Team:Sharon MA Aquila


The purpose of our project is to insert antifreeze protein (AFP) into yogurt cultures. Milk is converted to yogurt using Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus bacteria. These cultures ferment the lactose sugar present in the milk and convert it to lactic acid, which gives yogurt its distinctive taste and texture.

AFP is a protein produced by plants, fungi, bacteria, and some vertebrates to prevent the formation of dangerous ice crystals at subzero temperatures. AFP is about 300 times more effective than industrially produced antifreezes at the same concentration, so it have many possible commercial applications, including cryosurgery, hypothermia treatment, and farm fish production. Some companies have also started isolating AFPs from fish and introducing them into milk and yogurt products. The protein could help prevent freezer burn and improve the texture of the yogurt (frozen or otherwise).

Our project will instead introduce the AFP-producing gene directly into the Lactobacillus bulgaricus bacteria, so that it is constantly produced as the bacteria metabolizes lactose. Hooking up production of the protein to the lactose sensor already present in the bacteria would allow continuous production of the protein. Since transplantation of a small quantity of yogurt cultures can be used to produce another batch of yogurt, our altered bacteria would easily be able to replicate and produce AFP in new batches.