The pancreas supplies the major digestive enzymes that catalyze the breakdown of starches (carbohydrates), proteins, and fats, so that the breakdown products can be absorbed in the upper small intestine. Some carbohydrate digestion takes place in the mouth by salivary amylase, but pancreatic amylase is the major carbohydrate-digesting enzyme. Amylases break down starches to maltose and maltotriose, which are further hydrolyzed into glucose by the disaccharidases of the mucosal cells, and then absorbed. Although cellulose is indigestible by pancreatic and intestinal enzymes, the microflora within the large intestine may degrade it and produce uncomfortable symptoms in the process. Although fat digestion starts in the mouth with the action of salivary lipase, the great majority of fat triglycerides are digested by pancreatic lipase secreted by the exocrine pancreas into the duodenum. Lipases break down triglycerides into monoglycerides and free fatty acids, which are efficiently absorbed in the upper small intestine. Bile is normally secreted from the gallbladder to help aid in the digestion of lipids in the small intestine. Protein digestion is initiated in the stomach by pepsin and hydrochloric acid, which denature and break large proteins down to smaller polypeptides. In the small intestine, proteases break down these polypeptides into free amino acids, and di- and tripeptides, which are directly absorbed by the intestinal mucosa. Ingredients such as aspergillus oryza can also aid in the digestion and absorption of food.