Improvement of ethanol production of hydrothermally pretreated Eucalyptus wood by cheese whey incorporation

Abstract

Hydrothermal pretreatment has been used for the improvement of ethanol production from Eucalyptus globulus wood by simultaneous saccharification and fermentation process (SSF). Nevertheless, the ethanol concentration is limited to percentage of cellulose present in the pretreated biomass which resulted in a maximal concentration of 67 g/L [1]. Therefore, one of the limitation of lignocellulosic-to-ethanol process is the dif ficulty of using high solid loadings to attain high ethanol concentration (required to reduce distillation cost). On the other hand, cheese whey powder is a pollutant residue that can be fermented into ethanol by addition of microor ganism able to consume lactose [2]. In this work, a multi-waste valorization approach, mixing cheese whey and hydrothermally pretreated Eucalyptus globulus wood, was proposed for the improvement and intensification of lignocellulose-to- ethanol process to attain high ethanol concentration. For that, an experimental design was carried out to optimize the operational conditions (percentage of cheese whey and commercial enzymes loadings of β-galactosidase and cellulases) to produce ethanol by SSF using an industrial Ethanol Red® Saccharomyces cerevisiae strain [3]. Ethanol concentration of 93 g/L (corresponding to 94% yield) was obtained under optimized conditions. Moreover, Ethanol Red ® strain was genetically engineered for the production of β-galactosidase. Recombinant strain successfully fermented the mixture of sugars from pretreated Eucalyptus wood and cheese whey, achieving an ethanol yield of 96%