Degradation of terpenes and terpenoids from Mediterranean rangelands by mixed rumen bacteria in vitro

This in vitro study aimed at estimating the disappearance rates of 14 terpenes and terpenoids after 24-h incubation with mixed bacteria from caprine rumens. These compounds comprised nine monoterpene hydrocarbons (delta-3-carene, p-cymene, beta-myrcene, (E)- and (Z)-beta-ocimene, alpha-phellandrene, alpha-terpinene, gamma-terpinene and alpha-terpinolene), four oxygenated monoterpenes ((E)- and (Z)-linalool oxide, 4-terpinenol, alpha + gamma terpineol) and one sesquiterpene hydrocarbon (beta-cedrene). They were individually exposed to goat rumen microflora for 24 h in 70 ml culture tubes at an input level of 0.5 ml/l. Terpenoids were the least degraded, 100% of (E)-linalool oxide, 95% of (Z)-linalool oxide, 91% of 4-terpinenol and 75% of terpineol remained intact after 24-h incubation. In contrast, alpha-terpinolene concentration in fermentation broth extracts was below quantification limit, thus indicating an extensive, if not complete, degradation by rumen bacteria. Only 2% of the initial amounts of alpha-phellandrene were recovered. The other monoterpenes and beta-cedrene were partly degraded, with losses ranging from 67% for delta-3-carene to 90% for (E)-beta-ocimene. The corresponding rates of disappearance were between 2.67 and 4.08 mu mol/ml inoculum per day. in