In this work, microalgae cultivation trials were carried out in a membrane bioreactor to investigate fouling when the cultures of Chlorellavulgaris were grown under mixotrophic, heterotrophic, and phototrophic cultivation regimes. The Chlorella cultures were cultivated in wastewater as a source of nutrients that contained a high concentration of ammonium. In mixotrophic cultivation trials, the results showed that the elevated contents of carbohydrates in the soluble microbial product and proteins in extracellular polymeric substances probably initiated membrane fouling. In this case, the highest protein content was also found in extracellular polymeric substances due to the high nitrogen removal rate. Consequently, transmembrane pressure significantly increased compared to the phototrophic and heterotrophic regimes. The data indicated that cake resistance was the main cause of fouling in all cultivations. Higher protein content in the cake layer made the membrane surface more hydrophobic, while carbohydrates had the opposite effect. Compared to a mixotrophic culture, a phototrophic culture had a larger cell size and higher hydrophobicity, leading to less membrane fouling. Based on our previous data, the highest ammonia removal rate was reached in the mixotrophic cultures; nevertheless, membrane fouling appeared to be the fundamental problem.

• Klíčová slova
• cultivation, fouling, membrane bioreactor, microalgae, mixotrophy,
• MeSH
• amoniové sloučeniny * metabolismus   MeSH
• bioreaktory * MeSH
• bioznečištění MeSH
• Chlorella růst a vývoj   metabolismus   MeSH
• fototrofní procesy MeSH
• heterotrofní procesy MeSH
• membrány umělé * MeSH
• mikrořasy * metabolismus   růst a vývoj   MeSH
• odpad tekutý - odstraňování metody   MeSH
• odpadní voda * chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• amoniové sloučeniny * MeSH
• membrány umělé * MeSH
• odpadní voda * MeSH

Microalgae accumulate bioavailable selenium-containing amino acids (Se-AAs), and these are useful as a food supplement. While this accumulation has been studied in phototrophic algal cultures, little data exists for heterotrophic cultures. We have determined the Se-AAs content, selenium/sulfur (Se/S) substitution rates, and overall Se accumulation balance in photo- and heterotrophic Chlorella cultures. Laboratory trials revealed that heterotrophic cultures tolerate Se doses ∼8-fold higher compared to phototrophic cultures, resulting in a ∼2-3-fold higher Se-AAs content. In large-scale experiments, both cultivation regimes provided comparable Se-AAs content. Outdoor phototrophic cultures accumulated up to 400 μg g-1 of total Se-AAs and exhibited a high level of Se/S substitution (5-10%) with 30-60% organic/total Se embedded in the biomass. A slightly higher content of Se-AAs and ratio of Se/S substitution was obtained for a heterotrophic culture in pilot-scale fermentors. The data presented here shows that heterotrophic Chlorella cultures provide an alternative for Se-enriched biomass production and provides information on Se-AAs content and speciation in different cultivation regimes.

• Klíčová slova
• Chlorella, heterotrophic cultivation, methylselenocysteine, microalgae, phototrophic cultivation, selenium, selenocysteine, selenomethionine,
• MeSH
• aminokyseliny analýza   metabolismus   MeSH
• biomasa MeSH
• Chlorella klasifikace   růst a vývoj   metabolismus   účinky záření   MeSH
• fototrofní procesy MeSH
• heterotrofní procesy MeSH
• mikrořasy chemie   růst a vývoj   metabolismus   účinky záření   MeSH
• selen analýza   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• aminokyseliny MeSH
• selen MeSH

