Bioethanol from Spent Mushroom Sawdust Waste by Perchloric Acid: Easy Sugars Separation and Hydrolysis Without Charring

Spent mushroom sawdust substrate (SMSS), a waste product from a local, Pleurotus spp. mushroom-growing company, was appraised for its potential as a source for the production of ethanol. The successive growth of mushrooms weakens the lignocellulosic structure of the wood based substrate, thus making it more amenable to acid hydrolysis. Perchloric acid (70 %) was used to hydrolyze the cellulose into a glucose solution suitable for fermentation. This rather unusual catalyst bears the advantageous easy removal of neutralization products. The poor water soluble potassium perchlorate separates in crystalline form and enables the hydrolysis without external heating. A time course investigation indicated a hydrolysis treatment for 10 min at about 50°C as optimum conditions. Fermentation of the sugar solution with baker’s yeast, Saccharomyces cerevisiae, yielded up to 4 g ethanol/100 g ligno-cellulose. This translates to 40 L of biofuel per ton of dried substrate.