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Microalgae Biotechnology: Methods and Applications

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A special issue of Bioengineering (ISSN 2306-5354). This special issue belongs to the section "Biochemical Engineering".

Deadline for manuscript submissions: closed (15 October 2023) | Viewed by 12154

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Special Issue Editor

Dr. Fantao Kong

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Guest Editor

School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China
Interests: microalgae; lipid metabolism; synthetic biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microalgae are a group of unicellular photosynthetic microorganisms, which can utilize atmospheric CO₂ as a carbon source. They are regarded as sustainable feedstocks for the production of valuable bioactive molecules, biochemicals and biofuels. Moreover, microalgae have great potential to remove pollutants along with the production of value-added products due to their capability to remediate waste resources and pollutants. However, the industrial production of these products from microalgae is not economically viable due to biological and biotechnological limitations, and microalgae-based strategies to remediate waste resources and pollutants also have a low economic efficiency. Therefore, the development of microalgal biotechnology is urgently required to meet the increasing demand for microalgal-based commercial applications.

Research on microalgal biotechnology has experienced a rapid revival over the last decade, especially with the emergence of disruptive technologies with the potential to enable the commercial production of bioproducts. The development of genetic tools and techniques for microalgae engineering are fundamental, such as novel transformation methods and vector toolkits for transgene expression, state-of-the-art techniques for targeted genome editing and high-throughput screening approaches. Additionally, efficient and novel bioengineering and biotechnology strategies are required to reduce production costs during microalgae large-scale cultivations. Overall, microalgal biotechnology has great potential to potentiate microalgae as cell factories for the concurrent overproduction of valuable biomolecules, remediation of emerging pollutants, and realization of carbon neutralization.

Therefore, this Special Issue aims to collate recent achievements in genetic tools, which are useful for modifying microalgal species, as well as recent achievements in efficient and cost-effective microalgae production. We also welcome papers that focus on bioengineering and biotechnological strategies to enhance the production of biofuels and other value-added products in microalgae through CO₂ fixation and/or the use of carbon from waste resources and pollutants. The editors of this Special Issue welcome original research and review articles that focus on, but are not limited to, the following themes:

Novel transformation methods, improved vector toolkits, and modified strategies in genes stacking for transgene expression in microalgae;
The genetic engineering of key enzymes to generate robust microalgal strains;
Metabolic optimization to overaccumulate valuable metabolites in microalgae;
The development of novel production systems for efficient and cost-effective microalgae cultivation;
Bioprocess engineering for the concurrent overproduction of valuable biomolecules and remediation of emerging pollutants in microalgae.

Dr. Fantao Kong
Guest Editor

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Keywords

microalgae
biotechnology
bioresources
biofuels
bioactive molecules

Published Papers (5 papers)

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Research

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18 pages, 7422 KiB

Open AccessArticle

On-Site Pilot-Scale Microalgae Cultivation Using Industrial Wastewater for Bioenergy Production: A Case Study towards Circular Bioeconomy

by Juliana Abraham, Tobi Abimbola, Washington J. Braida, Amalia Terracciano, Tsan-Liang Su, Christos Christodoulatos, Agamemnon Koutsospyros, Abhishek RoyChowdhury, Benjamin Smolinski and Adeniyi Lawal

Bioengineering 2023, 10(12), 1339; https://doi.org/10.3390/bioengineering10121339 - 21 Nov 2023

Viewed by 1308

Abstract

This case study assesses the valorization of industrial wastewater streams for bioenergy generation in an industrial munition facility. On-site pilot-scale demonstrations were performed to investigate the feasibility of algal growth in the target wastewater on a larger outdoor scale. An exploratory field study followed by an optimized one were carried out using two 1000 L open raceway ponds deployed within a greenhouse at an industrial munition facility. An online system allowed for constant monitoring of operational parameters such as temperature, pH, light intensity, and dissolved oxygen within the ponds. The original algal seed evolved into an open-air resilient consortium of green microalgae and cyanobacteria that were identified and characterized successfully. Weekly measurements of the level of nutrients in pond liquors were performed along with the determination of the algal biomass to quantitatively evaluate growth yields. After harvesting algae from the ponds, the biomass was concentrated and evaluated for oil content and biochemical methane potential (BMP) to provide an estimate of the algae-based energy production. Additionally, the correlation among biomass, culturing conditions, oil content, and BMP was evaluated. The higher average areal biomass productivity achieved during the summer months was 23.9 ± 0.9 g/m²d, with a BMP of 350 scc/gVS. An oil content of 22 wt.% was observed during operation under low nitrogen loads. Furthermore, a technoeconomic analysis and life cycle assessment demonstrated the viability of the proposed wastewater valorization scenario and aided in optimizing process performance towards further scale-up. Full article

