Algal Green Chemistry

Recent Progress in Biotechnology

Rajesh Prasad Rastogi, Datta Madamwar, Ashok Pandey

• Publisher: Elsevier
• Year: 2017
• ISBN:
  9780444637949
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

Algal Green Chemistry: Recent Progress in Biotechnology presents emerging information on green algal technology for the production of diverse chemicals, metabolites, and other products of commercial value. This book describes and emphasizes the emerging information on green algal technology, with a special emphasis on the production of diverse chemicals, metabolites, and products from algae and cyanobacteria.

Topics featured in the book are exceedingly valuable for researchers and scientists in the field of algal green chemistry, with many not covered in current academic studies. It is a unique source of information for scientists, researchers, and biotechnologists who are looking for the development of new technologies in bioremediation, eco-friendly and alternative biofuels, biofertilizers, biogenic biocides, bioplastics, cosmeceuticals, sunscreens, antibiotics, anti-aging, and an array of other biotechnologically important chemicals for human life and their contiguous environment. This book is a great asset for students, researchers, and biotechnologists.

• Discusses high-value chemicals from algae and their industrial applications
• Explores the potential of algae as a renewable source of bioenergy and biofuels
• Considers the potential of algae as feed and super-food
• Presents the role of triggers and cues to algal metabolic pathways
• Includes developments in the use of algae as bio-filters

Chapter 1

Osmoprotectant and Sunscreen Molecules From Halophilic Algae and Cyanobacteria

H. Kageyama¹, R. Waditee-Sirisattha², Y. Tanaka¹, and T. Takabe^{1 1}Meijo University, Nagoya, Japan ²Chulalongkorn University, Bangkok, Thailand

Abstract

To survive under halophilic environments, halophilic microorganisms must have developed the special systems such as synthesis of osmoprotectant and sunscreen molecules. Osmoprotectants are small molecules that act as osmolytes and help organisms survive under extreme saline conditions. Examples of compatible solutes include betaines, amino acids, dimethylsulfoniopropionate, and sugars. These molecules accumulate in cells and balance the osmotic difference between the cell's surroundings and the cytosol. Compatible solutes have also been shown to play a protective role by maintaining enzyme activity under abiotic stress conditions. Their specific action is unknown but is thought that they are preferentially excluded from the proteins interface due to their propensity to form water structures. Here, we summarize recent progress on the research of osmoprotectant and sunscreen molecules in halophilic algae/cyanobacteria. Their possible biotechnological application in the field of green energy, biomedical research, and various biochemical industries were described.

Keywords

Amino acid transport; Aphanothece halophytica; Dimethylsulfoniopropionate; Glycine betaine; Halotolerant cyanobacteria; Marine algae; Mycosporine-2-glycine; Mycosporine-like amino acids; Osmoprotectant

Outline

1. Introduction

2. Osmoprotectants and Sunscreen Molecules (MAA)

2.1 Basic Features of Osmoprotectants in Cyanobacteria and Algae

2.2 Saccharides and Their Derivatives

2.2.1 Glucosylglycerol and Glucosylglycerate

2.2.2 Biosynthetic Pathway

2.3 Glycine Betaine

2.3.1 Accumulation and Response to Environment

2.3.2 Biosynthetic Pathway

2.3.3 Regulation of Related Enzyme Activity and Gene Expression

2.4 Glycerol

2.4.1 Accumulation and Response to Environment

2.4.2 Biosynthesis Pathway

2.5 Dimethylsulfoniopropionate

2.5.1 Accumulation and Response to Environment

2.5.2 Biosynthetic Pathway

2.5.3 Omics Approaches to Identify DMSP Biosynthetic Enzymes and Genes

2.6 Basic Features of Mycosporines and MAAs

2.7 Biosynthetic Pathway of MAAs

2.7.1 Genes and Proteins Responsible for Biosynthesis of MAAs

2.7.2 Regulation of Biosynthesis of MAAs

2.8 Biological Function of Mycosporines and MAAs

2.8.1 Sunscreen Role

2.8.2 Osmoprotectant Role

2.8.3 Antioxidant Role

2.8.4 Roles of MAAs in Halotolerant Cyanobacteria

3. Conclusions and Perspectives

References

1. Introduction

To survive under halophilic environments, halophilic microorganisms must have developed the special systems such as synthesis of osmoprotectant and sunscreen molecules. Osmoprotectants are small molecules that act as osmolytes and help organisms survive under extreme saline conditions. Examples of compatible solutes include betaines, amino acids, dimethylsulfoniopropionate (DMSP), and sugars. These molecules accumulate in cells and balance the osmotic difference between the cell's surroundings and the cytosol. Compatible solutes have also been shown to play a protective role by maintaining enzyme activity under abiotic stress conditions. Their specific action is unknown but is thought that they are preferentially excluded from the proteins interface due to their propensity to form water structures. Here, we summarize recent progress on the research of osmoprotectant and sunscreen molecules in halophilic algae/cyanobacteria. Their possible biotechnological application in the field of green energy, biomedical research, and various biochemical industries were described.

