Waste From Beer Fermentation Broth; A Potent Source of Bioethanol and Hydrolyzing Enzymes

Waste from beer fermentation broth; A potent source of bioethanol and hydrolyzing enzymes

Waleed Ahmad Khattak, Mazhar Ul-Islam, Minkyung Kang, Joong Kon Park*

Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, Korea

(parkjk@knu.ac.kr)

Abstract

 A semi solid discharged residue produced at the end of fermentation process, called as waste from beer fermentation broth (WBFB) showed tremendous potential for bioethanol production without the addition of saccharifying enzyme, microbial cells or carbohydrates. Number of hydrolyzing enzymes produced from malt in beer fermentation broth during brewing, were confirmed via sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) analysis. The enzymes extract from WBFB after partial purification was evaluated for their hydrolyzing activities. Various parameters including pH, temperature, thermal stability and buffer system was investigated for hydrolyzing activities. With gradual increase in temperature (25-70°), the presence of hydrolyzing enzymes in WBFB caused the degradation of yeast cell wall and reduced the live cell density to a greater extent. However, elevated temperature enhanced both the hydrolyzing activities and bioethanol production without additional enzyme, microbial cells and carbohydrates along with shortening the simultaneous saccharification and fermentation time. The enhanced bioethanol production at elevated temperature seems to be partially resulted via cell free enzymes system. Comparing to bare supernatant or sediments of the WBFB, the saccharification and bioethanol production efficacy of original WBFB were superior.

Key words; Waste from beer fermentation broth, Bioethanol, Hydrolyzing enzymes, Cell wall degradation, Cell free enzyme system