Photosynthetic Microorganisms: Culturing and Biotechnological Applications

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Microbial Biotechnology".

Deadline for manuscript submissions: closed (30 September 2024) | Viewed by 8326

Special Issue Editors


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Guest Editor
Research Institute on Terrestrial Ecosystems, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, FI, Italy
Interests: microalgae; photosynthesis; photobioreactor; fluorescence; immobilisation; photofermentation
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Guest Editor
Institute of BioEconomy, IBE, National Research Council, Rome, Italy
Interests: carotenoids; polyphenols; antioxidants; microalgae; plants; photosynthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microalgae, cyanobacteria, and purple bacteria are photosynthetic microorganisms used in many fields, such as agriculture, aquaculture, wastewater treatment, bioremediation, biomaterials production, and renewable energy generation. They are fast-growing microorganisms that achieve high biomass productivity, mainly use sunlight as the energy source, and have minimal nutrient requirements. The commercialization of photosynthetic microorganisms as feedstock for natural products and biofuels requires the use of efficient cultivation systems. These microorganisms can be grown by a variety of methods, including open and closed systems. Closed photobioreactors are the most popular systems because they allow optimal growth and reduce the danger of contamination.

This Special Issue will focus on the growth and biotechnological applications of photosynthetic microorganisms. You are invited to submit contributions (original articles, as well as critical reviews) concerning photosynthetic microorganism growth systems for the production of biomass, biomaterials, and bioenergy.

Dr. Eleftherios Touloupakis
Dr. Cecilia Faraloni
Guest Editors

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Keywords

  • bioenergy
  • environmental sustainability
  • biohydrogen production
  • renewable energy
  • bioplastic production
  • cell culture
  • photofermentation
  • immobilization
  • bioremediation
  • biotechnology
  • environment
  • microalgae
  • immobilization
  • photobioreactors
  • culture system
  • biofuels
  • cyanobacteria
  • purple bacteria
  • biomass productivity
  • light conversion efficiency

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Published Papers (5 papers)

