Alcoholic Fermentation with Self‐Flocculating Yeast in a Tower Upflow Reactor

Abstract

Ethanol production using self-flocculating yeast in a batch tower upflow reactor system operating with a recirculation loop was examined. Ethanol productivity, yield, and residual sucrose concentration were evaluated experimentally according to a central composite design with initial cell and sucrose concentrations and recirculation flow rate as independent variables. Yeast cell concentration strongly influenced the reactor performance. Alcoholic fermentation was conducted using this strain and reactor configuration which allowed for high productivity and high sucrose conversion. The ethanol yield was comparable with industrial yields. A kinetic study of the fermentation process under optimized conditions was performed using the experimental data and considering inhibition by sucrose and ethanol.

Ethanol Synthesis by <em>Saccharomyces cerevisiae</em>: Summary, Discovery, and Prospects

“…However, with the increase of substrate concentration, the osmotic pressure of the culture environment rises, and hyperosmolality can cause volume shrinkage of cells, which stresses the growth and vitality of cells [12,13]. In order to overcome the influence of high osmotic pressure and high ethanol concentration feedback inhibition, ethanol recovery with plate membrane pervaporation device [16], extraction fermentation [17], electrostatic fermentation [18], ultrasonic fermentation [19], immobilized fermentation [20], multi-stage reaction tower recycling fermentation [21][22][23] and so on have been widely studied (Table 1). But when the carbon source is used by S. cerevisiae to make ethanol, not only do these problems of high osmotic pressure and ethanol feedback inhibition occur, when multiple carbon sources are present, glucose and sucrose are always consumed first.…”

Continuous ethanol fermentation in tower reactors with cell recycling using flocculent Saccharomyces cerevisiae

“…[NH 4 ] 2 SO 4 (2 g/L), yeast extract (6 g/L), and varying sucrose concentrations according to the experiment [14]. All of the reagents used were of analytical grade, with the exception of the sugar, where sucrose for domestic use was employed.…”

Very High Gravity Bioethanol Revisited: Main Challenges and Advances

“…Commonly known for their high auto-immobilization capacity, self-flocculating strains seems to be superior to those immobilized on a physical support; they are naturally retained inside the reactor (when flocs of an appropriate size are formed) with no visible problems on cell growth, being recovered by a simple sedimentation, rather than using centrifuges [1,38,96]. Different reactor configurations have been tested with these strains including air-lift reactors [97][98][99][100], single-tower reactors [101,102], and two-tower reactors connected in series [103]. The particular use of flocculent yeasts on continuous processes goes back to the 1980s.…”