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Algal Biorefinery and Microbial Fuel Cells

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

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 30327

Special Issue Editor


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Guest Editor
School of Chemical and Biomolecular Engineering, Pusan National University (PNU), Busan 46241, Korea
Interests: microalgae; fermentation; bioenergy; biorefinery; biohydrogen; bioelectrochemical conversion
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fossil resource depletion and problems related to global warming are driving the demands for renewable and environmentally friendly fuels and chemicals in our society. Recently, photosynthetic microalgae- and electroactive bacteria-based biorefinery technologies have attracted great attention in both academic and industrial fields. Microalgal biomass can be applied to a variety of industrial applications such as bioenergy, animal/aquaculture feeds, food supplements, and nutraceuticals. In microbial fuel cells (MFCs), electricity and value-added products (such as ethanol and 3-hydroxyproionic acid) can be simultaneously produced from organic substrates. In addition, renewable electricity can be used to provide a reducing equivalent that is essential for the metabolism of diverse microorganisms  to produce alcohols and organic acids. This Special Issue covers recent achievements in microalgae and biofuel cell technologies, including biocatalysts, reactors, process optimization, power generation, bio-products diversification, and upscaling.

Assoc. Prof. You-Kwan Oh
Guest Editor

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Keywords

  • Microalgae
  • Biorefinery
  • Biofuel
  • High-value products
  • Microbial fuel cells
  • Biofuel cell
  • Electro-fermentation
  • Bio-electricity

Published Papers (3 papers)

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Research

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13 pages, 2523 KiB  
Communication
High-Density Microalgae Cultivation in Open Thin-Layer Cascade Photobioreactors with Water Recycling
by Torben Schädler, Anna-Cathrine Neumann-Cip, Karin Wieland, David Glöckler, Christoph Haisch, Thomas Brück and Dirk Weuster-Botz
Appl. Sci. 2020, 10(11), 3883; https://doi.org/10.3390/app10113883 - 3 Jun 2020
Cited by 17 | Viewed by 4814
Abstract
(1) Background: Recycling of water and non-converted nutrients is considered to be a necessity for an economically viable production of microalgal biomass as a renewable feedstock. However, medium recycling might also have a negative impact on algal growth and productivity due to the [...] Read more.
(1) Background: Recycling of water and non-converted nutrients is considered to be a necessity for an economically viable production of microalgal biomass as a renewable feedstock. However, medium recycling might also have a negative impact on algal growth and productivity due to the accumulation of growth-inhibiting substances. (2) Methods: Consecutive batch processes with repeated water recycling after harvesting of algal biomass were performed with the saline microalga Microchloropsis salina in open thin-layer cascade photobioreactors operated at a physically simulated Mediterranean summer climate. The impact of water recycling on culture performance was studied and the composition of the recycled water was analyzed. (3) Results: Water recycling had no adverse effect on microalgal growth and biomass productivity (14.9−21.3 g m−2 d−1) if all necessary nutrients were regularly replenished and KNO3 was replaced by urea as the nitrogen source to prevent the accumulation of K+ ions. Dissolved organic carbon accumulated in recycled water, probably promoting mixotrophic growth. (4) Conclusion: This study shows that repeated recycling of water is feasible even in high-density cultivation processes with M. salina of more than 30 g L−1 cell dry weight, increasing culture performance while reducing nutrient consumption and circumventing wastewater production. Full article
(This article belongs to the Special Issue Algal Biorefinery and Microbial Fuel Cells)
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10 pages, 1554 KiB  
Article
Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery
by Ramasamy Praveenkumar, Jiye Lee, Durairaj Vijayan, Soo Youn Lee, Kyubock Lee, Sang Jun Sim, Min Eui Hong, Young-Eun Kim and You-Kwan Oh
Appl. Sci. 2020, 10(2), 513; https://doi.org/10.3390/app10020513 - 10 Jan 2020
Cited by 24 | Viewed by 5565
Abstract
Haematococcus pluvialis accumulates astaxanthin, which is a high-value antioxidant, during the red cyst stage of its lifecycle. The development of a rigid cell wall in the cysts hinders the recovery of astaxanthin. We investigated morphological changes and cell disruption of mature H. pluvialis [...] Read more.
Haematococcus pluvialis accumulates astaxanthin, which is a high-value antioxidant, during the red cyst stage of its lifecycle. The development of a rigid cell wall in the cysts hinders the recovery of astaxanthin. We investigated morphological changes and cell disruption of mature H. pluvialis cyst cells while using high-pressure homogenization for astaxanthin extraction. When treated with French-press-cell (pressure, 10,000–30,000 psi; passage, 1–3), the intact cyst cells were significantly broken or fully ruptured, releasing cytoplasmic components, thereby facilitating the separation of astaxanthin by ethyl acetate. Fluorescence microscopy observations using three different fluorescent dyes revealed that a greater degree of cell breakage caused greater external dispersion of astaxanthin, chlorophyll, lipids, proteins, and carbohydrates. The mechanical treatment resulted in a high cell disruption rate of up to 91% based on microscopic cell typing and Coulter methods. After the ethyl acetate extraction, the astaxanthin concentration significantly increased by 15.2 mg/L in proportion to the increase in cell disruption rate, which indicates that cell disruption is a critical factor for solvent-based astaxanthin recovery. Furthermore, this study recommends a synergistic combination of the fast instrumental particle-volume-distribution analysis and microscope-based morphologic phenotyping for the development of practical H. pluvialis biorefinery processes that co-produce various biological products, including lipids, proteins, carbohydrates, chlorophyll, and astaxanthin. Full article
(This article belongs to the Special Issue Algal Biorefinery and Microbial Fuel Cells)
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Review

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27 pages, 1970 KiB  
Review
Flocculation Harvesting Techniques for Microalgae: A Review
by Ibrahim A. Matter, Vu Khac Hoang Bui, Mikyoung Jung, Jung Yoon Seo, Young-Eun Kim, Young-Chul Lee and You-Kwan Oh
Appl. Sci. 2019, 9(15), 3069; https://doi.org/10.3390/app9153069 - 29 Jul 2019
Cited by 108 | Viewed by 19272
Abstract
Microalgae have been considered as one of the most promising biomass feedstocks for various industrial applications such as biofuels, animal/aquaculture feeds, food supplements, nutraceuticals, and pharmaceuticals. Several biotechnological challenges associated with algae cultivation, including the small size and negative surface charge of algal [...] Read more.
Microalgae have been considered as one of the most promising biomass feedstocks for various industrial applications such as biofuels, animal/aquaculture feeds, food supplements, nutraceuticals, and pharmaceuticals. Several biotechnological challenges associated with algae cultivation, including the small size and negative surface charge of algal cells as well as the dilution of its cultures, need to be circumvented, which increases the cost and labor. Therefore, efficient biomass recovery or harvesting of diverse algal species represents a critical bottleneck for large-scale algal biorefinery process. Among different algae harvesting techniques (e.g., centrifugation, gravity sedimentation, screening, filtration, and air flotation), the flocculation-based processes have acquired much attention due to their promising efficiency and scalability. This review covers the basics and recent research trends of various flocculation techniques, such as auto-flocculation, bio-flocculation, chemical flocculation, particle-based flocculation, and electrochemical flocculation, and also discusses their advantages and disadvantages. The challenges and prospects for the development of eco-friendly and economical algae harvesting processes have also been outlined here. Full article
(This article belongs to the Special Issue Algal Biorefinery and Microbial Fuel Cells)
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