratio for probable commercial applications. [ABSTRACT FROM AUTHOR]

Anabaena variabilis and Tolypthrix ceytonica were selected for bioremediation of heavy metals-contaminated industrial effluents based on their high efficiency as metals accumulators. Sodium alginate immobilized individual or mixed cell cultures were examined to decontaminate Plastic and electrical industrial effluents in continuous mode (at 50 and 100 ml/h flow rates) for 6 h. Removal efficiency was a function of heavy metal type, concentration, microbial species and proportionally increased with exposure time. The maximum achieved removals recorded 94.45% for Fe2+ (A. variabilis at 50 ml/h), Zn2+ (98.98% by A. variabilis; 98.63% by A. variabilis and T. ceytonica mixture and 98.61% by T. ceytonica at 100 ml/h), 94.22% for Pb2+ (A. variabilis and T. ceytonica mixture at 100 ml/h) as well as 93.33% and 91.33% for Cu2+ by A. variabilis and T. ceytonica at 50 and 100 ml/h flow rates, respectively. Excellent selective metals bioremoval abilities were detected by the selected cyanobacterial species. Their manipulation in the proposed biotechnology provides an economic and excellent tool for remediation of industrial effluents and protection of the received environments. Moreover, treated wastewater may be reused in any purpose such as aqua-culturing or irrigation of agricultural edible and non-edible crops. [ABSTRACT FROM AUTHOR]

Highlights from the article: NHE for DMBQ are positive enough to take electrons from the I Z i -scheme.[7] Our previous study shows that the possible electron transfer sites are I Q i SB A sb or I F i SB d sb .[8] The amount of oxygen produced from water oxidation by I A. variabilis i was measured by the Clark-type oxygen sensor in a three-electrode setup under the irradiation at 450 and 660 nm, the dominant absorption wavelengths of chlorophyll (Figure). Being lipid soluble, DMBQ can pass through cell membranes and have access to the electron transfer chain located in the thylakoid membrane.[11] More electron take-up may induce more oxygen evolution from water oxidation. The cell activity test was done by measuring the oxygen evolution rate of I A. variabilis i with a Clark-type oxygen sensor (Hansatech Instruments Ltd., Norfolk, UK) under one sun illumination (McScience, Suwon, Korea).

The biological H 2 production industry would be independent from other industries if it has its own supply of organic materials especially in non-agricultural countries. In this study, acid hydrolyzed biomass of the potent extracellular polysaccharides (EPSs) producing cyanobacterium Nostoc commune and glycogen (as intracellular polysaccharide) enriched Anabaena variabilis NIES-2095 were used as a cheap organic carbon feedstock for biological H 2 production by two stages dark fermentation by Escherichia coli strain MWW and Clostridium acetobutylicum DSM-792 or Clostridium beijerinckii DSM-1820 and photofermentation by Rhodobacter capsulatus JCM-21090 under anaerobic conditions. Acid hydrolysis of air dried cyanobacterial biomass was conducted at optimum conditions of 4 M HCl at 120 °C in an autoclave for 30 min and subsequently neutralized and used as an organic carbon source for first stage dark fermentation followed by a second stage photofermentation. The facultative anaerobe Escherichia coli strain MWW was used for maintaining anaerobiosis. Escherichia coli strain MWW was isolated and identified by morphological and biochemical characterizations as well as molecular biological phylogenetic analysis of its 16S rDNA sequence. Nostoc commune was identified by morphological and microscopic characterizations and by 16S rDNA sequence phylogenetic analysis. The two stages dark fermentation by Escherichia coli and Clostridium acetobutylicum or Clostridium beijerinckii and photofermentation by Rhodobacter capsulatus produced in total 5.9 and 5.6 mol H 2 /mole reducing sugars of acid hydrolyzed Nostoc commune EPSs/biomass, respectively and 5.43 and 5 mol H 2 /mole reducing sugars of acid hydrolyzed biomass of glycogen enriched Anabaena variabilis , respectively. These results indicate a high potency of using cyanobacterial polysaccharides/biomass (extracellular polysaccharides and intracellular glycogen) as an organic carbon source for H 2 production which would be of importance for non-agricultural countries. Image 1 • N. commune extracellular polysaccharides/biomass was efficient for H 2 production. • Intracellular glycogen enriched Anabaena biomass was efficient for H 2 production. • E. coli was used for maintaining anaerobiosis for H 2 production by Clostridium. • H 2 production was efficiently conducted by two stages dark and photo-fermentation. • Cyanobacterial polysaccharides would be useful for non-agricultural countries. [ABSTRACT FROM AUTHOR]

