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A Journal on Biotechnology and Molecular Biology

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Minerva Biotecnologica 2007 June;19(2):65-70

language: English

Enhanced acid phosphatase yield by polyhydroxyethylmetacrylate gel-immobilized Humicola lutea cells

Aleksieva P. 1, Nacheva L. 1, Michailova L. 1, Kabaivanova L. 1, Tchorbanov B. 2

1 Institute of Microbiology Bulgarian Academy of Sciences, Sofia, Bulgaria
2 Institute of Organic Chemistry with Centre of Phytochemistry Bulgarian Academy of Sciences, Sofia, Bulgaria


Aim. The aim of the present study was to immobilize by entrapment the filamentous fungus Humicola lutea 120-5 spores in polyhydroxyethylmetacrylate gel and to use them for acid phosphatase production under the control of the inoculum level.
Methods. Control on gel inoculum volume was made by its reduction in half when inoculum/medium ratio in fermentation flask reached 50/50 ml. The distribution of the growing fungal cells in the whole interior of the gel blocks and some specific changes of the surface cell morphology were observed by scanning electron microscopy investigations.
Results. The effect of the control of inoculum amount on acid phosphatase production is evident: approximately two-fold longer half-life times – 10 runs for 10% polymer and 16 runs for 20% gel matrix; significant enhancement of relative acid phosphatase activities (over 150 and 200% in the case of 10 and 20% gel, respectively); almost two-fold higher enzyme yield was obtained compared to the maximal values in reuses without reduction of inoculum. A clear advantage of using immobilized H. lutea is the absence of free mycelium in the medium or on particle surface, therefore whole acid phosphatase detected in culture filtrates is a result of the growing immobilized cells in gel blocks.
Conclusion. All results obtained confirm the importance of inoculum size control during the cultivation of immobilized fungus for acid phosphatase production. The advantages of polyhydroxyethylmetacrylate biocatalyst make it an attractive source of fungal acid phosphatases and allow their use in food technology for mild hydrolysis of casein.

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