Lactobacillus fermentum

Lactobacillus fermentum is a Gram-positive species of bacterium in the genus Lactobacillus. It is associated with active dental caries lesions. It is also commonly found in fermenting animal and plant material. It has been found in sourdough. A few strains are considered probiotic or 'friendly' bacteria in animals and at least one strain has been applied to treat urogenital infections in women. Some strains of lactobacilli formerly mistakenly classified as Lactobacillus fermentum (such as RC-14) have since been reclassified as Lactobacillus reuteri. Commercialized strains of L. fermentum used as probiotics include PCC, ME-3 and CECT5716 Lactobacillus fermentum belongs to the genus Lactobacillus. Species in this genus are used for a wide variety of applications. These applications include food and feed fermentation. It has been found that some strains for Lactobacillus fermentum have natural resistances to certain antibiotics and chemotherapeutics. They are considered potential vectors of antibiotic resistance genes from the environment to humans or animals to humans. Lactobacillus fermentum can also be a normal inhabitant of the human intestinal tract and some strains have been associated with cholesterol metabolism. A microorganism is considered a probiotic by meeting certain characteristics, such as being of human origin, non-pathogenic, having high resistance to passing through the intestine, and being beneficial to the immune system. In general, they are seen as beneficial to the host’s body and the human health. Lactobacillus fermentum has been identified as potential probiotic.The use of gut microbes as probiotics in food is aimed towards preventing and treating various health problems. Among these health problems allergies, neoplastic growth, and inflammatory bowel disease are included. Recent areas of study have focused on the influence of probiotics on metabolic functions of their host. One area has been the metabolism of cholesterol by LABs acting as probiotics. Research has shown that Lactobacillus species have been proven to remove cholesterol in vitro through various ways such as assimilation, binding to the surface cells, and incorporation into cellular membranes. Testing of Lactobacillus fermentum against different pH concentration solutions revealed that it has a strong pH tolerance by its ability to grow and survive a few hours after being incubated in a 3-pH level solution. Strains of Lactobacillus fermentum have also been tested in different bile concentrations and demonstrated to have good bile tolerance when incubated with 3 g L-1 of bile salt. The pH and bile tolerance that L. fermentum demonstrates is significant in terms of its consideration as a probiotic. It has to be strong enough to survive the stresses of the digestive system. The stomach has a pH between 1.5 and 3, and the upper intestine contains 3-5 g L-1 of bile. Lactobacillus fermentum has been found to survive in these conditions further supporting the idea that it can act as a probiotic. One of the ways in which Lactobacillus fermentum has been seen as a probiotic is by its ability to reduce cholesterol levels. Tests conducted using several strains of Lactobacillus and cholesterol broths demonstrated that lactobacillus fermentum had the largest removal of cholesterol. One of the mechanisms by which L. fermentum may remove cholesterol through in vivo is by the absorption of cholesterol, which as a result accelerates cholesterol metabolism. Another method is by the incorporation of cholesterol in the host body into its cell membrane or walls. This would also increase resistance of the bacterial cell membranes to environmental challenge. A third mechanism is by causing the body to consume more cholesterol. L. fermentum would interfere with the recycling of bile salt and facilitate its elimination, which as a result would increase the demand for bile salt made from cholesterol. The strain Lactobacillus fermentum ME-3 has recently been discovered and identified as an antimicrobial and antioxidative probiotic. This strain of Lactobacillus fermentum was discovered from the analysis of human fecal samples in 1994. One of the important characteristics of a probiotic microbe is the tolerance to conditions in the digestive tract. Tests conducted on the ME-3 strain in different bile concentrations found that it was able to survive without large loss in numbers. It has also been found that Lactobacillus fermentum ME-3 has a tolerance to survive drops of pH levels. It can withstand a drop in values from 4.0 to 2.5 without decreasing in numbers. These characteristics of tolerance to bile concentrations and pH levels serve to classify ME-3 as a probiotic. Lactobacillus fermentum ME-3 has also been found to have the capability to suppress mainly gram-negative bacteria. To a lesser extent, ME-3 has also been observed to be able to suppress Enterococci and Staphylococcus aureus. This would serve a beneficial purpose to the host. ME-3 has several antimicrobial characteristics. These include acetic, lactic and succinic acids, and putrescine. Research on the antioxidant properties of strain ME-3 in soft cheese products revealed that it prevented spoilage.Experimentation has also been conducted on the consumption of the ME-3 strain. The consumption had a positive influence on the microbiota of the gut. Volunteers were given goat milk fermented by strain ME-3 and capsulated ME-3. After three weeks analysis of fecal samples revealed that the ME-3 strain increased the number of beneficial Lactobacilli in comparison to those who were given non-fermented milk.Several human clinical studies performed on ME-3 focused on parameters related to cardiovascular disease development. Consumption of ME-3 indeed results in a reduction of oxidized LDL cholesterol, which is a major contributor to atherosclerosis development. Several mechanisms may contribute to the antioxidant effect of ME-3: the strain modulates the ratio of reduced glutathione/oxidized glutathione in the blood, and increases the levels of paraoxonase, an antioxidant enzyme which protects LDL particles from oxidative modifications.