Abstract: The current study was examined the formation of the three Stereoisomers (SI) of 2, 6-Diaminopimelic Acid (DAP), lysine and pipecolic acid from aspartic acid by mixed rumen bacteria and protozoa. Mixed rumen bacteria and protozoa were isolated from the rumen of sheep given concentrate mixture and hay and incubated with and without aspartic acid (5 mM). The microbial suspensions were anaerobically incubated at 39°C for 12 h. The results showed that mixed rumen bacteria produced meso-DAP by 0.221 mM, LL-DAP by 0.013 mM, lysine by 0.211 mM during the 12 h incubation periods. This is the first finding to show the synthesis of DAP-SI and lysine from aspartic acid by rumen bacteria. Mixed rumen protozoa produced meso-DAP by 0.231 mM, lysine by 0.443 mM and pipecolic acid by 0.042 mM during the 12 h incubation periods. DD-DAP was not detected during the incubation periods of mixed rumen bacteria and protozoa and also LL-DAP was not detected by mixed rumen protozoa. The synthesis meso-DAP from aspartic acid by rumen protozoa was demonstrated for the first time. The results indicated that mixed rumen bacteria have the ability to synthesis meso-DAP, LL-DAP and lysine from aspartic acid meanwhile, the mixed rumen protozoa have the ability to produced meso-DAP, lysine and pipecolic acid from aspartic acid.