Sophie Overbeck, Weber State University
Late gas defects in aging cheese result in significant losses to the manufacturer. Lactobacillus wasatchensis, a novel non-starter lactic acid bacteria (NSLAB), has recently been identified as an important cause of late gas defect. Controlling growth of this unwanted NSLAB may be done by incorporation of bio-protective LAB cultures (BP-LAB) into the cheese during manufacture, which could inhibit its growth during cheese aging. Previous research has shown that several BP-LAB cultures inhibit Lb. wasatchensis to varying degrees but the exact mode of inhibition has not been determined. Quantification of inhibition between BP-LAB cultures and Lb. wasatchensis was done using the spot test with the agar-flip method then measuring inhibition zones in comparison to time incubated. MRS agar with 1% ribose (MRS-R) was inoculated with each BP-LAB and incubated anaerobically at 35°C for 48 h to form a spot colony. Inoculated agar was flipped over and a Lb. wasatchensis strain swabbed on the exposed surface then incubated anaerobically at 25°C for up to 72 h. In addition, potential synergistic quantification of inhibition by co-BP-LAB strains was tested by taking 1 mL each of two different BP-LAB strains growing them together, and then following the previous described protocol. The five most inhibitory BP-LAB cultures were Lactobacillus rhamnosus LB3, Lactobacillus paracasei P-210, Lactobacillus brevis 13648, Lactobacillus casei F19, and Lactobacillus paracasei Lila. Four different co-cultures were tested LB3/ P-210, LB3/P-220, P-200/P-210, and P-200/P-220. No significant increases in the inhibition zones were observed when BP-LAB cultures were paired versus individual strains. Results confirmed that selected BP-LAB strains can inhibit growth of Lb. wasatchensis. Currently, we are trying to isolate the bacteriocins produced by these BP-LAB.