Many contaminants which are toxic and adversely affect living organisms enter surface waters. Among them, there are endocrine compounds such as steroid hormones, which can disrupt the endocrine system causing an adverse effect on the physiology of aquatic organisms. In the literature, there is not enough information about the influence of steroid hormones on phytoplankton growth. Therefore, the aim of this research was to study the effect of estrogens (estrone, 17ß-estadiol, 17-α-ethinylestradiol, and estriol), progestagens (progesterone, 5-pregnen-3b-ol-20-one, and levonorgestrel), and androgens (testosterone) on the growth of the cyanobacterium Anabaena variabilis. To our best knowledge, the chronic toxicological effects of hormones on cyanobacteria are explored for the first time. From among single steroid hormones, progesterone and 17-α-ethinylestradiol are the most toxic (EC50 48.59 and 82.95 mg L−1). On the other hand, incubation in the presence of 5-pregnen-3b-ol-20-one, testosterone, and 17ß-estadiol caused slight inhibition of growth (EC50 283.50, 336.68, and 437.82 mg L−1), while estrone, estriol, and levonorgestrel showed no significant effect on the growth of this cyanobacterium. Hormone mixtures have been found to be more toxic than single substances and exposure to them leads to the potentiation of toxicity. The EC50 after 14 days of the test duration for the mixed steroid hormones were 45.14, 37.00, and 89.46 mg L−1. This research provides a basic understanding of hormone toxicity to aquatic organism, such as cyanobacteria, and asserts a more comprehensive view on ecological risk evaluation.The transport of steroid hormones in the envirnoment and their influence of the growth of cyanobacteria [ABSTRACT FROM AUTHOR]

Abstract Photosynthetic pigment-protein complexes are highly concentrated in thylakoid membranes of chloroplasts and cyanobacteria that emit strong autofluorescence (mainly 600–800 nm). In Raman scattering microscopy that enables imaging of pigment concentrations of thylakoid membranes, near infrared laser excitation at 1064 nm or visible laser excitation at 488–532 nm has been often employed in order to avoid the autofluorescence. Here we explored a new approach to Raman imaging of thylakoid membranes by using excitation wavelength of 976 nm. Two types of differentiated cells, heterocysts and vegetative cells, in two diazotrophic filamentous cyanobacteria, Anabaena variabilis , and Rivularia M-261, were characterized. Relative Raman scattering intensities of phycobilisomes of the heterocyst in comparison with the nearest vegetative cells of Rivularia remained at a significantly higher level than those of A. variabilis. It was also found that the 976 nm excitation induces photoluminescence around 1017–1175 nm from the two cyanobacteria, green alga (Parachlorella kessleri) and plant (Arabidopsis thaliana). We propose that this photoluminescence can be used as an index of concentration of chlorophyll a that has relatively small Raman scattering cross-sections. The Rivularia heterocysts that we analyzed were clearly classified into at least two subgroups based on the Chl a -associated photoluminescence and carotenoid Raman bands, indicating two physiologically distinct states in the development or aging of the terminal heterocyst. Graphical abstract Unlabelled Image Highlights • Heterocysts of two cyanobacteria are compared by Raman scattering microscopy. • Continuous-wave laser at 976 nm induces a photoluminescence from chlorophyll a. • Carotenoids not bound to photosystem I or II in the heterocysts are suggested. • Two stages in the development or aging of Rivularia heterocyst are detectable. [ABSTRACT FROM AUTHOR]

Abstract Industrial wastewater containing heavy metals is a major environmental problem that needs to be treated. This study reported the ability of two fresh water algae cyanobacteria (Nostoc muscorum and Anabaena variabilis) to remove lead from aqueous solutions of four different initial concentrations (0–50 mg/L−1) for 21 days under controlled laboratory conditions. Results obtained in this study showed a maximum removal of Pb(II) (97.8%) by N. muscorum at 15 mg/L−1 initial metal concentration however the maximum removal by A. variabilis at the same concentration was 71.4% after 16 day of incubation. These N. muscorum appeared to be more efficient than A. variabilis for removing Pb(II). Algal growth, pigments in the algae cells were measured during incubation period. Lower concentrations of lead increased biomass, OD, chlorophyll a and carotenoids in both algae. On the other hand, higher concentrations of lead were inhibitory for growth. Highlights • N. muscorum and A. variabilis were tested to remove lead from water for 21 days. • After 16 days of incubation, algae were reached to the saturation level. • There were increased in growth rate in both algae in lower concentrations of lead. • N. muscorum was more effective than A. variabilis for bioremovel of lead. [ABSTRACT FROM AUTHOR]