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Research

12 pages, 1669 KiB  
Article
Dark Anaerobic Conditions Induce a Fast Induction of the Xanthophyll Cycle in Chlamydomonas reinhardtii When Exposed to High Light
by Cecilia Faraloni, Eleftherios Touloupakis and Giuseppe Torzillo
Microorganisms 2024, 12(11), 2264; https://doi.org/10.3390/microorganisms12112264 - 8 Nov 2024
Viewed by 456
Abstract
Background: Dark anaerobiosis promotes the acidification of the thylakoid lumen and a reduction in the plastoquinone (PQ) pool. The relationship between the reduction in the PQ pool in the dark and the induction of the xanthophyll cycle under high light stress was investigated [...] Read more.
Background: Dark anaerobiosis promotes the acidification of the thylakoid lumen and a reduction in the plastoquinone (PQ) pool. The relationship between the reduction in the PQ pool in the dark and the induction of the xanthophyll cycle under high light stress was investigated in Chlamydomonas reinhardtii. Methods: To achieve a comprehensive oxidative/reductive (aerobic/anaerobic conditions) state of the PQ pool, cultures were bubbled with air or nitrogen for 4 h. To induce the xanthophyll cycle, the cultures were then irradiated with 1200 µmolphotons m−2 s−1 white light for 1 h. Results: The anaerobic cultures exhibited a stronger induction of the xanthophyll cycle with a 3.4-fold higher de-epoxidation state than the aerobic cultures. Chlorophyll fluorescence measurements showed that this response was influenced by the previous redox state of the PQ pool, and that dark anaerobiosis triggers physiological responses, such as exposure to high light. Thus, the photosynthetic apparatus in anaerobic cultures was already alerted, at the moment of high light exposure, to give an appropriate response to the stress with a stronger induction of the xanthophyll cycle than in aerobic cultures. Conclusions: Our results provide new information on the importance of the redox signaling pathway and highlight the importance of the reductive conditions of the PQ pool in regulating the physiological responses of photosynthetic organisms to stress. Full article
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19 pages, 2578 KiB  
Article
Symbiodiniaceae and Ruegeria sp. Co-Cultivation to Enhance Nutrient Exchanges in Coral Holobiont
by Yawen Liu, Huan Wu, Yang Shu, Yanying Hua and Pengcheng Fu
Microorganisms 2024, 12(6), 1217; https://doi.org/10.3390/microorganisms12061217 - 17 Jun 2024
Viewed by 1345
Abstract
The symbiotic relationship between corals and their associated microorganisms is crucial for the health of coral reef eco-environmental systems. Recently, there has been a growing interest in unraveling how the manipulation of symbiont nutrient cycling affects the stress tolerance in the holobiont of [...] Read more.
The symbiotic relationship between corals and their associated microorganisms is crucial for the health of coral reef eco-environmental systems. Recently, there has been a growing interest in unraveling how the manipulation of symbiont nutrient cycling affects the stress tolerance in the holobiont of coral reefs. However, most studies have primarily focused on coral–Symbiodiniaceae–bacterial interactions as a whole, neglecting the interactions between Symbiodiniaceae and bacteria, which remain largely unexplored. In this study, we proposed a hypothesis that there exists an inner symbiotic loop of Symbiodiniaceae and bacteria within the coral symbiotic loop. We conducted experiments to demonstrate how metabolic exchanges between Symbiodiniaceae and bacteria facilitate the nutritional supply necessary for cellular growth. It was seen that the beneficial bacterium, Ruegeria sp., supplied a nitrogen source to the Symbiodiniaceae strain Durusdinium sp., allowing this dinoflagellate to thrive in a nitrogen-free medium. The Ruegeria sp.–Durusdinium sp. interaction was confirmed through 15N-stable isotope probing–single cell Raman spectroscopy, in which 15N infiltrated into the bacterial cells for intracellular metabolism, and eventually the labeled nitrogen source was traced within the macromolecules of Symbiodiniaceae cells. The investigation into Symbiodiniaceae loop interactions validates our hypothesis and contributes to a comprehensive understanding of the intricate coral holobiont. These findings have the potential to enhance the health of coral reefs in the face of global climate change. Full article
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22 pages, 5331 KiB  
Article
Comparative Analysis of Laboratory-Based and Spectroscopic Methods Used to Estimate the Algal Density of Chlorella vulgaris
by György Fekete, András Sebők, Szandra Klátyik, Zsolt István Varga, János Grósz, Imre Czinkota, András Székács and László Aleksza
Microorganisms 2024, 12(6), 1050; https://doi.org/10.3390/microorganisms12061050 - 23 May 2024
Viewed by 1437
Abstract
Chlorella vulgaris is of great importance in numerous exploratory or industrial applications (e.g., medicals, food, and feed additives). Rapid quantification of algal biomass is crucial in photobioreactors for the optimization of nutrient management and the estimation of production. The main goal of this [...] Read more.
