Paper Information

Journal:   JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH   Spring 2003 , Volume 4 , Number 14; Page(s) 37 To 54.
 
Paper: 

THE APPLICATION OF LOOFA FOR THE IMMOBILIZATION OF NON FLOCCULATING YEAST CELLS

 
 
Author(s):  BONAKDARPOUR B., VAHABZADEH F., ABBASI AZADEH*
 
* 
 
Abstract: 
Loofa (loofa cylindrica) is a dried plant of the Aubergine family and the physical structure and specific characteristics of this plant, such as chemical, heat and microbiological stability, makes it a suitable carrier for the immobilization of microbial cells. This plant grows in the warm and humid areas in the north and south of Iran and has high porosity (75-84%) as well as low density (0.13-0.039 g/cm3) and compared to other existing carriers such as polyurethane foam, is very suitable for cell immobilization. However, the high specific volume of the pores in the structure of this carrier, in the range 16/48-19/2 g/ cm2, means that only cell flocs can be significantly entrapped inside the pores. In this study Loofa was used as a carrier for the immobilization of Sacharomyces cerevisae cells used in the production of ethanol from carbohydrate substrates. Since these cells do not have the ability to flocculate, chitosan, a cationic material, was used to induce the flocculation of S. cerevisae cells. The results showed that a concentration of 8 miligram per gram of cell results in 92% cell flocculation in a period of 1 hour. At this concentration, 60% of the cells where immobilized in the Loofa carrier in a period of two and a half hours with an initial inoculum of 0.1 gram cells per gram of Loofa. The use of such immobilized cells for the production of ethanol from a synthetic medium increased the productivity of ethanol production two folds compared to when free cells where used. However, during the course of the ethanol production process the concentration of free cells increased signifying the release of the yeast cells from the Loofa support. Addition of chitosan at specific points during the fermentation was shown to decrease this rate of cell release but also resulted in a decrease in the productivity of ethanol production which was attributed to the inhibitory effect of chitosan on the fermentative activity of S. cerevisae cells. Investigating the use of lower chitosan concentrations or the use of other non-inhibitory flocculents id suggested for future work.
 
Keyword(s): LOOFA CYLINDRICA, CELL IMMOBILIZATION, FLOCCULATION, CHITOSAN, S.CEREVISAE, ETHANOL FERMENTATION
 
References: 
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