A METHOD FOR PROCESSING OF KERATIN-CONTAINING RAW MATERIAL USING A KERATINASE-PRODUCING MICROORGANISM STREPTOMYCES ORNATUS S 1220

Abstract

Listen

Translate article

Abstract: The effect of substrate on mycelium growth, the optimal composition of the culture medium, and the optimal cultivation conditions for Streptomyces ornatus S 1220 have been investigated in the present work. The specific activity of keratinase has been monitored during cultivation and activity variation caused by addition of various salts to the cul-tivation medium has been analyzed. The results of the optimization study are reported and successful use of the culture studied in the present work in processes performed on an industrial scale is anticipated. Key words: keratin, secondary raw materials, processing, keratinase-producing microorganism, enzyme, protein, culti-vation, keratinase activity, bioconversion UDC 577.151.35:547.962.9 DOI 10.12737/2051 INTRODUCTION The amount of secondary raw material obtained dur-ing slaughter and processing of poultry can be as high as 45% of the live weight of the birds. Most of this materi-al is constituted by down and feathers, which have a high biological value, since they contain about 85% keratin. Keratins are abundant proteins found in epithelial cells. They are major structural components of skin, nails, hair, feathers, and wool. Analysis of the amino acid composition of keratins shows that these proteins are a rich source of essential amino acids. However, the transformation of natural keratin into a digestible form is problematic, since keratins are fibrillar proteins and their mechanical stability is higher than that of all other materials of biological origin except chitin. The conven-tional techniques used for the processing of keratin-containing raw materials are neither efficient nor ration-al. The use of physical and chemical processing meth-ods can result in formation of various toxic substances, as well as in loss of up to 75% of protein. Consequently, novel procedures for the processing and efficient use of the secondary raw material are needed. Enzymatic methods for the processing of protein-containing raw materials, which became available due to the development of biotechnology, allow for the preser-vation of all essential amino acids. The use of ready-made enzyme preparations on an industrial scale can lead to a significant increase in costs and expenses, and there-fore it is necessary to find solutions which enable the minimization of processing costs for the keratin-containing raw material. The use of live microorganism cultures in the processing of keratin-containing raw material allows for a reduction of the processing costs. The bioconversion method involves cultivation of the enzyme-producing strains on a substrate formed by the raw material to be processed. High efficiency of the sub-sequent decomposition of the substrate can be attained if this method is used. Selection of the optimal enzyme-producing microorganism and the optimal cultivation conditions is necessary in order to increase the rate and efficiency of bioconversion employing this method. With the requirements concerning the strain and its functional efficiency taken into account, we chose the keratinase-producing strain Streptomyces ornatus S 1220. Simple composition and low cost of cultivation media, high levels of keratinase production, short culti-vation time, and high enzyme yield [4] were the primary reasons for the choice of this strain. The aim of the present work, formulated with the current problems taken into account, was to define the optimal composition of the cultivation medium provid-ing for a high biomass yield of Streptomyces ornatus S 1220, to determine the most appropriate cultivation temperature and the period during which the rate of bi-omass accumulation is the highest, and to assess the effect of chemical additives on the specific enzyme ac-tivity. The tasks to be fulfilled in order to achieve the aim included analysis of the chemical composition of feathers, characterization of the effect of complex culti-vation media on the yield of keratinase produced by the microorganism, analysis of environmental effects on the growth and productivity of the microorganism under investigation, and optimization of the cultivation pa-rameters established.