CHARACTERIZATION OF GRANULAR-IMMOBILISED LACCASES REACTOR FOR CONVERSION OF SYNTHETIC DYES
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - Ib: Extraction & Remediation (T1-4b)
Keywords: laccases, enzyme immobilisation, kinetics, reactor
The use of immobilized enzymes is usually characterized by improved resistance of enzyme to denaturation and proteolysis, by enhanced enzyme recovery and recycling and by improvements in process throughput and intensification. Additional economical advantage may be achieved by using crude preparations of enzymes instead of the expensive highly purified enzyme [1]. Despite these apparent advantages, industrial processes based on immobilised enzymes represent a small fraction of the current enzyme-based industry. The poor characterization of systems based on immobilized enzymes has contributed so far to limit a more widespread recourse to such systems in the process industry.
The present paper reports on the assessment of an enzyme-based process for the bioconversion of polyaromatic hydrocarbons (synthetic dyes, polyphenols, ….). The process is based on the use of a crude mixture of laccases recovered from Pleurotus ostreatus cultures [2]. The enzymes were covalently immobilized on granular supports and the resulting biocatalysts used in the conversion process of Remazol Brilliant Blue R, an anthraquinonic dye. Acrylic activated granular resin (EUPERGIT©) [3] and perlite powders (SIPERNAT 22®) [4], modified with 3-aminopropyltriethoxysilane and treated with glutaraldehyde, were investigated as enzyme supports. The program subtasks were: i) the optimization of the immobilization protocol of the biocatalysts; ii) the selection of appropriate bioreactor configurations for the conversion of dye by means of immobilized laccases; iii) the kinetic characterization of both the dye conversion and biocatalyst deactivation under controlled operating conditions. Two fixed bed reactors were purposely designed, set-up and operated to assay the activity of the supported biocatalyst and to characterize the dye conversion kinetics. Time-resolved concentration data of substrates and/or products allowed to characterize the immobilized crude-laccases: activity, dye conversion rate and deactivation rate.
The kinetic data have been worked out in order to compare the performance of a Continuous Fixed Bed Reactor (CFBR), operated with granular-immobilized laccases, with that of a Stirred Tank Reactor (STR), operated with free laccases. The analysis was carried out taking into account the immobilization efficiency, the dye conversion kinetics and the laccases deactivation kinetics. It resulted that the CFBR is able to manage a larger amount of dye for a set initial amount of laccases. Moreover, the volume of the CFBR is about a order of magnitude smaller than that of the STR.
[1] Cowan D.A, and M.T. Tombs “BIOTECHNOLOGY. The Science and the Business”, V. Moses and R.E. Cape (Eds.) – Harwood acad. publish. – Chap.18 (1999)
[2] Palmieri et al., Enzyme and Microbial Technology 2005; 36: 17-24
[3] Katchalski-Katzir et al., J. of Molecular Catalysis B: Enzymatic 2000; 10: 157-176
[4] Park et al., Reactive and Functional Polymers 2002; 51 (2-3): 79-92
Presented Wednesday 19, 15:40 to 16:00, in session Sustainable & Clean Technologies - Ib: Extraction-Remediation (T1-4b).
