Effect of peptides from lactoferrin on some food spoilage bacteria

Peptide hydrolysates generated from pepsin digestion of lactoferrin and apo-lactoferrin were evaluated for their antibacterial action against non-pathogenic strains of Escherichia coli, Pseudomonas chlorophis, P. fragi (ATCC 4973) and P. fluoresens (ATCC 17400) in Tryptic Soy Broth (TSB). The treated samples and the control were incubated at {dollar}37spcircrm C{dollar} for E. coli and at {dollar}5spcircrm C,{dollar} {dollar}10spcircrm C{dollar} and {dollar}23spcircrm C{dollar} for the Pseudomonas spp. Pepsin digested lactoferrin (PDL) was not inhibitory against E. coli, P. fragi and P. fluorescens at 10 mg PDL/mL of TSB, but was bactericidal to P. chlorophis at 5 mg PDL/mL of TSB at {dollar}10spcircrm C.{dollar} The peptic digest of apo-lactoferrin (PD Apo-LF) was bactericidal at 20 mg/mL of TSB against P. fragi and P. fluorescens at {dollar}5spcircrm C,{dollar} {dollar}10spcircrm C{dollar} and {dollar}23spcircrm C.{dollar} At 20 mg PD Apo-LF/mL of TSB P. fluorescens was killed after 24 hr and P. fragi was killed after 48 hr incubation at {dollar}10spcircrm C.{dollar} The bactericidal effect was maintained after 72 hr of incubation. A bacteriostatic effect against P. fragi and P. fluorescens incubated at {dollar}5spcircrm C{dollar} was obtained at 10 mg PD Apo-LF/mL of TSB. Incubation temperature affected the rate of killing and the survival of unaffected bacteria. A higher rate of killing was observed at {dollar}23spcircrm C{dollar} than at {dollar}10spcircrm C{dollar} or {dollar}5spcircrm C{dollar} at 20 mg PD Apo-LF/mL of TSB. At {dollar}10spcircrm C{dollar} and {dollar}23spcircrm C,{dollar} the unaffected bacteria increased in number but the final bacterial concentration was about 1 {dollar}logsb{lcub}10{rcub}{dollar} less than the control. The inhibitory effect of PD Apo-LF was maximal at pH 6.5 and effective between 6.5 and 7.5. Slight growth inhibition due to PD Apo-LF occurred at pH 6.0. Growth of P. fluorescens was not affected at pH 5.5 in the presence of 10 mg PD Apo-LF/mL of TSB at {dollar}10spcircrm C{dollar} and {dollar}23spcircrm C.{dollar}...