Q56 - Microbial Succession During Cabbage Lactic Fermentation

Theoretical B Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Bioenergetics & Central Metabolism Overview

Lactic fermented vegetables are traditional food in many Asian cuisines. Microorganisms commonly found in the fermentation broth are lactic acid bacteria, yeast and filamentous fungi.

Fig.Q.56 below shows the flowchart of viable cell counts (log CFU/mL) of three different microbial groups and the pH value during the lactic fermentation course of cabbage. Oxygen dissolved in fermentation broth decreased with time and was completely consumed after the 22nd day.

Figure Q.56 Changes in microflora during lactic acid fermentation of cabbage.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. The drop in pH value from day 1 to day 3 was caused by only organic acids produced exclusively by lactic acid bacteria.

B. Lactic acid produced by lactic acid bacteria favours the growth of yeast cells from day 10 till day 26.

C. Yeast cells shifted from fermentation to aerobic respiration after day 22.

D. Some filamentous fungi showed tolerance to low pH.

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Question reproduced from IBO 2016, Theoretical Paper B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)