Cyclodextrin production by Bacillus firmus strain 37 immobilized on inorganic matrices and alginate gel

Immobilized Cells of Bacillus circulans ATCC 21783 on Palm Curtain for Fermentation in 5 L Fermentation Tanks

Palm curtain was selected as carrier to immobilize Bacillus circulans ATCC 21783 to produce β-cyclodextrin (β-CD). The influence for immobilization to CGTase activity was analyzed to determine the operation stability. 83.5% cyclodextrin glycosyltransferases (CGTase) of the 1st cycle could be produced in the 7th cycle for immobilized cells, while only 28.90% CGTase was produced with free cells. When palm curtain immobilized cells were reused at the 2th cycle, enzyme activities were increased from 5003 to 5132 U/mL, which was mainly due to physical adsorption of cells on palm curtain with special concave surface structure. Furthermore, conditions for expanded culture of immobilized cells in a 5 L fermentation tank were optimized through specific rotation speed procedure (from 350 r/min to 450 r/min with step size of 50 r/min) and fixed ventilation capacity (4.5 L/min), relations between biomass, enzyme activity, pH, and oxygen dissolution was investigated, and the fermentation periods under the two conditions were both 4 h shorter. Compared with free cell, immobilized cell was more stable, effective, and had better application potential in industries.

Immobilization of Glycoside Hydrolase Families GH1, GH13, and GH70: State of the Art and Perspectives

Glycoside hydrolases (GH) are enzymes capable to hydrolyze the glycosidic bond between two carbohydrates or even between a carbohydrate and a non-carbohydrate moiety. Because of the increasing interest for industrial applications of these enzymes, the immobilization of GH has become an important development in order to improve its activity, stability, as well as the possibility of its reuse in batch reactions and in continuous processes. In this review, we focus on the broad aspects of immobilization of enzymes from the specific GH families. A brief introduction on methods of enzyme immobilization is presented, discussing some advantages and drawbacks of this technology. We then review the state of the art of enzyme immobilization of families GH1, GH13, and GH70, with special attention on the enzymes β-glucosidase, α-amylase, cyclodextrin glycosyltransferase, and dextransucrase. In each case, the immobilization protocols are evaluated considering their positive and negative aspects. Finally, the perspectives on new immobilization methods are briefly presented.

Effective Immobilization of Agrobacterium sp. IFO 13140 Cells in Loofa Sponge for Curdlan Biosynthesis

Curdlan production by Agrobacterium sp. IFO13140 immobilized on loofa sponge, alginate and loofa sponge with alginate was investigated. There was no statistically-significant difference in curdlan production when the microorganism was immobilized in different matrices. The loofa sponge was chosen because of its practical application and economy and because it provides a high stability through its continued use. The best conditions for immobilization on loofa sponge were 50 mg of cell, 200 rpm and 72 h of incubation, which provided a curdlan production 1.50-times higher than that obtained by free cells. The higher volumetric productivity was achieved by immobilized cells (0.09 g/L/h) at 150 rpm. The operating stability was evaluated, and until the fourth cycle, immobilized cells retained 87.40% of the production of the first cycle. The immobilized cells remained active after 300 days of storage at 4 °C. The results of this study demonstrate success in immobilizing cells for curdlan biosynthesis, making the process potentially suitable for industrial scale-up. Additional studies may show a possible contribution to the reduction of operating costs.

Cyclodextrin glycosyltransferase production by free cells of Bacillus circulans DF 9R in batch fermentation and by immobilized cells in a semi-continuous process

Cyclodextrin glycosyltransferase (CGTase) catalyzes starch conversion into cyclic or linear oligosaccharides, important industrial products for the complexation of non-polar substances. In this work, conditions to increase CGTase production from Bacillus circulans strain DF 9R were optimized by two systems. On one hand, free cells were grown in batch fermentation experiments to optimize aeration and pH. The highest activity (1.47 ± 0.21 U ml(-1)) was achieved after 48 h of growth, aeration of 1.5 vvm and pH regulated to 7.6. On the other hand, bacterial cells were immobilized on loofa and synthetic sponge, and used for CGTase production in a semi-continuous process. An initial biomass of 30 mg of lyophilized cells and an immobilization time of 24 h with loofa or synthetic sponge were enough to achieve increased production of CGTase: 0.91 ± 0.10 and 0.95 ± 0.11 U ml(-1), respectively. Sponges with immobilized bacteria were reused in 12 successive cycles. Besides, in our conditions, CGTase was not adsorbed onto the supports used for immobilization, which ensured the total recovery of the enzyme from the culture medium. The two CGTase production processes studied showed similar productivity and could be potentially scaled up.

Improved production of cyclodextrins by alkalophilic bacilli immobilized on synthetic or loofa sponges

This study aimed to improve the production of β-cyclodextrin (β-CD) by microbial cells immobilized on synthetic or loofa sponges both with and without the use of alginate or chitosan. The most suitable matrix for the immobilization of Bacillus firmus strain 7B was synthetic sponge and for Bacillus sphaericus strain 41 was loofa sponge. After 330 days of storage, the β-CD production by Bacillus firmus and Bacillus sphaericus remained at around 41% and 49%, respectively, of initial levels. After 24 days of immobilization on loofa sponge, Bacillus sphaericus strain 41 achieved an improved operational stability, reaching 86.6 mM β-CD after 20 days of production, compared to only 32.8 mM of β-CD produced by free Bacillus sphaericus strain 41 cells. The expected increase in β-CD production by immobilized cells of Bacillus firmus strain 7B on synthetic sponge for 4 days was not statistically different to that for cells immobilized for 24 days. The application of this process on an industrial scale using loofa sponge, an inexpensive and renewable matrix, will allow the stable production of β-CD.

Preservation of Bacillus firmus strain 37 and optimization of cyclodextrin biosynthesis by cells immobilized on loofa sponge

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.

Biosynthesis of indole-3-acetic acid by new Klebsiella oxytoca free and immobilized cells on inorganic matrices

While many natural and synthetic compounds exhibit auxin-like activity in bioassays, indole-3-acetic acid (IAA) is recognized as the key auxin in most plants. IAA has been implicated in almost all aspects of plant growth and development and a large array of bacteria have been reported to enhance plant growth. Cells of Klebsiella oxytoca isolated from the rhizosphere of Aspidosperma polyneuron and immobilized by adsorption on different inorganic matrices were used for IAA production. The matrices were prepared by the sol-gel method and the silica-titanium was the most suitable matrix for effective immobilization. In operational stability assays, IAA production was maintained after four cycles of production, obtaining 42.80 ± 2.03 μg mL⁻¹ of IAA in the third cycle, which corresponds to a 54% increase in production in relation to the first cycle, whereas free cells began losing activity after the first cycle. After 90 days of storage at 4°C the immobilized cells showed the slight reduction of IAA production without significant loss of activity.