Evaluation of Prebiotic Fibers and Pectin on Probiotic Strains and Effect of Bacteriocin-like Substance on the Survival of Listeria Monocytogenes

Probiotics and prebiotics have been shown to provide beneficial effects on the host health and there are numerous research efforts being conducted on a variety of specific applications. However, most prebiotic carbohydrates are lower molecular weight oligosaccharides; and the health benefits of higher molecular weight pectins have not been fully evaluated. According to reviews, pectins are fermented in the large intestine due to the cooperative activities of colonic bacteria with complementary enzymatic activities. There are very few studies that demonstrate the fermentability of high methoxy pectin and low methoxy pectin by pure cultures of human isolates or probiotic bacteria. Thus, it is conceivable that lack of evidence/studies may be problematic for defining human health properties of pectin. In studying the fermentation of prebiotics by bacteria, optical density (OD) measurements can be used, but OD can be interfered with by other substances present in the media. Some studies have suggested the use of fluorescent dyes to observe the growth of bacteria which has the advantage of differentiating between live and dead cells. Finally, certain lactic acid bacteria or probiotics have the ability to inhibit or kill pathogens due to production of lactic acid or other antibacterial substance (eg: bacteriocin). Therefore, the objective of this research is to study the fermentability of fructooligosaccharides (FOS), galactooligosaccharides(GOS), inulin agave (IA), high methoxy pectin (HMP), and low methoxy pectin (LMP) with three strains of probiotic bacteria in order to find the suitable carbohydrates that could be used as synbiotics. In addition, we also aimed to explore the use of acridine orange as a method to monitor the growth response of bacteria. The antilisterial effects of Lactobacillus acidilactici are also studied using survival assays and spot-on-lawn assays. We determined that FOS, GOS, and IA are good substrates to support the growth of probiotic bacteria and although HMP fermentability is still not clear, this carbohydrate could be of benefit to use as a synbiotic as well due to its ability to enhance the survival of probiotic bacteria both in normal media and simulated gastric conditions. In addition, we found that most bacteria grown in the presence of GLU exhibit better survival during exposure to bile solutions. However, the study on the use of acridine orange did not confirm that this dye can be used instead of OD. Finally, the last study has shown an effect of Lactobacillus acidilactici on the reduction of Listeria which could be partly due to pH