Context:
UK scientists have developed a genetically-engineered banana that boasts an extended shelf-life and reduced browning.
Genetically-Engineered Banana
- Developed by: UK-based biotech company Tropic.
- Key Features:
- Remains fresh and yellow for 12 hours post-peeling.
- Less prone to browning during: Harvesting, Transportation.
- Objective:
- Increase yield.
- Extend shelf-life.
- Improve resistance to diseases like: Panama disease, Black Sigatoka.
- Technology Used:
- Advanced gene-editing tools like: CRISPR, GEiGS (Gene Editing induced Gene Silencing).
- Method:
- Production of enzyme polyphenol oxidase (PPO) disabled in banana genes.
- Modification prevents browning while allowing normal ripening.
- Significance:
- Food Waste Reduction: Reduces wastage by over 25%.
- CO2 Emissions: Cuts emissions by over 9 million tonnes, equivalent to removing 2 million cars annually.
- Adoption:
- Approved for production in the Philippines.
- Similar gene silencing used in:
- GM Arctic Apples, approved for sale in the US since 2017.
- Developed by Okanagan Specialty Fruits Inc.
Polyphenol Oxidase (PPO)
- PPO:
- A copper-containing enzyme found in plants, animals, fruits, bacteria, and fungi.
- Plays a key role in enzymatic browning and defense mechanisms.
- Functions:
- Responsible for the browning reaction in damaged or stressed plant tissues.
- Leads to the formation of dark pigments.
- Activity increases under stress or damage.
- Provides defense against herbivores and pathogens.
- Catalyzes oxidation of monophenols and o-diphenols to o-quinones in the presence of oxygen.
Factors Affecting Polyphenol Oxidase (PPO) Activity
- Optimal Temperature range: 30-50°C, varies by species.
- PPO is unstable outside its optimal pH range.
- Oxygen: Essential co-factor for PPO activity.
- Microorganisms can inhibit or stimulate PPO activity.
- Stress and nutrient deficiencies impact PPO expression and activity.
Industrial Applications of Polyphenol Oxidase (PPO)
- Food Industry: PPO-catalyzed browning is useful in producing prunes, dark raisins, black tea, and green coffee beans.
- PPO acts as a biocatalyst in developing biosensors.
- PPO, including tyrosinase and laccase, helps remove phenols from industrial wastewater.
- Used in bioremediation to eliminate pollutants.
- PPO serves as a biocatalyst in Pharmaceutical and Cosmetic industries.
What is Browning of Bananas?
- Ripening Process:
- Bananas change from green (raw) to yellow (ripe) and finally to brown (end of life cycle).
- The change is driven by the hormone ethylene.
- Ethylene Production:
- Bananas continue to produce ethylene post-harvest, unlike fruits like melons and citrus.
- Bruising triggers ethylene production, activating genes like those producing polyphenol oxidase (PPO).
- Higher ethylene levels from bruising accelerate ripening and browning.
- Polyphenol Oxidase (PPO):
- Responsible for the browning of bananas.
- PPO interacts with oxygen to break down yellow pigments, forming a brown hue.
- Blocking PPO production has shown similar results in tomatoes, melon, kiwifruits, and mushrooms.
Source: Indian Express
Previous Year Question
With reference to polyethylene terephthalate, the use of which is so widespread in our daily lives, consider the following statements:
1. Its fibres can be blended with wool and cotton fibres to reinforce their properties.
2. Containers made of it can be used to store any alcoholic beverage.
3. Bottles made of it can be recycled into other products.
4. Articles made of it can be easily disposed of by incineration without causing greenhouse gas emissions.
Which of the statements given above are correct?
[UPSC CSE – 2022 Prelims]
(a) 1 and 3
(b) 2 and 4
(c) 1 and 4
(d) 2 and 3
Answer: (a)
Explanation:
PET consists only of carbon, hydrogen, and oxygen, so if it is burned in the air (or in pure oxygen), the combustion products will be carbon dioxide and water. Hence statement 4 is incorrect. Storing alcohol in a plastic bottle is highly discouraged. Ethanol can slowly dissolve polymers, so you cannot store it in plastic. Hence statement 2 is incorrect.