Production of ethanol from enzymatically hydrolyzed orange peel by the yeast Saccharomyces cerevisiae.

We extended our previous investigations of enzymatic hydrolysis of polysaccharides in orange peel by commercial cellulase and pectinase enzymes to higher, more practical concentrations of orange peel solids. High yields of saccharification could be maintained even at substrate concentrations as high as 22-23%, but the rates of solubilization and saccharification decreased 2-3-fold. We also tested the fermentability of these hydrolysates by the yeast Saccharomyces cerevisiae, which revealed the presence of inhibitory compounds. These compounds could be removed by the filtration of hydrolyzed peel. Successful fermentations of filtered hydrolysates were achieved after pH adjustment with calcium carbonate.