Isolation and Identification of Lysinibacillus sp. and Its Effects on Solid Waste as a Phytate-Mineralizing Bacterium in an Aquaponics System

Abstract

Sedimentable solids generated in aquaponic systems are mainly composed of organic waste, presenting molecules such as phytate, which can be a potential source of inorganic nutrients through mineralization. This work aimed to isolate and identify phytase-producing bacteria and evaluate the inoculation effects of pure strains on mineralization and nutrient release from solid waste generated in aquaponic systems at different oxygen and temperature conditions. The bacteria were isolated from the settleable solids of a commercial aquaponic system and molecularly identified by amplifying the 16S rRNA gene. Subsequently, two tests were carried out: 1. Test for the biochemical identification of phytase-producing bacteria; 2. In vitro mineralization test, where the ability to mineralize phytate and release nutrients under different oxygen conditions [0 rpm (2.1 mg L−1) and 200 rpm (7.8 mg L−1)] and temperatures (24 and 37 °C) were evaluated. Our findings show that two pure strains of Lysinibacillus mangiferihumi can mineralize phytate under conditions of 200 rpm and 24 °C, mainly increasing the mineralization of PO4- and Ca, a property that has not yet been reported for this species. On the other hand, at 0 rpm and 24 °C, an increase in K was observed (control conditions), while the conditions of 200 rpm and 24 °C, regardless of bacterial inoculation, favored a rise in S, Mg, and Fe. The Lysinibacillus strains obtained in this investigation are of great importance due to their application in agriculture and the optimization of mineralization in aquaponic systems. A proper combination of oxygen and temperature will lead to a greater availability of nutrients for the growth and development of vegetables.