Combined effects of agitation and aeration on the chitinolytic enzymes production by the Antarctic fungus Lecanicillium muscarium CCFEE 5003

Massimiliano Fenice,Paolo Barghini,Laura Selbmann,Federico Federici

doi:10.1186/1475-2859-11-12

Abstract

BackgroundThe Antarctic fungus Lecanicillium muscarium CCFEE 5003 is one of the most powerful chitinolytic organisms. It can produce high level of chitinolytic enzymes in a wide range of temperatures (5-30°C). Chitinolytic enzymes have lot of applications but their industrial production is still rather limited and no cold-active enzymes are produced. In view of massive production of L. muscarium chitinolytic enzymes, its cultivation in bioreactors is mandatory. Microbial cultivation and/or their metabolite production in bioreactors are sometime not possible and must be verified and optimized for possible exploitation. Agitation and aeration are the most important parameters in order to allow process up-scaling to the industrial level.ResultsIn this study, submerged cultures of L. muscarium CCFEE 5003 were carried out in a 2-L bench-top CSTR bioreactor in order to optimise the production of chitinolytic enzymes. The effect of stirrer speed (range 200-500 rpm) and aeration rate (range 0.5-1.5 vvm) combination was studied, by Response Surface Methodology (RSM), in a medium containing 1.0% yeast nitrogen base and 1% colloidal chitin. Optimization was carried out, within a "quadratic D-optimal" model, using quantitative and quantitative-multilevel factors for aeration and agitation, respectively. The model showed very good correlation parameters (R2, 0.931; Q2, 0.869) and the maximum of activity (373.0 U/L) was predicted at ca. 327 rpm and 1.1 vvm. However, the experimental data showed that highest activity (383.7 ± 7.8 U/L) was recorded at 1 vvm and 300 rpm. Evident shear effect caused by stirrer speed and, partially, by high aeration rates were observed. Under optimized conditions in bioreactor the fungus was able to produce a higher number of chitinolytic enzymes than those released in shaken flasks. In addition, production was 23% higher.ConclusionsThis work demonstrated the attitude of L. muscarium CCFEE 5003 to grow in bench-top bioreactor; outlined the strong influence of aeration and agitation on its growth and enzyme production and identified the optimal conditions for possible production at the industrial level.

Highlights

The Antarctic fungus Lecanicillium muscarium Collection of Fungi from Extreme Environments (CCFEE) 5003 is one of the most powerful chitinolytic organisms
In this paper we studied by Response Surface Methodology (RSM) the combined effects of agitation and aeration on the production of chitinolytic enzymes by L. muscarium CCFEE 5003, cultivated in a 2-l bench-top CSTR bioreactor, in view of possible scale-up to the industrial level
As far as we know, this is the first paper dealing with the optimization of agitation and aeration in CSTR for the production of fungal chitinases by RSM

Summary

Introduction

The Antarctic fungus Lecanicillium muscarium CCFEE 5003 is one of the most powerful chitinolytic organisms It can produce high level of chitinolytic enzymes in a wide range of temperatures (5-30°C). Chitinolytic enzymes (generally called chitinases) have been widely studied and some produced by fungi are of great interest for possible applications These hydrolases could be employed in chitin hydrolysis, production of chitin derivatives, protoplast formation and bio-control of pathogenic organisms [1,2,3,4]. The cost of these enzymes is still too high and large scale applications are still expensive and scarcely profitable Already from their early works, Aloise et al [7] proposed an industrial process to obtain N-acetyl-D-glucosamine (NAG) using S. marcescens chitinolytic enzyme.

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