Biological systems provide many examples of specifically tailored, nanostructured molecules with highly optimized properties and characteristics. These biomaterials are composite materials and consist of an inorganic component and a special organic matrix. Crystalline bacterial cell surface layers (S-layers( are the outermost cell envelope component of many eubacteria and archaea and are composed of 2D crystalline arrays of identical protein or glycoprotein subunits. Present study was carried out to study the biosynthesis of Ti2O, in the presence of Lactobacillus sp with two concentrations (0 and 450µM) of humic acid (HA(. The products obtained were analyzed with XRD and Dynamic Light Scattering (DLS) analyzes. Results showed that HA resulted in reduction of percentage of Ti2O particles under 30nm, also the percentage of Ti2O particles above 30nm was increased.