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Canola meal (CM) is a byproduct of oil extraction from canola seeds. CM is used as an animal feed ingredient worldwide due to its high protein content, phosphorus, and low cost. Antinutritional factors such as glucosinolates, fiber, tannins, phytic acid, and phenolic compounds negatively affect CM’s nutritive value in animal production systems. However, the antimicrobial activity of phenolic acids may particularly contribute to reducing colonization of the chicken intestine with food-borne pathogens. The nutritive value of CM can be increased by fermentation. Feed fermentation with lactic acid bacteria has shown promise to reducing colonization of the chicken gut with Salmonella and Campylobacter. The aim of this study to identify strains of lactobacilli that ferment CM, to determine the conversion of phenolic compounds during fermentation, and to assess the in vitro antimicrobial activity of canola extracts against intestinal microorganisms.
Black canola seeds were ground, and oil was extracted. The meal was aerated and roasted in a toasting oven at 110 °C for 2 h. The soap pellets were collected and mixed with the roasted CM. The final CM was covered and stored at room temperature. Fermented CM was analyzed for phenolic composition using tandem mass spectrometry (LC–MS/MS) and high-performance liquid chromatography (HPLC). The inhibitory activities of phenolic compound extracts from CM and sinapic acid were determined against 10 indicator strains. Minimum inhibitory concentrations (MIC) were assessed and defined as the concentration that inhibited 50% of bacterial growth.
Fermentation generally increased inhibition by phenolic extracts except for strains of Salmonella and C. jejuni PCJ 481 and 494. Fermenting CM with Lp. plantarum significantly decreased the MIC of phenolic compounds against Fl. sanfranciscensis, L. johnsonii, and S. heidelberg. The sinapic acid concentrations in the samples fermented with Lp. plantarum and Ff. milii FUA3583 were consistently lower than the concentration of sinapic acid in extracts diluted to the MIC, indicating the presence of other compounds that contributed to the inhibitory activity. This result suggested that other than sinapic acid, the reduced phenolic acids but not the decarboxylated metabolites contributed to the antimicrobial activity.
In conclusion, this study demonstrated that fermentation CM with lactobacilli increased the antimicrobial activity of phenolic acids against Salmonella and Campylobacter. A chicken diet containing lactic-fermented CM thus would thus combine the presence of probiotic lactobacilli and antimicrobial phenolic compounds and could potentially reduce colonization of chicken with Salmonella and Campylobacter.