C. vulgaris in bio- and nano-technology

NanoMicrobiol NanoBiotechnol, 2022 (2), 202224

DOI:

Review

Chlorella vulgaris microalgae in biotechnology and nanotechnology

Sahar Kamali 1* and Reza Ramzanee 2

1 Doctor of Pharmacy (PharmD), Yasuj, Iran
2 Doctor of Pharmacy (PharmD), Shiraz, Iran
* Correspondence: shrkmli1992@gmail.com

Abstract

Microalgae are a large group of microscopic organisms that have been able to spread through a wide range of geographical and climatic diversity due to their high resistance and good adaptability. Among these microorganisms, there is a wide variety of different species with different biological and physiologic characteristics. Humans have long recognized the importance of these single-celled organisms and were able to identify harmless and valuable economical species of these organisms. Due to the low cost of cultivation and photosynthesis power, these organisms are very suitable options for application in various food, pharmaceutical, cosmetic and environmental activities. In this study, microalgae Chlorella vulgaris has been introduced as an economically valuable microalgae and the applications of this valuable creature was investigated.

Keywords: Algae; Micro algae; Chlorella vulgaris; Food industries; Pharmacy

1 Introduction

Algae are eukaryotic in terms of cellular structure and in terms of size variation, they range from less than one micrometer to species with sizes more than 10 meters (kelp forests). So far, about 10 million algae species have been identified, most of which are in microalgae group with microscopic dimensions (1). Algae have many similarities with plants in chlorophyll and photosynthesis ability. Aerial sections of trees and rocks are places on which algae can grow. Also, some algae can live in unusual environments such as salt lakes, glaciers, inside the body and tissues of living organisms (2, 3). Algae are located at the base of the energy pyramid of marine ecosystems and are known as the main producers of the food chain and nitrogen stabilizers. These organisms play a vital role in creating different ecosystems and providing suitable habitat for aquatic animals (4).

Microalgae are single-celled and microscopic algae, which exist individually, in chain, or as a group and are commonly found in freshwater and saline systems. Microalgae are able to perform photosynthesis, so they are particularly important in earth ecology. These organisms produce about half of atmospheric oxygen while simultaneously using carbon dioxide to grow phototrophically. Based on the type of pigments in algae, they are divided into green, red, brown and golden groups, and each group has several representatives in the microalgae group. Regardless of the variation in cell size and structure, microalgae show an eye-catching variation in the type of photosynthetic pigments, which is actually a kind of adaptation to the amount of light in the environment. Another microalga feature of C. vulgaris is the formation of biofilms. Biofilm or biolayer is a cumulative form of a particular microorganism such as fungi, bacteria or protozoa that are attached to a surface by extracellular secretions and in some cases have the ability to grow (5).

Microalgae have the ability to synthesize a variety of bioactive compounds that are very difficult to produce by chemical synthesis method. Bioactive compounds are commonly referred to as secondary metabolites, which are made by organisms, generally for specific purposes such as adapting to environmental conditions, or coping with stresses such as limited food sources or changing environmental conditions, and have no effect on any stage of organism differentiation (4). Researches show that microalgae are able to produce a wide range of bioactive substances with antimicrobial (6), antiviral (7), antifungal (8), antisensitivity (9), anticoagulant (10), anticancer (11), and antioxidant (12) activity. On the other hand, microalgae such as Spirulina sp. and Chlorella sp. has been used for many years and today it is used as natural food supplements to provide the active compounds needed by humans as well as feeding and breeding domestic animals and aquaculture. In addition, studies have been conducted on the phytoremediation capacity of microalgae in marine environments on heavy metals and agricultural pesticides (13). In recent decades, microalgae have been introduced as potential producers of antibiotic compounds. The obtained compounds are very diverse and contain a wide range of chemicals including alkaloids, indole, macrolides, peptides, phenols, fatty acids and halogenated hydrocarbons (14).

2 Chlorella vulgaris

Chlorella vulgaris is one of the oldest eukaryotes on the planet. This microalga is one of the richest species in terms of chlorophyll level compared to plants, which causes dark green color. Chlorella is a branch of single-celled, spherical green algae, which belongs to greenery or chlorophyta. Chlorella vulgaris, about 2 to 10 microns in diameter, lacks talc, contains photosynthetic pigments chlorophyll a and chlorophyll b in its chloroplasts and requires only carbon dioxide, water, sunlight and a small amount of minerals to replicate (15).

