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: Genetic modification of the Arabidopsis plant introduced three bacterial genes from Alcaligenes eutrophus essential for PHB biosynthesis:

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

These genes were integrated into the chloroplast genome of Arabidopsis, enabling the plant to synthesize PHB granules in its tissues, thereby functioning as a bioreactor for biodegradable plastic. Drawback of producing PHB via fermentation using Alcaligenes eutrophus: A significant limitation is the elevated production cost stemming from costly fermentation substrates and the requirement for extensive downstream processing for PHB extraction and purification from bacterial biomass. This impedes widespread commercial scaling.