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

Abstract

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, a 1 g terpineol) and one sesquiterpene hydrocarbon (b-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, 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.

In vitro screening of selected feed additives, plant essential oils and plant extracts for rumen methane mitigation

“…M. teretifolia contains the highest neral and geranial concentrations of all Melaleucas, while a major secondary constituent in M. ericifolia is linalool, all known to have antimicrobial properties . It has also been reported that terpenoids remain undegraded in the rumen for a prolonged period, hence their activity is extended. However, all EO tested here also inhibited overall microbial activity, a similar finding having previously been reported, suggesting that inclusion of EOs in diets at these doses could compromise energy supply to ruminants.…”

A response to Pennisi - “How do gut microbiomes help herbivores”, a hint into next-generation biocontrol solutions

“…Kim et al 2016). Furthermore, we know that numerous plant defence compounds, such as monoterpenes, diterpenes, phenolics and alkaloids can be metabolized by bacteria (Malecky et al 2012, Marmulla and Harder 2014, Hammer and Bowers 2015, Vilanova et al 2016, and crucially, some invasive insects seem able to tolerate (Piskorski et al 2011) and even benefit (Lefort et al 2015) from such compounds. The presence of gut microbial communities capable of metabolising plant defence compounds (Chung et al 2017) could explain why some phytophagous insects are invasive whilst others are not.…”

Gut microbiota of the pine weevil degrades conifer diterpenes and increases insect fitness

“…However, the ability to degrade and utilize terpenes is not limited to environmental microorganisms, but also occurs in symbiotic microbes associated with vertebrates and invertebrates. Goat rumen-associated bacteria can degrade several monoterpenes (Malecky, Albarello, & Broudiscou, 2012), and some members of the gut community of bark beetles are capable of in vitro degradation of monoterpenes and diterpenes (Boone et al, 2013;Xu, Lu, & Sun, 2015). However, whether bacterial degradation of terpenes occurs within the insects as well has not been explored.…”