Microwave-Resistant Microorganisms: Unexpected Applications

News 30 9 月, 2024

Microwave ovens have become a kitchen essential, using electromagnetic waves to heat food by causing water molecules to vibrate and generate heat. This process effectively kills many bacteria, viruses, and parasites. However, a recent study has revealed the presence of various microbes inside microwaves, primarily from the Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes phyla. These findings show that not all microorganisms can be eliminated by microwave radiation, high temperatures, or dryness. Some, known as thermophiles, are highly resistant to these conditions.

Thermophiles: Survivors in Extreme Environments

Thermophiles, a type of extremophile, can thrive in harsh conditions such as extreme temperatures, pressure, radiation, dryness, salinity, and pH levels. Due to their resilience, thermophiles have been widely studied. They are classified into three main categories:

1. Moderate Thermophiles: Survive at 45°C.
2. Extreme Thermophiles: Thrive between 70°C and 80°C.
3. Hyperthermophiles: Grow optimally at 80°C and can survive temperatures up to 110°C.

A notable discovery in deep-sea hydrothermal vents is Pyrococcus furiosus, which thrives at a minimum of 82°C, has an optimal growth temperature of 105°C, and can survive up to 110°C. Most hyperthermophiles have been isolated from environments with temperatures between 80-115°C.

Applications of Thermophiles

Thermophiles have significant potential in biotechnology. They are valuable sources of enzymes and biological materials used in human and veterinary medicine. Examples include:

• Enzymes for Starch Hydrolysis: Alpha-amylase.
• Paper Bleaching: Xylanases.
• Food Processing, Baking, Brewing, and Detergents: Proteases.

A thermally stable and alkaline protease derived from thermophiles is used to enhance wool properties and improve dye penetration in textile processing. Additionally, Taq polymerase, a DNA polymerase essential for PCR technology, was initially extracted from Thermus aquaticus found in the hot springs of Yellowstone National Park. Due to its heat tolerance, Taq polymerase has become crucial in food, chemical, and pharmaceutical industries (Figure 1).

Challenges in Thermophile Cultivation

Scaling up the cultivation of thermophiles and hyperthermophiles in laboratory and industrial settings remains a challenge. Current research focuses on optimizing growth conditions, using host cells like E. coli for protein expression, and employing bioprocesses for continuous fermentation. However, creating bioreactors capable of withstanding extreme temperatures, pH, and salinity remains a significant hurdle.

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References:

1. Iglesias A, Martínez L, Torrent D, et al. The microwave bacteriome: biodiversity of domestic and laboratory microwave ovens. Frontiers in Microbiology, 2024, 15: 1395751.
2. Arbab S, Ullah H, Khan MIU, Khattak MNK, Zhang J, Li K, Hassan IU. Diversity and distribution of thermophilic microorganisms and their applications in biotechnology. J Basic Microbiol. 2022;62(2):95-108.
3. den Besten HMW, Wells-Bennik MHJ, Zwietering MH. Natural Diversity in Heat Resistance of Bacteria and Bacterial Spores: Impact on Food Safety and Quality. Annu Rev Food Sci Technol. 2018, 25;9:383-410.