Screening of pigmented Bacillus aquimaris SH6 from the intestinal tracts of shrimp to develop a novel feed supplement for shrimp

Abstract

Aims: To develop a novel feed supplement for shrimp using pigmented spore-forming bacterial strains isolated from their gastrointestinal tracts. Methods and Results: Eight pigmented Bacillus strains were selected from the isolates based on high production of heat-stable spores, typical UV-Vis spectra of produced carotenoids (400–550 nm), and free radical scavenging activity of their extracts. Of the eight strains, the red-orange pigmented Bacillus aquimaris SH6 was selected because it showed the highest abundance in shrimp guts (70% population). Whiteleg shrimp (n = 30 per group) fed with SH6 spores, at >3 × 106 CFU g−1 pellet for 4 weeks had redder colour (score of 21–23 vs 20–22), 2·7-fold higher astaxanthin level (0·69 vs 0·25 μg g−1 shrimp), 34% higher weight gain (7·18 vs 5·32 g shrimp−1), and 85% higher phenoloxidase activity (OD490= 0·265 vs 0·143) than shrimp in the control group. Conclusions: The result supports the potential use of B. aquimaris SH6 as a feed supplement for promoting the colourization and weight gain, and for enhancing innate immunity of whiteleg shrimp. Significance and Impact of the Study: This study demonstrates that carotenoids produced by B. aquimaris SH6 can be successfully absorbed and converted to astaxanthin in whiteleg shrimp.