2. Osmoprotectants and Sunscreen Molecules (MAA)

2.1. Basic Features of Osmoprotectants in Cyanobacteria and Algae

Cyanobacteria and algae, as primary producers of ecosystems, have wide range of habitats from freshwater to hypersaline environments [1,2]. To survive under high salt conditions, special mechanisms are required to cope ionic/osmotic imbalance. Since salt stress is a major factor to decrease crop yield, extensive studies have been carried out on salt stress on plants. Unique systems and unique genes in halophilic algae and cyanobacteria could be applied to increase the crop yield of plants [3]. For the ionic regulation under high salinity conditions, the capacity of plants to maintain a high cytosolic K⁺/Na⁺ ratio is the key determinant of plant-salt-tolerance [4]. Besides the ionic regulation, the accumulations of alternative solutes without inhibiting metabolic activities inside the cells are necessary [2–4]. Such solutes are termed “compatible solutes,” which are organic molecules with low molecular weight, highly soluble in water, and usually without net charge. Based on their chemical structure, compatible solutes can be classified into several groups. The main groups are (1) disaccharides, (2) polyols, (3) heterosides, (4) zwitterionic quaternary ammonium and tertiary sulfonium compounds, and (5) amino acids [1–3]. In addition to their osmotic functions, compatible solutes have protective effect on proteins and membranes against denaturation under various abiotic stresses.

Cyanobacteria can be divided into three groups according to their salt tolerance, freshwater cyanobacteria (sensitive to salinity), marine type cyanobacteria (tolerant up to near 1 M NaCl), and halophilic cyanobacteria. Freshwater strains tend to accumulate disaccharides, marine strains generally use glucosylglycerol (GG), and halophilic strains accumulate glycine betaine (GB) [2]. In algae, because of the phylogenetic diversity, there seems to be a great variety of compatible solutes. The compatible solutes such as disaccharides in green algae, several kinds of heterosides in red algae, and polyols in brown algae have been reported. In marine micro- and macroalgae, accumulation of DMSP, GB, and proline has been reported [5]. The genus Dunaliella contains species whose normal habitats range from seawater of around 0.4 M NaCl to 5 M NaCl [1]. Dunaliella salina has adapted to survive in high salinity environments by accumulating glycerol to balance osmotic pressure.

In this chapter, we focus on saccharides, GB, and DMSP as osmoprotectants in cyanobacteria and algae.

2.2. Saccharides and Their Derivatives

2.2.1. Glucosylglycerol and Glucosylglycerate

Moderately salt-tolerant and marine cyanobacteria often accumulate GG as a compatible solute. GG-accumulating cyanobacteria Synechocystis sp. PCC 6803 can grow in freshwater and media with salt concentration higher than seawater [6]. Glucosylglycerate (GGA) is an uncommon compatible solute because it carries a net charge at physiological pH. GGA accumulation was found in marine picoplanktonic cyanobacteria, Prochlorococcus...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Editor's Biography
• Preface
• Chapter 1. Osmoprotectant and Sunscreen Molecules From Halophilic Algae and Cyanobacteria
• Chapter 2. UV Photoprotectants From Algae—Synthesis and Bio-Functionalities
• Chapter 3. Genome- and Proteome-Wide Analyses for Targeted Manipulation and Enhancement of Bioproducts in Cyanobacteria
• Chapter 4. Nutraceuticals From Algae and Cyanobacteria
• Chapter 5. Natural Antioxidants From Algae: A Therapeutic Perspective
• Chapter 6. Microalgae as a Source of Bioplastics
• Chapter 7. Microalgae-Based Carotenoids Production
• Chapter 8. Low-Molecular-Weight Nitrogenous Compounds (GABA and Polyamines) in Blue–Green Algae
• Chapter 9. Algal Pigments for Human Health and Cosmeceuticals
• Chapter 10. Role of Algae as a Biofertilizer
• Chapter 11. Modeling and Technoeconomic Analysis of Algae for Bioenergy and Coproducts
• Chapter 12. Polyamines: Stress Metabolite in Marine Macrophytes
• Chapter 13. Microalgal Biomass Cultivation
• Chapter 14. Algal Biofilms and Their Biotechnological Significance
• Index