Nitrogen is globally limiting primary production in the ocean, but some species of cyanobacteria can carry out nitrogen (N) fixation using specialized cells known as heterocysts. However, the effect of N sources and their availability on heterocyst development is not yet fully understood. This study aimed to evaluate the effect of various inorganic N sources on the heterocyst development and cellular growth in an N-fixing cyanobacterium, Anabaena variabilis. Growth rate, heterocyst development, and cellular N content of the cyanobacteria were examined under varying nitrate and ammonium concentrations. A. variabilis exhibited high growth rate both in the presence and absence of N sources regardless of their concentration. Ammonium was the primary source of N in A. variabilis. Even the highest concentrations of both nitrate (1.5 g L−1 as NaNO3) and ammonium (0.006 g L−1 as Fe-NH4-citrate) did not exhibit an inhibitory effect on heterocyst development. Heterocyst production positively correlated with the cell N quota and negatively correlated with vegetative cell growth, indicating that both of the processes were interdependent. Taken together, N deprivation triggers heterocyst production for N fixation. This study outlines the difference in heterocyst development and growth in A. variabilis under different N sources.

Highlights • A new, δ-specific cyanobacterial amino acid dioxygenase was isolated and recombinantly expressed in E. coli. • In the stereoselective S-oxidation of methionine, the dioxygenase shows inverse stereopreference to previously characterised hydroxylases. • The enzyme catalyses the regioselective hydroxylation of several branched-chain amino acids. • It is a promising catalyst for the synthesis of bioactive compounds and natural product derivatives. Abstract Optically pure hydroxy amino acids show several bioactivities and are valuable building blocks for the pharmaceutical industry. Fe(II)/α-ketoglutarate dependent dioxygenases catalyze the hydroxylation or sulfoxidation of l -amino acids with high regio- and stereoselectivity. While several β- and γ-specific enzymes have been described, only one δ-specific hydroxylase has been reported so far. Based on its similarity to the known l -leucine 5-hydroxylase from Nostoc punctiforme , an open reading frame from the cyanobacterium Anabaena variabilis was identified as putative l -leucine dioxygenase (AvLDO). Here we report the cloning and characterization of this dioxygenase. The enzyme showed a high preference for acidic conditions and moderate reaction temperatures. AvLDO catalyzed the regio- and stereoselective hydroxylation of several aliphatic amino acids in δ-position. In case of the sulfoxidation of l -methionine, AvLDO produced the opposite diastereomer than isoleucine dioxygenase. AvLDO is thus an interesting addition to the toolbox of Fe(II)/α-ketoglutarate dependent dioxygenases. On the genomic DNA of Anabaena variabilis ATCC 29413, the avldo gene is located on a gene cluster involved (2 S ,4 S)-4-methylproline biosynthesis, which is contained in bioactive peptides often found from cyanobacteria. This fact suggests the metabolic functional role of this amino acid dioxygenase in cyanobacteria. [ABSTRACT FROM AUTHOR]

Abstract: Tailored mutants of phenylalanine ammonia‐lyase from Petroselinum crispum (PcPAL) were created and tested in ammonia elimination from various sterically demanding, non‐natural analogues of phenylalanine and in ammonia addition reactions into the corresponding (E)‐arylacrylates. The wild‐type PcPAL was inert or exhibited quite poor conversions in both reactions with all members of the substrate panel. Appropriate single mutations of residue F137 and the highly conserved residue I460 resulted in PcPAL variants that were active in ammonia elimination but still had a poor activity in ammonia addition onto bulky substrates. However, combined mutations that involve I460 besides the well‐studied F137 led to mutants that exhibited activity in ammonia addition as well. The synergistic multiple mutations resulted in substantial substrate scope extension of PcPAL and opened up new biocatalytic routes for the synthesis of both enantiomers of valuable phenylalanine analogues, such as (4‐methoxyphenyl)‐, (napthalen‐2‐yl)‐, ([1,1′‐biphenyl]‐4‐yl)‐, (4′‐fluoro‐[1,1′‐biphenyl]‐4‐yl)‐, and (5‐phenylthiophene‐2‐yl)alanines. [ABSTRACT FROM AUTHOR]

