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Cassava Pulp Hydrolysis under Microwave Irradiation with Oxalic Acid Catalyst for Ethanol Production
Euis Hermiati1,*, ShuntaroTsubaki2,3 & Jun-ichi Azuma2,4
1R&D Unit for Biomaterials, Indonesian Institute of Sciences (LIPI),
Jalan Raya Bogor Km 46, Cibinong, Bogor 16911, Indonesia
2Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
3Oceanography Section, Science Research Center, Kochi University,
Akebono-cho, 2-5-1, 780-8520, Kochi, Japan
4 Graduate Schoolof Engineering, Osaka University,
Yamadaoka, Suita, 565-0871, Osaka, Japan
*Email: euis.hermiati@lipi.go.id
Abstract. Microwave irradiation is an alternative method of starch hydrolysis that offers a rapid process. The aim of this research was to improve microwave-assisted hydrolysis of cassava pulp by using oxalic acid as a catalyst. Suspension of cassava pulp in 0.5% oxalic acid (1 g/20 mL) was subjected to microwave irradiation at 140-230 °C for 5 minutes, with 4 minutes of pre-heating. One gram of fractured activated carbon made of coconut shell was added into a number of suspensions that were subjected to the same conditions of microwave irradiation. The soluble fraction of the hydrolysates was analyzed for its total soluble solids, malto-oligomer distribution, glucose content, pH value, and formation of brown compounds. The effects of the combined severity parameter at a substrate concentration of 5-12.5% on the glucose yield were also evaluated. The highest glucose yield (78% of dry matter) was obtained after hydrolysis at 180 °C without activated carbon addition. Heating above 180 °C reduced the glucose yield and increased the pH and the formation of brown compounds. The use of activated carbon in microwave-assisted acid hydrolysis of cassava pulp reduced the glucose yield, but suppressed the formation of brown compounds. The highest glucose yield (70-80% of dry matter) was attained at a severity parameter of 1.3-1.5.
Keywords: activated carbon; cassava pulp; glucose; hydrolysis; microwave; oxalic acid; severity parameter.
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