Phytate hydrolysing activity of the Aspergillus niger L-4 micromycete strain

N M Musta Ogly,N Yu Sharova

doi:10.21285/2227-2925-2020-10-2-232-239

Abstract

The aim of the study was to study the phytase synthesis capability of Aspergillus niger L-4 strain. The method for determining phytase activity is based on establishing the content of inorganic phosphates as a result of the action of phytase on the substrate under certain standard conditions by binding them with a vanadium-molybdenum reagent to form a coloured complex. The use of phytases for the hydrolysis of phytates in animal feed is important from the point of view of preserving the environment: when phytate complexes are destroyed, phosphorus is released, which performs an important structural and regulatory function, ensuring the normal development of bone and dental tissues and supporting their safety and integrity. Phosphoric acid is involved in the synthesis of kinases responsible for the normal course of chemical reactions in cells, in fat metabolism, as well as in the synthesis and breakdown of starch and glycogen. This reduces the release of undigested phosphorus into the environment. The object of the study consisted of native solutions obtained by culturing an industrial strain of acid-forming A. niger L-4 on various carbohydrate-containing media. The A. niger L-4 strain, previously selected at the All-Russian Scientific Research Institute of Food Additives for fermentation of molasses, has the ability to synthesise extracellular phytase. This paper presents the results of studies of phytase activity during the cultivation of A. niger L-4 on carbohydrate-containing media. It was found that in order components of the sucrose-mineral medium provide an elevated level of low-molecular-weight sugars necessary for increasing the productivity of phytase biosynthesis. Phytase activity in the native solution was shown to increase over 72 hours of fermentation to reach a value of 25.8±0.1 units/cm 3 . The phytase activity was 1.5 times higher than the fermentation process of a corn starch hydrolysate with a dextrose equivalent DE = 21±1 %, ensuring the productive biosynthesis of citric acid.

Highlights

Micromycete A. niger synthesises enzymes and organic acids
For the effective hydrolysis of phytates, phytases are used to catalyse the cleavage of phytate complexes to residues of myo-inositol and phosphoric acid, the latter representing a convenient source of phosphorus
Productive biosynthesis of target metabolites is affected by conditions such as age and amount of seed mycelium, fermentation temperature

Summary

Introduction

Micromycete A. niger synthesises enzymes (amylases, phytases, invertases, cellulases, etc.) and organic acids (citric, gluconic, itaconic, and kojic acids). For citation: Musta Ogly NM, Sharova NYu. Phytate hydrolysing activity of the Aspergillus niger L-4 micromycete strain. Previous studies have shown that the productive biosynthesis of amylolytic enzymes by A. niger micromycetic acid-forming strains is achieved using seed mycelium in an amount of 15 % of the volume of the nutrient medium having ages of 24–36 h at a fermentation temperature of 32±1 °C regardless of the carbohydrate source [17, 18].

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