Bioconversion Of Rice Husk To Polyhydroxybutyrate Via Pretreatment And Enzymatic Hydrolysis

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