Introduction Pegvaliase is a recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) enzyme under investigation for treatment of adult phenylketonuria (PKU). This manuscript describes results of a randomized discontinuation trial (RDT) designed to evaluate the effects of pegvaliase treatment on blood phenylalanine (Phe) and neuropsychiatric outcomes in adults with PKU. Methods PRISM-2 is a 4-part, Phase 3 study that enrolled adults with PKU receiving pegvaliase treatment (initiated in a prior Phase 2 or Phase 3 study). The RDT, Part 2 of PRISM-2, was an 8-week trial that evaluated change in blood Phe concentrations, neuropsychiatric and neurocognitive measures, and safety outcomes in PRISM-2 participants who had achieved at least a 20% blood Phe reduction from pre-treatment baseline with pegvaliase treatment. Participants were randomized 2:1 to either continue pegvaliase (20 mg/day or 40 mg/day) or switch to matching placebo. Results The pooled pegvaliase group enrolled 66 participants and each placebo group enrolled 14 participants. The primary endpoint of change in blood Phe concentration from RDT entry to RDT Week 8 was met with clinically meaningful and statistically significant differences between the pegvaliase and placebo groups. Mean (SD) blood Phe at the beginning of the RDT when all participants were receiving pegvaliase was 563.9 μM (504.6) in the group assigned to the 20 mg/day placebo group ( n  = 14), 508.2 μM (363.7) in those assigned to the 40 mg/day placebo group (n = 14), and 503.9 μM (520.3) in those assigned to continue pegvaliase treatment ( n  = 58). At Week 8 of the RDT, the least squares mean change (95% confidence interval) in blood Phe was 949.8 μM (760.4 to 1139.1) for the 20 mg/day placebo group and 664.8 μM (465.5 to 864.1) for the 40 mg/day placebo group in comparison to 26.5 μM (−68.3 to 121.3) for the pooled (20 mg/day and 40 mg/day) pegvaliase group ( P  < 0.0001 for pooled pegvaliase group vs each placebo group). Adverse events (AEs) were usually lower in the pooled placebo group when compared to the pooled pegvaliase group. The most common AEs for the pooled pegvaliase and pooled placebo groups were arthralgia (13.6% and 10.3%, respectively), headache (12.1% and 24.1%), anxiety (10.6% and 6.9%), fatigue (10.6% and 10.3%), and upper respiratory tract infection (1.5% and 17.2%). Conclusion Mean blood Phe reduction was sustained in the pegvaliase group, while placebo groups had mean blood Phe concentration increase toward pre-treatment baseline levels. Results from this study confirmed the efficacy of pegvaliase in maintaining reduced blood Phe concentrations with a manageable safety profile for most participants. [ABSTRACT FROM AUTHOR]

Untreated phenylketonuria (PKU) results in severe neurodevelopmental disorders, which can be partially prevented by an early and rigorous limitation of phenylalanine (Phe) intake. Enzyme substitution therapy with recombinant Anabaena variabilis Phe Ammonia Lyase (r Av PAL) proved to be effective in reducing blood Phe levels in preclinical and clinical studies of adults with PKU. Aims of present study were: a) to gather proofs of clinical efficacy of r Av PAL treatment in preventing neurological impairment in an early treated murine model of PKU; b) to test the advantages of an alternative delivering system for r Av PAL such as autologous erythrocytes. BTBR-Pah enu2−/− mice were treated from 15 to 64 post-natal days with weekly infusions of erythrocytes loaded with r Av PAL. Behavioral, neurochemical, and brain histological markers denoting untreated PKU were examined in early treated adult mice in comparison with untreated and wild type animals. r Av PAL therapy normalized blood and brain Phe; prevented cognitive developmental failure, brain depletion of serotonin, dendritic spine abnormalities, and myelin basic protein reduction. No adverse events or inactivating immune reaction were observed. In conclusion present study testifies the clinical efficacy of r Av PAL treatment in a preclinical model of PKU and the advantages of erythrocytes as carrier of the enzyme in term of frequency of the administrations and prevention of immunological reactions. [ABSTRACT FROM AUTHOR]

