Sains Malaysiana 45(4)(2016): 581–587

Ethanol Production Capability of Candida shehatae in Mixed Sugars and Rice Straw Hydrolysate

(Keupayaan Pengeluaran Etanol Candida shehatae dalam Campuran Gula dan Hidrolisat Jerami Padi)

PRAWPHAN YUVADETKUN^1,2 & MALLIKA BOONMEE^2,3*

¹Graduate School, Khon Kaen University, Khon Kaen 40002, Thailand

²Department of Biotechnology, Faculty of Technology, Khon Kaen University, KhonKaen 40002, Thailand

³Fermentation Research Center for Value Added Agricultural Products, Khon Kaen University

Khon Kaen 40002, Thailand

Received: 12 May 2015/Accepted: 5 November 2015

ABSTRACT

Ethanol fermentations by Candida shehatae TISTR 5843 at low (20 g/L) and high (80 g/L) sugar concentrations with various glucose to xylose ratios were investigated. Glucose was a preferred substrate as it was consumed first at a faster consumption rate. The type of sugar and ratio between glucose and xylose did not have an effect on ethanol produced. The average ethanol concentrations were 7.99 g/L when using 20 g/L sugar and 27.82 g/L when using 80 g/L sugar. Small amounts of xylitol and glycerol as by-products were presented when using 20 g/L sugar. Xylitol appeared to be the main by-product at high xylose concentration with elevated concentrations as xylose is increased. When using rice straw hydrolysate containing 34.75 g/L glucose and 21.29 g/L xylose, 19.37 g/L ethanol was produced with the ethanol yield and ethanol productivity at 0.49 g/g and 0.20 g/L.h, respectively. However, xylose was not completely consumed after fermentation was complete.

Keywords: Candida shehatae; ethanol; fermentation; lignocellulose; xylose

ABSTRAK

Penapaian etanol oleh Candida shehatae TISTR 5843 pada kepekatan gula rendah (20 g/L) dan tinggi (80 g/L) dengan pelbagai glukosa untuk nisbah xilosa dikaji. Glukosa adalah substrat pilihan kerana ia telah digunakan pertama pada kadar penggunaan yang lebih cepat. Jenis gula dan nisbah antara glukosa dan xilosa tidak mempunyai kesan ke atas etanol yang dihasilkan. Purata kepekatan etanol adalah 7.99 g/L apabila menggunakan 20 g/L gula dan 27.82 g/L apabila menggunakan 80 g/L gula. Sedikit xylitol dan gliserol hadir sebagai produk sampingan apabila menggunakan 20 g/L gula. Xylitol hadir menjadi produk sampingan utama pada kepekatan xilosa tinggi dengan kepekatan tinggi sebagai xilosa ditambah. Apabila menggunakan jerami padi hidrolisat mengandungi 34.75 g/L glukosa dan 21.29 g/L xilosa, 19.37 g/L etanol telah dihasilkan dengan hasil dan produktiviti etanol masing-masing pada 0.49 g/g dan 0.20 g/L.h. Walau bagaimanapun, xilosa tidak digunakan sepenuhnya selepas penapaian lengkap.

Kata kunci: Candida shehatae; etanol; lignoselulosa; penapaian; xilosa

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*Corresponding author; email: mallikab@kku.ac.th