In a previous study, a biological response modifier (BRM) specifically enhancing the function of B-cells was isolated from Korean fermented soybean paste (Kfsp), but not from non-fermented soybeans. In this study, we attempted to isolate the bacteria producing the BRM from Kfsp (KfspBRM) by ELISA using anti-KfspBRM and by B-cell proliferation. Five bacteria whose culture supernatants showed the BRM activities were isolated, and one of them was identified as Bacillus licheniformis E1. The bacterial BRM (bBRM) originated from a slime layer of B. licheniformis El had a molecular weight of 1,594 kDa, and contained $33\%;(w/w)$ of reduced sugar and $4.6\%;(w/w)$ of protein content. The bBRM appeared to be a glycoprotein that is physically, structurally, and functionally similar to the KfspBRM, suggesting that the isolates including B. licheniformis El may produce the KfspBRM in the fermentation process of soybean paste. The mass production of the BRM by the bacterium may help to study B-cells in immunology, and the enrichment of the BRM in Kfsp may help patients in future who are medically in need of potentiation of B-cell proliferation and antibody production.