Wood, Branzen; Oberg, Taylor; Culumber, Michele; Oberg, Craig (Weber State University)
Faculty Advisor: Oberg, Taylor (Utah State University, Nutrition and Food Science); Culumber, Michele (Weber State University, Microbiology); Oberg, Craig (Weber State University, Microbiology)
The unique flavorings and textures of Cheddar cheese are produced by the degradation of the major milk proteins. One of those proteins, casein, is degraded by the enzyme chymosin and a series of peptidases produced by the starter Lactococcus added to the milk. As casein is degraded, several small peptides accumulate. One of these peptides, ß-casein, can have an adverse bitter taste that is non-desirable and considered a defect in Cheddar cheese. The two main starter cultures used industrially in Cheddar cheese making are Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris. L. lactis subsp. cremoris has been used traditionally in Cheddar cheese making, however, L. lactis subsp. lactis ferments more quickly and is becoming more popular in the cheese industry. With the transition creameries have seen a sharp rise in bitterness during production. Our hypothesis was that while closely related, cremoris synthesizes some peptidases that help with ß-casein degradation that lactis does not. Peptidases found in cremoris include PrtP I and II, Pep X, Pep C, Pep A, Pep T, Pep Q, Pep N, Pep V among others. We searched the genomes of both strains using RAST bioinformatic software, and the databases NCBI and UniProt. The peptidases common in cremoris were also found in lactis. We are now trying to determine if the location of the peptidases on the genomes change how they are regulated or produced. Further, we will begin looking into the genome for other, novel, enzymes that might have peptidase activity that influence bitterness.