The Joint Effect of pH Gradient and Glucose Feeding on the Growth Kinetics of Lactococcus lactis CECT 539 in Glucose-Limited Fed-Batch Cultures

Probiotics in tilapia (Oreochromis niloticus) culture: Potential probiotic Lactococcus lactis culture conditions

Tilapia is one of the most extensively farmed fish on a global scale. Lately, many studies have been carried out to select and produce probiotics for cultured fish. Bacteria from the genera Bacillus, Lactiplantibacillus (synonym: Lactobacillus), and Lactococcus are the most widely studied with respect to their probiotic potential. Among these microorganisms, Lactococcus lactis has outstanding prospects as a probiotic because it is generally recognized as safe (GRAS) and has previously been shown to exert its probiotic potential in aquaculture through different mechanisms, such as competitively excluding pathogenic bacteria, increasing food nutritional value, and enhancing the host immune response against pathogenic microorganisms. However, it is not sufficient to simply select a microorganism with significant probiotic potential for commercial probiotic development. There are additional challenges related to strategies involving the mass production of bacterial cultures, including the selection of production variables that positively influence microorganism metabolism. Over the last ten years, L. lactis production in batch and fed-batch processes has been studied to evaluate the effects of culture temperature and pH on bacterial growth. However, to gain a deeper understanding of the production processes, the effect of hydrodynamic stress on cells in bioreactor production and its influence on the probiotic potential post-manufacturing also need to be determined. This review explores the trends in tilapia culture, the probiotic mechanisms employed by L. lactis in aquaculture, and the essential parameters for the optimal scale-up of this probiotic.

Production of a Potentially Probiotic Product for Animal Feed and Evaluation of Some of Its Probiotic Properties

Nowadays, probiotics have been proposed for substituting antibiotics in animal feed since the European Union banned the latter compounds in 2006 to avoid serious side effects on human health. Therefore, this work aimed to produce a probiotic product for use in animal feed by fed-batch fermentation of whey with a combination of kefir grains, AGK1, and the fermented whole milk used to activate these kefir grains. The probiotic culture obtained was characterized by high levels of biomass (8.03 g/L), total viability (3.6 × 10⁸ CFU/mL) and antibacterial activity (28.26 Activity Units/mL). Some probiotic properties of the probiotic culture were investigated in vitro, including its survival at low pH values, under simulated gastrointestinal conditions, after freezing in skim milk at −20 °C, and in the commercial feed during storage at room temperature. The viable cells of lactic and acetic acid bacteria and yeasts exhibited higher tolerance to acidic pH and simulated gastrointestinal conditions when the cells were protected with skim milk and piglet feed, compared with washed cells. The results indicated the feasibility of producing a probiotic product at a low cost with a potential application in animal feed.