Abstract
The preservation of Bacillus firmus strain 37 cells by lyophilization was evaluated and response surface methodology (RSM) was used to optimize the β-cyclodextrin (β-CD) production by cells immobilized on loofa sponge. Interactions were studied with the variables temperature, pH and dextrin concentration using a central composite design (CCD). Immobilization time influence on β-CD production was also investigated. B. firmus strain 37 cells remained viable after one year of storage, showing that the lyophilization is a suitable method for preservation of the microorganism. From the three-dimensional diagrams and contour plots, the best conditions for β-CD production were determined: temperature 60 °C, pH 8, and 18% dextrin. Considering that the amount of dextrin was high, a new assay was carried out, in which dextrin concentrations of 10, 15, and 18% were tested and the temperature of 60 °C and pH 8 were maintained. The results achieved showed very small differences and therefore, for economic reasons, the use of 10% dextrin is suggested. Increasing the immobilization time of cells immobilized on synthetic sponge the β-CD production decreased and did not change for cells immobilized on loofa sponge. The results of this research are important for microorganism preservation and essential in the optimization of the biosynthesis of CD.
Highlights
Microbiological tests are carried out in many industries such as the pharmaceutical, food and clinical ones
Influence of Immobilization Time on β-Cyclodextrin Production β-CD production by cells immobilized on loofa sponge and synthetic sponge was evaluated at different immobilization times
Lyophilization showed to be a suitable method for the microorganism preservation, especially for
Summary
Microbiological tests are carried out in many industries such as the pharmaceutical, food and clinical ones. These microorganisms need to be preserved for application of defined quantities and to obtain the desired product. In all cases the cost of preservation, maintenance and the length of time cultures remain viable determine the chosen preservation technique [1,2,3]. The purpose of this preservation is to keep the cultures without morphological, physiological or genetic changes, as well as maintaining their viability and stability [4]. The current industry standard for preserving microorganisms is freeze drying or lyophilization, and the anhydrous product obtained can be stored, tightly sealed under vacuum or under a protective atmosphere for long periods of time with good activity against rehydration [5]
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