Optimization of amylolytic enzymes production from bitter manihot esculenta using aspergillus niger /
Amylases are industrial enzymes which hydrolyze carbohydrate molecules to give diverse products including dextrins and progressively smaller polymers composed of glucose units. Due to their wide industrial applications, these enzymes account for 65 % of global enzyme market with microorganisms being...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur:
Kulliyyah of Engineering, International Islamic University Malaysia,
2014
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Amylases are industrial enzymes which hydrolyze carbohydrate molecules to give diverse products including dextrins and progressively smaller polymers composed of glucose units. Due to their wide industrial applications, these enzymes account for 65 % of global enzyme market with microorganisms being the predominant sources for enzyme production. Enzyme production on industrial level is still faced by challenges represented by high production costs, selection of appropriate microorganisms and improvement of medium composition and process condition parameters. Hence, the search is always on for means to decrease enzyme production costs and increase enzyme productivity. Utilization of agroindustrial residues like bitter Manihot esculenta as a substrate for amylase production is promising and economically convenient since it is rich in starch, abundant, cheap, not competing as food and environmentally friendly. In this study, five different strains of Aspergillus niger were investigated for their amylolytic productivity in terms of α-amylase and glucoamylase production capacity using bitter cassava as a substrate and the most promising strain was found to be Aspergillus niger O103A. Subsequently, successive statistical optimization techniques including Plackett-Burman (PB) design, one-factor-at-a-time (OFAT) method and Face centered central composite design (FCCCD) under response surface methodology (RSM) were used to develop an optimized fermentation medium for simultaneous production α-amylase and glucoamylase by Aspergillus niger O103A in shake flask cultures. Medium optimization developed a medium containing 10 g/L cassava, 3.2 g/L maltose and 2.2 g/L yeast extract which led to maximum production of α-amylase (48.5 U/ml) and glucoamylase (27.9 U/ml) after 72 hrs of fermentation. Using the optimized medium, Process condition parameters (initial pH, inoculum size and agitation rate) were further investigated in shake flask cultures using FCCCD under response surface methodology. On statistical analysis of the results, the optimum initial pH, inoculum size and agitation rate were found to be 4.8, 3.7% v/v and 260 rpm respectively, with maximum production of α-amylase (56 U/ml) after 48 hrs and glucoamylase production of 42.3 U/ml after 60 hrs. Following the optimization study, the produced α-amylase and glucoamylase enzymes were characterized based on their pH and temperature optima as well as the effects of different metal ions, chemicals and organic solvents on enzyme activity and stability. Maximum activity of α-amylase was achieved at pH 5 with an optimum temperature of 60°C to 70°C while glucoamylase exhibited maximum activity at pH 6 with an optimum temperature of 60°C. Among metallic ions, only Mn+2 and Co+2 stimulated activity for both enzymes while all organic solvents tested inhibited α-amylase and glucoamylase activity. Among different detergents and surfactants investigated, only Triton X–100 stimulated α-amylase activity. Furthermore, α-amylase activity suffered no activity loss by EDTA nor activity gain by Ca+2 which might indicate that the produced α-amylase is calcium independent. The findings of this study showed that bioconversion of bitter cassava for amylase production would hold a prominent position in future biotechnology mainly because of its eco friendliness and flexibility for economic development. |
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| Physical Description: | xvi, 172 leaves : ill. ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 140-164). |