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| ALGAE BY-PRODUCTS: THE FUTURE SAVIOR | | | Dr. Wahied Khawar Balwan | 6/21/2023 11:06:51 PM |
|  You must have noticed a green slippery layer growing either on top or below of different water bodies like ponds, lakes, oceans, rivers and even in snow, it could be anywhere on Earth and wondered what is it? That green layer consists of a plant-like living organism called “algae”. Till date approximately 1,65,290 species of algae and there infraspecific names have been known. On the basis of their physical and ecological features they can be categorized into different forms.
Majorly, they vary in size and can be categorized into microalgae and macroalgae. Algae can be single cellular or multicellular, and are capable to produce their own food as well as manufacture a range of useful products by the process of photosynthesis.
In few years, what brings the most focus on these organisms is their short doubling time, due to which they are considered to be the fastest growing creature. They have an ability to fix the sunlight, atmospheric carbon dioxide and other essential nutrients to convert into biomass. This end product has attracted many researchers to extract their food and fuel capabilities. Algae as a food have been explored for different applications as in production of single cell proteins, pigments, bioactive substances, pharmaceuticals and cosmetics. In fuel industry, algae biofuels have been developed as a solution with clean, nature friendly, cost effective solutions over other fuels. The present overview has been prepared to throw a light on few applications of algae as food and fuel on commercial basis. Commercially algae are grown in large areas to use the economies of scale. Solazyme, Exxonmobil and Sapphire energy are some giants in this area who are trying to make fuel derived from algae commercially viable.
The growth of algae is dependent upon various factors like temperature, pH, irradiance and growth media. The most common growth media are Zarrouk’s and BG11 as the product and biomass yield of algae is highest in these two media.
The change of any one of the above conditions can improve or diminish the growth of algae and bioproducts obtained significantly. Hence, to make the product obtained from algae commercially viable, optimization of the growth conditions is of prime importance. After the growth of algal species in suitable media and conditions, the algae are harvested. This step is necessary because algae are cultured in liquidrich media. Around 20-30% of the total expenditure can be accounted for in the harvesting stage, which may also increase up to 50% depending on various cases. The small size of the algae, the media it is grown in, the similar density of the microalgae and the frequent need for the harvesting techniques owing to the high growth rate of algae are the various challenges faced during harvesting. The harvesting technique is selected on the basis of the properties of the microalgae.
On the laboratory scale, the filtration method is used, which is followed by the centrifugation process corresponding to the dewatering phase (concentrating the algae slurry).
The main focus after the harvesting phase should be on processing the biomass separated from the culture media because it can be spoiled in a few hours in the hot climate. In addition to this, it has also been stated the biomass may be subjected to degradation induced by the process itself and also by the enzymes present in the algal cells.
An example for the same is the action of lipase contained in the cells which readily hydrolysed the cellular lipids into free fatty acids, which turns unsuitable for conversion into biodiesel. Some of the products obtained from algae are algae biofuel, pharmaceutical, natural colors etc.
ALGAL BIOFUEL
India has a population of 1.3 billion people and it is projected to be the world’s most populous country, surpassing China by 2027. Also, it will be the 3rd largest economy by 2025. With the growing population and improving the standard of living, the energy needs in India will increase exponentially in the future. Hence, there is a need to find alternative sources of energy that are commercially viable to ensure energy security, with the limited reserves of fossil fuels getting depleted. Also, finding alternative sources of biofuels instead of importing them will save India billions of foreign exchange money. The economic viability of firstgeneration biofuels was questionable as they are derived from food materials like starch, sugar, vegetable oils etc., and hence risking food security. Similarly, the idea of using secondgeneration biofuels was rejected as it was obtained from waste biomass such as stalks of wheat/ corn and had low yields. Third generation biofuels are obtained from algae and overcome the problems like rising food prices and food shortages and also the problem of inconsistent feed of the earlier two generations of biofuels. The algae have a higher lipid production rate in comparison to terrestrial plants due to the simple cellular structure being more efficient in photosynthesis and the growth of algae being 10 times faster than plants. It is estimated that algae can produce 30 times more lipid per unit area as compared to terrestrial plants and can grow in a variety of conditions. Using algae for biofuel production also has other advantages like high carbon dioxide sequestration capacity due to which algal plants can be opened near polluting industries serving two purposes at the same time.
With newer technologies being developed, wastewater can also be treated by using it to grow algae as it contains impurities in the form of organic material which can be used by algae as its food source. For the biofuel to be commercially viable, various researches have been completed and many are still undergoing to find the algal species with the highest lipid production and the suitable physiological conditions for it to grow. Botryococcusbraunii, Scenedesmus sp., Chlorella sp., Nannochloropsis sp. are some of the algal strains with the highest lipid content. The optimum conditions for their growth vary from 25 °C- 35°C in temperature, 8-12 hours of sunlight and 7-7.2 pH.
