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ENZYMATIC CEREAL HYDROLYSATES FOR CULTIVATION AND HALOBACTERIUM SALINARUM BIOMASS PRODUCTION

Ekaterina Murzina

Abstract

The most studied and promising for the biotechnological production among extreme halophiles are archaebacteria Halobacterium salinarum. Food additives for humans and animals based on these halobacteria have an immunostimulating, antioxidant effect, can be used in complex therapy of viral diseases, and contain biologically unique active substances, vitamins and microelements. High-price hydrolysates and enzymatic hydrolysates of high-quality raw materials are used for H. salinarum cultivation. This causes a high cost of the halobacterial biomass. The main sources of carbon of these microorganisms are amino acids. Carbohydrates can only stimulate growth and carotenoids production. The nutrient medium for halobacteria should also contain growth factors and microelements for the functioning of specific enzyme systems. To reduce the nutrient medium components cost and to further use the biomass of halobacteria as food and fodder additives, the possibility of using enzymatic hydrolysates of plant raw materials has been considered. Among the tested cereal, wheat, corn and barley cereals were selected as complex sources of nutrition. The modes of thermal / chemical pre-treatment were selected, a number of enzyme preparations were tested and the regimes of enzymatic hydrolysis were optimized. Enzymatic hydrolysates obtained by treatment with selected enzyme preparations and with the addition of glycerol were used without further purification as the only sources of organic components in the nutrient medium. The media compositions also contained carbohydrates of varying degrees of polymerization, which perform an important function of binding inhibitors / metabolites produced during cultivation. The own proteolytic activity of halobacteria during cultivation proved to be an important factor for the most complete protein uptake and depended on the presence of Mn2+, Zn2+, Fe2+ ions in the medium. The optimum concentrations of this ions were selected for each cereal culture. In batch experiments carried out on the developed media, up to 4.3 g / L of biomass was accumulated with the content of carotenoids up to 23 mg / 100 g of biomass. In the membrane reactor with hollow fibers with the flow of a nutrient medium consisting of enzymatic cereal hydrolysates, in the best cases, up to 46 g / L of biomass of halobacteria with a content of carotenoids up to 25 mg / 100 g of biomass was accumulated. After cultivation in the membrane reactor, the halobacteria biomass concentrate contained a large amount of polysaccharides and after additional concentration and centrifugation was sent to spray drying. Polysaccharides in this case served as protective agents and significantly influenced on the preservation of cells and biologically active substances of halobacteria.

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DOI resolver: doi.org/10.5593/sgem2017h/63/s25.030

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