ORIGINAL ARTICLES  BIOENCAPSULATION IN BIOTECHNOLOGY 

Minerva Biotecnologica 2007 June;19(2):57-63

Copyright © 2007 EDIZIONI MINERVA MEDICA

lingua: Inglese

Comparative study of two types of hybrid biocatalysts applied in a biodegradation process

Kabaivanova L. ¹, Emanuilova E. ¹, Chernev G. ², Samuneva B. ², Djambazki P. ², Miranda Salvado I. M. ³

¹ Department of Extremophilic Bacteria Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria 2 Department of Silicate Technology University of Chemical Technology and Metallurgy, Sofia, Bulgaria 3 Department of Ceramic and Glass Technology University of Aveiro, CICECO, Portuga

Aim. The aim of the present study was to carry out a biodegradation process of a mixture of nitriles by biocatalysts obtained by immobilization of thermophilic bacterial cells, producers of nitrilase in a laboratory column bioreactor.
Methods. The substrate solution subjected to degradation contained benzonitrile and 4-cyanopyridine in equal quantities with a total concentration of 20 mM. The nanocomposite hybrid matrices used for the immobilization of Bacillus sp.UG-5B cells, were prepared by the sol-gel method by replacing 5wt.% of the inorganic precursor tetramethylortosilicate (TMOS) with polyacylamide gel (PAAG) and agar-agar as an organic part.
Results. The optimal flow rate was 0.75 mL.min-1. Degradation of 54.6 mM of the substrate was achieved for nine hours with biocatalysts, at entrapment with 5wt.% PAAG compared to 60mM when the hybrid matrix contained 5 wt.% agar-agar. At chemical activation with 10% formaldehyde of the matrix with agar-agar, the degradation process was faster (7 hours) and the ammonia released corresponding to the quantity of degraded substrate was 63.8 mM.
The studied hybrids have an amorphous structure and the surface area of the pores from 365m2/g to 125m2/g with an average size of nanoparticles on the surface about several nanometers.
Conclusion. An effective biodegradation process was fulfilled for a short period of time at high temperature for the mixture of benzonitrile and 4-cyanopyridine in a column bioreactor. The used hybrid matrices are chemically inert and have great chemical and thermal resistance, not susceptible to organic solvents or microbial attack, as well as they do not affect cell activity and vitality.