New Insights into Microalgae Cultivation and Downstream Processes, Volume II

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Marine Science and Engineering".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 7542

Special Issue Editors


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Guest Editor
Faculty of Pharmacy, Federal University of Bahia, Salvador 40170-115, Brazil
Interests: bioprocess; microalgae; cultures; microorganism; Spirulina; Chlorella; photobioreactors

Special Issue Information

Dear Colleagues,

Microalgae and cyanobacteria represent a large taxonomic diversity, making them very attractive to produce valuable and diverse biomolecules (such as pigments, proteins, enzymes, biofuels, polyunsaturated fatty acids, and hydrocolloids). Research on microalgae has been abundantly published and patented in recent years, but the development and commercialization of these metabolites is still at its early stage, and only niche markets are currently available for microalgae products. Their low usage may be easily explained by the costs involved in microalgae production, linked to photoproduction, the harvest of microalgae in diluted media, the recycling of culture media, and the difficulty to refine this biomass. Much effort has been devoted by research groups and companies to improving these processes, actually limiting microalgae compounds’ applications to the field of high-value products. Some studies are focused on the increase in biomass and bioproducts productivities (new culture system designs, culture strategies, selection of strains, etc.), the use of wastewater to decrease medium costs, and downstream processes (harvesting, fractionation, biorefinery, etc.), in order to achieve a more sustainable and cost-effective production of biomass and bioproducts. The aim of this Special Issue is to provide recent reviews and original research articles highlighting the innovations and dynamism of research in the field of microalgae cultivation and downstream processes.

Prof. Dr. Céline Laroche
Dr. Kricelle Mosquera Deamici
Guest Editors

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Keywords

  • Microalgae
  • Photobioreactor
  • Culture systems
  • Downstream processes
  • Biorefinery
  • Bioproducts

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Published Papers (5 papers)

