Ceramic Carrier Research Articles

Simple carrier matrix modifications can enhance delivery of recombinant human bone morphogenetic protein-2 for posterolateral spine fusion.

A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate modifications to a plain collagen sponge to deliver recombinant human bone morphogenetic protein-2 (rhBMP-2). To evaluate the feasibility of enhancing the delivery of rhBMP-2 with the established collagen sponge carrier by adding biphasic ceramic phosphate (BCP) granules (15% hydroxyapatite, 85% tricalcium phosphate) or allograft chips to provide compression resistance for posterolateral spine arthrodesis. Recombinant human bone morphogenetic protein-2 was successfully delivered with a resorbable collagen sponge in a rabbit intertransverse process fusion model. Success in nonhuman primates required a higher dose (6-9 mg) of rhBMP-2 and a more compression-resistant matrix (ceramic) than plain collagen. The limitation of the ceramic carrier was its radiopacity, which made radiographic detection of new bone formation difficult. Nine adult rhesus monkeys underwent bilateral posterolateral intertransverse process arthrodesis at L4-L5. The animals were divided into three groups (n = 3 each) based on the graft material implanted: 1) autogenous iliac crest bone (5 cm3/side); 2) collagen sponge and 15:85 BCP granules loaded with rhBMP-2 (3 mg/side); and, 3) collagen sponge and allograft chips loaded with rhBMP-2 (3 mg/side). The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, computed tomographic scans, and histology were used to assess fusion. All six monkeys with rhBMP-2 delivered in the collagen/15:85 BCP carrier and the collagen/allograft chips carrier achieved solid spine fusions, whereas only one of three animals fused with autogenous bone graft. Histologic analysis of the bone induced by rhBMP-2 showed normal trabecular bone and bone marrow elements. The addition of either 15:85 BCP granules or allograft bone chips to the existing resorbable collagen sponge matrix enhanced delivery of rhBMP-2 in the posterolateral spine. The combination matrices were more compression resistant and had improved radiographic resorption properties that permitted easy radiographic visualization of new bone. In addition, a lower dose of rhBMP-2 (3 mg/side) was successful compared with the dose previously used with the plain collagen sponge (6 mg/side).

Wastewater treatment with bacteria immobilized onto a ceramic carrier in an aerated system

Biological treatment of the wastewater discharged from a food processing factory was continuously carried out in a packed bed bioreactor under aerobic conditions. The bacterium isolated from the wastewater was immobilized onto a new type of ceramic carrier by a vacuum method and high numbers of bacteria were colonized onto the carrier (2.9 × 10 9 cfu/g of dry ceramic carrier). The effect of the hydraulic retention time (HRT) and aeration rate on the removal of the chemical oxygen demand (COD) was investigated. The system was able on average to remove more than 82% of the influent COD during 160 d of operation and more than 87% of the influent COD on average was removed when the HRT was 30.17 h and the aeration rate was 2.0 vvm. Aeration rates in the range of 0.4 to 2.0 vvm do not affect the COD removal efficiency.

Improvement of Nitrogen Removal Efficiency of an Anaerobic Filter-Aerobic Biological Filtration Process by Using Nitrifying Bacteria Immobilized Pellets

In order to improve nitrogen removal efficiency, an anaerobic filter-aerobic biological filtration process was modified by filling. with nitrifying bacteria immobilized carrier made of polyethylene-alcohol (immobilized pellets) as a media for biological filtration tank. The effect of water temperature on T-N removal efficiency was investigated.When aeration was performed so that the immobilized pellets were fluidized above the ceramic carrier filled in the biological filtration tank, T-N was successfully removed. T-N removal efficiency was increased by increasing the filled ratio of immobilized pellets by replacing a portion of the ceramic carrier at the water temperature of 10°C. Conversely, the removal efficiency was lower when the filled ratio of immobilized pellets was 60%, due to the increase of suspended solids in the effluent. Therefore, a proper filled ratio of immobilized pellets was thought to be about 50%.The nitrification rate at the water temperature of 5°C was 17 mg·l-1·h-1 for the immobilized pellets and 3.9 mg·l-1·h-1 for the ceramic carrier, thus the nitrification rate of the former was 4.4 times that of the latter. Removal rates of the inflow carbon and nitrogen were 72% as carbon dioxide and 65% as nitrogen gas, respectively.

