Industrial cheesemaking secrets revealed

To produce more than a billion dollars’ worth of cheese each year, Australian cheesemakers rely on starter cultures that convert lactose to lactic acid. The bacterium Lactococcus, the most commonly used starter culture in cheese production in Australia, is revealing some of its secrets to UQ researchers.

A new discovery by University of Queensland School of Agriculture and Food Sciences researchers along with researchers from Columbia University and the University of Washington is providing the insights into Lactococcus. Two UQ PhD students in Associate Professor Mark Turner’s food microbiology research laboratory — Thu Vu and Huong Pham — have identified that the enzyme known as pyruvate carboxylase is essential for efficient milk acidification, an important industrial trait in Lactococcus starter cultures.

The enzyme is essential for synthesising the amino acid aspartate, and bacteria defective in the enzyme are unable to produce high levels of lactic acid in milk, which is required for the first stage of cheesemaking.

“Our collaboration also found that a recently discovered small molecule in bacteria, called cyclic-di-AMP, directly binds to and inhibits the pyruvate carboxylase enzyme,” Dr Turner said.

“The molecule is essential for growth in a wide range of bacteria, including many human pathogens, and we are only in the early stages of understanding how it controls important processes in bacteria.”

This project was funded at UQ by an ARC Linkage Project, ‘Smarter fermentations through starter culture genomics’, and co-funded by Dairy Innovation Australia Limited.

Dr Turner this year won the 2017 Australian Institute of Food Science and Technology Keith Farrer Award of Merit, which recognises achievements in food science and technology in research, industry and education.

The research has been published in the Proceedings of the National Academy of Sciences.