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

Overview & Synopsis

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 (d-3-carene, p-cymene, b-myrcene, (E)- and (Z)-b-ocimene, a-phellandrene, a-terpinene, g-terpinene and a-terpinolene), four oxygenated monoterpenes ((E)- and (Z)-linalool oxide, 4-terpinenol, a1g terpineol) and one sesquiterpene hydrocarbon (b-cedrene). They were individually exposed to goat rumen microflora for 24 h in 70ml 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, a-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 a-phellandrene were recovered. The other monoterpenes and b-cedrene were partly degraded, with losses ranging from 67% for d-3-carene to 90% for (E)-b-ocimene. The corresponding rates of disappearance were between 2.67 and 4.08 mmol/ml inoculum per day.