Chlorella vulgaris is of great importance in numerous exploratory or industrial applications (e.g., medicals, food, and feed additives). Rapid quantification of algal biomass is crucial in photobioreactors for the optimization of nutrient management and the estimation of production. The main goal of this study is to provide a simple, rapid, and not-resource-intensive estimation method for determining the algal density of C. vulgaris according to the measured parameters using UV–Vis spectrophotometry. Comparative assessment measurements were conducted with seven different methods (e.g., filtration, evaporation, chlorophyll a extraction, and detection of optical density and fluorescence) to determine algal biomass. By analyzing the entire spectra of diluted algae samples, optimal wavelengths were determined through a stepwise series of linear regression analyses by a novel correlation scanning method, facilitating accurate parameter estimation. Nonlinear formulas for spectrometry-based estimation processes were derived for each parameter. As a result, a general formula for biomass concentration estimation was developed, with recommendations for suitable measuring devices based on algae concentration levels. New values for magnesium content and the average single-cell weight of C. vulgaris were established, in addition to the development of a rapid, semiautomated cell counting method, improving efficiency and accuracy in algae quantification for cultivation and biotechnology applications. Full article
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19 pages, 3257 KiB  
Article
Achieving Discharge Limits in Single-Stage Domestic Wastewater Treatment by Combining Urban Waste Sources and Phototrophic Mixed Cultures
by Sandra Chacon-Aparicio, John Alexander Villamil, Fernando Martinez, Juan Antonio Melero, Raul Molina and Daniel Puyol
Microorganisms 2023, 11(9), 2324; https://doi.org/10.3390/microorganisms11092324 - 15 Sep 2023
Viewed by 1502
Abstract
This work shows the potential of a new way of co-treatment of domestic wastewater (DWW) and a liquid stream coming from the thermal hydrolysis of the organic fraction of municipal solid waste (OFMSW) mediated by a mixed culture of purple phototrophic bacteria (PPB) [...] Read more.
This work shows the potential of a new way of co-treatment of domestic wastewater (DWW) and a liquid stream coming from the thermal hydrolysis of the organic fraction of municipal solid waste (OFMSW) mediated by a mixed culture of purple phototrophic bacteria (PPB) capable of assimilating carbon and nutrients from the medium. The biological system is an open single-step process operated under microaerophilic conditions at an oxidative reduction potential (ORP) < 0 mV with a photoperiod of 12/24 h and fed during the light stage only so the results can be extrapolated to outdoor open pond operations by monitoring the ORP. The effluent mostly complies with the discharge values of the Spanish legislation in COD and p-values (<125 mg/L; <2 mg/L), respectively, and punctually on values in N (<15 mg/L). Applying an HRT of 3 d and a ratio of 100:7 (COD:N), the presence of PPB in the mixed culture surpassed 50% of 16S rRNA gene copies, removing 78% of COD, 53% of N, and 66% of P. Furthermore, by increasing the HRT to 5 d, removal efficiencies of 83% of COD, 65% of N, and 91% of P were achieved. In addition, the reactors were further operated in a membrane bioreactor, thus separating the HRT from the SRT to increase the specific loading rate. Very satisfactory removal efficiencies were achieved by applying an HRT and SRT of 2.3 and 3 d, respectively: 84% of COD, 49% of N, and 93% of P despite the low presence of PPB due to more oxidative conditions, which step-by-step re-colonized the mixed culture until reaching >20% of 16S rRNA gene copies after 49 d of operation. These results open the door to scaling up the process in open photobioreactors capable of treating urban wastewater and municipal solid waste in a single stage and under microaerophilic conditions by controlling the ORP of the system. Full article
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14 pages, 4390 KiB  
Article
Blue and Yellow Light Induce Changes in Biochemical Composition and Ultrastructure of Limnospira fusiformis (Cyanoprokaryota)
by Matilde Pelagatti, Giovanna Mori, Sara Falsini, Raffaello Ballini, Luigi Lazzara and Alessio Papini
Microorganisms 2023, 11(5), 1236; https://doi.org/10.3390/microorganisms11051236 - 8 May 2023
Cited by 2 | Viewed by 1668
Abstract
Limnospira fusiformis (also known as Spirulina) is a cyanobacterium that is widely cultivated due to its economic importance. It has specific pigments such as phycocyanin that allow it to grow at different light wavelengths compared to other cultivated algae. Our study investigated the [...] Read more.
Limnospira fusiformis (also known as Spirulina) is a cyanobacterium that is widely cultivated due to its economic importance. It has specific pigments such as phycocyanin that allow it to grow at different light wavelengths compared to other cultivated algae. Our study investigated the effect of yellow (590 nm) and blue (460 nm) light fields on various biochemical features, including the pigment concentration, protein content, dry weight, and cell ultrastructure of L. fusiformis. Our findings revealed that biomass growth was faster in yellow light compared to blue light, with a higher relative amount of proteins even after one day of exposure. However, after eight days, the relative protein content in yellow versus blue light was not statistically different. Furthermore, in yellow light, we observed a decrease in chlorophyll a, an increase in cyanophycin granules, and an increase in the amount of dilated thylakoids. On the other hand, in blue light, there was an increase in phycocyanin after one day, along with an increase in electron-dense bodies, which are attributable to carboxysomes. However, after eight days, the differences in pigment content compared to the control were not statistically significant. Our study showed that using specific wavelengths during the harvesting phase of spirulina growth can enhance phycocyanin content with blue light (after one day) and biomass, growth rates, and protein content with yellow light after six days. This highlights the biotechnological potential of this approach. Full article
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