Synbiotic system is characterized using vegetable bran (e.g., wheat and rice bran) processed by probiotic microorganisms (e.g., Bacillus and yeasts) as a supplementary organic carbon source for the system fertilization. Vegetable bran, as they are rich in carbohydrates and fiber, need to be broken down into more labile forms so that their absorption by microorganisms is enhanced. This can be achieved through processing by fermentation and/or microbial respiration by probiotic microorganisms. Considering the lack of consensus among the use of different strategies and the periods in which they can be used, these topics still need to be elucidated for better fertilization management in this system. Therefore, t he aim of this study was to evaluate the effect of fermentation (F; phase without aeration) and respiration (R; phase with aeration) processes and different processing times of synbiotic system fertilizer on the nursery phase and compare with biofloc technology system.
A nursery phase trial (stocking density : 2400 shrimp m⁻³) was carried out for 48 days testing the following treatments: CW: clear water (control); BFT: biofloc system; F12: fermentation for 12 hours; F12+R12: fermentation for 12 hours + respiration for 12 hours; F24: fermentation for 24 hours; F24+R24: fermentation for 24h + respiration for 24h; R12: respiration for 12 hours; R24: respiration for 24 hours. The fertilizer was composed of rice bran, a commercial probiotic blend (Bacillus subtilis and Bacillus licheniformis), sodium bicarbonate, molasses, and water.
Treatments F12+R12 and R24 had a faster control of TAN. A dominance by amoeba was observed in the treatments BFT, F12, F12+R12 and F24. Treatments F12+R12, F12 and F24+R24 showed a higher abundance of ciliates than treatments CW, BFT, F24 and R12 at the end of the experimental time. The abundance of vibrio at the end of the experimental time was higher in the F24+R24 treatment than in the other treatments. At the end of the experimental time, treatments F12, F12+R12, F24 and R12 had a lower FCR than CW treatment. Yield was higher in F12, F12+R12, R12 and R24 than in CW treatment. Our findings indicate that the reduction of fertilizer processing time can be considered for the synbiotic system fertilization, optimizing the management of the system. Therefore, we consider 12 hours of fermentation and 12 of respiration (F12+R12) the best fertilization strategy, as it provided a reduction in FCR, increased yield and produces significant effects on plankton composition.