Every year, one third of global food production -1.3 billion tons of food- is thrown away, partially due to the “best before” dating system. iGEM Groningen 2012 seeks to provide an alternative method of assessing edibility: the Food Warden. It uses an engineered strain of Bacillus subtilis to detect and report volatiles in spoiling meat. The introduced genetic construct uses a promoter to trigger a pigment coding gene. This promoter, identified by microarray analysis, is significantly upregulated in the presence of volatiles from spoiling meat. The activity of the promoter regulates the expression of the pigment reporter and will be visible to the naked eye. For safe usage of the system, spores of our engineered strain are placed into one half of a semi-permeable capsule, the second containing a calibrated amount of nutrients. Breaking the barrier between the two compartments allows germination and growth, thereby activating the spoiling-meat sensor.

Our main accomplishments

In the lab

Most importantly: we developed a construct which makes Bacillus subtilis sense spoiled meat and produce an output in the form of a yellow pigment visible by naked eye.

Design of the “Sticker”: semi-permeable capsule: bacteria are kept inside, volatiles can go through. Proof that Bacillus subtilis grows inside the sticker.

Development of BioBrick psac-cm for Bacillus subtilis.
Easy cloning in Bacillus subtilis in Biobrick fashion for the first time! Advantages: easy to check, BioBrick compatible, E. coli compatible, stable insertion into Bacillus subtilis chromosome.

Identification of spoiled meat sensors by transcriptome analysis. Usage of an innovative experimental setup which can be used to test more sensors in the future.

We made AmilCP and AmilGFP be expressed in Bacillus subtilis. These chromoproteins can be of significant value to the other Bacillus subtilis users in the BioBrick community.


Smart spores activation system: inspired by "glow in the dark stick", we designed a sticker with two compartments. One compartment holds the spores, the other the nutrients; when the nutrients compartment is braked, the spores start to germinate, activating the sticker.

We explored the definition of spoiled meat and different ways to test this.

We identified various compounds present in spoiled meat by Gas Chromatography - Mass Spectrometry.

We made a model which gives insight on how to tweak the growth of Bacillus subtilis based upon literature, experimental data and flux balance analysis.

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