Pediococcus acidolactici and Pediococcus pentosaceus isolated from a rainbow trout ecosystem have probiotic and ABF1 adsorbing/degrading abilities in vitro

ABSTRACT

Probiotics are being used in biological control of bacterial pathogens, as an alternative to antibiotics, to improve health and production parameters in fish farming. Fish farming production is severely affected by aflatoxins (AFs), which are a significant problem in aquaculture systems. Aflatoxins exert substantial impact on production, causing disease with high mortality and a gradual decline of reared fish stock quality. Some aspects of aflatoxicosis in fish, particularly its effects on the gastrointestinal tract, have not been well documented. The aim of the present study was to evaluate probiotic properties of lactic acid bacterial (LAB) strains isolated from rainbow trout intestine and feed. Moreover, AFB₁-binding and/or degrading abilities were also evaluated to assess their use in the formulation of feed additives. Growth at pH 2, the ability to co-aggregate with bacterial pathogens, inhibition of bacterial pathogens, and determination of the inhibitory mechanism were tested. Aflatoxin B₁ (AFB₁) adsorption and degradation ability were also tested. All strains were able to maintain viable (10⁷ cells ml^–1) at pH 2. Pediococcus acidilactici RC001 and RC008 showed the strongest antimicrobial activity, inhibiting all the pathogens tested. The strains produced antimicrobial compounds of different nature, being affected by different treatments (catalase, NaOH and heating), which indicated that they could be H₂O_2, organic acids or proteins. All LAB strains tested showed the ability to coaggregate pathogenic bacteria, showing inhibition percentages above 40%. Pediococcus acidilactici RC003 was the one with the highest adsorption capacity and all LAB strains were able to degrade AFB₁ with percentages higher than 15%, showing significant differences with respect to the control. The ability of some of the LAB strains isolated in the present work to compete with pathogens, together with stability against bile and gastric pH, reduction of bioavailability and degradation of AFB₁, may indicate the potential of LAB for use in rainbow trout culture.

KEYWORDS:

• Rainbow trout
• acid lactic bacteria
• probiotic
• aflatoxin B1
• adsorption
• degradation

Highlights

• The predominant species isolated from rainbow trout intestine and fish feed were Pediococcus acidolactici and Pediococcus pentosaceus.

• LAB strains isolated from trout intestine and feed showed probiotic characteristics.

• All strains showed resistance to pH 2.0 and bile salts.

• Strains were able to bind 10–22% AFB₁ in vitro.

• All strains were able to degrade 15–36% AFB₁.

Acknowledgements

This study was supported by grants from UNRC, CONICET and Truchas Boca del Rio from Las Tapias, Córdoba, Argentina.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Proyecto de Investigación en Ciencia y Tecnología (PICT) [grant number 1607/11]; Secretaría de Ciencia y Técnica (SeCyT) (UNRC) [Res. 331/16]; Fondo Nacional de Ciencia y Tecnología- Proyecto de Investigación en Ciencia y tecnología (FONCyT-PICT) [grant number 1606/12]; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) [grant number PIP 2013-2015 GI 11220120100156 4166].