(This article belongs to the Special Issue Microalgae Biotechnology: Methods and Applications)

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15 pages, 3628 KiB

Open AccessArticle

Effect of LED Illumination Cycle and Carbon Sources on Biofilms of Haematococcus pluvialis in Pilot-Scale Angled Twin-Layer Porous Substrate Photobioreactors

by Thanh-Tri Do, Toan-Em Quach-Van, Thanh-Cong Nguyen, Pau Loke Show, Tran Minh-Ly Nguyen, Duc-Hoan Huynh, Dai-Long Tran, Michael Melkonian and Hoang-Dung Tran

Bioengineering 2023, 10(5), 596; https://doi.org/10.3390/bioengineering10050596 - 16 May 2023

Viewed by 1736

Abstract

Light-emitting diodes are increasingly used as artificial light sources in Haematococcus pluvialis cultivation due to the fact of their energy advantages. The immobilized cultivation of H. pluvialis in pilot-scale angled twin-layer porous substrate photobioreactors (TL-PSBRs) was initially performed with a 14/10 h light/dark cycle and showed relatively low biomass growth and astaxanthin accumulation. In this study, the illumination time with red and blue LEDs at a light intensity of 120 µmol photons m⁻² s⁻¹ was increased to 16–24 h per day. With a light/dark cycle of 22/2 h, the biomass productivity of the algae was 7.5 g m⁻² day⁻¹, 2.4 times higher than in the 14/10 h cycle. The percentage of astaxanthin in the dry biomass was 2%, and the total amount of astaxanthin was 1.7 g m⁻². Along with the increase in light duration, adding 10 or 20 mM NaHCO₃ to the BG11-H culture medium over ten days of cultivation in angled TL-PSBRs did not increase the total amount of astaxanthin compared with only CO₂ addition at a flow rate of 3.6 mg min⁻¹ to the culture medium. Adding NaHCO₃ with a 30–80 mM concentration inhibited algal growth and astaxanthin accumulation. However, adding 10–40 mM NaHCO₃ caused algal cells to accumulate astaxanthin at a high percentage in dry weight after the first four days in TL-PSBRs. Full article

(This article belongs to the Special Issue Microalgae Biotechnology: Methods and Applications)

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17 pages, 2163 KiB

Open AccessArticle

A Low-Cost Fertilizer Medium Supplemented with Urea for the Lutein Production of Chlorella sp. and the Ability of the Lutein to Protect Cells against Blue Light Irradiation

by Chiu-Mei Kuo, Yi-Chun Yang, Wen-Xin Zhang, Jia-Xun Wu, Yu-Tso Chen, Cheng-Han Lin, Meng-Wei Lin and Chih-Sheng Lin

Bioengineering 2023, 10(5), 594; https://doi.org/10.3390/bioengineering10050594 - 15 May 2023

Cited by 4 | Viewed by 1662

Abstract

This study aimed to investigate the use of organic fertilizers instead of modified f/2 medium for Chlorella sp. cultivation, and the extracted lutein of the microalga to protect mammal cells against blue-light irradiation. The biomass productivity and lutein content of Chlorella sp. cultured in 20 g/L fertilizer medium for 6 days were 1.04 g/L/d and 4.41 mg/g, respectively. These values are approximately 1.3- and 1.4-fold higher than those achieved with the modified f/2 medium, respectively. The cost of medium per gram of microalgal biomass reduced by about 97%. The microalgal lutein content was further increased to 6.03 mg/g in 20 g/L fertilizer medium when supplemented with 20 mM urea, and the cost of medium per gram lutein reduced by about 96%. When doses of ≥1 μM microalgal lutein were used to protect mammal NIH/3T3 cells, there was a significant reduction in the levels of reactive oxygen species (ROS) produced by the cells in the following blue-light irradiation treatments. The results show that microalgal lutein produced by fertilizers with urea supplements has the potential to develop anti-blue-light oxidation products and reduce the economic challenges of microalgal biomass applied to carbon biofixation and biofuel production. Full article

