VALORIZATION OF RICE HUSK FOR CITRIC ACID PRODUCTION USING ASPERGILLUS NIGER BY SOLID STATE FERMENTATION
VALORIZATION OF RICE HUSK FOR CITRIC ACID PRODUCTION USING ASPERGILLUS NIGER BY SOLID STATE FERMENTATION
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Date
2017-10
Authors
TANIMU, JAMILA
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Abstract
The utilization of agro-residues as substrate to generate new products of commercial interest through a bioprocess is considered as an important strategy for the development of sustainable technologies. Citric acid production was carried out from various pretreated (acid, alkaline, hydrogen peroxide and un-pretreated) rice husk by solid state fermentation (SSF) using Aspergillus niger. Pyridine-acetic acid anhydride method was used for quantitative analysis of the citric acid produced. Placket Burman Design (PBD) was used to screen ten media components ((NH4)2SO4, MgSO4.7H2O, NH4NO3, KH2PO4, FeCl3.6H2O, CuSO4, FeSO4, ZnSO4, MnSO4, and Molasses) required by Aspergillus niger (A. niger) to enhance citric acid production. Face Centered Central Composite Design (FCCCD) was used to select the most contributing nutrients for the production. Thin layer chromatography, Fourier Transform Infra-Red (FTIR) analysis and melting point determination of both standard and citric acid produced were also carried out. The result obtained from PBD indicated that hydrogen peroxide pretreated rice husk was the best pretreatment method with citric acid yield of 3.65 ± 0.26g/kg RH which is statistically higher (p < 0.05) than that of acid, alkaline and un-pretreated rice husk whose yields were 2.94 ± 0.83, 1.97 ± 1.24 and 2.34 ± 0.13 g/kg RH, respectively. Among the media components NH4NO3, KH2PO4, and molasses were found to be vital in citric acid production using rice husk as a substrate with the optimum concentrations of 2.5g/L, 3.25g/L and 0.2275g/L, respectively with citric acid yield of 4.765±0.001. The coefficient of determination"R2"was found to be 0.9790 and is in reasonable agreement with the "Adjusted R2" of 0.9601 at p < 0.05. Both the standard and A. niger produced citric acid gave similar Rf value of 0.242 and melting point of 153 ± 0.00 ⁰C and 153 ± 0.02 ⁰C, respectively, wavenumbers corresponding to O-H and C=O of 3338.7 cm-1and 1565.5 cm-1 and 3324.8 cm-1and 1625.1 cm-1 for standard and citric acid produced, respectively. The result of this study has therefore, revealed the potential of rice husk to produce citric acid with similar characteristic to that of standard citric acid. It also showed the importance of using a statistical design like Face Centred Composite Design (FCCCD) of Response surface methodology (RSM) to optimize the production of citric acid using rice husk as a substrate by A niger as it is proved to be a useful tool in establishing optimum conditions for citric acid production.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A MASTER OF SCIENCE DEGREE IN BIOCHEMISTRY DEPARTMENT OF BIOCHEMISTRY,FACULTY OF LIFE SCIENCES,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
VALORIZATION,, RICE HUSK,, CITRIC ACID,, ASPERGILLUS,, NIGER,, FERMENTATION,