188. A culture can grow independently in two carbon sources, glucose and hexadecane. Identify which one of the
following statements is TRUE?
1. The biomass growth yield is more in hexadecane than in glucose
2. The biomass growth yield is lower in hexadecane than in glucose
3. The oxygen consumed is higher for glucose when compared to hexadecane
4. The CO2 produced will be more in glucose than in hexadecane

Introduction:

When studying microbial growth, carbon sources play a critical role in determining the efficiency and yield of the growth process. Two common carbon sources used by microbes are glucose and hexadecane, a long-chain alkane. Each of these carbon sources has its unique characteristics that influence growth yield, oxygen consumption, and CO2 production.

In this article, we will explore how glucose and hexadecane compare in terms of their biomass growth yield, oxygen consumption, and CO2 production during microbial growth.

Key Concepts:

1. Biomass Growth Yield: Biomass growth yield refers to the amount of microbial biomass (cells) produced per unit of carbon source consumed. The growth yield is influenced by the carbon source’s ability to be utilized efficiently by the microbe.

2. Oxygen Consumption: Oxygen consumption is tied to the rate of cellular respiration, where oxygen is used in the electron transport chain to produce energy. The carbon source affects how much oxygen is required for the growth of the microbial culture.

3. CO2 Production: During metabolism, microbes release CO2 as a byproduct of aerobic respiration. The amount of CO2 produced is indicative of the metabolic activity and the type of carbon source being utilized.

Comparing Glucose and Hexadecane:

1. Biomass Growth Yield:

• Glucose is a simple sugar and is readily metabolized by most microbes via glycolysis and the citric acid cycle, yielding high biomass growth with efficient energy conversion.

• Hexadecane, on the other hand, is a long-chain alkane and must be converted into intermediates through additional steps before it can enter the central metabolic pathways. This often results in lower efficiency compared to glucose.

Thus, the biomass growth yield is typically lower in hexadecane than in glucose due to the extra energy required for its initial breakdown.

2. Oxygen Consumption:

• Glucose metabolism is more efficient in terms of oxygen consumption, as it enters the glycolysis pathway directly, and each molecule of glucose produces a significant amount of energy through aerobic respiration.

• Hexadecane requires more oxygen to break down its longer carbon chain, and the energy yield is less efficient compared to glucose metabolism.

As a result, the oxygen consumed is typically higher for hexadecane compared to glucose due to the additional steps required to metabolize the long-chain alkane.

3. CO2 Production:

• In both cases, CO2 is produced as a byproduct of aerobic respiration. However, the number of carbon atoms involved in the breakdown of hexadecane (which has 16 carbon atoms) is higher than in glucose (which has 6 carbon atoms).

• As a result, more CO2 is produced per molecule of hexadecane compared to glucose.

Answer:

The correct statement is:

2. The biomass growth yield is lower in hexadecane than in glucose.