Caribbean populations of the elkhorn coralAcropora palmatahave declined due to environmental stress, bleaching, and disease. Potential sources of coral mortality include invasive microbes that become ...trapped in the surface mucus and thrive under conditions of increased coral stress. In this study, mucus from healthyA. palmatainhibited growth of potentially invasive microbes by up to 10-fold. Among cultured bacteria from the mucus ofA. palmata, 20% displayed antibiotic activity against one or more tester strains, including the pathogen implicated in white pox disease. A novel mucus-mediated selection for coral symbionts revealed a discrete subset of bacteria and selected for isolates that produce antibiotics. This result suggests that coral mucus plays a role in the structuring of beneficial coral-associated microbial communities and implies a microbial contribution to the antibacterial activity described for coral mucus. Interestingly, antibiotic activity was lost when mucus was collected during a summer bleaching event. Isolates from apparently healthyA. palmatatissue during this event lacked antibiotic-producing bacteria and were dominated by members of the genusVibrio, including species implicated in temperature-dependent bleaching of corals worldwide. This indicates an environmental shift from beneficial bacteria, and variability in the protective qualities of coral mucus, which may lead to an overgrowth of opportunistic microbes when temperatures increase. Finally, coral mucus inhibited antibiotic activity and pigment production in a potentially invasive bacterium, illustrating that coral mucus may inactivate mechanisms used for bacterial niche establishment.
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•Three isolates of marine-derived fungi Talaromyces albobiverticillius have been identified as red pigment producers.•The production of orange and red pigments was followed by ...spectrophotometry and colorimetry all over the growth in liquid medium.•Significant results on pigment and biomass yields were determined.•Monascus-like pigments were identified by HPLC-PDA-LC–MS analysis in the panel of molecules produced.•Color values in CIELAB system for the three strains productions are presented.
Filamentous fungi produce many chemical classes of metabolites bound to be used in various fields of industrial applications such as food, cosmetics, paper, textiles, medicine, biodegradation, waste remediation, etc. In this trend, scientists are actively looking for new fungal strains synthesizing original molecules with new potentialities. The present study is focused on pigment production from Talaromyces albobiverticillius strains, which were recently isolated from marine environments around Reunion Island, Indian Ocean. This study demonstrates their ability to produce a range of colored compounds exhibiting specific orange/red hues under submerged fermentation in potato dextrose broth (PDB), both seen in the mycelia and liquid medium. For the most promising strain, maximum levels of extracellular orange-yellow pigments (22.39 UA at 470 nm) and red pigments (18.67 UA at 500 nm) were attained in 8 days with an initial pH of 5.0 at 24 °C. Among the 12 components of the color hue, two compounds were produced in larger amounts in comparison with the total pigmented extracts (compound 4, red colored, presents two absorbance maxima: λ1 = 422 nm, λ2 = 511 nm; and compound 8, orange colored, absorbs at λ1 = 469.8 nm as a maximum). The color characteristics of the extracellular fungal products measured by L*a*b* quantitative colorimetric system indicated variations between the three strains productions, as well as between the intracellular and extracellular colored molecules produced. An evolution of the colored compounds synthesized is thus highlighted, in relation with the growth phases of the fungus. These results provide information about the future directions towards large-scale cultivation of these fungi, which might support the industrial applications of the red pigments.
