Microorganism, enzyme preparation, industrial application

Immobilization is the method of cultivation of microorganisms that allows a repeated use of biocatalysts (be it enzyme or whole cells), creating prerequisites for the production of valuable products in an automated continuous mode. The most considerable problem in using biocatalysts is related to mass transfer. In aerobic systems, low solubility of oxygen in carriers, especially in some gels and polymers, can decrease the effectiveness of biocatalyst action. In this respect, propionic acid bacteria, which do not require aeration, show certain advantages over aerobic cultures. At present, about eight different processes that use immobilized enzymes and cells have found industrial applications. These are mainly one-or two-step processes used in the manufacture of foods and pharmaceutical preparations (Vorobjeva et al, 1978). An essential characteristic of a biocatalyst is productivity. 

Despite the previously mentioned examples vhich clearly prove the synthetic value of BY, there are several drawbacks that limit its vhdespread application to preparative organic chemistry (i) very low substrate concentrations tolerated by the microorganism that lead to an intrinsically too low productivity (ii) difficult work-up, due to the troublesome separation of the product from a huge amount of biomass (iii) typically incomplete conversion and occurrence of side reactions that imply the use of industrially unappealing chromatographic steps (iv) presence of enzymes with the same specific biocatalytic activity that might have different enantioselectivity. 

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