Adjustment of Yeast Growth Media for the Fermentation of Lignocellulosic Sugars
Mezule, L.
Dalecka, B.
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Mezule L., Dalecka B., 2017, Adjustment of Yeast Growth Media for the Fermentation of Lignocellulosic Sugars, Chemical Engineering Transactions, 57, 25-30.
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Efficient ethanol production from lignocellulosic biomass is closely linked to the selected pre- treatment/hydrolysis technique, fermentable sugar yield and composition, microorganism of choice and presence of inhibitory compounds. In this study the applicability of lignocellulosic hydrolysates was evaluated with respect to the overall cell yields and sugar consumption rate. The effect of most popular additional nutrients, like, yeast extract and peptone, was assessed. Fermentable sugar hydrolysates were prepared with simple mechanical pre-treatment and enzymatic hydrolysis. The results showed that nutrient media or biomass hydrolysate gave similar Saccharomyces cerevisiae biomass increase, 2.7 and 2.34 log increase after 48 hours respectively. At the same time sugar consumption rate in nutrient media was more than 3 times faster than in hydrolysates. Addition of extra C6 carbohydrate to the hydrolysate increased sugar consumption rate and cell biomass yields to only a certain extent, afterwards it became inhibitory. Concentration of reducing sugars, did not resulted into higher efficiency of hydrolysates, however, the results showed that peptone and yeast extract did not have any significant (p > 0.05) effect on cell growth or sugar consumption. Moreover, hydrolysate showed to be a good base medium when opposed to clean water. In conclusion, the results demonstrated that pure enzymatically hydrolysed biomass can be used as a single resource for yeast fermentation.
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