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: 30 September 2024 | Viewed by 3685

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
Special Issues, Collections and Topics in MDPI journals

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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

Manuscript Submission Information

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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

Published Papers (3 papers)

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Research

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
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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
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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 1 | Viewed by 1307
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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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Isolation and cultivation of salt pans microalgae and cyanobacteria

Currently, there is lack of universally recognized protocols for isolating microalgae and cyanobacteria from salt pans, salterns, and analogous natural habitats. The establishment of axenic laboratory cultures is essential for identifying novel species thriving in high-salinity environments and exploring the synthesis of high-value metabolites by these microorganisms ex situ. Our ongoing research is primarily centered on photosynthetic microorganisms with substantial biotechnological promise, particularly in the realm of skincare applications. By combining data from existing literature with our own empirical findings, we suggest a standardized pipeline for the laboratory cultivation of microalgae and cyanobacteria originating from aqueous environments characterized by elevated salt concentrations, such as solar salterns.

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