CHAPTHER ONE
INTRODUCTION
1.0 DIOSCOREA ALATA (YAM)
Dioscorea alata L (DA) is a species of yam, a tuberous root vegetable that is bright lavender in color. It is wide spread in distribution being grown in tropics and subtropics of Africa, America, Asia and Caribbean [Chiedozie et al; 2003]. In Indian traditional medicine, the tuber is used as a diuretic, aphrodisiac, anthelminitic and antidiabetic [Rodrignez-sosa et al; 1992]. Researchers have shown that Dioscorea alata L. contain most notably carotenoids and anthocyanins like potato [Brown et al; 2001]. Dioscoreaceae (D. alata, D. batatas, D. bulbilfera, D. opposita) has health beneficial compounds such as dioscorin [Hou et al; 2001, liu et al; 2007. Chan et al; 2006]. diosgenin [Chou et al; 2006. Brown et al; 2008. Yang and Lin; 2008] and water soluble polysaccharides (WSP) [Liu and Lin; 2009]. Dioscorin is the major storage protein in yam and functions against angiotensin, which converts enzyme to cause hypertension [Hsu et al; 2002]. Diosgenin is used in making progesterone and other steroid drugs [Zava et al; 1998]. Some studies showed that WSP had hypoglycemic effect [Teti estiasih et al; 2012].
ENZYMES
Enzymes are among the most important products obtained for human needs through plants, animals and microbial source. Nowadays, the use of enzymes in industrial sector is increasing due to increase of industries especially in food, beverages, textiles, leather and paper industries. Amylases are the enzymes that break down starch or glycogen. The Amylases can be derived from several sources such as plants, animals and microbes. The major advantages of using micro-organisms for production of Amylases in economical bulk production capacity and microbes are also easy to manipulate to obtain enzyme of desired characteristics [Vidyalakshmi, R. et al., 2009]. Amylases have been derived from several fungi, yeast, bacteria and actinomycetes but members of the genus Bacillus are heterogeneous and they are very versatile in their adaptability to the environment. Amylases have been purified earlier from various Bacillus species such as Bacillus megaterium [Oyeleke, S. B. et al., 2010] from Bacillus subtilis [Riaz, N. et al., 2003], from Bacillus licheniformis SPT 27 [Aiyer, P. V. D., 2004]. The enzyme of amylase family has a great significance due to its wide area of potential application. Amylases can be divided into two categories, endoamylases and exoamylases. Endoamylases catalyze hydrolysis in a random manner in the interior of starch molecules producing linear and branched oligosaccharides of various chain lengths. Exoamylases act from the non-reducing end successively resulting in short end products [Reddy, N. S. et al., 2003]. The production of microbial amylases from bacteria is dependent on type of strain, composition of medium, method of cultivation, cell growth, nutrient requirements, metal ions, pH, temperature, time of incubation and thermostability [Haq, I. et al., 2010]. Spectrum of application of amylase has widened in many sectors such as food, textile, baking and detergent industries. Besides its use in the saccharification or liquefication of starch, the enzyme is also used for the warp sizing of textile fibres, the clarification of haze formed in beer or fruit juices and for pretreatment of animal feed to improve digestibility [Nusrat, A and Rahman, S. R., 2008].
1.1 Statement of Problem
There is an increasing demand for industrial by-products obtained from starch such as glucose, glucose syrup, drugs formulation, supplements of foods, and increasing economic value of products. There is a high need for the starch to be broken down into useful products of economic and academic importance. The need to gelatinized starch for effective enzyme activity is important to actualise the yearning desire of the people. Therefore Dioscorea alata which is of high medicine value and a strong starch is used for the work to ascertain the importance of geletinization to enzyme penetration to yield required products.
1.2 Aims of the Work
The effect of gelatinization on enzyme hydrolysis of starch obtained from Dioscorea alata
1.3 Objectives of the Work
To determine the effects of gelatinization on enzyme hydrolysis of starch obtained from Dioscorea alata
Hypothesis:
: Geletinization of starch will enable the enzyme to break the starch more easily and effectively.
1.4 Justification
This work is very important to industries such as pharmaceutical, brewery, food and agricultural industries whose job is to produce more products to meet the demand of their customers and uses mainly raw starch in their production process.
