Immobilization of yeast cells in acrylamide gel matrix

Microencapsulation of Baker’s Yeast in Gellan Gum Beads Used in Repeated Cycles of Glucose Fermentation

The purpose of this work is to prepare ionically cross-linked (with CaCl2) gellan particles with immobilized yeast cells for their use in repeated fermentation cycles of glucose. The study investigates the influence of ionic cross-linker concentration on the stability and physical properties of the particles obtained before extrusion and during time in the coagulation bath (the cross-linker solution with different CaCl2 concentrations). It was found that by increasing the amount of the cross-linker the degree of cross-linking in the spherical gellan matrix increases, having a direct influence on the particle morphology and swelling degree in water. These characteristics were found to be very important for diffusion of substrate, that is, the glucose, into the yeast immobilized cells and for the biocatalytic activity of the yeast immobilized cells in gellan particles. These results highlight the potential of these bioreactors to be used in repeated fermentation cycles (minimum 10) without reducing their biocatalytic activity and maintaining their productivity at similar parameters to those obtained in the free yeast fermentation. Encapsulation of Saccharomyces cerevisiae into the gellan gum beads plays a role in the effective application of immobilized yeast for the fermentation process.

Mitigation of bactericidal effect of carbon nanotubes by cell entrapment

This study investigated the effects of the alginate and polyvinyl alcohol (PVA) entrapment on the viability of Escherichia coli cells exposed to single wall carbon nanotubes (SWCNTs) with a diameter of 1-2nm. Viability was examined using a galactosidase enzyme assay, LIVE/DEAD BacLight assay, and total ribonucleic acid quantity. Variables studied included SWCNT concentration (5, 10, 20, 50, 100, 200, 500, and 1000μg/ml), SWCNT length (0.5-2μm for short SWCNTs and 5-30μm for long SWCNTs), and initial bacterial concentration (6.5 log10 CFU and 9 log10 CFU per test). Results showed that both alginate and PVA entrapments mitigate the bactericidal effect of SWCNTs. At the highest SWCNT concentration tested (1000μg/ml), the viability of the cells relative to controls (systems with only E. coli, no SWCNTs), was 0-60% for free cells and 60-90% for alginate and PVA entrapped cells. The bactericidal effect depended on SWCNT type and concentration, and bacterial concentration. In general, long SWCNTs (5-30μm) caused significantly greater reductions in the viability of entrapped cells than the short SWCNTs except for the two highest SWCNT concentrations studied, 500 and 1000μg/ml. Microscopy showed that the entrapment matrices prevented SWCNTs from entering the beads. This study shows that bacterial entrapment is effective at limiting the bactericidal effect of SWCNTs.

Biosynthesis of gibberellic acid from milk permeate in repeated batch operation by a mutant Fusarium moniliforme cells immobilized on loofa sponge

Gibberellic acid (GA) production from milk permeate was studied by 28 mutants of Fusarium moniliforme, among which mutant gamma-14 was selected as the best producer. Experiments were carried out in shaker flasks and fermentative process was analyzed with free and immobilized cells. Immobilization of mutant gamma-14 cells onto loofa sponge discs was studied with respect to the optimization of the incubation temperature, initial pH, inoculum size (number of discs) and its reusability for GA production. Best yield of GA (2.40 gl(-1)) was recorded by immobilized cells under optimized cultural conditions (4 immobilized discs, 30 degrees C and pH 5). Data obtained during four reusable cycles showed high stability of GA production and reduction in the initiation time of acid production, resulting in higher levels of GA in shorter time duration. Immobilization of mutant gamma-14 cells onto loofa sponge discs, permitted repeated reuse under the specified fermentation conditions for GA production from milk permeate.

Pantoprazole-Na Release from Poly(acrylamide-co-crotonic acid) and Poly(acrylic acid-co-crotonic acid) Hydrogels

Poly(acrylamide-co-crotonic acid) (PAAmCA), poly(acrylic acid-co-crotonic acid) (PAACA), PAA and PAAm hydrogels were prepared by free radical polymerization and ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The variations of swelling values (%) with time, temperature, and pH were determined for four types of hydrogels. The PAACA hydrogel was swollen 2300% at pH = 7.4 and 37°C. The drug release from pantoprazole-Na loaded PAACA and PAAmCA hydrogels was followed at pH = 7.4, 37°C for 30 h. The release from PAACA hydrogel was faster than that from PAAmCA hydrogel; therapeutic levels for both hydrogels are obtained within 1 hour. Non-Fickian diffusion was determined for both hydrogels.

