Figure 2

The effect of yeast-available nitrogen on ethanol production rates by fermentation of sucrose/watermelon juice feedstocks at pH 3. The initial concentration of total fermentable sugars in the fermentations was ~20% (w/v). Closed triangles = 857 mg N/L (33.6 μmol amino N/ml) from watermelon juice of 2007 Terral, OK, USA crop; closed squares = 890 mg N/L (33.9 μmol amino N/ml) from watermelon juice of 2008 Louisiana, USA crop; closed diamonds = 415 mg N/L (17.7 μmol amino N/ml) from watermelon juice of cv. 'Sangria', 2008; open circles = 230 mg N/L (10.6 μmol amino N/ml) from watermelon juice of cv. 'Sangria', 2008 from which part of the free amino acids had been removed; open diamonds = 138 mg N/L (6.7 μmol amino N/ml) from watermelon juice of cv. 'Sangria', 2008 from which part of the free amino acids had been removed; open triangles = 46 mg N/L (2.7 μmol amino N/ml) from watermelon juice of the 2007 Hinton, OK, USA crop from which the free amino acids had been removed. Other conditions for the fermentations are described in the text.