(This article belongs to the Special Issue Microalgae Biotechnology: Methods and Applications)

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13 pages, 2075 KiB

Open AccessArticle

Secretory Expression and Application of Antilipopolysaccharide Factor 3 in Chlamydomonas reinhardtii

by Yaohui Ou, Huilin Zhuang, Ruoyu Chen, Danqiong Huang and Chaogang Wang

Bioengineering 2023, 10(5), 564; https://doi.org/10.3390/bioengineering10050564 - 8 May 2023

Viewed by 1303

Abstract

Anti-lipopolysaccharide factor is a class of antimicrobial peptides with lipopolysaccharide-binding structural domains, which has a broad antimicrobial spectrum, high antimicrobial activities, and broad application prospects in terms of the aquaculture industry. However, the low yield of natural antimicrobial peptides and their poor expression activity in bacteria and yeast have hindered their exploration and utilization. Therefore, in this study, the extracellular expression system of Chlamydomonas reinhardtii, by fusing the target gene with the signal peptide, was used to express anti-lipopolysaccharide factor 3 (ALFPm3) from Penaeus monodon in order to obtain highly active ALFPm3. Transgenic C. reinhardtii T-JiA2, T-JiA3, T-JiA5, and T-JiA6, were verified using DNA-PCR, RT-PCR, and immunoblot. Additionally, the IBP1-ALFPm3 fusion protein could be detected not only within the cells but also in the culture supernatant. Moreover, the extracellular secretion containing ALFPm3 was collected from algal cultures, and then its bacterial inhibitory activity was analyzed. The results showed that the extracts from T-JiA3 had an inhibition rate of 97% against four common aquaculture pathogenic bacteria, including Vibrio harveyi, Vibrio anguillarum, Vibrio alginolyticus, and Vibrio parahaemolyticus. The highest inhibition rate of 116.18% was observed in the test against V. anguillarum. Finally, the minimum inhibition concentration (MIC) of the extracts from T-JiA3 to V. harveyi, V. anguillarum, V. alginolyticus, and V. parahaemolyticus were 0.11 μg/μL, 0.088 μg/μL, 0.11 μg/μL, and 0.011 μg/μL, respectively. This study supports the foundation of the expression of highly active anti-lipopolysaccharide factors using the extracellular expression system in C. reinhardtii, providing new ideas for the expression of highly active antimicrobial peptides. Full article

(This article belongs to the Special Issue Microalgae Biotechnology: Methods and Applications)

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Review

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34 pages, 536 KiB

Open AccessReview

Emerging Applications of Chlorella sp. and Spirulina (Arthrospira) sp.

by Ana P. Abreu, Rodrigo Martins and João Nunes

Bioengineering 2023, 10(8), 955; https://doi.org/10.3390/bioengineering10080955 - 11 Aug 2023

Cited by 4 | Viewed by 5257

Abstract

Chlorella sp. and Spirulina (Arthrospira) sp. account for over 90% of the global microalgal biomass production and represent one of the most promising aquiculture bioeconomy systems. These microorganisms have been widely recognized for their nutritional and therapeutic properties; therefore, a significant growth of their market is expected, especially in the nutraceutical, food, and beverage segments. However, recent advancements in biotechnology and environmental science have led to the emergence of new applications for these microorganisms. This paper aims to explore these innovative applications, while shedding light on their roles in sustainable development, health, and industry. From this state-of-the art review, it was possible to give an in-depth outlook on the environmental sustainability of Chlorella sp. and Spirulina (Arthrospira) sp. For instance, there have been a variety of studies reported on the use of these two microorganisms for wastewater treatment and biofuel production, contributing to climate change mitigation efforts. Moreover, in the health sector, the richness of these microalgae in photosynthetic pigments and bioactive compounds, along with their oxygen-releasing capacity, are being harnessed in the development of new drugs, wound-healing dressings, photosensitizers for photodynamic therapy, tissue engineering, and anticancer treatments. Furthermore, in the industrial sector, Chlorella sp. and Spirulina (Arthrospira) sp. are being used in the production of biopolymers, fuel cells, and photovoltaic technologies. These innovative applications might bring different outlets for microalgae valorization, enhancing their potential, since the microalgae sector presents issues such as the high production costs. Thus, further research is highly needed to fully explore their benefits and potential applications in various sectors. Full article

(This article belongs to the Special Issue Microalgae Biotechnology: Methods and Applications)

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