Starter cultures derived from dairy bacteria are responsible for properties of fermented dairy products – for instance cheese, yogurt or buttermilk – such as flavour, texture and shelf life.
NIZO said that, due to greater numbers of strains, plant lactococci were more versatile than dairy lactococci, and therefore had good potential to provide dairy products with new functionalities.
But Dr Herwig Bachman from NIZO told DairyReporter.com that plant isolates had not traditionally grown well in milk, and as a result had rarely been used within industrial applications.
However, in a new study that he co-authored in Genome Research, Bachmann said his team had propagated a plant isolate strain of L.Lactis (a bacteria used in cheese production) in the laboratory that did grow well in milk.
Significantly, characterisation of the evolved strains showed a significant increase in growth and acidification rates, biomass yield and improved fitness in milk compared with natural dairy isolates.
Said Bachman: “The basic idea of the project was to take a strain, lactococci or L.Lactis, that you find either in the plant environment or in the dairy environment.
“The suggestion has always been that dairy strains have evolved from plant strains. There is circumstantial evidence but no direct proof.
So we took a plant isolate of lactococci, put it as it was in milk for 1000 generations (roughly five months) then we had a look and asked ‘does it now perform better in milk?’ compared to a natural dairy isolate.”
Bachman said his team had evolved plant-derived strains that did perform better, and were able to grow to higher cell densities and solidify milk a lot faster.
Asked about potential improved functionality, he said: “They [plant isolates] might have certain metabolic pathways that produce new flavour compounds, or flavour compounds that we already know but at higher levels.
He added: “There might be things that relate to texture, and there might also be probiotic strains that come from a plant environment, but currently [prior to this research] they do not perform well in milk.
Designer dairy future
Since NIZO possessed a large strain collection of lactococci and lactobacilli, Bachman said the firm was able to screen them for functional properties demanded by customers in any dairy products where such bacteria were used.
He said: “Once you find them, it doesn’t matter so much whether they are growing in milk or not, because we know there is a big likelihood that we can actually adapt them to grow in milk and use them in a product in the end.
“The exciting this is that we now have access to many more strains than before – when we presumed that we cannot use these plant strains anywhere in the dairy environment,” Bachman added. “That whole presumption is crumbling. You can, if you know how to adapt them.”
For instance, said Bachman, if you used a bacteria as a probiotic it might function well, but not survive particularly well. “Many probiotic strains do the trick but don’t survive. Now you have a host of other bacteria that you can select for their effect that could survive,” he said.
There was also a lot of industrial interest in NIZO’s work as non-GM method of finding “very nice new strains with new functionalities; that’s hot at the moment,” Bachman added.
And when could such ‘designer’ dairy products using plant isolates reach retail shelves? “If a client came to us now, and said ‘we want to find a new functionality for a certain product’, it could take a couple of months for screening and finding them, and a couple of months for adapting them,” he said.
Bachman added: “Within a year, you could be able to make product trials and establish pilot plant production.”
Title: 'Microbial domestication signatures of Lactococcus lactis can be reproduced by experimental evolution'
Authors: H.Bachmann, M.J.C Starrenburg, Douwe Molenaar, M.Kleerebezem, J.E.T van Hylckama Vlieg
Source: Genome Research, published online ahead of print on November 11, 2011. doi:10.1101/gr.121285.111