It was observed that the percentage of titratable acidity increased, but not as much as the value of treatment 1, because this treatment already underwent alcoholic fermentation carried out by the added yeast, Saccharomyces cerevisiae. In this treatment, sugar was used as a substrate and yeast to produce alcohol and carbon dioxide. Alcohol hinders the growth and survival of unwanted microorganisms because it denatures their membrane. Additionally, alcoholic fermentation is used in the manufacturing of alcoholic beverages like beer and wine. According to Rahman (2007), regarding the oxygen supply, this treatment underwent anaerobic fermentation due to the dissimilation of carbohydrates in which oxygen does not intervene, but rather other substances, aldehydes and pyruvic acid which serve as a hydrogen acceptor. On the other hand, the increase in the percentage of titratable acidity occurred because of the carbon dioxide molecules that had already reacted with the water, forming carbonic acid which made the mixture more acidic compared to to treatment 1. This occurred since carbonic acid is a weak acid which causes a slight drop in pH, thus making the mixture more acidic. However, carbon dioxide alone is not acidic (Pederson,