The Investigation of the Pathway and Production of Sugar Alcohols in Lactobacillus florum

Student Name: Sean Thomas
UCD Department: Food Science and Technology
UCD Mentor: Dr. Maria Marco

Erythritol is a naturally occurring, zero calorie sweetener produced by fermentation and is used as an additive in many foods and beverages. Erythritol is produced commercially through yeast fermentation using an expensive filtration process. The discovery of a microbe that could produce erythritol in comparable amounts could provide an alternative to this process, especially if it is a food grade microbe that could remain in the finished product. Lactobacillus florum is a novel, heterofermentative, lactic acid bacteria that has been found to produce erythritol making it a potential candidate.  Two strains of Lactobacillus florum, 8D and 2F, previously isolated from an unripe king palm fruit and a Valencia orange leaf, respectively, were tested for their ability and efficiency in producing erythritol when given glucose, fructose, or a combination of the two. Other metabolites, such as mannitol, acetic acid, lactic acid, and ethanol were also measured for. Since the erythritol pathway is not known in L. florum, enzyme assays were conducted to measure for the activity of enzymes responsible for erythritol production in Oenococcus oeni and yeast, erythritol 4-phosphate dehydrogenase and erythrose reductase, respectively. The results described will increase our knowledge of Lactobacillus florum, the pathway by which it can produce erythritol, and lead to areas of study for an alternative means of erythritol production. Both 8D and 2F were found to be capable of erythritol production when provided glucose, fructose, and the glucose-fructose combination, with 8D producing more than 2F.