BACKGROUND, AIMS AND SCOPE: Microcystins (MCs) are a family of natural toxins produced by cyanobacteria (blue-green algae). As a result of eutrophication, massive cyanobacterial blooms occur more frequently and MCs represent important contaminants of freshwater ecosystems. Bacterial biodegradation is considered a main mechanism for MC breakdown in environmental conditions. While existing studies were mostly focused on MC biodegradation by planktonic bacteria, our experiments examined the fate and kinetics of MC degradation in river-originated phototrophic biofilms and investigated factors influencing the rate of MC removal. METHODS: The fate of dissolved MCs was studied in laboratory microcosms with different composition (containing water only, water with phytoplankton and/or phototrophic biofilms). Biofilms originated from river ecosystem were pre-incubated under various conditions (with/without presence of cyanobacterial biomass or model organic substrates: glucose and protein--casein). Changes in MC concentration (0-14 days) in water columns were measured by HPLC-DAD after external additions of purified MCs (160 microg L(-1), MC-LR and MC-YR), and halftimes (t1/2) of MC removal were estimated. RESULTS AND DISCUSSION: The slow degradation of MC was revealed in tap water (t1/2 approximately 14 days) and river water without cyanobacteria (t1/2 approximately 8 days). Enhanced removal occurred in the presence of natural planktonic cyanobacteria (t1/2 approximately 44 h), most probably due to microorganisms associated with the biomass of cyanobacterial bloom. More rapid MC elimination occurred in the variants containing phototrophic biofilms, and was particularly pronounced at those biofilms pre-cultivated in the presence of cyanobacterial blooms (t1/2 approximately 20 h). Much slower removal was observed in the variants simulating possible substrate-dependent induction of microorganism metabolism (biofilms pre-incubated with glucose: t1/2 approximately 35 h, and casein: t1/2 approximately 80 h). After termination of experiments, total amounts of MCs accumulated in the biofilms were below 5% of the initial toxin level revealing significant biodegradation processes. CONCLUSION: The microcosm studies contributed to understanding of the environmental fate of MCs and revealed a rapid biodegradation by phototrophic biofilms. The rate of MC elimination depends on history of biofilm community, previous contact with cyanobacteria seems to be a selective factor improving the biodegradation potential. RECOMMENDATION AND OUTLOOK: Our results experimentally showed a positive role of biofilms in MC elimination during water treatment processes such as bank filtration or slow sand filtration, and could eventually serve for further research of biofilm-based technological applications for MCs removal in small-scale drinking water treatment facilities.

• MeSH
• bakteriální toxiny izolace a purifikace   metabolismus   MeSH
• biodegradace účinky léků   MeSH
• biofilmy * MeSH
• chemické látky znečišťující vodu izolace a purifikace   metabolismus   MeSH
• Chlorophyta metabolismus   MeSH
• čištění vody metody   MeSH
• cyklické peptidy izolace a purifikace   metabolismus   MeSH
• glukosa farmakologie   MeSH
• kaseiny farmakologie   MeSH
• mikrocystiny MeSH
• řeky MeSH
• rozsivky metabolismus   MeSH
• sinice metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální toxiny MeSH
• chemické látky znečišťující vodu MeSH
• cyklické peptidy MeSH
• glukosa MeSH
• kaseiny MeSH
• microcystin MeSH Prohlížeč
• mikrocystiny MeSH

Phototrophic microorganisms are promising resources for green biotechnology. Compared to heterotrophic microorganisms, however, the cellular economy of phototrophic growth is still insufficiently understood. We provide a quantitative analysis of light-limited, light-saturated, and light-inhibited growth of the cyanobacterium Synechocystis sp. PCC 6803 using a reproducible cultivation setup. We report key physiological parameters, including growth rate, cell size, and photosynthetic activity over a wide range of light intensities. Intracellular proteins were quantified to monitor proteome allocation as a function of growth rate. Among other physiological acclimations, we identify an upregulation of the translational machinery and downregulation of light harvesting components with increasing light intensity and growth rate. The resulting growth laws are discussed in the context of a coarse-grained model of phototrophic growth and available data obtained by a comprehensive literature search. Our insights into quantitative aspects of cyanobacterial acclimations to different growth rates have implications to understand and optimize photosynthetic productivity.

• Klíčová slova
• computational biology, growth model, infectious disease, light limitation, microbiology, photoinhibition, phototrophic growth laws, proteome allocation, resource allocation, systems biology,
• MeSH
• biotechnologie MeSH
• fotosyntéza genetika   MeSH
• fototrofní procesy genetika   MeSH
• proteom genetika   MeSH
• sinice genetika   růst a vývoj   metabolismus   MeSH
• světlo MeSH
• Synechocystis genetika   růst a vývoj   MeSH
• velikost buňky MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteom MeSH

