Question

Transgenic plants can be used as factories to produce polyhydroxybutyrate (PHB) on a large scale. How was Arabidopsis plant engineered for the same? State the drawback of producing PHB by fermentation using bacterium Alcaligenes eutrophus.

Hint:

Transgenic plants with bacterial PHB biosynthesis genes can produce biodegradable plastics; bacterial fermentation is costly for large scale PHB production.

Answer 1

Engineering of Arabidopsis for PHB production: The Arabidopsis plant was genetically engineered by introducing three bacterial genes from Alcaligenes eutrophus responsible for PHB biosynthesis:

• phbA: Encodes β-ketothiolase.
• phbB: Encodes acetoacetyl-CoA reductase.
• phbC: Encodes PHB synthase.

These genes were introduced into the chloroplast genome of Arabidopsis to enable the plant to produce PHB granules in its tissues, effectively turning the plant into a bioreactor for biodegradable plastic production. Drawback of producing PHB by fermentation using Alcaligenes eutrophus: The major drawback is the high production cost due to expensive fermentation substrates and the need for downstream processing to extract and purify PHB from bacterial cells. This limits large-scale commercial production.