Biochemical characterization and optimization of cellulases for empty fruit bunch Saccharification
Empty (palm) fruit bunch (EFB) is one of the abundant agro-wastes generated by the oil palm sector in Malaysia. The EFB waste is normally returned to the plantation to replenish the soil or burnt in incinerators for energy generation. Besides the environmental consequences of these practices, substa...
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Online Access: | https://eprints.ums.edu.my/id/eprint/26570/1/Biochemical%20characterization%20and%20optimization%20of%20cellulases%20for%20empty%20fruit%20bunch%20Saccharification.pdf https://eprints.ums.edu.my/id/eprint/26570/ |
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| Summary: | Empty (palm) fruit bunch (EFB) is one of the abundant agro-wastes generated by the oil palm sector in Malaysia. The EFB waste is normally returned to the plantation to replenish the soil or burnt in incinerators for energy generation. Besides the environmental consequences of these practices, substantial amount of the EFB remains unutilized. However, EFB is a lignocellulosic biomass with high potential for the production of biochemicals such as bioethanol. The possible conversion of this feedstock into high value-added products would present high economic benefit to the oil palm industry and the country at large. In this research, a cell surface display technology, called the autodisplay system, was used to express recombinant cellulases for the saccharification of EFB. An investigation of a suitable expression platform between Escherichia coli and Pseudomonas putida revealed the latter as the better host (expression) system for the recombinant cellulase. The biochemical characterization of the cellulases (i.e., endoglucanase, BsCel5A; exoglucanase, CelK: β-glucosidase, BglA) revealed that the enzymes are active over a broad range of pH (4-10) and temperature (30-100 oC). The pH and temperature optima were BsCel5A (pH 6; 60 oC), CelK (pH 6; 60-70 oC), and BglA (pH 6; 50 oC). Also, in an attempt to improve the functionality of the enzymes, different additives (e.g., salts and surfactants) were studied for their influence on the cellulases. The results showed that CaCl2 and Tween 20 improve the synergistic performance of the enzymes on cellulose. Lastly, since cellulose depolymerization requires the three cellulases in different proportions, a simplex-lattice mixture design was employed to identify the optimum blend composition of the whole cell biocatalyst. The results revealed a blend ratio of 1: 1.6: 1.4 of endoglucanase: exoglucanase: β-glucosidase as the “sweet spot” for optimum sugar yield. The application of this blend generated about 0.354 and 0.446 g/l of reduced sugars from filter paper and 2.5% pretreated EFB, respectively. The supplementation of the enzyme blend with CaCl2 and Tween 20 resulted in a significant increase in sugar yield. The overall outcome of this research is a step in the right direction for wealth from the abundant EFB waste. |
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