Modifying microbial fermentation conditions can improve probiotic survival
New techniques that identify and modify the fermentation conditions and genes that are involved in human gastrointestinal tract persistence may help to improve the survival of probiotics – so helping industry to select and develop probiotic strains and starter cultures with improved robustness end effectiveness, finds the new research carried out as part of the TI Food and Nutrition network.
Carried out by Hermien van Bokhorst-van de Veen of Wageningen University, and in conjunction with NIZO Food Research, the research looked for ways to identify and manipulate stress responses of probiotic bacteria that may modify digestive tract robustness and survival.
Speaking with NutraIngredients, van Bokhorst-van de Veen said her work has found that that small variations in growth conditions of bacteria such as Lactobacillus plantarum have a large effect on survival and the expression levels of certain genes.
The Dutch researcher created a new in vitro assay that mimics the action of the digestive tract in order to test the survival and robustness of probiotic strains in a quick and inexpensive way. She then used this assay to test how different strains reponses to stress during their fermentation affected survival in the digestive tract.
“The results showed a large variation in survival based on how the stress responses the strain had been put through,” explained van Bokhorst-van de Veen.
She added that in view of the wide use of these bacteria in the food industry, the new findings will help industry to select and develop products with probiotics that are more robust to survival within the gut.
Further work carried out in humans by van Bokhorst-van de Veen and her colleagues followed the survival of 10 strains through the digestive tract finding that when one streain survived well, it did so in all people - something that van Bokhorst-van de Veen said is ‘quite remarkable’ given the differences between people and their microbiota make up.
“The findings in humans were also linked to the findings from the in vitro assay,” she said. “There was significant correlation between the in vitro results and the lab tests on people.”
“Since the persistence measured in the human volunteers could be correlated with the survival found in the in vitro model, we can use this fast and inexpensive model to predict actual gastrointestinal tract survival.
“In addition, combining strains reduces the amount of work and time needed for industry to test promising strains for food applications.”
Using the toolkit of assays and methods to ‘shock’ cultures in fermentation, the Dutch researcher suggests that industry can test and increase a number of traits in friendly bacteria.
“Industry could use the assay to test many different traits, and not just survival in the digestive tract,” she added.