Introduction : Systems utilizing Biofloc technology (BFT) exhibit the capacity to rear specific aquatic species, notably shrimp and tilapia, at remarkably high stocking densities. The maturation process of b iofloc is characterized by a prolonged duration before achieving full functionality. Initialization of a biofloc system typically involves a low initial density of aquatic organisms, coupled with an input of feed and an external carbon source. Drawbacks associated with this method encompass extended waiting periods, fluctuating water quality, and limited animal densities. Therefore, developing simple Biofloc preservation and reinoculation protocols is an interesting tool in aquaculture production. Material and Methods : Microbiological preservation tests were performed on concentrated B ofloc samples to ascertain the most effective preservation techniques. Total cell counts, heterotrophic and nitrifying bacterial growth were evaluated after the samples were subjected to various preservation methodologies.. Experimental groups included a positive control ( concentrated and unpreserved Biofloc) and five experimental groups: refrigerated (RF), frozen with 15% glycerol (F-GLI), frozen with 15% glucose (F-GLU), frozen (F), and freeze-dried (LF). Notably, the F-GLI and F-GLU groups exhibited the highest levels of heterotrophic and nitrifying bacteria growth, with the F-GLI group demonstrating superior cell viability among the experimental cohorts (Figure 1).
Subsequently, an experiment was conducted utilizing Penaeus vannamei shrimp to assess the efficacy of preserved b iofloc samples. Experimental groups encompassed refrigerated in vacuum bags (V), frozen at -80°C with 15% glycerol (F-GLI), and dried (D). Control groups included a negative control (C-), devoid of Biofloc, and a positive control (C+), inoculated with fresh Biofloc. Utilizing 80L tanks with an initial biomass of 80 grams and an inoculum concentration of 1g/L conserved for 5 days, water quality was periodically analyzed via chemical assessment of ammonium and nitrite concentrations. Results and discussion: After 21 days, observations indicated complete transformation of ammonium to nitrite in groups V and F-GLI. While nitrite accumulation was absent in group V, group F-GLI exhibited minimal nitrite accumulation albeit at very low concentrations. Conversely, group D displayed higher nitrite accumulation compared to the negative control, albeit with a more rapid stabilization of ammonium. These findings suggest the feasibility of short-term (one-week refrigeration) and long-term (freezing) preservation of b iofloc to expedite the maturation of b iofloc tanks accommodating high animal densities.
Acknowledgments: The study was funded by the Research Project: “Optimizing shrimp feeding and nutrition in biofloc system (BioFlango)” (PID2020-114574RB-C21). S. Ferrando-Juan contract by MICIN Research Personnel Training Grant (PRE2021-098367). J. Gómez-Aguilera contract was supported by European Union Next Generation-Plan of Conselleria d’innovació, Universitats, Ciència i Societat Digital of Generalitat Valenciana (INVEST/2022/434).