Rhodopsin photosystems convert light energy into electrochemical gradients used by the cell to produce ATP, or for other energy-demanding processes. While these photosystems are widespread in the ocean and have been identified in diverse microbial taxonomic groups, their physiological role in vivo has only been studied in few marine bacterial strains. Recent metagenomic studies revealed the presence of rhodopsin genes in the understudied Verrucomicrobiota phylum, yet their distribution within different Verrucomicrobiota lineages, their diversity, and function remain unknown. In this study, we show that more than 7% of Verrucomicrobiota genomes (n = 2916) harbor rhodopsins of different types. Furthermore, we describe the first two cultivated rhodopsin-containing strains, one harboring a proteorhodopsin gene and the other a xanthorhodopsin gene, allowing us to characterize their physiology under laboratory-controlled conditions. The strains were isolated in a previous study from the Eastern Mediterranean Sea and read mapping of 16S rRNA gene amplicons showed the highest abundances of these strains at the deep chlorophyll maximum (source of their inoculum) in winter and spring, with a substantial decrease in summer. Genomic analysis of the isolates suggests that motility and degradation of organic material, both energy demanding functions, may be supported by rhodopsin phototrophy in Verrucomicrobiota. Under culture conditions, we show that rhodopsin phototrophy occurs under carbon starvation, with light-mediated energy generation supporting sugar transport into the cells. Overall, this study suggests that photoheterotrophic Verrucomicrobiota may occupy an ecological niche where energy harvested from light enables bacterial motility toward organic matter and supports nutrient uptake.

• MeSH
• Bacteria * genetika   MeSH
• biologický transport MeSH
• fototrofní procesy MeSH
• fylogeneze MeSH
• rhodopsiny mikrobiální genetika   metabolismus   MeSH
• RNA ribozomální 16S genetika   metabolismus   MeSH
• rodopsin * genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• rhodopsiny mikrobiální MeSH
• RNA ribozomální 16S MeSH
• rodopsin * MeSH

Microalgae are mostly phototrophic microorganisms present worldwide, showcasing great adaptability to their environment. They are known for producing essential metabolites such as carotenoids, chlorophylls, sterols, lipids, and many more. This study discusses the possibility of the mixotrophic abilities of microalgae in the presence of food waste oils. The utilization of food waste materials is becoming more popular as a research subject as its production grows every year, increasing the environmental burden. In this work, waste frying oil and coffee oil were tested for the first time as a nutrition source for microalgae cultivation. Waste frying oil is produced in large amounts all over the world and its simple purification is one of its greatest advantages as it only needs to be filtered from leftover food pieces. Coffee oil is extracted from waste spent coffee grounds as a by-product. The waste frying oil and coffee oil were added to the basic algal media as an alternative source of carbon. As a pilot study for further experimentation, the effect of oil in the medium, algal adaptability, and capability to survive were tested within these experiments. The growth and production characteristics of four algae and cyanobacteria strains were tested, of which the strain Desmodesmus armatus achieved exceptional results of chlorophyll (8.171 ± 0.475 mg/g) and ubiquinone (5.708 ± 0.138 mg/g) production. The strain Chlamydomonas reindhartii showed exceptional lipid accumulation in the range of 30-46% in most of the samples.

• Klíčová slova
• coffee oil, cyanobacteria, lipids, metabolites, microalgae, waste frying oil,
• Publikační typ
• časopisecké články MeSH

In most oxygenic phototrophs, including cyanobacteria, two independent enzymes catalyze the reduction of protochlorophyllide to chlorophyllide, which is the penultimate step in chlorophyll (Chl) biosynthesis. One is light-dependent NADPH:protochlorophyllide oxidoreductase (LPOR) and the second type is dark-operative protochlorophyllide oxidoreductase (DPOR). To clarify the roles of both enzymes, we assessed synthesis and accumulation of Chl-binding proteins in mutants of cyanobacterium Synechocystis PCC 6803 that either completely lack LPOR or possess low levels of the active enzyme due to its ectopic regulatable expression. The LPOR-less mutant grew photoautotrophically in moderate light and contained a maximum of 20 % of the wild-type (WT) Chl level. Both Photosystem II (PSII) and Photosystem I (PSI) were reduced to the same degree. Accumulation of PSII was mostly limited by the synthesis of antennae CP43 and especially CP47 as indicated by the accumulation of reaction center assembly complexes. The phenotype of the LPOR-less mutant was comparable to the strain lacking DPOR that also contained <25 % of the wild-type level of PSII and PSI when cultivated under light-activated heterotrophic growth conditions. However, in the latter case, we detected no reaction center assembly complexes, indicating that synthesis was almost completely inhibited for all Chl-proteins, including the D1 and D2 proteins.

