ARS | Publication request: The effect of Dry matter content on the simultaneous saccharification and fermentation of citrus processing waste

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Proceedings
Publication Acceptance Date: November 1, 2009
Publication Date: March 19, 2010
Citation: Zhou, W., Widmer, W., Grohmann, K. 2009. The effect of dry matter content on the simultaneous saccharification and fermentation of citrus processing waste. Proceedings of Florida State Horticultural Society. 122:316-318.

Interpretive Summary: Ethanol production from citrus processing waste (CPW) is attractive in Florida. Each year, the Florida citrus juice industry produces about 3.5-5.0 million tons of wet CPW. Currently, this material is dried and sold as cattle feed. The process of making ethanol from CPW consists of four parts: pretreatment, simultaneous saccharification and fermentation (SSF), distillation and waste disposal. In order to make ethanol production economically viable, it is desirable to obtain a high ethanol concentration in a low viscous fermented mash using a substrate with high solid content and small enzyme loading requirement in the SSF. In this study, we investigated the effects of dry matter content and enzyme loading on SSF and the viscosity of fermented CPW. It was found that the ethanol yield (as percentage of the theoretical) obtained from 10%-dry-matter substrate was similar to that obtained from 20%-dry-matter substrate. At 20%-dry-matter content, as pectinase loading was reduced from 11 mg/100 g substrate to 1.4 mg/100 g substrate, ethanol yield and the viscosity of fermented CPW did not change significantly. These results could lead to significant savings in enzyme and distillation costs for ethanol production from CPW.

Technical Abstract: Citrus processing waste (CPW) is an attractive feedstock for making fuel ethanol. In order to make ethanol production from citrus waste economically viable, it is desirable to obtain a high ethanol yield and concentration with a small amount of enzymes. In this study, we investigated the effects of dry matter content and pectinase loading on the simultaneous saccharification and fermentation of pretreated CPW. Two levels of substrates (10% and 20% dry matter) were compared at three different pectinase loadings. It was found that the ethanol yield (as percentage of the theoretical) obtained from 20%-dry-matter substrate was similar to that obtained from 10%-dry-matter substrate. These results could lead to significant savings in enzyme and distillation costs for ethanol production from CPW.