Development of Micro-porous Beads for Immobilization of Aerobic Organisms

Development of Micro-porous Beads for Immobilization of Aerobic Organisms.

ABSTRACT  

Biocatalytic efficiency of immobilized cells has been known to be significantly higher than that of free cells. Increases in specific rates of substrate uptake and product excretion have been reported for immobilized cells. However, for immobilized (entrapped) aerobic organisms, significant substrate concentration gradients may exist as the polymer gel exerts its own resistance to mass transfer.

Cells located at the periphery are most likely to have adequate oxygen and nutrients while cells located relatively further away (central part) are under oxygen and nutrient limitation. This work focused on the reduction of mass transfer limitations in entrapped aerobic cells by entrapping the cells in micro porous beads. Micro porous beads were prepared by mixtures of different ratios of starch or granulated sugar and sodium alginate.

They were gelled by dropping in calcium chloride solution and the starch or granulated sugar was leaked out of the bead into the cross linking/curing agent (2% CaCl2.H20), there-by producing micro pores. The effects of sodium alginate and starch or granulated sugar concentrations on the porosity, bead stability, immobilized cell concentration, cell leakage and cell distribution were studied.

The results showed that the optimum sodium alginate concentration for both normal and micro porous beads was 2% while optimum concentrations of starch and granulated sugar mixtures were 0.4% and 1.2%, respectively. However, STA represented 2.0% sodium alginate – 0.4% starch micro porous bead while GSA represented 2.0% sodium alginate – 1.2% granulated sugar micro porous bead. 

INTRODUCTION  

Immobilization of microorganisms refers to the act of limiting or preventing movement of microorganism (Yu.Qung, 2004). Whole cell immobilization can also be defined as the confinement or localization of inert cells to a certain defined region of space with the preservation of some desired activity (Karel et al.,1990). Cell immobilization technology has wide applications in life. It is used in food industry, water treatment, production of antibiotics, amino acids, organic acids, enzymes and ethanol production (Hamedaan and Kato, 2003).

Immobilized cell system possesses many advantages when compared with suspended cell technology. These include: realization of continuous fermenter operation without danger of washout, easy detachment of product and recovery of cells from the medium at the end of fermentation. In addition, cell immobilization provides conducive condition for cell differentiation and cell to cell communication by encouraging the production of high yield of secondary metabolites (Joo, et al., 2001).

Similarly, high biomass, high metabolic activities, reusability of the cells and strong resistance to toxic substances are all advantages of immobilized systems. The overriding force in the interests over cell immobilization is the enhancement in specific rate of substrate utilization and improved specific rate of metabolite excretion. Cell immobilization methods include:  

1. Attachment to surface  
2. Entrapment within a porous matrix  
3. Containment behind barrier 
4. Self aggregation(flocculation) 

REFERENCES

Abdalwahab, S.A., Ibrahim, S.A. and Dawood, E.S. (2012). Culture condition for the production
of glucoamylase enzyme by different strains of Aspergillus Spp. International Food
Research Journal 19 (3): 1261 – 1266.

Abe, J., Bergman, K., Obeta, K. and Hikuri, S. (1988). Production of raw starch digesting
amylase by Aspergillus K-27. Applied Microbiology and Biotechnology 27:447-450

Abraham, T.E., Jamuna, R., Bansilal, C.V. and Ramakrishna, S.V. (1991). Continous synthesis
of glucoamylase by immobilized fungal mycellium of Aspergilus niger Starch-Starke;
43: 113-116.

Adekunle,O.A., Olanike, O. and Olabisi, A. (2012). Production of amylase from Aspergillus
niger using a defined synthetic growth medium and also rice (Oryza sativa) as growth
substrate. E3 Journal of Medical Research 1(7):091-094.

Akpan, I., Bankole, M.O., Adesemowo, A.M. (1999a). A rapid plate culture method for
screening of alpha amylase producing micoorganism. Biotechnology 13: 411 – 413.

Akpan, I., Bankole, M.O., Adesemowo, A.M., Lantunde-Data, G.O. (1999b). production of
alpha-amylase by Aspergillus niger in a cheap solid medium using rice bran and
Agricultural material. Tropical Science 39: 77 – 79.

Aneje, K.R (2000). Experiments in Microbiology, Plant Pathology Tissue Culture and
Mushroom Production Technology.New Age Publishers, New Delhi.

Angelova, M.B., Pashova SB. and Slokoska, L.S. (2000).Comparison of antioxidant enzyme
biosynthesis by free and immobilized Aspergillus niger cells. Enzyme Microbial
Technology 26:544–9.

StudentsandScholarship Team.