4 Introduction

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  1 CHAPTER 1 INTRODUCTION Rice is the main source of food for occupants in developing countries such as Malaysia. Rice bran is a by-product of the rice milling industry, thus making rice  bran a valuable source for the solid substrate. The source for the solid substrate used in this experiment is rice bran or also known as paddy husk. Rice bran has found its uses as chicken feed in the poultry industry. Rice bran is available abundantly and is labeled as agro-industrial waste. Rice bran has many food applications in prepared foods, nutraceuticals, and functional foods (Agamuthu and Nithiya, 2008). Some of the common applications of rice bran are in snack foods, bakery products, cereals, crackers, pasta products, dough conditioners, beverages, gluten-free foods, and medical foods (Anto et al.,  2006). Although in the field of biotechnology, the number one ranking substrate with the highest glucoamylase activity is wheat bran, rice bran has gained importance especially where wheat bran is not available (such as in Malaysia) or other waste containing starch are generated in abundance (Anto et al  ., 2006). Furthermore, rice  bran along with other nutrients is considered as a support for the fungal growth during glucoamylase production (Arasaratnam et al  ., 2001). Rice bran is used as the sample for this research because agro-industrial residue are generally considered as the best substrate for solid state fermentation process and enzyme production by solid state fermentation is not an exception to that. Therefore, rice bran can be used as an ideal non-edible starch source for amylase production (Agamuthu and Nithiya, 2008).  2 Glucoamylase are produced by various microorganisms, including bacteria, fungi and yeasts, but a single strain can produce both these enzymes very well (Ellaiah et al  ., 2002). Therefore for this particular study, strains from  Aspergillus niger   will be used to produce glucoamylase. As mentioned by Selvakumar et al  ., (1998) that the exclusive production of this enzyme is achieved by  Aspergillus niger  . Filamentous fungi have a number of properties which make them important  both scientifically and industrially. The industrial importance of filamentous fungi is illustrated by applications ranging from production of organic acids (e.g. citric acid and antibiotics (e.g. penicillin) to a number of industrial enzymes.  Aspergillus niger   is most commonly found in mesophilic environments such as litter in compost, decaying vegetation or soil and plant material (Schuster et al  ., 2002). Hence, it is an important filamentous fungi because it has been a useful resource to be used for many biotechnology purpose where it has the ability to accumulate and secrete large amounts of metabolites and large amounts of heterologous and homologous proteins (Karaffa and Kubicek, 2003). Furthermore,  Aspergillus niger   is considered to be one of the most important microorganism used in the biotechnology field.  Aspergillus niger   has been used for decades due to its ability to produce food enzymes and citric acid. Moreover, this research was conducted using  Aspergillus niger  because the enzyme produced by it are considered as “Generally Regarded As Safe” (GRAS) by the United States Food and Drug Adminstration, USFDA. Pectinase, protease and amyglucosidase (glycoenzyme) were the first to be exploited, and were srcinally produced in surface culture (Schuster et al  ., 2002). The traditional method of producing glucoamylase was done by using submerged fermentation (SmF). However, in recent years the solid-state fermentation (SSF) processes have been increasingly applied for the production of this enzyme (Ellaiah et al  ., 2002). In this study the production of glucoamylase is done through solid state fermentation by utilizing rice bran as the substrate and also the fungus  Aspergillus niger  . Solid state fermentation is defined as any fermentation process occurring in the absence or near absence of free water, employing a natural substrate as above, or an inert substrate used as solid support. Solid state fermentation utilizes agro-industrial wastes as the substrates in the enzyme production (Agamuthu and  3  Nithiya, 2008). Solid-state fermentation (SSF) has emerged as an appropriate technology for the management of agro-industrial residues and for their value addition. Among the advantages for SSF processes it is often cited that enzyme titers are higher than in SmF. Solid substrate fermentation provides tremendous result and has great potential for the production of enzymes. It can be of special interest in these processes where the crude fermented  product maybe used directly as enzyme source. According to Couto and Sanroman, (2005) in solid state fermentation processes, the solid substrate act as either inert or non-inert material, supporting the fermentation process, moreover inert substrates only act as an anchorage for the fungal growth, while non-inert substrate also supply nutrients for the fungal growth. SSF is a suitable process for enzyme production using filamentous fungi since, SSF is well adapted to the metabolism of the fungus and it gives the natural habitat for fungal growth (Singhania et al  ., 2009). Amylase is an enzyme well recognized to have properties for degrading starch and has been well characterized through the study of various microorganisms. There are three major types of amylase, which are α - amylase, β - amlylase and γ - amylase. γ -amylase is also known as glucoamylase. Glucoamylase is a well recognized amylolytic enzyme, due to its significant benefit when used commercially in the food industry for the production of starch syrups, chocolate syrup and dextrose, the preparation of starch derived adhesives, grain alcohol and fruit cakes, improving utilization of enzymatically treated barley in poultry calf raising and the clarification of fruit juice for jelly manufacture in food processing industry (Paulchamy, 2008). Glucoamylases are industrially important biocatalyst and extensively used in the manufacture of crystalline glucose or glucose syrup either as soluble or immobilized enzymes (Abraham et al  ., 2004). Furthermore, these enzymes have found wide application in the processed food industry, fermentation industry, textile and paper industries (Selvakumar et al  ., 1998).  4 Keeping in view the significance of glucoamylase to the research work has been done with the following objectives: 1.   To determine the best strain of  Aspergillus niger   in producing glucoamylase. 2.   To determine the optimum level of inoculum for the production of glucoamylase. 3.   To determine the optimum nitrogen source in producing the highest yield of glucoamylase. 4.   To determine the optimum carbon source supplemented in the media for  producing the highest yield of glucoamylase.

For Exam

Jul 23, 2017


Jul 23, 2017
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