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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