Growth behaviour of microbial cells immobilised within hydrogel spheres

The effect of immobilization on cell growth in MRS medium and cell survival during exposure to acidic medium were studied in this project. The growth kinetic models of L.casei 01 were developed using initial rate method and Lineweaver-Burke plot. Growth kinetics of immobilized cell was found to follow a competitive model

A cost effective integrated process for production of probiotic cells as poultry antibiotic substitute

The overall aim of this project was to develop a cost-effective probiotic cell production system for poultry use by integrating encapsulation technology to existing process technologies. The research focused on three areas 1) to study the effect of process parameters on encapsulation process 2) to study the effect of capsule designs, materials and fermentation conditions on cell production in repetitive batch fermentation 3) to study the effect of process parameters on drying of encapsulated cells and their stability. A detailed study on the effect of process variables on size and shape of capsules for encapsulation applications has been conducted. The prediction models for shape and size of beads or capsules produced through the extrusion method were developed. They could be used for optimization and to evaluate process limitations. The effect of different encapsulation materials (i.e. alginate, pectin, chitosan) were used for cell production in repetitive batch fermentations. Coated pectin-core capsules were found to be more stable than the alginate and alginate/pectin core capsules. However, alginate was preferred as it is more economical. Subsequent studies focused on improving the stability of alginate capsules during repetitive batch fermentations. Encapsulation cell fermentation was found to improve productivity of cell production by 40% which could give significant economic advantage to manufacturer. The effect of drying method and condition on the cell survival and stability were investigated next. Incorporation of_ suitable additives was found to be critical in stabilizing the cells which may also give significant economic advantage manufacturers. In addition, packed-bed drying has been shown to be a potential drying method to replace freeze-drying as the method involves lower capital and operating cost

Production of precision K-Carrageenan Microcapsule by Co-Flowing Microfluidic system

The formation of hydrogel microcapsule using microfluidic device was investigated in this project. The primary objective of this work is to evaluate the potential of co-flowing microfluidic device in producing quality microcapsule. The first part of this work involved the construction of a co-flowing microfluidic device that can be used to produce hydrogel particle. The second part of the project focused finding the effect of process parameters on the droplet/microcapsule formation behavior and droplet/microcapsule properties. The third part aimed at developing a mathematical model to predict the droplet/microcapsule size from the affecting parameters. The final part investigated the scale-up potential of the studied system. In this research, three types of droplet formation modes were distinguished: dripping, narrowing jetting and widening jetting. The transition points between each type of breakup modes were found to be influenced by the interplay among inertial force, viscous force and interfacial force of the system. The transition points were then compared to a theoretical model. It was also found that the droplet size produced in liquid-liquid system affected by the combined influence of the liquids properties, flow dynamics combinations and geometry of the system setup. A two-stage model was developed and was found to be consistent with the experimental data and the average absolute deviation (AAD) lies within 5% of the calculated values. On the other hand, the breakup mechanism of liquid jets in liquid-liquid system was found to be consistent with the Rayleigh's instability theory and the drop size was well predicted from existing model. In the scale-up study, it was suggested that the droplet formation in the system should remain in the dripping mode. Using the two­stage model, a simulation was performed to scale-up the productivity of the liquid-liquid dispersion system. Optimum operating conditions was able to be determined through the simulation

Ca-alginate liquid core capsule for lactobacili fermentation

Lactic acid bacteria (LAB) have been used for food fermented products since ancient time, which not limited to dairy products. Some Asian traditional food is produced through LAB fermentation. LAB consist of the Gram-positive genera including lactobacillus, which produce lactic acid as the end product of a carbohydrate fermentation. Lactobacillus is one of the important LAB that have been widely applied in food fermentation because of their fermentative ability to enhance food safety, nutrition and to improve health related benefits (as probiotics bacteria). Lactobacillus also received much attention for lactic acid production. This is because lactic acid is highly demanded for the production of poly-l-lactate biodegradable plastics in recent days. The viability and microbial growth of Lactobacilli have been known to be inhibited by its end product (i.e. lactic acid). One of the common solutions to overcome the inhibition issue is by using encapsulation technology. Encapsulation offers several advantages for lactobacilli fermentation which included protection to the bacterial from harsh environments (e.g. pH, temperature, shear stress), retaining cells in continuous process, and allowing reuse of the bacteria. Encapsulation can be achieved in two forms; beads or capsules. Apart from beads, the capsules consisted of a defined inner core which surrounded by a semi permeable membrane. The content of the inner core could be in the form of liquid or solid. Liquid core capsules provide plenty of space for microbial growth (in inner core), eliminate cell release to fermentation medium and minimize mass transfer resistance of solutes. The main focus of this review was on the liquid core capsules produced by Ca-alginate bio-gel. In general, Ca-alginate liquid core capsules can be produced using single step methods or multiple steps methods. The details of the method used to produce the liquid core capsules were described and discussed. The use of the capsules for lactobacilli fermentation is limited because they are easily destabilized by chelating agents and eventually dissolved. The counter measures to strengthen the stability of the capsules were discussed. The previous studies showed that the viability, microbial growth and productivity of the encapsulated lactobacilli (in liquid core capsule) were better than those of either free cell and entrapped lactobacilli (in beads). Lastly, the authors give several recommendations to expand the potential of using the liquid core capsules to improve Lactobacilli fermentation

Core-shell versus inert polymer grafted adsorbents for the negative chromatography of virus-like particle