FvatfA
from the maize pathogen
Fusarium verticillioides
putatively encodes the
Aspergillus nidulans
AtfA and
Schizasaccharomyces pombe
Atf1 orthologous bZIP-type transcription factor, FvAtfA. In this ...study, a
ΔFvatfA
deletion mutant was constructed and then genetically complemented with the fully functional
FvatfA
gene. Comparing phenotypic features of the wild-type parental, the deletion mutant and the restored strains shed light on the versatile regulatory functions played by FvAtfA in (i) the maintenance of vegetative growth on Czapek-Dox and Potato Dextrose agars and invasive growth on unwounded tomato fruits, (ii) the preservation of conidiospore yield and size, (iii) the orchestration of oxidative (H
2
O
2
, menadione sodium bisulphite) and cell wall integrity (Congo Red) stress defences and (iv) the regulation of mycotoxin (fumonisins) and pigment (bikaverin, carotenoid) productions. Expression of selected biosynthetic genes both in the fumonisin (
fum1
,
fum8
) and the carotenoid (
carRA
,
carB
) pathways were down-regulated in the
ΔFvatfA
strain resulting in defected fumonisin production and considerably decreased carotenoid yields. The expression of
bik1
, encoding the polyketide synthase needed in bikaverin biosynthesis, was not up-regulated by the deletion of
FvatfA
meanwhile the
ΔFvatfA
strain produced approximately ten times more bikaverin than the wild-type or the genetically complemented strains. The abolishment of fumonisin production of the
ΔFvatfA
strain may lead to the development of new-type, biology-based mycotoxin control strategies. The novel information gained on the regulation of pigment production by this fungus can be interesting for experts working on new,
Fusarium
-based biomass and pigment production technologies.
Key points
• FvatfA regulates vegetative and invasive growths of F. verticillioides.
• FvatfA also orchestrates oxidative and cell wall integrity stress defenses.
• The ΔFvatfA mutant was deficient in fumonisin production.
• FvatfA deletion resulted in decreased carotenoid and increased bikaverin yields.
Pseudomonas aeruginosa is an opportunistic, Gram-negative bacterium and is one of the most commercially and biotechnologically valuable microorganisms. Strains of P. aeruginosa secrete a variety of ...redox-active phenazine compounds, the most well studied being pyocyanin. Pyocyanin is responsible for the blue-green colour characteristic of Pseudomonas spp. It is considered both as a virulence factor and a quorum sensing signalling molecule for P. aeruginosa. Pyocyanin is an electrochemically active metabolite, involved in a variety of significant biological activities including gene expression, maintaining fitness of bacterial cells and biofilm formation. It is also recognised as an electron shuttle for bacterial respiration and as an antibacterial and antifungal agent. This review summarises recent advances of pyocyanin production from P. aeruginosa with special attention to antagonistic property and bio-control activity. The review also covers the challenges and new insights into pyocyanin from P. aeruginosa.
This study describes the response of Arthrospira platensis to a variety of temperature conditions as reflected in variations of photosynthetic parameters, pigmentation, and biomass productivity in ...indoor photobioreactor (PBR) cultivations. These experiments are designed to better understand the impact of temperature, seasonal variations, and acclimation effects on outdoor biomass production. The irradiance level and temperature range (20–39°C) are chosen to enable modeling of semi‐continuous operation of large‐scale outdoor PBR deployments. Overall, the cultivations are quite stable with some pigment‐related instabilities after prolonged high‐temperature exposure. Changes in productivity with temperature, as reflected in measured photosynthetic parameters, are immediate and mainly attributable to the temperature dependence of the photosaturation parameter, a secondary factor being variation in pigment content on a longer time scale corresponding to turnover of the culture population. Though pigment changes are not accompanied by significant changes in productivity, prolonged exposure at 35°C and above yields a clear degradation in performance. Productivities in a semi‐continuous operation are quantitatively reproduced with a productivity model incorporating photosynthetic parameters measured herein. This study confirms the importance of temperature for biomass and pigment production in Arthrospira cultivations and provides a basis for risk assessments related to temperature mitigation for large‐scale outdoor cultivations.
In this paper the authors examine temperature effects in laboratory cultivations designed to model semi‐continuous production of Arthrospira platensis in large outdoor arrays of 6 × 0.9 × 0.02 meter (100 L) photobioreactors. The response of Arthrospira platensis to a variety of temperature conditions is reflected in variations of photosynthetic parameters, pigmentation, and biomass productivity. These experiments are designed to better understand the impact of temperature, seasonal variations, and acclimation effects on outdoor biomass production. Coupled with photosynthetic and optical models, the results provide a high degree of predictability for scaling laboratory performance to large outdoor deployments.