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Research

15 pages, 1509 KiB  
Article
The Influence of the Ultrasound Disintegration of Microalgal–Bacterial Granular Sludge on Anaerobic Digestion Efficiency
by Marcin Dębowski, Marta Kisielewska, Marcin Zieliński and Joanna Kazimierowicz
Appl. Sci. 2023, 13(13), 7387; https://0-doi-org.brum.beds.ac.uk/10.3390/app13137387 - 21 Jun 2023
Cited by 2 | Viewed by 707
Abstract
It has been proven that the biocenosis of microalgae and bacteria improves the chemical properties of biomass for its use in anaerobic digestion. However, this anaerobic digestion can be limited by the strong, compact, and complex structure of granulated biomass. Therefore, there is [...] Read more.
It has been proven that the biocenosis of microalgae and bacteria improves the chemical properties of biomass for its use in anaerobic digestion. However, this anaerobic digestion can be limited by the strong, compact, and complex structure of granulated biomass. Therefore, there is a need to search for an effective method for microalgal–bacterial granular sludge pretreatment, which has not been undertaken in previous scientific works. In this study, ultrasonic pretreatment was used to determine the effects of sonication on anaerobic digestion efficiency. Anaerobic digestion was performed in batch respirometric reactors. It was found that the ultrasonic pretreatment enhanced the biomass solubility; thus, the organic matter concentration increased more than six times compared to the variant without pretreatment. The study showed a positive effect of sonication on the kinetics of the anaerobic process and methane production. The highest methane yield was found in the variants in which the ultrasonication lasted from 150 s to 200 s, and this yield was from 534 ± 16 mL CH4/g VS to 561 ± 17 mL CH4/g VS. The data analysis confirmed strong correlations between the pretreatment time, the amount of biogas and methane production, and the gross energy gain. The highest net energy output and net energy gain were obtained for 150 s of sonication, and, respectively, were 4.21 ± 0.17 Wh/g VS and 1.19 ± 0.18 Wh/g VS. Full article
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25 pages, 11159 KiB  
Article
LED Illumination Modules Enable Automated Photoautotrophic Cultivation of Microalgae in Parallel Milliliter-Scale Stirred-Tank Bioreactors
by Philipp Benner, Finn Joshua Lüdtke, Nina Beyer, Nikolas von den Eichen, José Enrique Oropeza Vargas and Dirk Weuster-Botz
Appl. Sci. 2023, 13(8), 5064; https://0-doi-org.brum.beds.ac.uk/10.3390/app13085064 - 18 Apr 2023
Viewed by 1216
Abstract
Scalable lab-scale photobioreactors are needed for the exploration of new and improved photoautotrophic bioprocesses. Microbioreactor systems in which parallel bioreactors operate automatically are frequently employed to increase the speed of strain selection as well as the bioprocess-based exploration of heterotrophic fermentation processes. To [...] Read more.
Scalable lab-scale photobioreactors are needed for the exploration of new and improved photoautotrophic bioprocesses. Microbioreactor systems in which parallel bioreactors operate automatically are frequently employed to increase the speed of strain selection as well as the bioprocess-based exploration of heterotrophic fermentation processes. To enable the photoautotrophic operation of a commercially available parallel microbioreactor system with 48 stirred-tank bioreactors, LED illumination modules were designed to allow for individual light supply (400–700 nm) for each of the parallel bioreactors automated by a liquid handling station that performs both individual pH control and OD750 detection. The illumination modules enable dynamic variation of the incident light intensities of up to 1800 µmol m−2 s−1. Automated liquid level detection and volume control of each individual mL-scale gassed photobioreactor has to be established to compensate for evaporation because of the long process times of several days up to weeks. Photoautotrophic batch processes with Microchloropsis salina that employ either varying constant incident light intensities or day and night dynamics resulted in a standard deviation of OD750 of up to a maximum of 10%, with the exception of high-photoinhibiting incident light intensities. The established photoautotrophic microbioreactor system enables the automated investigation of microalgae processes in up to 48 parallel stirred photobioreactors and is thus a new tool that enables efficient characterization and development of photoautotrophic processes with microalgae. Full article
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19 pages, 2516 KiB  
Article
Identifying Key Environmental Indicators in the Assessment of the Proof-of-Concept in Pigment Production from the Marine Cyanobacterium Cyanobium sp.
by Fernando Pagels, Ana Arias, A. Catarina Guedes, António A. Vicente, Vitor Vasconcelos and Maria Teresa Moreira
Appl. Sci. 2022, 12(24), 12999; https://0-doi-org.brum.beds.ac.uk/10.3390/app122412999 - 18 Dec 2022
Cited by 1 | Viewed by 1534
Abstract
Cyanobacteria have long attracted market interest as a source of natural compounds such as pigments with proven bioactivity (carotenoid and phycobiliproteins). The cultivation and extraction processes for such compounds have been developed at different levels, from laboratory trials to photobioreactors on a demonstration [...] Read more.
