Biodetoxification of waste tire rubber using laccase from white rot fungus prior to biodevulcanization by bacteria /
The present work is an initiative to recycle used tires wherein the ground tire rubber (GTR) was detoxified using crude laccase from white rot fungus, Resinicium bicolor ATCC 64897 and then biodevulcanized by T. ferrooxidans. The physical and chemical factors important for laccase production by subm...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2016
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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: | The present work is an initiative to recycle used tires wherein the ground tire rubber (GTR) was detoxified using crude laccase from white rot fungus, Resinicium bicolor ATCC 64897 and then biodevulcanized by T. ferrooxidans. The physical and chemical factors important for laccase production by submerged fermentation in R. bicolor were screened using PBD and their optimum values were determined using OFAT method and further optimized using Box-Behnken design. Optimization of biodetoxification was performed using FCCCD with %detoxification as a response under RSM to optimize process parameters such as laccase activity (2U ml-1 – 5U ml-1), pulp density (3% - 9%) and incubation period (2 hrs – 12 hrs) under submerged condition. The %detoxification was measured by absorbance method. Biodevulcanization was performed by growing bacterium T. ferrooxidans both on biodetoxified (BDT)-GTR and non-detoxified (NDT)-GTR and the sulfate content of medium after devulcanization was measured by precipitation gravimetric analysis. Both the (BDT) and biodevulcanized (BDV)-GTR were analyzed by FT-IR. Substrate (yellow flame bark powder), pH, CuSO4 concentration, incubation period and agitation were found significant for laccase production. The optimum values from OFAT were: pH=5, CuSO4 concentration=3mM, Substrate concentration=4%, Incubation period=2 days and Agitation=180 rpm. The ANOVA of Box-Behnken design indicates the model to be not significant with R2=0.8138. The detoxification achieved under optimum condition was 98.5% and was 1.5 fold more compared to normal condition. The ANOVA for biodetoxification shows the model to be highly significant with R2=0.9857. The 3D-response surface plots confirm enzyme activity to be the most significant factor for biodetoxification. FT-IR analyses of (BDT)-GTR shows bond stretching in O-H group indicating oxidized phenols, nitrogen functions and five membered lactams confirming the chemical change due to laccase interaction. The increased growth of bacteria on (BDT)-GTR compared to non-detoxified (NDT)-GTR during one week of biodevulcanization demonstrates that detoxification had occurred. FT-IR analyses of both BDV-(BDT)-GTR and BDV-(NDT)-GTR show bands for sulfoxide which was due to sulfur oxidation present on GTR surface. The sulfate content of the medium after devulcanization was calculated as 1.84 gL-1 and 1.95 gL-1 for NDV-GTR and BDT-GTR respectively which indicates that bacteria acted more efficiently on BDT-GTR compared to NDT-GTR. |
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| Physical Description: | xv, 110 leaves : ill. ; 30cm. |
| Bibliography: | Includes bibliographical references (leave 94-108). |