Recent approaches have been made with regard to successful association of in vitro oil palm materials and diazotrophs. But, no biochemical study was revealed to explain possible relationship between the diazotroph and in vitro oil palm plant proliferation processes. In this study, calli and embryogenic calli of oil palm (Elaeis guineensis Jacq.) were treated with different inoculums of Herbaspirillum seropedicae strain Z78 (ATCC 35893) namely, sonicated cells and pellet cells. Treated oil palm tissues were observed for total amino acids, proteins, phenolics and sugar levels which were extracted and quantified every 10 days throughout 60 days of culturing. Results reveal a reduction of total sugar levels, increment of phenolics, amino acids and protein contents of bacterised calli with Z78 pellet cells which can explain rapid progression of embryogenic development. High content of phenolic compounds, sugar levels with the reduction of amino acids and proteins in bacterised embryogenic calli with Z78 sonicated cells would elucidate accelerated embryo regeneration and maturation. These results provide a novel explanation for biochemical profiles of bacterised oil palm calli and embryogenic calli. With the understanding of biochemical patterns, this can act as a guide for further in-depth study on in vitro plant cells-microbe interactions.