Tan , Inn Shi (2015) The Production Of Third-Generation Bioethanol From Eucheuma Cottonii Using Dowex (TM) DR-G8. PhD thesis, Universiti Sains Malaysia.
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Abstract
Eucheuma cottonii (EC) adalah sejenis makroalga merah yang dianggap sebagai biomass generasi ketiga, dan mengandungi karbohidrat dalam jumlah yang besar and boleh difermentasi secara mudah menjadi bioethanol. Sehingga kini, penggunaan asid pemangkin cecair telah dilaporkan untuk menukar karbohidrat daripada pelbagai biomass kepada gula fermentasi melalui proses hidrolisis. Walau bagaimanapun, asid pemangkin pepejal yang boleh diasingkan secara mudah dan boleh diguna semula adalah dianggap penting dalam proses hidrolisis. Dalam kajian ini, Dowex (TM) Dr-G8 telah diterokai sebagai pemangkin berpotensi buat kali pertama bagi menghidrolisis karbohidrat daripada EC atau makroalga ekstrak (ME) kepada gula sebelum proses fermentasi. Sebanyak 43.2% and 49.4 % hasil gula optimum telah dicapai apabila dirawat dalam keadaan proses optimum iaitu bagi EC (6 % w/v Dowex (TM) Dr-G8, 120 oC, 1 Jam) dan ME (8 % w/v Dowex (TM) Dr-G8, 120 ºC, 1 Jam) (49.4 %). Keputusan ini adalah lebih rendah apabila berbanding dengan ME diguna sebagai bahan mentah. Kebolehgunaan Dowex (TM) Dr-G8 turut disiasat dalam kajian ini, hasil galactose yang dikekalkan iaitu kira-kira 46.7% sehingga larian kelima. Ini menunjukkan bahawa Dowex (TM) Dr-G8 tidak ketara dinyahaktifkan walaupun selepas berulang kali digunakan. Selain itu, Dowex (TM) Dr-G8 digunakan di proses prarawatan dijalankan untuk meningkat proses enzim bagi menukar MCR menjadi gula. Dalam keadaan yang optimum (10 % (w/v) Dowex (TM)-Dr G8, 120 oC, and 30 min), hasil gula optimum sebanyak 99.8 % telah dicapai apabila MCR yang dirawat (P-MCR) telah digunakan sebagai substrat untuk proses hidrolisis enzim selepas 30 jam. Di samping itu, satu konsep yang baru untuk mensintesis matriks polimer hibrid yang stabil telah dijalankan dalam kajian ini. Kajian ini telah mengimobilisasi enzim di κ-carrageenan dengan meggunakan kaedah kovalen melalui polyethyleneimine and glutaraldehid. Imobilisasi enzim itu telah digunakan untuk menghidrolisis P-MCR untuk menghasilkan gula yang sebanyak 73.4 %. Apabila asid hidrolisat yang mengandungi 35 g/L galaktosa telah difermentasi dengan jumlah yis yang sebanyak 16.0 g/L, nilai optimum boleh mencapai sebanyak11.63 g/L (64.6 % daripada nilai teori) selepas 72 jam. Bioetanol hasil daripada proses PSSF (prahidrolisis dan saccharification serentak dan penapaian) diperhatikan lebih berkesan daripada proses SHF (hidrolisis berasingan dan penapaian) yang menghasil bioetanol sebanyak 5.80 mg/mL (hasil teori sebanyak 91 %). Peningkatan jumlah proses SHF yang menggunakan acid hydrolysate telah dijalankan di 5 L fermenter telah menghasilkan sebanyak 61.6 % bioetanol, di mana dalam kajian proses PSSF telah dijalankan di 5 L fermenter dengan syarat-syarat yang optima menghasilkan sebanyak 87.1 % bioetanol adalah hampir sama seperti proses yang menggunakan kelalang kon. Keputusan ini menunjukkan bahawa proses penapaian menggunakan makroalga biomass boleh dipertingkatkan kepada jumlah besar dalam fermenter tanpa menjejaskan prestasinya. Anggaran kos bagi penghasilan bioetanol dengan makroalga adalah sebanyak 0.77 USD $/L. Berbanding dengan biomass yang lain, kos penghasilan bioetanol daripada makroalga dapat bersaing dari segi ekonomi. Penilaian kitar hayat (LCA) dan analisis exergy berasaskan makroalga-bioetanol telah dijalankan. Keputusan menunjukkan bahawa permurnian bioetanol (S6) didapati mempunyai kesan yang tertinggi dalam semua kategori kesan yang dipertimbangkan. Teknologi yang dicadangkan dalam kajian ini menggunakan asid pemangkin pepejal didapati sesuai untuk menghasilakan bioetanol dari EC. ________________________________________________________________________________________________________________________ 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.
| Item Type: | Thesis (PhD) |
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| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2874 |
| Subjects: | T Technology T Technology > TP Chemical Technology > TP200-248 Chemicals: Manufacture, use, etc. |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Kimia (School of Chemical Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 12 Jul 2018 07:15 |
| Last Modified: | 16 Aug 2018 08:49 |
| URI: | http://eprints.usm.my/id/eprint/41010 |
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