Cyanobacteria have long attracted market interest as a source of natural compounds such as pigments with proven bioactivity (carotenoid and phycobiliproteins). The cultivation and extraction processes for such compounds have been developed at different levels, from laboratory trials to photobioreactors on a demonstration scale. Based on this experience, it is possible to propose how the different stages of the process can be improved based on environmental performance indicators. The Life Cycle Assessment (LCA) methodology allows to identify the hotspots that represent the greatest environmental impacts and to propose strategies to focus on those stages that can be improved. The general environmental indicators have been identified and the results showed that cyanobacteria cultivation has the greatest influence on environmental impact for all scales considered (from 20 L to 100 m3), which is attributed to the energy requirements. The main changes proposed to reduce the impact should focus on the stages of reactor cleaning, culture medium sterilisation and biomass drying. The implementation of these improvement alternatives can reduce the impact of the production and extraction processes by 85%. This work demonstrates how technological development must go hand in hand with impact assessment to make the best decisions in the overall process. Full article
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13 pages, 1206 KiB  
Article
Microalgal Growth in Aquaculture Effluent: Coupling Biomass Valorisation with Nutrients Removal
by Ana F. Esteves, Sara M. Soares, Eva M. Salgado, Rui A. R. Boaventura and José C. M. Pires
Appl. Sci. 2022, 12(24), 12608; https://0-doi-org.brum.beds.ac.uk/10.3390/app122412608 - 08 Dec 2022
Cited by 8 | Viewed by 1417
Abstract
Natural resources are becoming increasingly scarce, and the need to control their consumption and recycle their use is growing. Water is one of the essential resources for human survival. Therefore, there has been an increasing interest in ways to save, recycle and treat [...] Read more.
Natural resources are becoming increasingly scarce, and the need to control their consumption and recycle their use is growing. Water is one of the essential resources for human survival. Therefore, there has been an increasing interest in ways to save, recycle and treat water supplies. Aquaculture is one of the most polluting activities as it produces a significant wastewater volume, which needs proper treatment before being discharged into the environment or recycled. Microalgae are a potential solution for wastewater treatment. Due to their numerous advantages, the use of microalgal biomass is being studied, and, at present, there is already a market and room for profit in the sale of microalgal components in various forms, such as animal and human supplements. From a biorefinery point of view, it is important to take advantage of all the qualities and benefits that microalgae have by combining their great capacity to treat wastewater and exploit the produced biomass, analysing its composition for subsequent valorisation, for example. In this study, Chlorella vulgaris was used to treat aquaculture wastewater from a trout farm aquaculture facility, and the treatment efficiency was evaluated. To valorise the resulting biomass, its composition was also assessed. C. vulgaris successfully grew in the effluent with growth rates of 0.260 ± 0.014 d−1 and with average productivity of 32.9 ± 1.6 mg L−1 d−1. The achieved removal efficiencies were 93.5 ± 2.1% for total nitrogen, 98.0 ± 0.1% for nitrate-nitrogen and 92.7 ± 0.1% for phosphate-phosphorus. Concerning biomass composition, the lipids (15.82 ± 0.15%), carbohydrates (48.64 ± 0.83%), and pigment contents (0.99 ± 0.04% for chlorophyll a + b and 0.21 ± 0.04% for carotenoids) were similar to the values of similar studies. However, the protein content obtained (17.93 ± 1.21%) was lower than the ones mentioned in the literature. Full article
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12 pages, 2755 KiB  
Article
Magnetic Field Action on Limnospira indica PCC8005 Cultures: Enhancement of Biomass Yield and Protein Content
by Kricelle Mosquera Deamici, Michele Greque de Morais, Lucielen Oliveira dos Santos, Fabrice Gros, Jorge Alberto Vieira Costa and Céline Laroche
Appl. Sci. 2022, 12(3), 1533; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031533 - 31 Jan 2022
Cited by 3 | Viewed by 1919
Abstract
The effects of a magnetic field (MF) on the cyanobacteria Limnospira indica PCC 8005 growth rate and biomass composition were investigated. A device to apply the MF during the cultivation was built and the cyanobacteria were exposed to a steady 11 mT transverse [...] Read more.
The effects of a magnetic field (MF) on the cyanobacteria Limnospira indica PCC 8005 growth rate and biomass composition were investigated. A device to apply the MF during the cultivation was built and the cyanobacteria were exposed to a steady 11 mT transverse MF. The growth increased with MF application, and when it was applied for 1 h per day, 123% more biomass was produced than in the control group. The protein content in the biomass cultured under this condition increased, achieving 60.4 w/w, while the Chl-a increased by 326%. The MF application for 1 h per day was found to be more efficient than when applied continuously for 24 h per day, in addition to being more economical and sustainable. This study showed an inexpensive and non-toxic way to enhance biomass concentration, leading to amounts more than 100% higher than those obtained in the control group. Furthermore, the high protein content in the biomass gave us several possibilities to increase the nutritional value of food. Full article
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