Which factor among the following may play role in the bad odor from mouth,When the mucosal surface dry out.

For oral malodor, the unpleasant smell of the breath mainly originates from VSCs, especially hydrogen sulfide (H S), methylmercaptan (CH SH), and less important dimethyl sulfide , as first discovered by Tonzetich. However, in certain conditions (e.g., when the saliva dries out on the mucosal surfaces), other compounds in mouth air may also play a role such as diamines (e.g., putrescine, cadaverine), indole, skatole, and volatile organic acids like butyric or propionic acid. Most of these compounds result from the proteolytic degradation by oral microorganisms of peptides present in saliva (sulfur-containing or non–sulfurcontaining amino acids, shed epithelium, food debris, gingival crevicular fluid (GCF), interdental plaque, postnasal drip, and blood. In particular, gram-negative, anaerobic bacteria possess such proteolytic activity.