Katelyn Cabeza, Melissa De La Luz, Giovanni Rebolledo and Dr. Nikita Parmar
Abstract
Non-traditional sweeteners (other than glucose and sucrose) are flooding the global western market and are found in a wide variety of foods today, particularly in zero-calorie sugar substitutes. Contradictory results have been observed from research conducted on animals about the safety of these sweeteners. In our project, we sought to analyze the impact of ten different sugar substitutes-maltitol, xylitol, sorbitol, acesulfame-K, lactitol, monk fruit, stevia, cyclamate, sucralose, and erythritol on bacterial growth. In the first experiment, E. coli cells were grown on minimal media lacking glucose but supplemented with the substitutes. Bacterial cells were exposed to 0.4% of the compounds (standard glucose concentration) and grown on media plates at 37oC. Positive control included exposure to glucose while the negative control media lacked any sugars. Experiments were done in triplicates. Growth was observed on plates containing monk fruit, stevia and sorbitol 36-48 hours post streaking and no growth was observed in the presence of any of the other sweeteners. Robust growth was observed in the presence of glucose while no growth was evident in the negative control plates. Our results indicate that bacteria are able to metabolize monk fruit extract (containing mogrosides), stevia extract (steviol glycosides containing rebaudioside A), and sorbitol (a sugar alcohol). In our second experiment, we conducted a dose-dependent profile to monitor bacterial growth at different concentrations of the sweeteners ranging from 0.1% to 1.0%. We observed that while growth was strong in sorbitol even at low doses (0.1-0.3%), in stevia and monk fruit plates, growth was slow and sparse at low doses although with an increase in the incubation time, growth improved. All sweeteners showed ample growth at concentrations of 0.4% and above, indicating that these are not toxic to the bacteria at higher doses.
