TABLE 5.

Specific activities of CFEs of L. lactis LM0230 expressing L. helveticus CNRZ32 endopeptidases towards β-CN (f193-209) and αS1-CN (f1-9) in a single-peptide reaction, in the defined peptide mix, and in Cheddar cheese serum

Peptide and peptidasebMean (SD) spact ina:
Single-peptide reactionDefined peptide mixCheddar cheese serum
β-CN (f193-209)
    Control16 (2.0)†,*9.0 (2.0)†,†27 (3.0)‡,*
    PepENDNDND
    PepO264 (1.5)*,†42 (10)*,*120 (32)*,*
    PepO381 (7.0)*,*40 (6.0)*,*61 (23)†,*
αS1-CN (f1-9)c
    Control4.0 (4.0)‡,*4.0 (0.2)§,*23 (3.0)‡,†
    PepE190 (14)*,*120 (7)*,†31 (17)‡,‡
    PepO2240 (10)*,*84 (20)†,‡150 (40)*,†
    PepO341 (19)†,*38 (9.0)‡,*63 (25)†,*
  • a Specific activity is measured in nmoles of substrate hydrolyzed per h per mg of protein. Values were corrected by subtracting the mean values obtained in the control treatments from CFE of L. lactis LM0230(pTRKH2). Means with different symbols are statistically different at an α value of ≤0.05. Lightface symbols compare values within a column, and boldface symbols compare values within a row. Assays were performed under cheese-ripening conditions (pH 5.0 to 5.2, 4% NaCl, 10°C). ND, not detected.

  • b CFEs were prepared from L. lactis LM0230(pTRKH2) (control), L. lactis LM0230(pSUW666) (PepE), L. lactis LM0230(pSUW665) (PepO2), or L. lactis LM0230(pSUW664) (PepO3).

  • c In the case of αS1-CN (f1-9) hydrolysis, average specific activities are reported.