Toxin production by bacterial endosymbionts of a Rhizopus microsporus strain used for tempe/sufu processing

Area of Science:

• Food Science
• Microbiology
• Toxicology

Background:

• Mould fungi are crucial in food spoilage and fermentation, particularly in Asian countries for soy-based products like tempeh and sufu.
• The fermentation of soybeans and tofu into tempeh and sufu commonly involves various Rhizopus strains.

Purpose of the Study:

• To investigate the presence of toxinogenic bacteria in starter cultures used for sufu production.
• To identify potential health risks associated with the symbiotic relationship between fungi and bacteria in food processing.

Main Methods:

• Metabolic profiling of the fungus under standard tempeh and sufu production conditions.
• Identification and characterization of toxinogenic bacteria within the starter culture.
• Development of a Polymerase Chain Reaction (PCR) method for detecting endofungal bacteria.

Main Results:

• Toxinogenic bacteria were identified in a starter culture used for sufu production.
• Critical amounts of toxins from the rhizoxin complex were found to be produced.
• Rhizoxins are potent toxins with significant antimitotic activity, posing a health risk.

Conclusions:

• The study reveals a health-threatening symbiosis in food processing, specifically in sufu production.
• The presence of toxinogenic bacteria can lead to the formation of harmful levels of mycotoxins.
• A simple PCR method is proposed for the routine detection of toxinogenic endofungal bacteria in starter cultures to ensure food safety.