Core-shell and polymer grafted adsorbents are new generation media developed for the separation of virus-like particle (VLP) in a negative chromatography. The inert shell and grafted polymer chain are designed to exclude the big biomolecules such as VLP from adsorbing onto the ligands situated on the surface of the adsorbents. Meanwhile, these exclusion layers should be permeable for the smaller impurities which will be adsorbed by the ligands to prevent its presence in the flowthrough fractions. In this study, the performance of these negative chromatography media were compared in the purification of recombinant hepatitis B VLPs (HB-VLPs) from clarified E. coli feedstock. The core-shell adsorbents with different shell thickness (InertShell and InertLayer 1000) and poly[(ethylene glycol) methacrylate] grafted adsorbents (SQ) were studied in a packed bed mode. SQ adsorbed more impurities, thus achieving a higher purity in flowthrough while core-shell adsorbents recovered more HB-VLPs and recorded nearly 100% recovery in InertShell. This suggests the shielding effect of the core shell layer is higher than the inert polymer chain. For core-shell adsorbents, there was a trade-off between the purity and recovery of flow-through HB-VLPs due to the shell thickness. A thicker shell allows more HB-VLP exclusion but less impurities adsorption. Prolonging the residence time of the negative chromatography only resulted in a slight improvement in the impurities adsorption in all adsorbents, but the recovery of HB-VLPs in InertShell was reduced substantially. Atomic force microscopic (AFM) analysis revealed funnel-shaped pore channels on the shell layer which may contribute to the entrapment of HB-VLPs on core-shell adsorbents, thus decreasing the HB-VLP recovery. Overall, SQ performed better than the core-shell adsorbents in handling feedstock with high concentration

Production and characterization of biopowders made from gel-forming polymers

To date, many bioactive compounds have been encapsulated within microparticles to achieve specific purpose such as stabilization, protection, isolation, controlled-release, taste-masking, improving aesthetic and handling qualities. However, much work is still needed particularly to determine the way to control the size and shape of microparticles produced using the air-atomization method. In addition, the effect of drying on the properties of dried biopowders has yet to be evaluated. These problems form the missing gap that will be addressed by this project. In this work, alginate was chosen as a model polymeric material to form the biopowders. The first part of this work was to determine the key physical properties of the polymer solution since they have significant influence on the characteristics (i.e. size) of the particles formed. The density of Na-alginate solution increased slightly as the alginate concentration increased whereas the solution apparent viscosity at zero shear rates exhibited a typical exponential increment. A new method, LCP coefficient method, to measure surface tension of viscous biopolymer solutions has been developed. The surface tension at low alginate concentration (5 -20 g/L) was about 68 -72mN/m and it showed a decreasing trend as the concentration increased. Air-assist external mixing atomization with low mair/rituqwas developed to produce wet particles of wide range of mean diameters, from 50 to 2300 µm. A semi-empirical size prediction model was developed to assist and enhanced the productivity of desired size by changing the physical properties of the operating conditions. Increased in Weber number produced smaller particles size, wider particles size distribution and more spherical particles. Finally, biopowders were formed by drying the wet particles. The results showed that drying temperature, intermittent mixing, sample thickness and wet particle size were among factors affecting the drying kinetics. Effective diffusivity value of wet alginate particles was ranged from 5.4 x 10·10 to 8.0 x 10·9 m2/s while the activation energy was ranged from 15 to 20 KJ/mol. The drying kinetic was modelled according to a logarithmic model. In addition, smaller wet particles (75 µm) were found to agglomerate during the oven-drying process whereas larger particles (1300 µm) did not agglomerate. Freeze­drying process did not cause agglomeration for both particle sizes. The type of drying method (oven-drying or freeze-drying) was found to have significant influence on the size, size distribution and physical appearance of the biopowders formed

Calcium Pectinate Beads Formation: Shape and Size Analysis

The aim of this study was to investigate the inter-relationship between process variables and the size and shape of pectin solution droplets upon detachment from a dripping tip as well as Ca-pectinate beads formed after gelation via image analysis. The sphericity factor (SF) of the droplets was generally smaller than 0.05. There was no specific trend between the SF of the droplets and the pectin concentration or the dripping tip radius. The SF the beads formed from high-concentration pectin solutions and a small dripping tip was smaller than 0.05. The results show that the Reynolds number and Ohnesorge number of the droplets fall within the operating region for forming spherical beads in the shape diagram, with the exception to the lower boundary. The lower boundary of the operating region has to be revised to Oh = 2.3. This is because the critical viscosity for Ca-pectinate bead formation is higher than that of Ca-alginate beads. On the other hand, the radius of the droplets and beads increased as the dripping tip radius increased. The bead radius can easily be predicted by Tate's law equation

Comparison of alginate and pectin based beads for production of poultry probiotic cells.

A comparative study on the stability and potential of alginate and pectin based beads for production of poultry probiotic cells using MRS medium in repeated batch fermentation was conducted. The bead cores, made of three types of materials, i.e., ca-alginate, ca-pectinate and ca-alginate/pectinate, were compared. The effect of single and double layer coatings using chitosan and core material, respectively, on the bead stability and cell production were also studied. The pectin based beads were found to be more stable than that of the alginate beads and their stability was further improved by coating with chitosan. The cell concentration in pectin based beads was comparable to that in the alginate beads. On the other hand, pectin based beads gave significantly lower cell concentration in the growth medium for the initial fermentation cycles when compared to the alginate beads. In conclusion, pectin was found to be potential encapsulation material for probiotic cell production owing to its stability and favourable microenvironment for cell growth