Selection and screening of bacteria from African nightcrawler, Eudrilus eugeniae (Kinberg, 1867) as potential probiotics in aquaculture (original) (raw)

World Journal of Microbiology and Biotechnology

Abstract

Earthworms are used as an alternative protein source in aquaculture. These organisms serve as an ideal and favorable site for bacterial growth and activity. Hence, in our present study, we isolated and screened potential probiotic bacteria from African nightcrawler (Eudrilus eugeniae). Among 45 bacterial isolates, four (ANSCI9, BFAR9, RM3, and RM10) were selected based on their hydrophobicity, hydrolytic enzyme production, pH and fsh bile tolerance, aggregation, and antimicrobial properties. The selected isolates showed good hydrophobicity (≥30%) and enzyme production (≥10 mm clearing zones), tolerance to pH and fsh bile, and inhibitory properties against pathogenic microorganisms. The isolates were identifed as Bacillus sp. RM3 (MH919306), Bacillus sp. RM10 (MH919308), Bacillus sp. ANSCI9 (MH919310) and Bacillus sp. BFAR9 (MH919302). These isolates were individually incorporated in the diets of Nile tilapia (Oreochromis niloticus) fngerlings for 14 days to assess their biosafety. The results showed that the survival rates in all treated groups (98.75±2.5 to 100.00±0.0%) were not signifcantly diferent (P<0.05) from the control group (commercial diet) (96.25±2.5%), suggesting that isolates have no adverse efect on the host. This study revealed the presence of potential probiotic microorganisms in E. eugeniae that are benefcial to the aquaculture industry.

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