Optimization of bioethanol production from intermediates of sugar beet processing by response surface methodology

Bioethanol production in batch culture by free Saccharomyces cerevisiae cells from intermediates of sugar beet processing was investigated and compared with molasses, traditionally used substrate. The overall fermentation efficiency of different yeasts was examined and there is no statistical difference between them indicating that the criteria for yeast strain choice should be based on availability and cost-effective factor. When raw, thin and thick juices and molasses were used, under anaerobic conditions for 60 h, at the temperature of 30 °C and agitation rate 3.3 Hz, obtained ethanol contents were 82.87 dm3 m−3, 80.31 dm3 m−3, 80.70 dm3 m−3 and 73.96 dm3 m−3, respectively. The ethanol yield amounted 490 g kg−1 for media based on intermediates and 450 g kg−1 for mash prepared with molasses. Response surface methodology was used for description of ethanol production. By obtained mathematical model (second degree polynomial), optimal fermentation duration is estimated on 36 h for intermediates, while for molasses it reaches 50 h. Bioethanol production from intermediates of sugar beet processing is technically possible and enables higher effectiveness of process.