• MeSH
• 2D gelová elektroforéza MeSH
• aktivace enzymů MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• buněčná membrána enzymologie   metabolismus   MeSH
• chlorofyl biosyntéza   genetika   MeSH
• elektroforéza v polyakrylamidovém gelu MeSH
• fenotyp MeSH
• fotosystém I (proteinový komplex) genetika   metabolismus   MeSH
• fotosystém II (proteinový komplex) genetika   metabolismus   MeSH
• fototrofní procesy MeSH
• oxidoreduktasy působící na CH-CH vazby genetika   metabolismus   MeSH
• protochlorofylid metabolismus   MeSH
• regulace genové exprese enzymů * MeSH
• regulace genové exprese u rostlin MeSH
• světlo MeSH
• Synechocystis enzymologie   genetika   metabolismus   účinky záření   MeSH
• transformace genetická MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• chlorofyl MeSH
• fotosystém I (proteinový komplex) MeSH
• fotosystém II (proteinový komplex) MeSH
• oxidoreduktasy působící na CH-CH vazby MeSH
• protochlorofylid MeSH
• protochlorophyllide reductase MeSH Prohlížeč

Poly-β-hydroxybutyrate (PHB) is a potential source of biodegradable plastics that are environmentally friendly due to their complete degradation to water and carbon dioxide. This study aimed to investigate PHB production in the cyanobacterium Synechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5 g L-1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7 ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturing Synechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB by Synechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics. KEY POINTS: • High PHB production by cyanobacteria in outdoor raceway pond • Urban wastewater used as a sole source of nutrients for phototrophic growth • Potential for cost-effective and sustainable production of biodegradable plastics.

• Klíčová slova
• Biodegradable plastics, Polyhydroxybutyrate, Raceway pond cultivation, Synechocystis, Urban wastewater,
• MeSH
• biologicky odbouratelné plasty * MeSH
• hydroxybutyráty MeSH
• odpadní voda MeSH
• oxid uhličitý MeSH
• polyestery MeSH
• rybníky MeSH
• Synechocystis * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologicky odbouratelné plasty * MeSH
• hydroxybutyráty MeSH
• odpadní voda MeSH
• oxid uhličitý MeSH
• poly-beta-hydroxybutyrate MeSH Prohlížeč
• polyestery MeSH

The cyanobacterial genus Synechocystis is of particular interest to science and industry because of its efficient phototrophic metabolism, its accumulation of the polymer poly(3-hydroxybutyrate) (PHB) and its ability to withstand or adapt to adverse growing conditions. One such condition is the increased salinity that can be caused by recycled or brackish water used in cultivation. While overall reduced growth is expected in response to salt stress, other metabolic responses relevant to the efficiency of phototrophic production of biomass or PHB (or both) have been experimentally observed in three Synechocystis strains at stepwise increasing salt concentrations. In response to recent reports on metabolic strategies to increase stress tolerance of heterotrophic and phototrophic bacteria, we focused particularly on the stress-induced response of Synechocystis strains in terms of PHB, glycogen and photoactive pigment dynamics. Of the three strains studied, the strain Synechocystis cf. salina CCALA192 proved to be the most tolerant to salt stress. In addition, this strain showed the highest PHB accumulation. All the three strains accumulated more PHB with increasing salinity, to the point where their photosystems were strongly inhibited and they could no longer produce enough energy to synthesize more PHB.

• Klíčová slova
• Glycogen, Pigments, Poly(3-hydroxybutyrate), Salt stress, Synechocystis sp.,
• Publikační typ
• časopisecké články MeSH

The synthesis of renewable bioproducts using photosynthetic microorganisms holds great promise. Sustainable industrial applications, however, are still scarce and the true limits of phototrophic production remain unknown. One of the limitations of further progress is our insufficient understanding of the quantitative changes in photoautotrophic metabolism that occur during growth in dynamic environments. We argue that a proper evaluation of the intra- and extracellular factors that limit phototrophic production requires the use of highly-controlled cultivation in photobioreactors, coupled to real-time analysis of production parameters and their evaluation by predictive computational models. In this addendum, we discuss the importance and challenges of systems biology approaches for the optimization of renewable biofuels production. As a case study, we present the utilization of a state-of-the-art experimental setup together with a stoichiometric computational model of cyanobacterial metabolism for quantitative evaluation of ethylene production by a recombinant cyanobacterium Synechocystis sp. PCC 6803.

• Klíčová slova
• MIMS, biofuels, biotechnology, cyanobacteria, ethylene, genome-scale models (GSM), photobioreactors, systems biology,
• MeSH
• biopaliva MeSH
• ethyleny biosyntéza   MeSH
• fotosyntéza MeSH
• metabolické inženýrství metody   MeSH
• počítačová simulace MeSH
• Synechocystis metabolismus   MeSH
• systémová biologie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biopaliva MeSH
• ethylene MeSH Prohlížeč
• ethyleny MeSH