Simultaneous saccharification and fermentation (SSF) of industrial wastes for the production of ethanol

Abstract

During the past decades considerably large efforts have been made to optimize the production of lignocellulose derived fuel ethanol production in order to develop a process configuration which is economically feasible and competitive with gasoline. One of the process alternatives uses cellulase enzymes for the conversion of cellulose content of lignocellulosic biomass to fermentable glucose. Due to the relatively similar process conditions in the enzymatic hydrolysis and ethanol fermentation, the option of carrying out these two-steps together in one vessel exists. The application of simultaneous saccharification and fermentation (SSF) for the conversion of lignocellulosics to alcohol would result in a more cost-effective process. In the present study various lignocellulosic substrates, i.e. Solka Floc, OCC waste cardboard, and paper sludge, were examined in SSF experiments for the production of ethanol. Two yeast strains were compared, a commercially available baker’s yeast and a thermotolerant Kluyveromyces marxianus, in two types of SSF experiments, i.e. isothermal SSF and SSF with temperature profiling. The results showed that OCC waste and paper sludge could be used as substrates for ethanol production in SSF. There was no significant difference observed between Saccharomyces cerevisiae and K. marxianus when the results of SSF were compared. The ethanol yields were in the range of 0.31–0.34 g/g for both strains used. SSF resulted in higher ethanol yields compared to non-isothermal SSF (NSSF; SSF with temperature profiling).