Production of plant growth regulatory metabolites of Rhizopus arrhizus KB-2

Yana Evstatieva, Aleksandra Ilieva, Violeta Valcheva and Dilyana Nikolova

Abstract: The genus Rhizopus is a well recognized filamentous fungus, inhabiting soil, rotting fruits, vegetables, food, etc. Rhizopus arrhizus is widely used in biotechnology and is technologically important producer of organic acids and hydrolytic enzymes.
The aim of this study was to estimate the capability of Rh. arrhizus KB-2 strain to produce metabolites with plant growth regulatory activity. Morphological characteristics, biosynthesis of hydrolytic enzymes and production of regulatory metabolites were defined during the batch cultivation. The presence of some plant regulatory metabolites in the free-cell cultural liquid, such as gibberellic acid, trans-zeatin, indol–3 acetic acid and cis, trans-abscisic acid were determined by liquid chromatography-tandem mass spectrometry analysis.
A molecular phylogenetic identification of Rh. arrhizus was done for the first time in the present study. The identity of our strain Rhizopus arrhizus KB-2 was conformed to the species Rhizopus arrhizus. The strain produced various metabolites with different concentrations in different fermentation media and time and the cell free supernatant from 216 h and 264 h increased 32% of the root length of Lactuca sativa. In cell free supernatant of Rh. arrhizus KB-2 was determined the presence of the phytohormones (auxins and gibberellins), which influenced the seed germination and root formation.

Keywords: hydrolytic enzymes; regulatory metabolites; Rhizopus arrhizus; seed germination

Date published: 2020-06-29