Production of bioethanol by fermentation of lemon (Citrus limon L.) peel wastes pretreated with steam explosion

The application of steam explosion and enzymatic hydrolysis pretreatments on lemon (Citrus limon L.) citrus peel wastes was studied to obtain bioethanol, galacturonic acid and other co-products, such as d-limonene and citrus pulp pellets. Steam explosion pretreatment and recovery of lemon citrus essential oils was carried out at pilot plant scale. The effect of steam explosion on lignocellulosic composition of lemon peel wastes was studied by thermogravimetric analysis. The antimicrobial activity of lemon essential oil on Saccharomyces cerevisiae and its influence on ethanol production during fermentation were also studied. The steam-exploded lemon peel wastes were processed by sequential and simultaneous hydrolysis and fermentation. Concentrations of sugars, galacturonic acid and ethanol were analyzed to measure the efficiency of these processes. Significant antimicrobial activity of lemon essential oils has been observed on S. cerevisiae at concentrations above 0.025%. The steam explosion pretreatment has shown an interesting effect on lemon peel wastes processing for obtaining ethanol and galacturonic acid. This pretreatment reduces the residual content of essential oils below 0.025% and significantly decreases the hydrolytic enzyme requirements. Ethanol production in excess of 60 L/1000 kg fresh lemon peel biomass can be obtained.

► Lemon CPW is a good feedstock for simultaneous production of bioethanol and galacturonic acid.
► Lemon CPW is a good feedstock for production of lemon CEOs recovered by steam explosion.
► SSF processing of steam exploded lemon CPW produced more than 60 L ethanol/1000 kg fresh lemon CPW.
► Residual concentration of CEOs must be lower in lemon CPW than in other CPW to obtain bioethanol.