In terms of reproduction, Chlorella vulgaris has exclusively asexual reproduction. The chlorella vulgaris cell with a size of 3 microns grows in freshwater during the photosynthesis process with the help of sunlight and carbon dioxide, and when the cell size reaches 8 to 10 microns, the nucleus of the cell is divided twice and produces four nuclei (16).

 Chlorella vulgaris is a potential food source because its protein and other essential nutrients are high, when dried, it has about 45% protein, 20% fat, 20% carbohydrates, 5% fiber and 10% minerals and vitamins. This microorganism contains 50% to 60% protein in the form of 19 amino acids, among which there are 8 essential amino acids and because of its high protein content, it is used in space travel as a food source for astronauts (17). Microalgae Chlorella vulgaris, is a rich source of vitamins, minerals (sodium, potassium, selenium, iron, magnesium, copper, calcium), beta-carotene, methylcobalamin, chlorophyll, sporopolenin, unsaturated fatty acids (alpha and gamma linoleic acid), Chlorella growth factor (CGF), and other valuable substances (18).

1. 1. vulgaris is an important tool for physiological examinations (19). This microalga is widely used in studies related to photosynthesis and air purification. There are a variety of reports of Chlorella species about their pharmacological and therapeutic effects, for example, hypoglycemia in mice with diabetes by streptoscin, prevention of dyslipidic disorders, hypotension, anticancer effects, and stimulating effects on the production of cytokines (20). C. vulgaris biomass in the form of powders and tablets, is available as a valuable dietary supplement in the global market. In Japan, the cultivation of various Chlorella strains is used in special tanks for biomass production. This alga has been considered in Japan as a factor in raising the body’s health and has more than 10 million consumers as the first and richest dietary supplement. C. vulgaris is extracted from natural preservative compounds, which are used as fruit and vegetable preservatives (21).

3 Applications of microalgae

3.1 Applications in food industries

One of the challenges of the 21st century is providing food with good quality for humans. High nutritional value and easy access to some microalgae has caused this group of organisms to be placed in the food basket of humans and animals. Microalgae are rich in carbohydrates, proteins, fibers and enzymes and have significant amounts of B, C and A vitamins as well as minerals such as iodine, potassium, iron, magnesium and calcium. On the other hand, it is very low in calories and can be used as dietary supplements in different diets. Nowadays, oils high in unsaturated fatty acids and antioxidants in photosynthetic pigments of microalgae (carotenoids) have been widely used in marine food industries. Currently, species such as C. vulgaris, Haematococcus pluvialis, Dunaliella salina, and Spirulina maxima are widely used in the world to produce dietary supplements for humans and as nutrient additives to animal food (22). Microalgae are also very suitable food sources for aquaculture and aquaculture nutrition industries (23).

3.2 Application in pharmaceutical industries

Microalgae are able to synthesize various bioactive compounds that are seen among these compounds, substances with unique therapeutic properties. Studies have shown that marine microorganisms have high potential in the production of natural medicinal compounds (24). Different strains of cyanobacteria are able to produce intracellular and extracellular metabolites with different activities such as antibacterial, antifungal and antiviral properties. Several studies have proved the anti-cancer properties, immune system enhancement, detoxification, antidiabetic, anti-inflammatory and antihypertensive activities of Chlorella and Spirulina (25). The use of microalgae as sources of antibiotics has many advantages. Among them, they have a great variety, and using inexpensive culture media are able to grow in large-scale bio-reservoirs and can be maintained by freezing method (26).

3.2.1 Antimicrobials

Nowadays, the problem of increasing the resistance of bacteria to existing antibiotics has encouraged researchers to use new sources of antibiotics and focus on the extraction of bioactive compounds from alternative sources. One of these alternative sources is potential compounds in eukaryotic microalgae and cyanobacteria with chlorophyll a, which have high potential in the production of secondary metabolites with antibiotic properties (27). The metabolites obtained from eukaryotic microalgae are very diverse and contain a wide range of chemical compounds including alkaloids, indole, macrolides, peptides, terpenes, phenols, polyketides, non-ribosomal peptides, polyunsaturated fatty acids, and halogenated hydrocarbons that some of which have the ability to inhibit the growth of pathogenic microorganisms (28).

