The filamentous fungi are traditionally used for human alimentation to flavor, to modify the texture and the nutritional properties of vegetal and animal protein.
Owing to the development of submerged fermentation, recently the applicable biotechnological domain of fungi has been considerably enlarged, notably for the production of organic acids, antibiotics, enzymes and the bioconversion of steroids. The enzyme, which is bioconversion catalyser, is generally soluble, seldom stable, expensive and difficult to use in the presence of organic solvents. In addition, enzymatic reaction is most frequently realised disconlinuously and it is very difficult to recover the soluble enzyme after the reaction.
Enzyme immobilization and their utilisation in the continuous reactor permit to ameliorate considerably the competition of the enzymatic bioconversion processes.
Recently the researchers orient themselves to the immobilization of organelles and whole cells. In the case of whole cells immobilization, the enzyme is stabilized by his natural environment and the purification steps are not necessary any more.
This study consists of two parties.
1) The immobilization of whole cells of fungus. Aspergillus phoenicis and the study of β-galactosidase activity.
2) The bioconversion of the progesterone by native and immobilized Aspergillus phoenicis.
One strain, Aspergillus phoenicis which gives a good β-galactosidase activity was selected among many other fungi.
The coreticulation was chosen as the principal method of immobilization. Mechanical property of immobilized form was controlled by electronic microscope analysis. The stability of not only native and immobilized whole cells but also native and immobilized crude β-galactosidase were studied, also. The kinetic behavior in the continuous fixed bed reactor was investigated.
The bioconversion of steroids and especially the hydroxylation reaction constitute an important industrial problem.
Their synthesis needs generally the first chemical step which arrives at the progesterone. The bioconversion plays an important role to obtain the final high value products from the reacting progesterone.
One uses therefore the whole cell to preserve tlue enzyme systems with cofactor regeneration which is indispensable to the transformation. The culture medium must permit at the same time the growth of microorganism and the substrate solubilisation.
The choice of solvent and the character of the hydroorganic medium are decisive for these syntheses. Aspergillus phoenicis is found to have not only β-galactosidasic activity but catalyse also the transformation of the progesterone into four interesting principal products: 11α-hydroxyprogesterone, 15β-hydroxyprogesterone, 6β-hydroxyprogesterone and 16β-hydroxyprogesterone.
The most remarkable one is 11α-hydroxyprogesterone. 11α-hydroxyprogesterone is an important product because it can be converted easily and cheaply into cortisone whose influence on the medical treatment like rhumatism is very efficient. The effects of various culture and reaction conditions on the transformation activity were investigated.
With six different types of immobilization, the variation of product compositions was observed.
The results are discussed thoroughly and the methods for the amelioration of the transformation activity are proposed.
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