Introduction

Have you ever thrown away some bananas because they were too ripe?
Are you one of many that hates waiting ages to eat the immature kiwis that you find at the supermarket?
Do you know how banana and other fruits are picked green from the tree and arrive to the supermarket ready to be sold and eaten?
Do you ever think of the huge fruit waste fruits in restaurants, markets, and industry?
We have decided to solve both these problems by designing and engineering a bacterial system able to control fruit's ripening in response to different stimulations: B. fruity.

Furthermore, we have planned two different commercial products in order to eliminate waste of food and to make the consumption of these fruits accessible even in unusual places like schools and offices: the "B.Fruity Vending Machine" and the "B. fruity Home Edition".

How does B. fruity work?
We have designed an started to build a genetic circuit that activates fruit maturation thanks to ethylene production, a molecule produced by climateric plants that affects growth, development, ripening, and senescence (C. J. Brady, 1987). However, B. fruity does not exploit the complicated ethylene production patwhay of plants, because of the undesirable production of Cyanide (Shang Fa Yang et Al., 1984)!!! We instead, decided to follow a different metabolic pathway that is present in Pseudomonas syringae which involves a single enzyme: 2-Oxoglutarate Oxygenase/Decarboxylase, commonly named the Ethylene Forming Enzyme (EFE).

To inhibit maturation we selected methyl salicilate, an ester also known as wintergreen oil, that is produced many plants and that it was shown to slow down at high concentration (5 mM) the ripening process in tomatoes (Chang-Kui Ding et Al., 2002). To achieve methyl salicilate production we were lucky to use many of the parts submitted by the 2006 MIT iGEM team, as well as others built by us.

How B.Fruity is activated?
We have coupled this system to a Blue light photoinducible receptor succesfully used by other labs and iGEM teams in the past. Our system in the OFF state (no Blue light) will produce methyl salicilate and stop unwanted ripening, while in the ON state ( Blue light exposure) will produce ethylene and repress methyl salicilate production, thus promoting fruit ripening.




You can check our DATA page for a full description of the circuit.

Why B. fruity?
We engineered the full system and characterize each component of the system in E. coli.
We have also tried to demonstrate the functionality of the enzymes involved in Bacillus subtilis.
In order to develop a possible commercial product it is more desirable to use a chassis capable to resist for a certain amount of time without nutrients and so we tought that Bacillus subtilis could fit perfectly our purpose! It can makes spores and it's easy to re-activate by removing the source of stress and adding, for example, water/nutrients. Moreover, B. subtilis is not a human pathogen. It can, however, degrade or may contaminate food, and modify them, but rarely causes food poisoning. Therefore, with the right precautions and attention this chassis appear like the best system for our project.