Molasses-based fermentations — For efficient ethanol and related industrial fermentations, the initial sugar concentration of molasses feed is typically maintained in which range?

Introduction / Context:
Molasses is a common carbon source in industrial fermentations (e.g., ethanol). The starting sugar concentration must balance osmotic stress, viscosity, and yeast performance to maximize yield and prevent stuck fermentations or contamination.

Given Data / Assumptions:

• Higher sugar raises osmotic pressure and inhibits yeast; too low sugar wastes reactor volume and reduces productivity.
• Molasses composition varies; process targets accommodate practical yeast tolerance and mass transfer.
• We seek the typical recommended range for initial fermentable sugar in molasses mashes.

Concept / Approach:
Industrial practice often sets initial fermentable sugar around 12–16% (w/w), falling within a broader safe window of approximately 10–18% to keep osmotic stress manageable while achieving good ethanol titers. Values above ~20% frequently impair yeast performance without fed-batch strategies.

Step-by-Step Solution:

Verification / Alternative check:
Process manuals for distilleries and bioethanol plants commonly cite ~12–16% sugars for robust fermentations with Saccharomyces strains.

Why Other Options Are Wrong:

• 20–30% and 30–38%: typically too high for batch without controlled feeding; risk of inhibition.
• 4–5%: too dilute for economical production.

Common Pitfalls:
Assuming “more sugar = faster fermentation.” Excessive sugar slows or stalls yeast due to osmotic and ethanol stress.

Final Answer:
10-18%