Question 1

What are polyhydroxyalkanoates and why do bacteria produce them?

Accepted Answer

Polyhydroxyalkanoates (PHAs) are biodegradable polymers synthesized by bacteria as intracellular carbon and energy storage materials. Bacteria like Cupriavidus necator and Pseudomonas putida accumulate PHAs as granules when grown under carbon-abundant but nitrogen- or phosphorus-limited conditions, allowing them to store excess carbon for later use.

Question 2

How are PHAs extracted and purified from bacterial cells?

Accepted Answer

Bacterial cells are first harvested and lysed using physical methods like bead milling or chemical agents that degrade cell walls. The lysate is treated with organic solvents such as chloroform and gently heated to dissolve PHAs. The polymer is then purified through precipitation and downstream processing into usable materials.

Question 3

What renewable resources do microbes use to produce bioplastics?

Accepted Answer

Microbes utilize renewable resources including agricultural waste and industrial waste to produce bioplastics. These sustainable feedstocks are metabolized by bacteria during fermentation processes, redirecting carbon sources toward PHA synthesis when nutrient limitation occurs, creating an environmentally friendly alternative to petroleum-based plastics.

Question 4

What are the main applications of bioplastics in industry?

Accepted Answer

Bioplastics derived from PHAs are used as biodegradable packaging material, agricultural mulch films, and drug delivery systems. Their non-toxic and compostable nature makes them suitable for diverse applications where environmental impact and biocompatibility are important considerations for sustainable product development.

Question 5

How do bioplastics break down in the environment?

Accepted Answer

Bioplastics undergo microbial degradation after disposal, breaking down into simple compounds through environmental processes. Under aerobic conditions, they decompose into carbon dioxide and water, while under anaerobic conditions they produce methane, completing a closed-loop lifecycle that significantly reduces environmental pollution compared to conventional plastics.

Question 6

Why are nitrogen and phosphorus limitation important for PHA production?

Accepted Answer

When bacteria are grown under nitrogen- or phosphorus-limited conditions with abundant carbon, they redirect carbon sources toward PHA synthesis rather than cell growth. This nutrient limitation triggers intracellular granule accumulation, making it an essential strategy for maximizing bioplastic yield in fermentation processes and industrial production.

Question 7

What solvents and temperatures are used in PHA extraction?

Accepted Answer

Organic solvents such as chloroform or green solvents are used to selectively dissolve PHAs from lysed cells during recovery. The extraction process is conducted below 200°C to prevent polymer degradation, ensuring the integrity and quality of the bioplastic material during purification and downstream processing.

Bioplastics

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