Immobilization of yeast cells with ionic hydrogel carriers by adhesion-multiplication

The mixture of an ionic monomer, 2-acrylamido 2-methylpropanesulfonic acid (TBAS), and a series of poly(ethylene glycol) dimethacrylate (nG) monomers were copolymerized with 60Co gamma-rays, and the produced ionic hydrogel polymers were used for immobilization of yeast cells. The cells were adhered onto the surface of the hydrogel polymers and intruded into the interior of the polymers with growing. The immobilized yeast cells with these hydrogel polymers had higher ethanol productivity than that of free cells. The yield of ethanol with poly(TBAS-14G) carrier was the highest and increased by 3.5 times compared to the free cells. It was found that the ethanol yield increased with the increase of glycol number in poly(ethylene glycol) dimethacrylate. The state of the immobilized cells was observed with microscope, and it was also found that the difference in the ethanol productivity is mainly due to the difference in the internal structure and properties of polymer carrier, such as surface charge, hydrophilicity, and swelling ability of polymer carrier.

Diffusion and transfer of antibody proteins from a sugar-based hydrogel

Diffusion of antibody protein from hydrogel films and hydrogel encapsulated in a microcapillary was studied. Thin hydrogel films were formed by crosslinking 6-acryloyl-B-O-methylgalactoside with N,N'-methylene-bis-acrylamide and the diffusive transport of monoclonal antimouse IgG-FITC into and out of the hydrate films was measured. Diffusion coefficients in 2 and 4% crosslinked hydrogel films were measured. The measured diffusion constants determined for IgG in both the 2 and 4% hydrogel films were comparable to the free diffusion of IgG in bulk water (Dmean approximately 10(-7) cm2/s). In addition, 2% crosslinked hydrogels were prepared in a capillary tube and the transport of antimouse IgG-FITC into and out of the hydrated hydrogel was measured. Kinetic analysis indicated that the protein transport through the capillary hydrogel was faster than would be expected for a simple diffusion process. Finally, by utilizing the diffusion of antibody from the capillary hydrogel, transfer of antibody to a silica surface was demonstrated. A capillary hydrogel loaded with antimouse IgG-FITC was used to transfer the protein to a silica surface forming a 30-micron spot of antibody, which was imaged using fluorescence microscopy. These results may lead to the development of a nonlithographic method of patterning antibodies on surfaces for use in integrated microimmunosensors.

5-Fluorouracil release from copolymeric hydrogels of itaconic acid monoester. I. Acrylamide-co-monomethyl itaconate

The aim of this work was to test the application of new copolymeric poly (acrylamide-co-monomethyl itaconate) (A/MMI) hydrogels to 5-fluorouracil (5-FU) release. Three different compositions of copolymers have been studied, 90A:10MMI 75A:25MMI and 60A:40MMI. The equilibrium swelling degree in saline solution was between 76 and 80% depending on the copolymer composition. 5-FU, as the sodium salt, was trapped in the gels by including it in the feed mixture of polymerization. The swelling kinetics of the hydrogels in saline solution were studied at four temperatures, and the diffusion coefficient and the activation energy of the process were obtained. The 5-FU release as a function of temperature and disc load was studied; the diffusion coefficient and the activation energy of the release process were also obtained. The diffusion studies follow Fick's second law.

Biotechnological developments in Turkey

Turkey is a country not usually associated with industrial biotechnology. However, when current research potential in universities and other R & D centers and particularly contributions made to the international literature since the mid-1980s are taken into account, high-quality international-level work is now commonplace, especially in areas such as industrial microbiology, enzyme technology, biomaterials and biological wastewater treatment. Work in plant biotechnology is at a relatively early stage, but is expected to become a rapidly developing force in the near future. The present article documents current potential in Turkey, based on significant publications produced during the last 8 years.