Heng , King Sern
(2016)
Bioconversion Of Rice Husk To Polyhydroxybutyrate Via Pretreatment And Enzymatic Hydrolysis.
PhD thesis, Universiti Sains Malaysia.
Abstract
Beras merupakan antara sumber makanan yang terbesar di seluruh dunia. Di
Malaysia, purata penghasilan padi adalah lebih daripada 2 juta tan setahun. Daripada
hasil padi yang dituai, sekitar 20% komposisinya adalah sekam padi yang biasanya
akan terbuang. Sekam padi (RH) terdiri daripada lignoselulosa yang boleh ditukar
kepada substrat untuk fermentasi. Kajian ini telah dijalankan untuk menilai potensi
sekam padi sebagai sumber karbon untuk penghasilan polihidroksialkanoat (PHA),
iaitu sejenis bioplastik yang dihasilkan oleh pelbagai jenis bakteria. Untuk mengatasi
sifat ketahanan dan kekerasan biojisim ini, kaedah prarawatan fizikokimia telah
dijalankan ke atas sekam padi dalam keadaan yang berbeza dan keberkesanannya
telah dibanding berdasarkan penghasilan gula selepas hidrolisis enzim. Antara
kaedah prarawatan yang telah diuji, didapati kalium hidroksida (KOH) dengan
gabungan suhu dan tekanan tinggi, merupakan kaedah yang paling berkesan untuk
meningkatkan penghadaman enzim bagi RH, iaitu 70% hasil gula atas jumlah
kandungan karbohidrat. Hasil gula meningkat ke 87% apabila muatan enzim dan
substrat dioptimakan untuk hidrolisis menggunakan dua enzim komersial, Celluclast 1.5L and Novozyme 188.
Rice is one of the largest sources of food worldwide. In Malaysia, average
paddy production is more than 2 million tonnes annually. From the yield of harvested
paddy, approximately 20% of it consists of the husks, which are typically disposed.
Rice husks (RH) consist mainly of lignocellulose, which can be converted to
substrates for fermentation. This study was conducted to evaluate the potential of RH
as a carbon source for the production of polyhydroxyalkanoate (PHA), a bioplastic
produced by many types of bacteria. To overcome the recalcitrant nature of this
biomass, physicochemical pretreatments were performed on the rice husks under
different conditions and their efficiencies were compared in terms of sugar yield
upon enzymatic hydrolysis. Based on all the pretreatment methods tested, the use of
potassium hydroxide (KOH) combined with high temperature and pressure, was
found to be most effective in increasing the enzymatic digestibility of the material,
resulting in 70% sugar yield per total carbohydrate content. The sugar yield was
increased to 87% when enzyme and substrate loading were optimized for enzymatic
hydrolysis using two commercial enzymes, Celluclast 1.5L and Novozyme 188.
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