CHAPTER ONE
1.0 INTRODUCTION
Cassava (Manihot esculenta) is the third largest source of food carbohydrates in the tropics, after rice and maize (Fauquet and Fargette, 1990). History revealed that cassava was introduced to Africa by Portuguese traders from Brazil in the 16th century. Maize and cassava are now important staple foods, replacing native African crops (FAO, 2001). Cassava is sometimes described as the bread of the tropics (Adams et al., 2009). But should not be confused with the tropical and equatorial bread free (Encephalartos), the breadfruit (Artocarpus altilis) or the African breadfruit (Treculia africana). Nigerian is the world’s largest producer of cassava. However, based on the statistics from food agriculture organization (FAO), United Nation of Thailand is the largest exporting country of dried cassava, with a total of 77% of world export in 2015. The second largest exporting country is Vietnam, with 13.6%, followed by Indonesia (5.8% and Costa Rica (2.1%). Worldwide cassava production increased by 12.5% between 1998 and 1990. Cassava has been a raw material globally for industrial production of textiles, papers, adhesives, pharmaceutical and various food products because it is rich in carbohydrate with high energy density and has generated great impact in world economics (Aigbe and Remison, 2010).
Scientific Classification
Kingdom: Plantae
Class: Angiosperm
Unranked: Eudicots
Order: Malpighiales
Family: Euphorbiaceae
Subfamily: Crotonoideae
Genus: Manihot
Species: Manihot esculenta
In the vernacular languages of places where it is cultivated, Nigeria for example, cassava is called Akpu (Igbo), Paki/Ege (Yoruba) and Rogo (Hausa).
Cassava root contains about 30% starch and significant amount of calcium (50 mg/100 g), phosphorus (40 mg/100 g) and vitamin C (25mg /100 g). Various food applications take advantages of cassava starch’s odourless, clear paste and high freeze – thaw stability properties. Starchy cassava roots can be processed into garri, lafun, fufu, Kpokpogari or bobozi, it is also used for making tapioca. Industries take advantage of cassava starch clear appearance and sticky texture of its cooked paste in the manufacture of adhesives and glue (Aigbe and Remison, 2010).
It is also one of the important food crops that survive conditions of low nutrient availability and drought. Cassava and its product are renewable source of energy that pose no threat to the environment and has been used by several researchers in the production of biofuel (Musatto and Teixira, 2010). Cassava tubers and hay are used worldwide as animal feed. Cassava hay is harvested at a young growth stage three to four months when it reaches about 30 – 45 cm (12-18 m) above ground; it is then sundried for one to two days until it has final dry matter content of less than 85%. It is valued as good roughage source for ruminants such as dairy or beef cattle, buffalo, goats and sheep, whether by direct feeding or as a protein source in concentrate mixtures. Cassava is also used as a number of commercially available laundry products especially as store for shirts and garments. Medicinally, cassava root has been promoted for bladder and portrait cancer (Abeygunasekera, 2013). However, according to America Cancer Society ‘there is no convincing scientific evidence that cassava or tapioca is effective in preventing treating cancer’.
It has been estimated that 2.96 million metric tons of cassava peels is generated annually in Nigeria for processing cassava to various food product (Nwabueze and Otunwa, 2006). Recently, cassava starch has equally been found by a very raw material for the production of high biodegradable plastic (Steven, 2002). There are many microorganism that are associated with cassava such as bacteria, fungi, yeast, actinomycetes and virus. Industrially, these microbes used cassava as substrate for the production of enzyme that is economically important such organism include Bacillus spp, Aspergillus spp, and Saccharomyces cerevisiae. Amylase, pectinase, and protease are the enzyme produce by these organisms. However large tons of cassava peels are discarded annually in cassava producing country (Nigeria) when cassava is processed to various food products. This was usually ends up in an open dumps site or drainage system, threatening both surface and ground water quality including plant life. Cassava feed can be used as livestock feeds, but the constrain that hinders this characteristic are their fiber content, low calorific value and heavy loads of anti nutrients like cyanide, tannins and phytates (Aro, 2008). However, various treatment such as microbial and enzyme hydrolysis and fermentation of the peels effective remove the constrain militating against the use of cassava peels as animal feedstock (Olowofeso et al., 2013). Industrial and local processing of cassava to food and other products has led to generation of economic waste that is dump in drainage rather than transferring them into useful product. Those waste end up polluting the surface and underground water (Oluwabiwoninu and Odunfa, 2012; Muhammed et al., 2013). It is therefore necessary to convert these peels waste into useful ends products rather than allowing them to become problematic in the environment.
1.1 Aim
The aim of this research work is to produce amylase from cassava peels (substrate) using Bacillus subtilis.
1.2 Objectives
The overall objectives of this work are:
- To identify Bacillus subtilis using nutrient and starch agar.
- To determine and verify Bacillus subtilis as an amylolytic activity producing bacteria.
- To produce amylase using Cassava peels as substrate in solid state fermentation (SSF).
- To evaluate the effect of substrate, pH, temperature, and incubation period on amylase activity.
1.3 Justification
The use of chemicals in industries has pose many effect ranging from high cost, environmental pollution, and negative effect on product quality to circumvent all these challenges. This research work is aimed at studying the way of transforming cassava peels to valuable products, by using it to produce amylolytic enzyme like amylase that are environmental friendly and cost effective which will serve as alternative to the chemical used by the industries to process their raw materials effectively.