Wastewater Treatment with Bacteria Immobilized onto a Ceramic Carrier in an Aerated System.

Wastewater Treatment with Bacteria Immobilized onto a Ceramic Carrier in an Aerated System.

Reliability of Flip Chip Applications with Ceramic and Organic Chip Carriers

Reliability of Flip Chip Applications with Ceramic and Organic Chip Carriers

A low-power 8-PAM serial transceiver in 0.5-μm digital CMOS

An 8-PAM CMOS transceiver is described in this paper. Pre-emphasis is implemented without an increase in DAC resolution or digital computation. The receiver oversamples with three fully differential 3-bit ADCs. The prototype transmits at up to 1.3 Gb/s and has a measured bit error rate of less than 1 in 10/sup 13/ for an 810-Mb/s pseudorandom bit sequence transmission. The device, packaged in a 68-pin ceramic leadless chip carrier, is implemented in 0.5-/spl mu/m digital CMOS, occupies 2 mm/sup 2/, and dissipates 400 mW from a 3.3-V supply.

Delivery of recombinant human bone morphogenetic protein-2 using a compression-resistant matrix in posterolateral spine fusion in the rabbit and in the non-human primate.

A rabbit and rhesus monkey model of posterolateral intertransverse process spine arthrodesis was used. To test two new soft tissue compression resistant ceramic/collagen sponge carriers for recombinant human bone morphogenetic protein-2. After determining that a plain collagen sponge was too compressible for large animals in a posterolateral fusion application, the authors demonstrated good bone induction using biphasic ceramic phosphate granules (60% hydroxyapatite/40% tricalcium phosphate) as the carrier matrix for recombinant human bone morphogenetic protein 2 in rhesus monkeys. A limitation of 60:40 biphasic ceramic phosphate was its slow resorption time caused by the high hydroxyapatite content, making radiographic detection of new bone formation very difficult. Adult New Zealand white rabbits (n = 14) underwent posterolateral spine arthrodesis at L5-L6 using 5:95 biphasic ceramic phosphate (5% hydroxyapatite/95% tricalcium phosphate) impregnated Type I collagen sponges (17 x 35 x 2.5 mm, two per side) loaded with 0.86 mg recombinant human bone morphogenetic protein 2. Additional rabbits (n = 14) received 60:40 hydroxyapatite-tricalcium phosphate granules as the carrier for bone morphogenetic protein 2. Adult rhesus monkeys (n = 6) underwent posterolateral arthrodesis at L4-L5 with ceramic/collagen sponge carrier loaded with 9 mg recombinant human bone morphogenetic protein 2 per side. Two monkeys received ceramic/collagen sponges containing 15:85 biphasic ceramic phosphate (15% hydroxyapatite/85% tricalcium phosphate) with two pieces per side; two received sponges containing 5:95 biphasic ceramic phosphate with two pieces per side, and two received sponges containing 5:95 biphasic ceramic phosphate with four pieces per side. The rabbits were killed after 5 weeks and the monkeys after 24 weeks; the spines were evaluated by manual palpation, radiographs, tensile mechanical testing (rabbits only), and histology. The recombinant human bone morphogenetic protein 2 delivered in the 5:95 biphasic ceramic phosphate/collagen sponge achieved fusion in 100% of rabbits and had improved handling properties compared with the biphasic ceramic phosphate granules. Biomechanical results with 5:95 biphasic ceramic phosphate/collagen carrier were comparable to those obtained with the 60:40 biphasic ceramic phosphate granules and superior to those of autogenous bone graft (P < 0.05). The recombinant human bone morphogenetic protein 2 delivered in the 15:85 or the 5:95 biphasic ceramic phosphate/collagen sponge carrier (two pieces per side) induced fusion in nonhuman primates with normal bone histology, less residual ceramic, and more bone in the center of the carrier matrix in comparison with BCO granules alone. The 15:85 biphasic ceramic phosphate/collagen sponge resulted in fusion mass sizes closer to the original size of the matrix implanted than did the 5:95 biphasic ceramic phosphate/collagen sponge, which was considered a desirable feature. The monkeys with 9 mg recombinant human bone morphogenetic protein 2 spread over four sponges per side instead of two had half the effective recombinant human bone morphogenetic protein 2 concentration per sponge and inferior results. The new compression-resistant biphasic ceramic phosphate/collagen sponge matrices were biologically compatible with recombinant human bone morphogenetic protein 2 bone formation, resulted in biomechanically stiffer fusion masses than autograft, better space maintenance than plain collagen sponges, and improved handling and radiographic resorption properties over the ceramic carriers previously tested.

