Identifying and exploring biohydrogenating rumen bacteria with emphasis on pathways including trans-10 intermediates

Background Bacteria involved in ruminal formation oftrans-10 intermediates are unclear. Therefore, this study aimed at identifying rumen bacteria that producetrans-10 intermediates from 18-carbon unsaturated fatty acids. Results Pure cultures of 28 rumen bacterial species were incubated individually in the presence of 40 mu g/mL 18:3n-3, 18:2n-6 ortrans-11 18:1 under control or lactate-enriched (200 mM Na lactate) conditions for 24 h. Of the 28 strains,Cutibacterium acnes(formerlyPropionibacterium acnes) was the only bacterium found to producetrans-10 intermediates from 18:3n-3 and 18:2n-6, irrespective of the growth condition. To further assess the potential importance of this species in thetrans-11 totrans-10 shift, different biomass ratios ofButyrivibrio fibrisolvens(as atrans-11 producer) andC. acneswere incubated in different growth media (control, low pH and 22:6n-3 enriched media) containing 40 mu g/mL 18:2n-6. Under control conditions, atrans-10 shift, defined in the current study astrans-10/trans-11 >= 0.9, occurred when the biomass ofC. acnesrepresented between 90 and 98% of the inoculum. A low pH or addition of 22:6n-3 inhibitedcis-9,trans-11 CLA andtrans-10,cis-12 CLA formation byB. fibrisolvensandC. acnes, respectively, wherebyC. acnesseemed to be more tolerant. This resulted in a decreased biomass ofC. acnesrequired at inoculation to induce atrans-10 shift to 50% (low pH) and 90% (22:6n-3 addition). Conclusions Among the bacterial species studied,C. acneswas the only bacterium that have the metabolic ability to producetrans-10 intermediates from 18:3n-3 and 18:2n-6. Nevertheless, this experiment revealed that it is unlikely thatC. acnesis the only or predominant species involved in thetrans-11 totrans-10 shift in vivo