Ethanol production from Kinnow mandarin (Citrus reticulata) peels via simultaneous saccharification and fermentation using crude enzyme produced by Aspergillus oryzae and the thermotolerant Pichia kudriavzevii strain

Abstract

The aim of this study was to assess the potential of using the crude filtrate extract (CFE) produced by a newly isolated strain of Aspergillus oryzae and fermentation with a novel thermotolerant strain of Pichia kudriavzevii for the production of ethanol from kinnow peel waste (KP) via simultaneous saccharification and fermentation (SSF). High-performance liquid chromatography determination showed that pre-hydrolysis of KP with CFE at 3 cellulase filter paper units/g dry substrate (FPU/g-ds) at 50°C resulted in 24.87 ± 0.75 g l-1 glucose, 21.98 ± 0.53 g l-1 fructose, 10.86 ± 0.34 g l-1 sucrose and 6.56 ± 0.29 g l-1 galacturonic acid (GA) along with insignificant amounts of arabinose, galactose and xylose. Simultaneous saccharification and fermentation of hydrothermally pretreated KP at a substrate concentration of 15% (w v-1) was conducted in a 2.5-l laboratory fermentor with P. kudriavzevii at 40°C after a 3-h pre-hydrolysis. Oligosaccharides were not produced during the SSF process. Ethanol production leveled off after 12 h, resulting in an ethanol concentration and productivity of 33.87 g l-1 and 2.82 g l-1 h-1, respectively. These results demonstrate the potentiality of SSF using crude enzymes and P. kudriavzevii for the scale-up production of ethanol from KP.