Dosimetric characterization of a newly designed encapsulated interstitial brachytherapy source of iodine-125—model LS-1 BrachyseedTM

A newly designed encapsulated 125I source has been introduced (Model LS-1 BrachySeed TM manufactured by DRAXIMAGE Inc.) for interstitial brachytherapy . In this source 125I radionuclide is contained in two ceramic beads positioned at each end of a titanium capsule. The source contains a rod of Pt–Ir, which serves as a radiographic marker for source localization in the patient. Principle photon emissions are 27.4 and 31.0 keV X-rays and a 35.5 keV gamma-ray. The 22.2 and 25.5 keV silver X-rays produced by fluorescence of the silver dopant in the ceramic bead radioisotope carriers, are also emitted. In this work, the dosimetric characteristics of the 125I source were measured with micro LiF TLD chips and dosimetry parameters were characterized based upon the American Association of Physicists in Medicine, Task Group, No. 43 formalism. The corrected 1999 National Institute of Standards and Technology standard for low energy interstitial brachytherapy sources was used to specify the air kerma strength of the sources used in this study. The dose rate constant of the sources was determined to be 1.02±0.07 cGyh −1 U −1. The radial dose function was measured and was found to be similar to that of the silver-based model 6711 125I source. However, the anisotropy function of the Model LS-1 BrachySeed TM source is considerably better than that of model 6711 125I source, especially on the points along and close to the longitudinal axis of the source. The BrachySeed TM model LS-1 provides more isotropic angular dose distribution in tissue than model 6711 125I source. The anisotropy constant for the model LS-1 source was determined to be 1.006, which is considerably better than the value of 0.93 for the model 6711 source.

Technical Features of Ceramic Foam Catalyst Carriers in Relation to their Manufacture

Technical Features of Ceramic Foam Catalyst Carriers in Relation to their Manufacture

Hydroxyapatite implants with designed internal architecture.

Porous hydroxyapatite (HA) has been used as a bone graft material in the clinics for decades. Traditionally, the pores in these HAs are either obtained from the coralline exoskeletal patterns or from the embedded organic particles in the starting HA powder. Both processes offer very limited control on the pore structure. A new method for manufacturing porous HA with designed pore channels has been developed. This method is essentially a lost-mold technique with negative molds made with Stereolithography and a highly loaded curable HA suspension as the ceramic carrier. Implants with designed channels and connection patterns were first generated from a Computer-Aided-Design (CAD) software and Computer Tomography (CT) data. The negative images of the designs were used to build the molds on a stereolithography apparatus with epoxy resins. A 40 vol% HA suspension in propoxylated neopentyl glycol diacrylate (PNPGDA) and iso-bornyl acrylate (IBA) was formulated. HA suspension was cast into the epoxy molds and cured into solid at 85 degrees C. The molds and acrylate binders were removed by pyrolysis, followed by HA green body sintering. With this method, implants with six different channel designs were built successfully and the designed channels were reproduced in the sintered HA implants. The channels created in the sintered HA implants were between 366 microm and 968 microm in diameter with standard deviations of 50 microm or less. The porosity created by the channels were between 26% and 52%. The results show that HA implants with designed connection pattern and well controlled channel size can be built with the technique developed in this study.