3.2.2 Anticancer and antioxidants

The occurrence of oxidative processes in cells causes cancer progression. Antioxidants are compounds that prevent the formation of free radicals in cells, so they play an important role in preventing cancer. These compounds are also able to reduce premalignant lesions. Studies have shown that algae are able to reduce oxidative damage by inhibiting free radicals and reducing reactive oxygen, thus preventing the formation of cancer cells (29).

3.2.3 Health & Cosmetics Industries

Microalgae are able to produce bioactive compounds such as antibiotics, allgisids and toxins, all of which have applications in the cosmetics industry (30). Algae is widely used in cosmetic products as thickening or bulking agents, hydrant compounds and antioxidants. Many microalgae species such as Chlorella and Spirulina are used in the production of cosmetic creams and skin care products (31). Microalgae are also widely used in the production of hair care products and sunscreen. Known types of algae such as Irish moss crispus Chondrus, also known as carrageenan moss, contain protein, vitamin A, sugar, starch, vitamin B1, iron, sodium, phosphorus, magnesium, copper and calcium, which has applications in the health and cosmetics pharmaceutical industry (32).

3.2.4 Applications in energy

Due to the increasing population and limitation of fossil fuels, humans need new fuel sources. Phytoplankton have a high potential in the production of fuel oils that produce less carbon dioxide compared to fossil fuels, so today the use of biofuels is considered as the best alternative to fossil energy. In species of microalgae, such as Porphyridium, Schizochytrium, Tetraselmis, Isochrysis, Chlorella and Dunaliella there are between 20 and 50 percent oil (33). Biodiesel or biofuel is a mixture of fatty acid alkyl ester, containing 90-98% triglycerides, diglycerides and monoglycerides (34). In the process of biodiesel production from microalgae, after the liquefying process, the cellular contents are divided into phases of water, oil, gas and final residue and extracted from their oil during the cracking process of biodiesel (34). Also, it is possible to provide fuel by producing methane gas using biological reactions or temperatures that break down organic carbon in microalgae biomass. In addition, ethanol can be obtained by fermentation process, which is one of the main biofuels.

3.2.5 Applications in ecosystems refinery

Nowadays, one of the key issues in environmental protection is finding ways to remove different types of pollutants from the environment. Among these pollutants are mercury, heavy metals, petroleum pollutants and nitrate and phosphate ions, which enter surface and underground water resources through municipal and industrial wastewater and agricultural drainage, causing disturbance of material cycle balance in aquatic ecosystems and have undesirable effects on the ecosystem. Microalgae have high potential for wastewater treatment and on the other hand, removal of nutrients in effluents such as nitrate and phosphate by microalgae can be considered due to advantages such as valuable biomass production, lack of pollution production, nutrient regeneration, simple technology, high efficiency and low cost (35). So far, the optimum performance of Chlorella, Scenedesmus, Spirulina and some cyanobacteria has been proved to remove phosphorus and nitrogen from aquatic environments. These species use phosphate and nitrate for their growth and reduce it in the environment (35). Among natural systems, microalgae as biofilters are able to maintain them as metal organic compounds in their vacuoles by adsorption and by bonding peptides with heavy metals, thereby reducing heavy metals in the environment (36). Agricultural pesticides and pesticides are also one of the environmental problems, especially aquatic ecosystems, which its removal is physically expensive and inefficient. Research has shown that the use of Scenedesmus and Chlamydomonas microalgae in pesticide removal is cost effective (37).

Conclusion

Microalgae chlorella vulgaris is considered as a safe and completely harmless microalga. This microalga has attracted much attention in biotechnology and other biological technologies due to its high adaptability to different cultivation conditions. Since this microalga has been identified and approved by the U.S. Food and Drug Administration and other international health organizations as safe microorganism, it has also found wide applications in biomedical sciences and pharmaceutical industries. Therefore, this microalga can be considered as a valuable source of bioactive compounds and valuable dietary compounds. Also, the applications of this microorganism in engineering industries and sciences are also being formed and expanded.

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