The consumer sensitivity toward application of synthetic colors led to exploitation of food grade bio-colors from bacteria. Pseudomonas aeruginosa is an opportunistic, gram-negative bacteria that ...secrete a variety of redox-active phenazine pigmented compounds, which are significant for a variety of biological activities. Pyocyanin, a water soluble blue green phenazine pigment producing P. aeruginosa was screened from aquatic habitats of isolation of Pakistan, identified and compared by 16S rRNA gene sequence for genetic variability. The similarity of selected strain was found 99% with P. aeruginoas DSM 50071 with accession no CP012001.1 in gene bank. Pyocyanin from the identified strain was extracted after 72 h of incubation by chloroform and purified with 0.1 N HCl and 1 N NaOH. Protective effects of the extracted pyocyanin as food colorant were evaluated against multiple biological activities. Pyocyanin showed anti-oxidant potential with 58.0% inhibition of 2,2-diphenyl-1-picrylhydrazyl radical compare to Trolox (68.5%) and BHT (88.1%) and 52.5% free radical scavenging of 2,2′-azinobis-(3-ethylbenzothiazoline-6- sulfonic acid) in comparison to Trolox (67.4%) and BHA (86.0%) at 50 μg/ml concentration. The anti-microbial efficacy of pyocyanin was assessed against food borne pathogenic bacteria and fungi by agar well diffusion method. Pyocyanin exhibited anti-bacterial activity with distinct zone of inhibition against B. spizizenii (16 mm), S. aureus (19 mm), E. aerogenes (14 mm), S. enterica (13 mm), P. aeruginosa (13 mm) and E. coli (12 mm) at 50 μg/ml concentration. Pyocyanin was more susceptible at the same concentration against fungal strains with zone of inhibition measuring 21 mm, 18 mm and 17 mm for F. oxysporum, A. niger and A. fumigatus respectively. Anti-biofilm profile of pyocyanin exhibited significant inhibition of the biofilm formation against biofilm forming bacteria B. cereus (81%), S. aureus (80%), P. aeruginonsa (78%) and K. pneumonia (76%) when assessed by crystal violet assay at 50 μg/ml concentration. Similar effects at the same concentration were observed in disruption of pre-formed biofilm against B. cereus (77%), S. aureus (76%), P. aeruginonsa (74%) and K. pneumonia (73%). The presented remarkable biological activities of pyocyanin against food borne pathogens augment the utilization of chromogenic microbes existing in Pakistani aquatic resource as an alternative potent source for efficient production of natural pigment and their application as natural color and bio-preservative in food industries.
Scandium (Sc), declared a critical raw material in the European Union (EU), could face further supply issues as the EU depends almost entirely on imports from China, Russia, and Ukraine. In this ...study, a tandem nanofiltration-solvent extraction procedure for Sc recovery from titania (TiO2) acid waste was piloted and then augmented by antisolvent crystallization. The new process, comprising advanced filtration (hydroxide precipitation, micro-, ultra-, and nanofiltration), solvent extraction, and antisolvent crystallization, was assessed in relation to material and energy inputs and benchmarked on ScF3 production. From ∼1 m3 of European acid waste containing traces of Sc (81 mg L–1), ∼13 g of Sc (43% yield, nine stages) was recovered as (NH4)3ScF6 with a purity of approximately 95%, demonstrating the technical feasibility of the approach. The production costs per kilogram of ScF3 were lower than reported market prices, which underscores a competitive process at scale. Although a few technical bottlenecks (e.g., S/L separation and electricity consumption) need to be overcome, combining advanced filtration with solvent extraction and antisolvent crystallization promises a future supply of this critical raw material from European secondary sources.
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