Introduction:
The production of butanol and acetone from starch is carried out by certain bacteria through a process called acetone-butanol-ethanol (ABE) fermentation. This fermentation process involves the conversion of sugars present in starch into butanol and acetone, which are valuable chemicals used in various industries. Among the given options, the bacteria Clostridium acetobutylicum is used for the production of butanol and acetone from starch.

Explanation:
Here's why Clostridium acetobutylicum is the correct answer:

1. Clostridium acetobutylicum: Clostridium acetobutylicum is a gram-positive, anaerobic, spore-forming bacteria. It is one of the most well-known and extensively studied bacteria used for the production of butanol and acetone through ABE fermentation.

2. ABE Fermentation: ABE fermentation is a two-step process. In the first step, starch is hydrolyzed to glucose and other simple sugars. This step is usually carried out by amylase enzymes. In the second step, the produced sugars are converted into butanol, acetone, and ethanol by the metabolic activities of Clostridium acetobutylicum.

3. Metabolic Pathway: Clostridium acetobutylicum utilizes a complex metabolic pathway to convert sugars into butanol and acetone. This pathway involves several enzymatic reactions, including glycolysis, acidogenesis, solventogenesis, and sporulation.

4. Acidogenesis: In the acidogenic phase, Clostridium acetobutylicum ferments glucose and other sugars into organic acids such as acetic acid and butyric acid. This phase is characterized by the production of acids and a decrease in pH.

5. Solventogenesis: In the solventogenic phase, the bacteria switch from acid production to the production of solvents, primarily acetone and butanol. This phase is characterized by the accumulation of solvents and a shift in pH towards neutrality.

6. Product Recovery: After the fermentation process, the butanol and acetone produced by Clostridium acetobutylicum can be recovered by various methods such as distillation, liquid-liquid extraction, or adsorption.

7. Industrial Applications: Butanol and acetone produced from starch using Clostridium acetobutylicum have several industrial applications. Butanol is used as a solvent in the chemical industry, as a biofuel additive, and in the production of plastics and synthetic rubber. Acetone is widely used as a solvent, in the production of chemicals, and in the pharmaceutical industry.

Conclusion:
In conclusion, Clostridium acetobutylicum is the bacteria used for the production of butanol and acetone from starch. This bacterium utilizes the ABE fermentation process to convert sugars into butanol and acetone, which have significant industrial applications.

The bacteria Clostridium acetobutylicum is used to produce butanol and acetone from starch. This bacteria was first used by Chaim Weizmann in 1920.