Energy Beet Alcohol Fermentation Conditions For Production Optimization

The technics of producing alcohol from energy beet was researched in three parts in this paper. The first part contained the solid-state fermentation of beet, including factors affecting the fermentation stage. In the second part, the yeast strains were immobilized by chitosan-sodium alginate beads. The fermentation conditions of the immobilized yeast were optimized. The third part was mainly about the medium optimization of solid-state fermentation and immobilized fermentation of Saccharomyces cerevisiae strain Nanyang CICC1308-1 using response surface method. The alcohol production was maximized by the application of the most suitable yeast strain and the optimal fermentation style, which could be scaled up in industrial production. The main conclusions of this paper are listed as follows:Firstly, the optimal solid-state fermentation conditions of energy beet for alcohol production were obtained: the sterilized medium was supplemented with 10 g/L KH₂PO₄, and the inoculated quantity was 15-20 ml. The pH of the medium was not adjusted, and the ration for medium to water was 1:3.0. The fermentation temperature was controlled between 30-31℃. Under these conditions, the maximum alcohol production was achieved after 40 hour's fermentation. The activation time for ADY strain was 60-90 min, and ideal usage of ADY was 0.1% (m/m). Although the application of cellulase could facilitate the high-gravity fermentation of energy beet, the production cost would be increased simultaneously. Thus, cellulase was not used to promote alcohol production in the present technics.Secondly, the optimal preparation conditions for chitosan-alginate beads were: 4% sodium alginate, 0.9-1.2% chitosan, 4 h for immobilization and 20 min for membrane coverage. The beads obtained under these conditions had the highest hardness. The chitosan-alginate beads demonstrated a nice stability. The fermentation conditions for alcohol production using immobilized beads were: 4% sodium alginate, 0.9% chitosan, fermentation temperature 30-35℃, and with a immobilization usage of 0.25 g/ml. Saccharomyces cerevisiae immobilized by chitosan-alginate beads were used to ferment beet in bioreactors, the immobilized Saccharomyces cerevisiae could maintain fermentability for a long time and could be used continuously, which would be beneficial in the continuous production in industry.Finally, the media of solid-state fermentation and immobilized fermentation of Saccharomyces cerevisiae strain Nanyang CICC1308-1 were optimized using response surface method.(1) Based on the application of Plackett-Burman design, the main factors affecting the immobilized fermentation were concentration of sodium alginate, substrate concentration and fermentation temperature. (2) The regression equation of important factors for immobilized fermentation obtained from response surface method was: Y₁=84.5940-0.7565X₁+0.1366X₅-0.9020X₈-0.3293X₁X₁-0.2232X₅X₅+0.5591X₈X₈-0.1500X₁X₅-0.0250X₁X₈-0.1750X₅X₈ (X₁: alginate concentration; X₅: substrate concentration; X₈: fermentation temperature). The alginate concentration, substrate concentration and fermentation temperature were 12%, 4% and 31℃, respectively.