The effect of extended reaction times on the regio- and enantioselectivity of the phenylalanine ammonia lyase (PAL)-catalysed amination of a subset of cinnamate derivatives was investigated. This was done using a PAL from the cyanobacterium Anabaena variabilis and incubation in a concentrated ammonia buffer. Whilst early time point analyses revealed excellent selectivities to give mostly the well-documented (S)-α-amino acid products, subsequent accumulation of other regio-/stereo- isomers was seen. For many para-substituted substrates, the β-regioisomer, a previously-unreported product with this enzyme class, was found to become more abundant than the α-, after sufficient incubation, with slight preference for the (R)-enantiomer. Although attempts to tune the selectivity of the PAL toward any of the three side products were largely unsuccessful, the results provide insight into the evolutionary history of this class of enzymes and reinforce the prominence of the toolbox of specific and selective cinnamate-aminating enzymes. [ABSTRACT FROM AUTHOR]

In Gram-negative bacteria, transport of ferric siderophores through outer membrane is a complex process that requires specific outer membrane transporters and energy-transducing TonB–ExbB–ExbD system in the cytoplasmic membrane. The genome of the non-siderophore-producing cyanobacterium Synechocystis sp. PCC 6803 encodes all putative components of the siderophore-mediated iron uptake system. So far, there has been no experimental evidence for the existence of such a pathway in this organism. On the contrary, its reductive iron uptake pathway has been studied in detail. We demonstrate that Synechocystis sp. PCC 6803 is capable of using dihydroxamate xenosiderophores, either ferric schizokinen (FeSK) or a siderophore of the filamentous cyanobacterium Anabaena variabilis ATCC 29413 (SAV), as the sole source of iron. Inactivation of the tonB gene or the exbB1–exbD1 gene cluster resulted in an inability to utilize these siderophores. At the same time, the inactivation of the feoB gene encoding FeoB plasma membrane ferrous iron transporter, or one of the futB or futC genes encoding permease and ATPase subunit of FutABC ferric iron transporter, did not impair the ability of cells to utilize FeSK or SAV as the sole source of iron for growth. Our data suggest that cyanobacterium Synechocystis sp. PCC 6803 is capable of acquiring iron–siderophore complexes in a TonB-dependent manner without iron reduction in the periplasm. [ABSTRACT FROM AUTHOR]

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Four previously isolated methanogenic anaerobic consortia, which were originally cultivated on a cellulose-containing substrate (filter paper), were used as inocula for the anaerobic conversion of the biomass of Anabaena variabilis into biogas at 55°C. The cumulative methane yield in the biogas produced by the most active consortia reached 64%. However, the biotransformation was only efficient in the course of the single inoculation and pretreatment of the cyanobacterial biomass by its concentration and freeze-thawing. The DGGE analysis of the structure of the selected microbial consortia, cultivated on the filter paper, revealed qualitative variations in the biodiversity of predominant Bacteria, showing differences in band number and intensity. The composition of methanogenic Archaea in these consortia was similar, with the presence of the genera Methanoculleus and Methanosarcina. The efficiency of the microbial consortia selection, and the role of the various microbial trophic groups in bioconversion of the substrates, such as cellulose and the biomass of phototrophic microorganisms are discussed. [ABSTRACT FROM AUTHOR]

The survival of altered and hybrid Vibrio cholerae O1 El Tor in association with a cyanobacterium, Anabaena variabilis in pond (fresh) and brackish water microcosms was investigated. Survival of culturable bacteria was monitored on taurocholate tellurite gelatine agar plate. Viable but nonculturable (VBNC) bacteria were examined using fluorescent antibody (FA) technique. In pond water, altered and hybrid El Tor survived with cyanobacteria 10 and 18 days respectively and in control water 6 and 12 days respectively in culturable state. In pond water VBNC state altered and hybrid El Tor were found to persist 48 and 53 days respectively but in brackish water 65 and 70 days respectively in association with cyanobacteria. Brackish water was found to be a better habitat than pond water for the survival of these strains. Hybrid El Tor survived longer inside the mucilaginous sheath of A. variabilis than altered El Tor both in pond and brackish water microcosms. [ABSTRACT FROM AUTHOR]