In situ synthesis of binderless ZSM-5 zeolitic coatings on ceramic foam supports

In situ synthesis of binderless ZSM-5 zeolite coatings on ceramic foam supports was studied. The effects were investigated of the rotation of the autoclaves during synthesis, the reaction mixtures SiO 2/Al 2O 3 and dilution ratios, the reaction mixture-to-support surface area ratio, the synthesis temperature and time as well as the composition of the support material (α-Al 2O 3, SiC/Al 2O 3 and ZrO 2/Y 2O 3 foam). X-ray diffraction patterns showed highly crystalline ZSM-5 structures superposed on the ceramic foam carrier pattern. The deposition of ZSM-5 was quantified by measuring mass increase and BET surface of the samples. Uniform and continuous ZSM-5 coatings with overall specific surface areas of up to 200 m 2/g were obtained. SEM micrographs showed coffin-like, partly intergrown crystals of 5–10 μm that appeared to be attached firmly to the support.

Free-space parallel multichip interconnection system

A parallel data-communication scheme is described for interchip communication with free-space optics. We present a proof-of-concept and feasibility demonstration of a practical modular packaging approach in which free-space optical interconnect modules can be simply integrated on top of an electronic multichip module (MCM). Our packaging architecture is based on a modified folded 4-f imaging system that is implemented with off-the-shelf optics, conventional electronic packaging techniques, and passive assembly techniques to yield a potentially low-cost packaging solution. The prototype system, as built, supports 48 independent free-space channels with eight separate laser and detector chips, in which each chip consists of a one-dimensional array of 12 devices. All chips are assembled on a single ceramic carrier together with three silicon complementary metal-oxide semiconductor chips. Parallel optoelectronic (OE) free-space interconnections are demonstrated at a speed of 200 MHz. The system is compact at only 10 in.(3) (~164 cm(3)) and is scalable because it can easily accommodate additional chips as well as two-dimensional OE device arrays for increased interconnection density.

Substrate integrated packaging for RF‐applications

In this paper, Substrate Integrated Packaging (SIP) based on thin film multilayer technology is presented. Coplanar waveguide feedthroughs calculated with 3D‐Finite Differential Methods were manufactured using a ceramic or silicon carrier, gold conductors and polyimide as dielectric. The substrate integrated packages were realized with metallic frames and lids mounted on the thin film circuitry. S‐parameter measurements show the superior quality of the feedthroughs. To verify the new packaging concept, a 10GHz and a 58GHz amplifier module were realized. From these modules the potential of the SIP‐technology is demonstrated.

Posterolateral Lumbar Intertransverse Process Spine Arthrodesis With Recombinant Human Bone Morphogenetic Protein 2/Hydroxyapatite-Tricalcium Phosphate After Laminectomy in the Nonhuman Primate

Study Design. A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA- TCP) carrier as a complete bone graft substitute. Objectives. To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. Summary of Background Data. The reported nonunion rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombi nant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for postero lateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. Methods. Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 × 0.5 × 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. Results. Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. Conclusion. Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Cementum-forming cells are phenotypically distinct from bone-forming cells.

Normal human cementum-derived cells (HCDCs), expanded in vitro, formed mineralized matrix when attached to a ceramic carrier and transplanted subcutaneously into immunodeficient mice. The mineralized matrix elaborated by transplanted HCDC exhibited several features identical to cementum in situ and was significantly different from bone deposited by similarly transplanted human bone marrow stromal cells (BMSCs). No bone marrow formation and very few or no tartrate-resistant acid phosphatase (TRAP)-positive cells (osteoclasts and osteoclastic precursors) were found in HCDC transplants. In contrast, in BMSC transplants both hematopoiesis and TRAP-positive cells were routinely observed. Furthermore, compared with BMSC-derived matrix, HCDC-derived matrix was less cellular, numerous empty lacunae were present, and fewer cells were found on the cementum matrix/ceramic carrier interface. The organization of collagen fibers in HCDC-derived matrix, as visualized by using the Picrosirus red staining method, was similar to cementum, with typical unorganized bundles of collagen fibers. In contrast, bone matrix elaborated by transplanted BMSC had lamellar structure, identical to mature bone in situ. Finally, cementocytes embedded in the cementum-like matrix were immunopositive for fibromodulin and lumican, whereas osteocytes within the bonelike matrix were negative. This pattern is consistent with the cementum and bone in situ, respectively. These results indicate that human cementum cells are phenotypically distinct from bone cells and provide further validation of the combined in vitro/in vivo model of human cementogenesis recently developed in our laboratory.

Autologous bone marrow stromal cells loaded onto porous hydroxyapatite ceramic accelerate bone repair in critical-size defects of sheep long bones.

