A silica monolith was prepared from commercial silica powder dispersed in water containing polymeric water soluble bio-organics (SBOs) isolated from composted urban vegetable wastes. The monolith and the pristine powder were characterized for their morphology and reactivity for immobilizing soybean peroxidase (SBP). Compared to the pristine powder, the monolith exhibited lower specific surface area (about 30% less), total pore volume and pore size (of about 200 angstrom of width), and bond less SBP under the same experimental conditions. The immobilized SBP products were tested for their catalytic activity in the reaction of hydrogen peroxide, 3-(dimethylamino)benzoic acid (DMAB) and 3-methyl-2-benzothiazolinone hydrazone (MBTH), by comparison with the same reaction performed with native SBP in solution. The reaction performed in the presence of immobilized SBP was slower than that catalyzed by native SBP in solution. However, in spite of its lower SBP content, monolith immobilized SBP (M-SBP) was found kinetically more active than the powder immobilized SBP (P-SBP). Also, M-SBP allowed to achieve the same reagents conversion as native SBP (95% of reagent conversion), although in longer time, whereas the maximum reagent conversion achieved with P-SBP was much lower (75% of reagent conversion). The M-SBP was more easily recovered from the reaction medium and found more stable than P-SBP upon repeated catalyst recycling (after 20 cycles 75-80% of the initial activity was retained by both immobilized samples, slightly higher in the case of M-SBP). (C) 2012 Elsevier Ltd. All rights reserved.