Effect of Molecular Weight of Chitosan on Microbial Growth and γ-cyclodextrin Production from Bacillus cereus GU-02

Abstract

Effects of chitosan with different molecular weight on gamma-cyclodextrin (γ-CD) production and bacterial cell growth of Bacillus cereus GU-2 was elucidated. Optimum pH and temperature for bacterial growth and γ-CD production were estimated to be pH 8~10 and 37oC, respectively. Interestingly, among bioactive substances chitosan showed molecular weight dependentinhibitory effect (over 80%) on growth of B. cereus GU-2. Among, MMWC-2 (3,500 Da) revealed the highest (92%) inhibitory effect on bacterial cell growth, considerable as a limiting factor. Consequently, no significant inhibitory effect of both high molecular weight chitosan (HMWC, 200 kDa) and MMWCs on the production of γ-CD was observed. These results made us to hypothesize that γ-CD synthesized by B. cereus GU-2 may be a key modulator involved in bacterial cell viability.