The ability of marrow-derived osteoprogenitor cells to promote repair of critical-size tibial gaps upon autologous transplantation on a hydroxyapatite ceramic (HAC) carrier was tested in a sheep model. Conditions for in vitro expansion of sheep bone marrow stromal cells (BMSC) were established and the osteogenic potential of the expanded cells was validated. Ectopic implantation of sheep BMSC in immunocompromised mice led to extensive bone formation. When used to repair tibial gaps in sheep, cell-loaded implants (n = 2) conducted a far more extensive bone formation than did cell-free HAC cylinders (n = 2) over a 2-month period. In cell-loaded implants, bone formation was found to occur both within the internal macropore space and around the HAC cylinder while in control cell-free implants, bone formation was limited mostly to the outer surface and was not observed in most of the inner pores. As tested in an indentation assay, the stiffness of the complex HAC-bone material was found to be higher in cell-loaded implants compared to controls. Our pilot study on a limited number of large-sized animals suggests that the use of autologous BMSC in conjunction with HAC-based carriers results in faster bone repair compared to HAC alone. Potentially this combination could be used clinically in the treatment of extensive long bone defects.

Application of Inorganic Porous Materials to Biofilm Carriers

ABSTRACT In order to investigate the applicability of inorganic porous material, the anaerobic/aerobic processes(A2O process) for wastewater treatment were carried out with 4 types of biofilm carriers. The average removal ratio of COD were 88.3%, 86.6%, 84.9% and 84.4% for the inorganic porous material(Type A), the activated carbon(Type B), the light ceramic carrier(Type C) and the fibrous polymer carrier(Type D) respectively. After two weeks, they were 96.5%, 74.4%, 95.5% and 92.9% in the same order. For the nitrogen removal, type B showed that the removal ratio became worse with increasing treatment time. However, the removal ratios of the others showed a similar trend at the initial period, but type A showed the highest removal ratio. From this study, type A developed in our laboratory could be applied for practical wastewater treatment using biofilm carriers.

Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatite-tricalcium phosphate after laminectomy in the nonhuman primate.

A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA-TCP) carrier as a complete bone graft substitute. To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. The reported non-union rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombinant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for posterolateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 x 0.5 x 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Integrated Thermal Analysis of Natural Convection Air Cooled Electronic Enclosure

In the present paper, a methodology is described for the integrated thermal analysis of a laminar natural convection air cooled nonventilated electronic system. This approach is illustrated by modeling an enclosure with electronic components of different sizes mounted on a printed wiring board. First, a global model for the entire enclosure was developed using a finite volume computational fluid dynamics/heat transfer (CFD/CHT) approach on a coarse grid. Thermal information from the global model, in the form of board and component surface temperatures, local heat transfer coefficients and reference temperatures, and heat fluxes, was extracted. These quantities were interpolated on a finer grid using bilinear interpolation and further employed in board and component level thermal analyses as various boundary condition combinations. Thus, thermal analyses at all levels were connected. The component investigated is a leadless ceramic chip carrier (LCCC). The integrated analysis approach was validated by comparing the results for a LCCC package with those obtained from detailed system level thermal analysis for the same package. Two preferred boundary condition combinations are suggested for component level thermal analysis.

Effect of matrix on ( S)- p-chlorodiphenylmethanol production by immobilized Debaryomyces marama

The product ( S)- p-chlorodiphenylmethanol is obtained through stereoselective reduction of p-chlorobenzophenone using Debaryomyces marama cells, immobilized on Raschig rings. This process involved continuous fermentations in bioreactors for a period of 10 days. The conversion was 86% with a volumetric productivity of 0.248 litre −1 d −1. Comparative experiments with D. marama cells, incorporated in alginate, k-carrageenan or agar–agar gels were also performed. These results demonstrated superiority of the immobilization on ceramic carriers compared to other methods. Passive immobilization of D. marama cells on ceramic carriers has many advantages in comparison with gel-incorporation of the cells. For example, during a long bioreactor run, only a limited amount of cells could remain incorporated within the gel. Therefore immobilized cell preparations will be a convenient methodology in the production of optically active compounds such as pharmaceutical drugs.