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<p>The main objective of this research is to develop core-shell encapsulated, bacteriocin-producing lactic acid bacteria to improve the safety, quality and nutritional value of foods. Specifically,</p><p>(1) we will encapsulate LAB (e.g. mundticin L - producing Enterococcus mundtii and Nisin-producing Lactococcus lactis) in alginate microcapsules using both conventional and newly developed core-shell encapsulation techniques. We will control the microcapsule size, permeability and mechanical strength, and the bacteria density in the microcapsules.</p><p> (2) We will then assess and quantify the antimicrobial activity of the encapsulated LAB and compare the results with the non-encapsulated LAB control.</p><p> (3) We will lastly assess the survival of the encapsulated LAB in simulated adverse conditions such as the artificial gastric fluid (pH=1.5). The viabilities of the encapsulated bacteria, in conventional microcapsules or in the core-shell microcapsules, and the non-encapsulated bacteria will be compared.</p>
<p>In order to protect LAB from the environment and enhance their survival, the bacteria will be encapsulated into alginate hydrogel microcapsules using both conventional and the new core-shell, two-fluidic electrostatic spraying techniques. The size and properties of the microcapsules will be tuned by adjusting the alginate concentration, spraying nozzle design and processing parameters such as the electric field strength, and the flow rates. The two-fluidic approach produces core-shell microcapsules where only the core contains the bacteria and is therefore expected to provide better encapsulation and protection than the conventional single-fluidic one. We will use the bacteria provided by our collaborator Dr. Randy Worobo. His research group has several bacteriocin-producing strains that are capable of killing a range of pathogenic microorganisms and heat-resistant molds. We will then determine the bacteriocin activity against B. cereus F4552 as AU/ml by a modified microtiter plate assay method where one arbitrary unit (AU) is defined as the amount of bacteriocin that causes a 50% growth inhibition when compared with the control. We will also measure and compare the viabilities of the free and encapsulated bacteria, with or without the treatment of simulated gastric fluid. The bacteria encapsulated in both conventional and core-shell microcapsules will be extracted by dissolving the hydrogel using phosphate buffer solution. Appropriate dilutions will be poured on to MRS agar plates. The plates will be incubated and the number of colony-forming units (CFU) will be counted.</p>