Effect of isolated bacteria and microalgae on the biofloc characteristics in the Pacific white shrimp culture

At present, the Pacific white shrimp Litopenaeus vannamei Boone, 1931, is one of the species with the greatest potential to be reared under biofloc Technology (BFT). Although BFT presents promising culture methods, some of these require improvements in efficiency by the use of native microalgae and bacteria (BFNO) as an alternative to commercial organism probiotics (BFCO). This experiment was developed using a culture system for the shrimp L. vannamei to a stocking density of 400 in./m3 for 44 days. Schizochytrium sp. and recently isolated Latobacillus plantarum (class: Bacilli), a probiotic strain (used as experimental biofloc), were incorporated to geomembrane tanks holding 28 m3 seawater to evaluate if these presented bioregulating effects influencing water quality and growth performance of L. vannamei. These microorganisms were compared with the BFCO. Results showed that both promoted bioflocs maintained optimal concentrations of total ammonium, nitrites, and nitrates for L. vannamei cultures. However, the BFCO required to be supplied every 10 days, whereas the experimental biofloc only required an initial stocking and maintenance of sodium carbonate levels >100 mg L−1 and pH > 7.5. Additionally, the load of Vibrio spp. in experimental biofloc was less than that observed for BFCO. Furthermore, the results of growth performance did not demonstrate differences between both treatments. Therefore, it is suggested that Schizochytrium sp. and the bacterial strain of L. plantarum should be used as initiator and basic constituents of the biofloc-based culture systems for L. vannamei, maintaining good water quality and avoiding periodical probiotic supplementation in cultures. Keywords: Induced biofloc, B. plantarum, L. vannamei, Microalga