Q.53 Which one or more processes listed below DOES NOT/DO NOT produce carbon
dioxide during fermentation?
(A) Brewing wine using yeast.
(B) Baking bread using yeast.
(C) Making yogurt using lactobacillus.
(D) Making cheese using fungus.

Answer: (C) Making yogurt using lactobacillus does not produce carbon dioxide during fermentation.

Lactobacillus in yogurt fermentation performs homolactic fermentation, converting lactose primarily to lactic acid without generating CO2 as a major byproduct. Other options involve alcoholic fermentation by yeast or processes that release CO2.

Fermentation processes not produce carbon dioxide in specific microbial pathways, crucial for CSIR NET Life Sciences. This guide analyzes yeast alcoholic fermentation versus Lactobacillus lactic acid fermentation.

Option Analysis

Brewing Wine (A): Yeast (Saccharomyces cerevisiae) ferments grape sugars anaerobically via glycolysis to pyruvate, then decarboxylation produces acetaldehyde and CO2, reduced to ethanol. CO2 release causes bubbling during winemaking.

Baking Bread (B): Yeast ferments flour sugars, producing CO2 that forms gas bubbles trapped in gluten for dough rising during proofing. Ethanol evaporates in oven heat.

Yogurt Making (C): Lactobacillus (e.g., L. bulgaricus, L. acidophilus) uses homolactic fermentation: glucose → 2 lactic acid via Embden-Meyerhof pathway (90-95% lactic acid, minimal CO2). No significant gas production, unlike heterolactic strains.

Cheese Making with Fungus (D): Fungal molds (e.g., Penicillium in blue cheese) or ripening produce CO2 via respiration or secondary fermentation. Some bacteria like Propionibacterium also generate CO2 for eye formation in Swiss cheese.

Fermentation Pathways Table

Homolactic fermentation by yogurt Lactobacillus avoids CO2, distinguishing it for CSIR NET questions on microbial metabolism.