Modifying lactic acid bacteria
Ida Rud can change good bacteria so they do exactly as she wants. Almost...
Lactic acid bacteria are found in very many food products, including cured meats, sourdough bread, yoghurt and cheese.
"Lactic acid bacteria are usually only positive and are very good to have in foods. They can kill or inhibit dangerous bacteria, improve the shelf life of products and make a positive contribution to taste and texture," explains Ida Rud. Acidulating food to make it keep longer is a very old tradition and deliberately adding a start culture (in the form of lactic acid bacteria) has been done for a long time. But it is only in recent years that we have begun to really learn just why these bacteria are so useful.
Important to understand
Nofima Mat (formerly Matforsk) at Ås is systematically carrying out basic research into lactic acid bacteria so as to understand what happens during the production of food and thereby help to make food more stable, better and safer. In the work she has been carrying out for her doctorate, Ida Rud has got to know a great deal about lactic acid bacteria. Or more specifically, she has been studying glycolysis – the pathway from glucose (sugar) to lactic acid.
By developing and using new molecular biological techniques, she has begun to tread new paths in gene technology. "I try to change some of these good bacteria, so that they have the properties I want. Lactic acid bacteria can also produce other acids and compounds, which also contribute to the taste and consistency of food – acetic acid and formic acid for example. You can go a long way with this. One of the things they are working on in the Netherlands is to get the bacteria to produce the sweetener sorbitol," explains Ida Rud.
Just like all other living organisms, lactic acid bacteria need energy. They get it by breaking down glucose. Adenosine Triphosphate (ATP) is then created, a wonder molecule that all living organisms depend on. ATP is an energy carrier and is used in almost all processes in the cell.
Rud’s trial has shown that faster lactic acid production can be achieved by removing part of the ATP from the cells. This is done by inserting specific genes into the bacteria, which then compensate by making glycolysis run a little faster and thereby produce a little more acid. "In food production we want bacteria that produce lactic acid as fast as possible. The faster the better. We can see that the bacteria have the potential to produce lactic acid faster than they do naturally," says Ida Rud. She has developed a tool to "turn on" the genes in a completely stable way.
Not so easy
"What happens to the bacteria when you add new genes?"
"Like most other bacteria, lactic acid bacteria are fairly easy to modify genetically. But they are also very flexible, so it isn’t so easy to change them in the direction I want them to go. I really annoy them and they get up to all kinds of things to try to maintain the status quo."
"How can the knowledge you are gaining here be used by industry?"
"We can’t genetically modify the start cultures. What I have been doing in controlled laboratory trials would never be allowed in food. But by understanding these bacteria better, we can develop more optimum processes in the longer term, in the industry too," Ida Rud believes. Now she is dreaming about discovering the entire network of processes within the lactic acid bacteria. One way of doing this is to try to read and understand the bacterium’s whole genome (the genetic information that is coded within the organism’s DNA). Only then can we see the full potential of these bacteria.
Ida Rud had her doctoral disputation on Friday 19 September 2008. The English title of her thesis was "Primary metabolism in Lactobacillus – A study of control and regulation of acid production".
The scholarship was financed by the Foundation for Research Levy on Agricultural Products and Nofima Mat. After her disputation, Ida Rud has continued as a researcher at Nofima Mat – initially she has been mainly occupied with the analysis of microbial communities.