Employment of phosphate solubilising bacteria on fish scales - Turning food waste into an available phosphorus source


The increased use of fertilisers is a well-known problem; linked to this, there is an always higher demand for phosphorus (P). Because of this, it is crucial to use P from all possible sources and, if necessary, turn it into a soluble form, available for plants/crops. In this paper we report the use of aerobic phosphate solubilising bacteria (PSB) on the scales of the tilapia (Coptodon rendalli) fish, a waste from the food industry; this is the first time that PSB were employed on fish scales to mediate the available P. The scales were calcined to 700 degrees C to obtain a nanoscale powdery material (more easily solubilised), made of hydroxyapatite, Ca-10(PO4)(6)(OH)(2), a calcium phosphate with very low solubility. Seventeen different PSB strains were tested for their ability to solubilise phosphate (commercial tricalcium phosphate - TCP) and hydroxyapatite from fish scale (FSHA). The best performing bacterial strain (Acidovorax oryzae ZS 1-7) led to a P solubilisation more than 60 times higher than the negative control - at 325 mg/L, almost 40% of the available P was solubilised - one of the highest increased efficiencies reported for PBS. Such solubilisation was linked to a decrease of the pH to more acidic values of about 4. The strain ZS 1-7 showed higher P solubilisation efficiency with fish-derived FSHA than with commercial TCP. This approach showed a promising strategy for the valorisation of residues of the fish industry, turning them into a source of P, to be used for sustainable agriculture.



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Santana, CA; Piccirillo, C; Pereira, SIA; Pullar, RC; Lima, SM; Castro, PML

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This work was supported by National Funds from FCT - Fundacao para a Ciencia e a Tecnologia through projectUID/Multi/50016/2019. Clara Piccirillo would like to thank Fondazione con il Sudfor financial support (project HApECOrk, reference 2015-0243). R.C. Pullar thanks FCT Grant IF/00681/2015, and this work was developed within the scope of the FCT project CICECO-Aveiro Institute of Materials (FCT UID/CTM/50011/2019), financed by national funds through the FCT/MCTES. Cristiane Avila Santana would like to thank Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) for financial support (project PDSE 88881.132572/2016-01).

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