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

Abstract

This study demonstrates that carotenoids produced by B. aquimaris SH6 can be successfully absorbed and converted to astaxanthin in whiteleg shrimp.

Fate of carotenoid-producing Bacillus aquimaris SH6 colour spores in shrimp gut and their dose-dependent probiotic activities

“…An orange-pigmented B . aquimaris SH6 strain isolated from the gut of white-leg shrimp and characterized from a previous study was used for growing spores [20]. In brief, SH6 spores were formed in Difco Sporulation Medium (DSM), pH 8, at 33°C and shaking for 48 h in a flask.…”

“…The upper phase was collected for carotenoid level determination by measuring at absorbance 480 nm (A 480 ) following the method described by Ngo et al . [20]. The spores and the carotenoid extract from SH6 bacterial cells (hereafter named as “SH6 carotenoids”) were then stocked, aliquoted, and stored at -20°C for further analysis.…”

“…Commercial shrimp feed pellet (Universal President, Tainan, Taiwan) was first autoclaved to kill any live probiotic strains and was then used as the basal diet for supplementing with either SH6 spores at three different concentrations, Carophyll Pink (powder containing 10% synthesized astaxanthin, DSM, Heerlen, the Netherlands) or SH6 carotenoids; a similar method has been reported elsewhere [20]. For the three experimental groups, the feed was mixed with SH6 spores at the following final concentrations: 5 × 10 6 CFU/g pellet (high concentration, labelled as SH6 spore-H group), 1 × 10 6 CFU/g pellet (medium concentration, labelled as SH6 spore-M), 2 × 10 5 CFU/g pellet (low concentration, labelled as SH6 spore-L).…”

“…Among these studies, there is only one recent publication by our group on the screening of a Bacillus sp . strain producing carotenoids isolated from shrimp gastrointestinal tracts [20]. In that study, the best carotenoid producing orange-pigmented B .…”

“…aquimaris SH6 strain was isolated and screened from the gut of white-leg shrimp. The strain was characterized for its potential probiotic effect on shrimp health, as indicated by increased PO activity, weight gain and improved red colour score and astaxanthin levels [20]. Nevertheless, there are still other factors regarding the application and mechanism of probiotic activity that need to be addressed, including the identification of the optimal feeding regime of SH6 spores as cost-effective feed supplements, the verification of whether the SH6 orange spores can colonize and germinate into vegetative cells during the transition of feed through the shrimp intestine in order to produce carotenoids and whether the persistence of SH6 effects in the gut microbiota confer beneficial effect.…”