CHAPTER ONE
1.0INTRODUCTION
1.1     Background of the study
Protease constitutes a large and complex group of enzymes that plays an  important nutritional and  regulatory  role in nature. Proteases are (physiologically) necessary for  living organisms; they are ubiquitous and found in a wide diversity of sources. Protease is the most important industrial enzyme of interest accounting for about 60% of the total enzyme market in the world  and  account  for approximately 40% of the total worldwide enzyme sale (Godfrey and West, 1996; Chouyyok et al., 2005). They are generally used in detergents (Barindra et al., 2006), food industries, leather, meat processing, cheese making, silver recovery from photographic film, production of digestive and certain medical treatments of inflammation and virulent wounds (Rao et al., 1998; Paranthaman et al., 2009). They also have medical and pharmaceutical applications.
Microbial  proteases  are  degradative  enzymes  which catalyze the total hydrolysis of proteins (Raju et al., 1994; Haq et al., 2006). The molecular weight of proteases ranges from 18 – 90 kDa  (Sidney and Lester, 1972). These enzymes are found in a wide diversity of sources such as plants, animals and microorganisms but they are mainly produced by bacteria and fungi. Microbial proteases are predominantly extracellular and can be secreted in the fermentation medium.
In the production of protease, it has been  shown to be inducible and was affected by the nature of the substrate used in fermentation. Therefore, the choice of an appropriate inducing substrate is of great importance. Different carbon sources such as wheat bran, rice straw, rice bran, cotton  and  bagasse have been studied for the induction and biosynthesis of protease. However, wheat bran is a superior carbon source for the production of protease by Aspergillus flavus. So the further studies were carried out by using wheat bran as carbon source.
The use of agro-industrial residues as the basis for cultivation media is a matter of great  interest, aiming to decrease the costs of enzyme production and meeting the increase  in  awareness  on  energy  conservation  and recycling (Singh et al., 2009). Major  impediments to the exploitation of commercial enzymes are their yield, stability, specificity and the cost of production. New enzymes for use in commercial applications with desirable biochemical and physiochemical characteristics and low production cost have been focus of much research (Kabli, 2007). Solid state fermentation (SSF) was chosen for the present research because it has been reported to be of more grated  productivity than that of submerged fermentation (Ghildyal  et al., 1985; Hesseltine, 1972). Economically, SSF offers many advantages including superior volumetric productivity, use of simpler machinery, use of inexpensive  substrates, simpler downstream  processing, and lower energy requirements when compared with submerged fermentation (Paranthaman et al., 2009).
1.2     Aim of the study
The aim of  this  study  was  to produce  protease from Aspergillus flavus using wheat bran as a substrate under Solid State Fermentation.
1.3     Objectives of the study
The objectives of the study include:
·        To isolate Aspergillus  flavus from spoilt bread in Gwagwalada.
·        To determine the frequencies of occurrence of  the isolated Aspergillus flavus from spoilt bread using simple percentages.
·        To determinethe proteolytic potential of the isolated fungi using basal medium.
·        To determine the quantity of the protease enzyme produced by the isolated fungi using spectrophotometer.