FED-BATCH SIMULTANEOUS SACCHARIFICATION AND ETHANOL FERMENTATION OF NATIVE CORN STARCH.

Background. The most important innovations in boethanol production in the last decade were: simultaneous saccharification and fermentation processes (SSF), high gravity fermentation, the use of new enzyme preparation able to hydrolyse native granular starch and construction of genetically modified strains of microorganisms able to carry out simultaneous production of hydrolytic enzymes and fermentation of C6 and C5 sugars. The aim of this study was to assess the efficiency of ethanol fermentation using new type of amylolytic enzymes able to hydrolyse native corn starch in a SSF process. Material and methods. The simultaneous saccharification and fermentation of raw corn flour by fed-batch processes using Saccharomyces cerevisiae strain Red Star Ethanol Red and Stargen 001 enzyme preparation was performed. As experimental variable were investigated: fermentation temperature (35-37-40°C), rate of mash stirring (100 and 200 rpm), fermentation time (0-92 h) and dosage of corn flour (different portion and different time). Results. It was found that optimal temperature for fed-batch SSF process was 37°C at initial pH of 5.0. However, the yeast intensively fermented the saccharides also at 40°C. The fermentation stirring rate has significant effect on starch utilization and fermentation production. The prolongation of fermentation time over 72 h has no substantiation in additional ethanol production. In all experimental fermentations the level of produced organic acids was very low, significantly below toxic concentration for the yeast. Conclusions. It was stated that the use of new method of starch raw material preparation resulted in satisfied fermentation yield and allowed to reduce energy requirements for starch liquefaction. [ABSTRACT FROM AUTHOR]