The objective of this studywas to isolate and identify bacteria of the genus Bacillus sp. froma super-intensive culture
system with Litopenaeus vannamei microbial flakes, and evaluate their potential of affecting the water quality,
performance and immunological parameters when added to the water and diet. Bacillus spp. isolates were
evaluated in vitro for the ability to inhibit pathogens, antagonistic activity. After selection, Bacillus spp. was
added to the water to assess the influence in the formation and maintenance of microbial flakes in post-larvae
culture. In order to verify the performance and hemato-immunological parameters of L. vannamei for 42 days
of culture, they were incorporated in formulated diets. Four bacteria were isolated from the microbial flakes
super-intensive system: Bacillus thuringiensis CPQBA 571-12 DRM 06 (N99%), Bacillus licheniformis CPQBA 571-
12 DRM 07 (N99%), B. licheniformis CPQBA 571-12 DRM 08 (N99%) and Bacillus cereus CPQBA 571-12 DRM 09
(N99%). B. licheniformis CPQBA 571-12 DRM07 was the only isolate that showed in vitro inhibitory characteristics
against the pathogen Vibrio alginolyticus (BCCM 2068) with a 20 mm diameter inhibition zone and the isolates
did not show any antagonistic activity. For the test of formation and maintenance ofmicrobial aggregates generated
in the post-larvae culture super-intensive system, a significant differencewas observed (p b 0.05) in the microbiological
count of the water on the seventh day of testing, when the total count of Vibrio spp. in water was
lower in the groups treated with Bacillus spp. (1 × 104 CFU·mL−1) than in the control group. In the fattening
test, supplementation with Bacillus spp. did not affect the performance of shrimp, however, therewere no significant
differences (p b 0.05) in the immunological parameters, Bacillus spp. strains were able to increase the total
count of hemocytes, the serum binder content and the total protein in serum, and decrease the hemolymph
phenoloxidase (PO) activity. There was also an increase (p b 0.05) in the intracellular production of superoxide
anion stimulated by laminarin (β-1,3 glucans) and PMA (Phorbol myristate acetate) compared to the baseline.
The conclusion is that the Gram-positive bacteria Bacillus spp., isolated from microbial bioflakes, are important
for the cultivation and maintenance of the health and growth of L. vannamei, and can be used as probiotics or
as biocontrol for water in super-intensive culture systems.
Statement of relevance: Bacillus spp. were isolated from biofloc systemwater and can be supplemented in shrimp
(L. vannamei) feed to increase immunocompetence and used as biocontrol for Vibrio spp. in water.