title: Ethanol production from alkali-treated rice straw via simultaneous saccharification and fermentation using newly isolated thermotolerant Pichia kudriavzevii HOP-1.
abstract: In this study, simultaneous saccharification and fermentation (SSF) was employed to produce ethanol from 1% sodium hydroxide-treated rice straw in a thermostatically controlled glass reactor using 20 FPU gds⁻¹ cellulase, 50 IU gds⁻¹ β-glucosidase, 15 IU gds⁻¹ pectinase and a newly isolated thermotolerant Pichia kudriavzevii HOP-1 strain. Scanning electron micrograph images showed that the size of the P. kudriavzevii cells ranged from 2.48 to 6.93 μm in diameter while the shape of the cells varied from oval, ellipsoidal to elongate. Pichia kudriavzevii cells showed extensive pseudohyphae formation after 5 days of growth and could assimilate sugars like glucose, sucrose, galactose, fructose, and mannose but the cells could not assimilate xylose, arabinose, cellobiose, raffinose, or trehalose. In addition, the yeast cells could tolerate up to 40% glucose and 5% NaCl concentrations but their growth was inhibited at 1% acetic acid and 0.01% cyclohexamide concentrations. Pichia kudriavzevii produced about 35 and 200% more ethanol than the conventional Saccharomyces cerevisiae cells at 40 and 45°C, respectively. About 94% glucan in alkali-treated rice straw was converted to glucose through enzymatic hydrolysis within 36 h. Ethanol concentration of 24.25 g l⁻¹ corresponding to 82% theoretical yield on glucan basis and ethanol productivity of 1.10 g l⁻¹ h⁻¹ achieved using P. kudriavzevii during SSF hold promise for scale-up studies. An insignificant amount of glycerol and no xylitol was produced during SSF. To the best of our knowledge, this is the first study reporting ethanol production from any lignocellulosic biomass using P. kudriavzevii.
authors: Central Institute of Post Harvest Engineering and Technology, Ludhiana 141004, India. hari_manu@yahoo.com
authors: Harinder Singh
authors: HS
authors: Oberoi
authors: Neha
authors: N
authors: Babbar
authors: Simranjeet Kaur
authors: SK
authors: Sandhu
authors: Sandeep Singh
authors: SS
authors: Dhaliwal
authors: Ujjal
authors: U
authors: Kaur
authors: B S
authors: BS
authors: Chadha
authors: Vinod Kumar
authors: VK
authors: Bhargav
mesh_terms: D056804:Biofuels; D002480:Cellulase / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D006868:Hydrolysis; D007218:Industrial Microbiology; D012275:Oryza / Q000378:metabolism*; D010843:Pichia / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism
chemical_list: D056804:Biofuels; D000431:Ethanol; D001617:beta-Glucosidase; D002480:Cellulase