Sains Malaysiana 45(6)(2016): 955–962

Effects of Alkaline Combined with Ultrasonic Pretreatment and Enzymatic Hydrolysis of Agricultural Wastes for High Reducing Sugar Production

(Kesan Gabungan Alkali dengan Ultrasonik Prarawatan dan Hidrolisis Enzim Sisa Pertanian

untuk Penurunan Pengeluaran Gula yang Tinggi)

WAESARAT SOONTORNCHAIBOON¹, SANG MOO KIM² & RATCHAPOL PAWONGRAT¹*

¹Department of Liberal Arts and Science, Kasetsart University, Nakhon Pathom 73140

Thailand

²Department of Marine Food Science and Technology, Gangneung-Wonju National University

Gangneung 25457, Republic of Korea

Diserahkan: 10 Februari 2015/Diterima: 11 Januari 2016

ABSTRACT

The effects of six pretreatments of five agricultural wastes (corn cob, pineapple waste, bagasse, rice straw and water hyacinth) on the chemical composition and total reducing sugar yield were investigated. Six pretreatments were: 1% NaOH with ultrasound for 60 min; 1% NaOH with ultrasound 100% duty; 2% NaOH with ultrasound for 60 min; 2% NaOH with ultrasound 100% duty cycle; 1% NaOH by standing in the oven at 60°C for 90 min; and 2% NaOH by standing in the oven at 60°C for 90 min. Among them, the highest cellulose content of 55.15% was obtained from bagasse by pretreating with 1% NaOH with ultrasound 100% duty cycle. It subsequently yielded the highest total reducing sugar of 36.21% (36.21 g reducing sugar/100 g substrate). The lignin content of all samples significantly decreased, but ultrasonic pretreatment increased the cellulose content. However, the best pretreatment method for each sample was different. Based on SEM analysis, the morphologies of all samples were changed after pretreatment. In addition, the increase of enzyme loading from 250 to 550 CMC U/g biomass led to more than 20% increase in the total reducing sugar. It was found that the higher enzyme loading (700 CMC U/g dried biomass) did not improve the total reducing sugar for all samples.

Keywords: Agricultural waste; alkaline; hydrolysate; pretreatment; ultrasonic

ABSTRAK

Kesan enam prarawatan ke atas lima sisa pertanian (tongkol jagung, sisa nanas, hampas tebu, jerami padi dan keladi bunting) terhadap komposisi kimia dan jumlah hasil penurunan gula telah dikaji. Enam prarawatan adalah: 1% NaOH dengan ultrabunyi untuk 60 min; 1% NaOH dengan ultrabunyi tugas 100%; 2% NaOH dengan ultrabunyi untuk 60 min; 2% NaOH dengan ultrabunyi kitar tugas 100%; 1% NaOH dengan dirian di dalam relau pada suhu 60°C selama 90 min; dan 2% NaOH dengan dirian di dalam relau pada suhu 60°C selama 90 min. Antara semua, kandungan selulosa tertinggi adalah 55.15% telah diperoleh daripada hampas tebu dengan prarawatan 1% NaOH dengan ultrabunyi kitar tugas 100%. Ia kemudiannya menghasilkan jumlah penurunan gula yang paling tinggi sebanyak 36.21% (36.21 g penurunan gula/100 g substrat). Kandungan lignin daripada semua sampel menurun dengan ketara, tetapi rawatan awal ultrasonik meningkatkan kandungan selulosa. Walau bagaimanapun, kaedah rawatan awal yang terbaik bagi setiap sampel adalah berbeza. Berdasarkan analisis SEM, morfologi semua sampel telah berubah selepas rawatan awal. Di samping itu, peningkatan muatan enzim sebanyak 250-550 CMC U/g biojisim membawa kepada 20% peningkatan dalam jumlah penurunan gula. Didapati bahawa pemuatan enzim yang tinggi (700 CMC U/g biojisim kering) tidak meningkatkan jumlah penurunan gula untuk semua sampel.

Kata kunci: Alkali; hidrolisat; prarawatan; sisa pertanian; ultrasonic

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*Pengarang untuk surat-menyurat; email: faasrpp@ku.ac.th