The potential beneficial effects of probiotics are known to be strain specific, meaning that a potential immune-boosting effect of one strain is not matched by another. The formulation of functional foods presupposes the stability of probiotic strain in the final product, but actual studies to support this quality is lacking and ‘surprising’, according to researchers from the University of Turku in Finland.
“The lack of such reports is surprising, especially considering the early findings on changes in the in vitro properties of early L. rhamnosus GG strains following different production processes and a long-term series of reinoculations, suggesting deterioration of adhesion properties and the report on production lot differences in an L. acidophilus strain influencing the outcome of human intervention studies,” they wrote in the British Journal of Nutrition.
Led by Lukasz Grzeskowiak, the researchers examined the effects of the processes used to produce a specific probiotic strain, Lactobacillus rhamnosus GG. Their research showed that the production process and conditions do indeed affect the strain’s properties
“This finding sets important prerequisites for quality control in probiotics,” they wrote. “Ensuring the original properties is especially important when the strain or product is used in human intervention studies, as small changes may significantly influence the outcome.
“The finding also presupposes new quality-control measures for the manufacture of probiotics for food use to preserve the original properties, which may have an impact on efficacy in human studies,” they added.
Commenting independently on the study’s findings, Professor Gregor Reid from the Canadian R&D Centre for Probiotics at the Lawson Health Research Institute, and The University of Western Ontario said the concept is “interesting but you would need to study the actual characteristics”.
Examples of the characteristics that would need additional study include the surface structures, time to reach various growth phases, and the time to production of hydrogen peroxide, said Prof Reid. All of these studies would need to be done “in a model mimicking the application to the human gut (this could be the artificial gut or in humans using nasogastric sampling after ingestion, and look at viability, replication, gene expression differences) in order to really know the effect of manufacturing”.
The Turku-based scientists obtained 15 different L. rhamnosus isolates, 14 of which were specifically labeled as L. rhamnosus GG, from specific probiotic products, and characterized the phenotypes and genotypes. Using a human intestinal mucus model, the researchers also analyzed the adhesion properties of the isolates.
Results showed that all the isolates were confirmed as members of the L. rhamnosus species, but all except one “showed randomly amplified polymorphic DNA, enterobacterial repetitive intergenic consensus and pulsed-field gel electrophoresis profiles identical to that of L. rhamnosus GG (ATCC 53103)”, said the researchers, whereas the bacteria’s tolerance to acid was similar, and all were able to bind to mucus from the human colonic mucus.
The researchers also note that there was also significant variation between the L. rhamnosus isolates tested on their ability to exclude and inhibit certain pathogenic bacteria.
“The results suggest that different sources of the same probiotic may have significantly altered strain properties,” wrote the researchers.
“[…] we conclude that the original properties used in the selection of specific probiotic strains may indeed be influenced by industrial production processes and conditions as well as by the food matrix used,” they added.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114510004496
“Manufacturing process influences properties of probiotic bacteria”
Authors: L. Grzeskowiak, E. Isolauri, S .Salminen, M. Gueimonde