Optimization of the Chitinase Production by Different &amp;lt;i&amp;gt;Metarhizium anisopliae&amp;lt;/i&amp;gt; Strains under Solid-State Fermentation with Silkworm Chrysalis as Substrate Using CCRD

Cynthia Barbosa Rustiguel,Luis Henrique Souza Guimarães,João Atílio Jorge

doi:10.4236/aim.2012.23032

Abstract

Entomopathogenic fungi, such as Metarhizium anisopliae, are able to control various insect pests. These fungi attack the integument of the host using an enzymatic complex. Among the enzymes found in this complex, chitinase is an important component. However, the relation between the chitinase production and the virulence from different M. anisopliae strains has not been analyzed. In this manuscript it is presented the chitinase production by four M. anisopliae strains with different potential of virulence in Solid-State Fermentation using silkworm chrysalis as substrate. The higher chitinase level was obtained with the strain IBCB 360 (7.14 U/g of substrate) with potential virulence of 68% on Diatrea saccharalis. The enzyme production was optimized for all strains using a factorial planning (CCRD) considering the cultivation time and medium humidity as independent variables. The maximal production of chitinase was obtained at a range from 8 to 12-days old cultures and from 45% to 62% of moisture according to the surface response plot, with high R2 value. The enzyme production by the strain IBCB 167 was increased two-folds under optimized conditions, while for the strains IBCB 360 and 425 the chitinase production was increased four-folds and nine-folds for the strain IBCB 384.

Highlights

The entomopathogenic fungi are pathogens with a broadspectrum of action which are able to attack insects that live in different ecological niches in different stages of development
The entomopathogenic fungus Metarhizium anisopliae is a deuteromycete from Monoliaceae family widely distributed in the nature that can be found in the soil
Higher levels of chitinase were obtained when the substrate silkworm chrysalis was moistened with yeast extract (1%) at the ratio 1.3:1 (m/V) for the strains IBCB 167, 360 and 425, differing than that observed for the strain IBCB 384 with best enzyme production when the substrate was moistened with Khanna salt solution

Summary

Introduction

The entomopathogenic fungi are pathogens with a broadspectrum of action which are able to attack insects that live in different ecological niches in different stages of development. Most of these species are specialized in penetrating the tegument [1]. The strain IBCB 167, for example, was able to kill around 55% of D. saccharalis while the strains IBCB 360, IBCB384 and IBCB 425 showed a mortality power of 68% - 90% These different values can be attributed to the enzymatic complex associated to the virulence, including chitinase

Methods

Results

Conclusion