The production of third-generation bioethanol from eucheuma cottonii using dowex (TM) DR-G8
| dc.contributor.author | Tan Inn Shi | |
| dc.date.accessioned | 2021-05-07T00:37:18Z | |
| dc.date.available | 2021-05-07T00:37:18Z | |
| dc.date.issued | 2015-09-01 | |
| dc.description.abstract | The red macroalgae, Eucheuma cottonii (EC) is a third-generation biomass, and it contains large amount of carbohydrate that can be readily fermented into bioethanol. Up to now, the use of the liquid acid-catalyst have been reported for the hydrolysis of carbohydrates from various biomass to fermentable sugar. However, the need of easily separable and reusable solid acid catalyst is considered essential in the hydrolysis process. In this study, for the first time, Dowex (TM) Dr-G8 was explored as a potential solid catalyst to hydrolyze carbohydrates from dried raw EC or macroalgae extract (ME) and pretreatment of macroalgae cellulosic residue (MCR), to simple reducing sugar prior to the fermentation process. The reaction condition for hydrolysis of EC (6 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 h) and ME (8 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 h) resulted to a galactose yield of 43.2 % and 49.4 %, respectively. This result was slightly lower compared with the feedstock by using ME. However as for MCR, the solid acid catalyst (Dowex (TM) Dr-G8) was used in the pretreatment process to enhance enzymatic conversion of MCR to reducing sugar. Reusability of Dowex (TM) Dr-G8 was also investigated in this study, the galactose yield maintained at around 46.7 % till the fifth run. This shows that Dowex (TM) Dr- G8 was not significantly deactivated even after repeated used. The pretreatment condition for MCR is 10 % (w/v) Dowex (TM)-Dr G8, 120 oC, and 30 min. An optimum sugar yield of 99.8 % was attained when pretreated MCR (P-MCR) was used as substrate for enzymatic hydrolysis after 30 h. Catalyst recyclability study were performed and a sixth-times reuse was accomplished without any loss of catalytic activity. In addition, a novel concept for the synthesis of stable polymer hybrid matrix was developed. In this study, glutaraldehyde crosslinked κ-carrageenan was used for the immobilization of β-glucosidase using the covalent method via polyethyleneimine and glutaraldehyde. The immobilized β-glucosidase was then used to hydrolyze PMCR for the production of reducing sugar and a hydrolysis yield of 73.4% was obtained. When a solid acid hydrolysate containing 35 g/L of galactose were fermented with an inoculums amount of 16.0 g/L, an optimum bioethanol production of 11.63 g/L was achieved (64.6 % of the theoretical value) after 72 h. Bioethanol production by PSSF (prehydrolysis and simultaneous saccharification and fermentation) process was observed to be more effective than the SHF (separate hydrolysis and fermentation) process, producing 5.80 mg/mL of bioethanol, with a theoretical yield of 91 %. Scale up of SHF of solid acid hydrolysate was carried out in a 5 L fermenter resulting to 61.6 % of bioethanol yield, while scale up study of PSSF process was carried out in a 5 L fermenter conducted with optimized conditions resulting to 87.1 % of bioethanol yield, which is almost the same as in shaking flasks. This result indicated that the fermentation process using macroalgae biomass could be easily scaled-up to large fermenter without compromising its performance. On the other hand, the estimated bioethanol production cost using macroalgae was 0.77 USD $/L. Compared to other feedstocks, bioethanol production cost from macroalgae are competitive and economically viable. A consequential life cycle assessment (LCA) and exergy analysis of macroalgae-based bioethanol were performed. Results suggested that the purification of bioethanol (S6) is found to have the highest impact in all the impact categories considered. The proposed technology in this study using solid acid catalyst was found feasible for the production of bioethanol from EC. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/13345 | |
| dc.language.iso | en | en_US |
| dc.title | The production of third-generation bioethanol from eucheuma cottonii using dowex (TM) DR-G8 | en_US |
| dc.type | Thesis | en_US |
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