Influence of osmolarity and the presence of an osmoprotectant on lactococcus lactis growth and bacteriocin production

Abstract

Growth inhibition of Lactococcus lactis provoked by increasing osmolarity is reversed when glycine betaine (GB) or its analogs are added to a defined medium. Lacticin 481 production increased sharply with growth medium osmolarity in the absence of osmoprotectant but remained unaffected when GB was supplied in media of increasing osmolarity.

FIG. 1

Natural-abundance ¹³C-NMR spectra of ethanol-soluble fractions of L. lactis ADRIA 85LO30 grown on CDM without NaCl (A), with 0.4 M NaCl (B), and with 0.4 M NaCl added to 1 mM GB (C). The peaks were identified in comparison with reference spectra of commercial compounds: GB (b) and lactic acid (l).

FIG. 2

Effect of NaCl and GB on lacticin 481 production during the growth of L. lactis ADRIA 85LO30. Cells were cultivated at 30°C without shaking on CDM with increasing NaCl concentrations or with 0.4 M NaCl added to 1 mM GB. Turbidimetry was monitored at 570 nm, and bacteriocin production (expressed in arbitrary units per milliliter) was evaluated. To quantify lacticin 481, twofold dilutions of produced bacteriocin were assayed by the supernatant diffusion method (15). The supernatants were dialyzed against CDM without NaCl and concentrated against solid polyethylene glycol 8000 for 48 h at 4°C in dialysis membranes with a molecular mass cutoff of 500 Da. The values are the means of triplicate experiments; the standard deviation was less than 20%. The solid symbols represent bacterial growth for each condition, and the open symbols represent bacteriocin production. Square, 0 M NaCl; diamond, 0.2 M NaCl; circle, 0.4 M NaCl; triangle, 0.4 M NaCl with 1 mM GB.