Industrial lactic acid fermentation using corn dextrose medium is commonly carried out by which microorganism?

Introduction / Context:
Lactic acid is a high-volume platform chemical used in food, pharmaceuticals, and as a monomer for polylactic acid plastics. Choice of microorganism depends on substrate (e.g., corn dextrose) and desired optical purity (L- or D-lactic acid). The question targets the organism widely used for fermenting corn dextrose to lactic acid.

Given Data / Assumptions:

• Feedstock: corn dextrose (glucose).
• Process requires robust, homofermentative lactic acid production.
• Industrial criteria include tolerance to low pH, high sugar, and osmotic stress.

Concept / Approach:
Homofermentative Lactobacillus species are preferred for high yields of lactic acid with minimal by-products. Lactobacillus delbrueckii (and certain subspecies such as L. delbrueckii subsp. bulgaricus for dairy) are classic workhorses on dextrose, giving high productivity and optical control depending on the strain. Alternatives like Lactobacillus pentosus utilize pentoses effectively, while Streptococcus lactis is more dairy-oriented for starter cultures.

Step-by-Step Solution:
Select a homofermentative Lactobacillus suited to glucose.Consider strain performance on corn dextrose in low-pH fed-batch operations.L. delbrueckii meets the industrial criteria and historical usage.Confirm optical purity and downstream purification compatibility.

Verification / Alternative check:
Process literature and patents frequently cite L. delbrueckii for glucose-based lactic acid fermentations with high titers and yields.

Why Other Options Are Wrong:
L. bulgaricus: important in yogurt cultures; not the canonical industrial choice for bulk lactic acid from dextrose.L. pentosus: efficient on pentoses, not the default on corn dextrose.Streptococcus lactis: used in dairy starter contexts rather than bulk lactic acid production.

Common Pitfalls:
Ignoring optical purity needs and assuming all lactic acid bacteria behave similarly on glucose feedstocks.

Final Answer:
Lactobacillus delbrueckii