After the growth and harvesting of algae, the extraction of biofuels is done. There are 3 ways in which it can be done. These are pressing oil from the algae by which up to 70% of the oil can be retrieved, chemical oil extraction using hexane solvents for extraction of 95% of the total biofuels and finally the most expensive and technologically advanced method supercritical oil extraction which uses carbon dioxide at critical temperature and pressure. 99.99% of oil can be extracted by this method. Hence, to meet the future energy demands and for a sustainable future, more ventures in this field are required along with support from the government in the form of incentives and policy interventions.
PHARMACEUTICALS
The market of pharmaceuticals and nutraceuticals runs in billions and is continuously growing. Algae are a rich source of bioactive substances, and a variety of medicinal products made from algae have a high market value, but industrialization is still in its infant stage.
The pharmaceutical product obtained from algae includes antivirals, antimicrobials, antifungal, therapeutic proteins and drugs. Bioactive compounds are physiologically active compounds that have tremendous uses in the functional properties of the human body. There has been a recent increase in the number of researches being carried out to identify new commercially viable bioactive compounds because of their numerous health benefits.
There have been numerous researches on bioactive compounds obtained from various algal strains like Chlorella vulgaris, Dunaliellasalina, Botryococcusbraunii.
These researches have led to the identification of their antibacterial, antifungal and antiviral activities.
Spirulina, one of the most extensively studied blue-green algae, has shown tremendous opportunities in the treatment of HIV, Hyperlipidemia, obesity, cancer and general improvement to the immune response in renal protections against heavy metals.
Nostoc is other blue-green alga that has found applications in medicine for its anti-inflammatory and anti-microbial properties, as well as a food supplement due to its high protein, fatty acid and vitamin content. Intensive research has been carried out only on a handful of microalgal species. Additional studies into these bioactive substances are needed to confirm their beneficial effects on humans as well as their overall consequences on the environment and animals when released. Hence, there is a need to realize the untapped potential of algae in the field of pharmaceuticals and capitalize on tremendous global market opportunities.
DIRECT USES OF ALGAE
Algal biomass, like algal by-products, also finds its usage in a number of fields. Algal Biomass has been used for direct human consumption since ancient times as recorded in Chinese literature dating back to 2500 years. Due to its high protein content, as well as vitamins and phenolics; Spirulina platensis is gaining worldwide interest as a food supplement. Many nutrients remain in the biomass after the recovery of oil from algae. Algal species include several chemicals that encourage blooming, left or stem growth, and germination, hence this left biomass can be employed as a biofertilizer. Other applications include paper fibers, carrageenan as emulsifying and stabilizing agents in various foods, aquaculture feed, and so on.
SOURCE OF NATURAL COLORS
Colorants are added to food items, drinks and cosmetics to make them look more attractive, natural and fresh. Colorants can be derived from either natural sources or synthetic sources. Synthetic dyes are obtained from petroleum products whereas natural sources include plants and microalgae. Although the use of synthetic colorant is used more than the natural ones because of their high yield compared to natural sources, there has been a gradual shift in the recent years towards the natural sources.
Synthetic colorants are banned in various countries because of their unsafe nature and associated health risks. Some commonly used synthetic colorants are known carcinogens, allergens and irritants.
Production of colors from microalgae has many advantages over synthetic sources like cheaper, easily extractable, no lack of raw material and seasonal variation. Carotenoids and phycobiliproteins are major pigments of the microalgae which may be used as a color. Carotenoids are color compounds that are lipid-soluble and are found in higher plants and algae and also non-photosynthetic organisms like fungi and bacteria. More than 600 carotenoids are known and β-carotene, which acts as Provitamin-A is one of them. Various researchers have found β-carotene to be anti-carcinogenic and prevent the risk of heart diseases.
Dunaliella, Chlorella zofingiensis are some of the suitable candidates for carotenoids production.
Phycobiliproteins are water-soluble photosynthetic pigments and their major producers which are exploited for commercial uses are cyanobacterium Arthrospira Spirulina and the rhodophyte Porphyridium. Like other byproducts, the amount of Phycobiliproteins produced also depends upon the intensity and quality of light. The number of phycobiliproteins produced by Spirulina varies from 11-12.7% at different light intensities. These phycobiliproteins are used in food as natural dyes, cosmetics, and biomedical research as fluorescent dyes.
CONCLUSION
Algae by-products are promising sources of biofuels, pharmaceuticals, food additives, cosmetics and numerous other substances. Although the number of by-products produced by algae and their uses is vast, there is still some room for improvement for better commercial exploitation of algae and minimizing the negative effects on the environment.
Hence, there is a need to spend more on R&D for targeted research on algae for better yield of by-products to make them commercially viable in these multibillion-dollar industries for a better and sustainable future.
‘Any Error in this Manuscript is silent testimony of the fact that it was a Human effort’
Dr. Wahied Khawar Balwan
Senior Assistant Professor & Head
Department of Zoology
Govt. Degree College Kilhotran, Doda
E-mail: [email protected] |
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