Purification and characterization of thermophilin T, a novel bacteriocin produced by Streptococcus thermophilus ACA-DC 0040

Abstract

ACA‐DC 0040 produced an antimicrobial agent, which was named thermophilin T, active against several lactic acid bacteria strains of different species and food spoilage bacteria, such as Clostridium sporogenes C22/10 and Cl. tyrobutyricum NCDO‐1754. The crude antimicrobial compound is sensitive to proteolytic enzymes and α‐amylase, heat‐stable (100 °C for 30 min), resistant to pH exposure at pH 1–12 and demonstrates a bactericidal mode of action against the sensitive strain Lactococcus cremoris CNRZ‐117. The production of bacteriocin was optimized approximately 10‐fold in an aerobic fermenter held at constant pH 5·8 and 6·2. Ultrafiltration experiments with culture supernatant fluids containing the bacteriocin, and further estimation of molecular weight with gel filtration chromatography, revealed that bacteriocin in the native form has a molecular weight in excess of 300 kDa. SDS‐gel electrophoresis of partially purified thermophilin T showed that bacteriocin activity was associated with a protein band of approximately 2·5 kDa molecular mass.

Purification and characterization of thermophilin ST-1, a novel bacteriocin produced by Streptococcus thermophilus ACA-DC 0001

“…Similar results have been reported for thermophilin ST10 [5], thermophilin T [1] and thermophilin A [38]. On the contrary, the maximum activity of thermophilin 347 was detected in the mid-log phase of growth and rapidly declined after further incubation [36].…”

“…bulgaricus [13,15,34,35]. On the contrary, other bacteriocins from different S. thermophilus strains such as thermophilin A [38], thermophilin 347 [36], thermophilin ST-13 [18] and thermophilin T [1] seem to be included in the non-lantibiotic heat-stable group of bacteriocins with small molecular mass. The above properties differentiate thermophilin ST-1 and make it unique.…”

“…Similarly to thermophilin 13 and thermophilin 347 [18,36], thermophilin ST-1 was not affected by a-amylase and lipase. Conversely, thermophilin A [38], bacteriocin ST10 [5] and thermophilin T [1], also isolated from S. thermophilus strains, were sensitive to a-amylase. The ability of thermophilin ST-1 to withstand inactivation from rennin, makes it a more favorable agent for technological applications in cheese manufacturing.…”

“…Previous studies have shown that thermophilin 347 and thermophilin ST-13 exhibit an antilisterial activity [18,36], whereas thermophilin T is inhibitory against Clostridium sp. [1]. However, the inhibitory spectrum of several thermophilins appears to be limited only to some closely related lactic acid bacteria [5,9,38].…”

“…The ability of various S. thermophilus strains to produce several antibacterial agents has been studied in the past [1,5,18,24,36,38]. The aim of this study was to purify and characterize a new bacteriocin produced by the "wild" strain S. thermophilus ACA-DC 0001, isolated from traditional Greek yogurt.…”