Organic compound not decomposed by microbes in biogas plants is

Options

A. Protein
B. Lignin
C. Cellulose
D. Phospholipid

Answer

To determine the organic compound that is not decomposed by microbes in biogas plants, we can follow these steps:

### Step 1: Understand the Role of Microbes in Biogas Plants
Biogas plants utilize microbes, particularly methanogenic bacteria, to break down organic materials. These bacteria convert complex organic compounds into simpler molecules, which can then be used to produce biogas.

**Hint:** Consider what types of organic compounds these microbes are typically able to decompose.

### Step 2: Analyze the Options
The options given are:
- Protein
- Lignin
- Cellulose
- Phospholipid

We need to evaluate each of these compounds in relation to their decomposition by microbes.

**Hint:** Think about the structure and complexity of each compound and how they relate to microbial degradation.

### Step 3: Evaluate Each Compound
1. **Protein**: Proteins are complex polymers made of amino acids. Methanogenic bacteria can break down proteins into simpler amino acids and then further into simpler compounds.

2. **Cellulose**: Cellulose is a polysaccharide composed of glucose units. Certain microbes can secrete enzymes (cellulases) to break down cellulose into simpler sugars.

3. **Phospholipid**: Phospholipids are components of cell membranes and can also be broken down by microbes, although they are more complex than simple fats.

4. **Lignin**: Lignin is a complex polysaccharide found in the cell walls of plants. It has a highly branched structure and is resistant to microbial degradation. Lignin can only be broken down by specific fungi (like actinomycetes) or through chemical processes.

**Hint:** Identify which of these compounds is known for its resistance to microbial breakdown.

### Step 4: Identify the Correct Answer
Based on the analysis, lignin is the organic compound that is not decomposed by microbes in biogas plants. It is resistant to biological degradation due to its complex structure.

**Final Answer:** The organic compound not decomposed by microbes in biogas plants is **lignin**.