ABSTRACT
Algae are large and diverse group of microorganisms that can carry out photosynthesis since they are able to capture energy from sun light. Algae may range in size from single cells as small as one micrometer to large seaweeds that grow to over 50 meters. Algae grow in the wide and are prompt to attack by predators and can easily be invaded which could result to competition that will eventually lead to low production of biomass which are important to organisms and the ecosystem. Chlorella viriabilis recently renamed Chlorella viriabilisNC64A that is a bona fide member of the true Chlorella genus, belonging to the Trebouxiophyceae was used in this present research. Chlorellaviriabilis was propagated in BG11 media enriched with 0.5g/L of glucose for mixotrophic growth and in autotrophic growth condition. The cell culture was monitored using the hemocytometer for increase in cells concentration. At the end of three weeks, the cells were harvested after centrifugation and dried in the oven. The mixotrophic dried biomass weighed 0.5g/L and that of the autotrophic weighed 0.1g/L. The results for protein analyses for both mixotrophic and autotrophic yielded 1.118g/L &0.07g/L respectively. Also, the results for the glucose was obtained using the Mercz protocol, the mixotrophic had higher glucose content than the autotrophic with 0.0564g/L & 0.0266g/L respectively. The cell concentration was more in the autotrophic than in mixotrophic but the mixotrophic cell culture had bigger cell size which showed the presence of accumulated materials. Glucose enhanced the production of algal biomass.
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF STUDY
Smith (1955) defined algae based on characters of the sex-organs. He said-in algae the sex organs are usually unicellular and when they are multicellular as in most brown algae, all cells are fertile (Smith, 1995). There are approximately 1800 genera with 21,000 species which are highly diverse with respect to habitat, size, organization, physiology, biochemistry and reproduction (Pandey, 2009).
Algae may range in sizes from single cell as small as one micrometer to large seaweeds that may grow to over fifty meters (Vymagal, 1995). Algae are ubiquitous, they occur in almost every habitable environment on earth, soil, permanent ice, snow fields, hot and cold desert. Biochemically and physiologically, algae are similar in many aspects to other plants. Furthermore, algae are the major primary producers of organic compounds and play a central role as the base of the food chain in aquatic systems. Besides forming the basic food source for these food chains, they also produce oxygen necessary for the metabolism of the consumer organism (Lee,et al., 1989).
Algal biomass is always made up of these three main components: Carbohydrates, Protein and Natural oils. The most important component for biodiesel production is the natural oils that can be converted to biodiesel. The percentage lipid composition varies and so the fatty acid
In addition, the presence of algae leads to reduced erosion by regulating the water flow into soils. Similarly, they play a role in soil fertility, soil reclamation, and bio-controlling of agricultural pest, formation of microbiological crust, agricultural wastewater treatment and recycling of treated water. Human civilization depends on agriculture for its existence.
They are aquatic, both marine and fresh water, and occur on or within soil and on moist stones and woods as well as in association with fungi and certain animals. The algae are of great importance as primary producers of energy rich compounds which form the basis for this purpose, the planktonic algae are of special importance, since they serve as food for many animals. It is thought that 90% of the photosynthesis on earth is carried on by aquatic or by aquatic plants, the planktonic (suspended) algae are chiefly responsible this while photosynthesizing, they oxygenate their habitat, thus increasing the level of dissolved oxygen in their environment. Certain blue-green algae like some bacteria can use gaseous nitrogen from the atmosphere in building their protoplasm and in this way; they increase the nitrogenous compounds in water and soils of their habitat.
Light conditions affect directly the growing and photosynthesis of microalgae (duration and intensity). Microalgae needs a light/dark regime for productive photosynthesis, it needs light for a photochemical phase to produce Adenine triphosphate(ATP), Nicotinamide adenine
1.2 RELEVANCE OF STUDY
The relevance of this project was to grow algae using glucose in a sterile bioreactor for better yield of protein which can be used for nutritional enrichment of cereals, pharmaceutical, animal feeds and other purposes.
1.3 STATEMENT OF PROBLEM
World Health Organization (WHO) report in 2012 states that malnutrition is the underlying contributory factor in over one third of all child deaths, making children more vulnerable to severe diseases. The increasing world deficiency of protein is becoming a main problem of humankind. Since the early fifties, intense efforts have been made to explore new, alternate and unconventional protein. Research has shown that the chance of infection with HIV virus might be reduced in individuals who have good nutrition status with micro nutrients (Egal & Valstar, 1999).
Algae in the oceans, rivers, and lakes of the world are thought to produce about half of all the oxygen produced on the planet. Given that the total biomass of the world’s algae is but a tenth of the biomass of all the other plants, the efficiency of the algae is impressive and of interest in terms of producing biofuels. Cyanobacteria currently cultivated in large scale systems are economically viable sources of protein used in food because they often meet the requirements of nutrient in the diets. Moreover, through them you can get other human consumer products (Kuhad et al., 1997). A cyanobacterium as a source of single-cell protein has certain advantages over the use of other microorganisms because of its rapid growth and quantity and quality of protein (Molina et al., 2002). Among the microalgae, the genus Spirulina contains about 60 to 70% of proteins, nucleic acids and amino acids recommended by the Food and Agriculture Organization (Pelizer,et al., 2003). It also contains betacarotene and absorbable iron, and other minerals and high levels of vitamins, phenolic compounds, gammalinolenic acid and other essential fatty acids (Belayet al., 1993: Von et al., 2000).
The protein content of Spirulina varies between 50% and 70% of its dry weight. These levels are quite exceptional, even among microorganisms. Moreover, the best sources of vegetable protein achieve only half these levels; for example, soya flour contains “only” 35% crude protein. However, the protein content varies by 10-15% according to the time of harvesting inrelation to daylight. The highest values being obtained at early daylight (Association française pour l'a1gologie appliquée (AFAA) (1982).
1.4 AIM AND OBJECTIVES
The broad aim of this research was to grow algae mixotrophically using glucose as organic substrate with the following objectives:
Ø To culture and compare the algal growth using glucose
Ø To harvest and purify algal biomass.
Ø To evaluate the nutritional content of the algal biomass.
1.5 HYPOTHENSIS
Ø There is no significant difference in the amount of algal biomass cultivated in glucose and ethanol.
Ø There is a significant difference in the nutritional content of algae cultivated in glucose and ethanol.
1.6 SCOPE OF THE STUDY
The scope of this study was governed around Chlorellaviriabilis,a strain of Chlorella spp isolated from our local environment
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