INTERFERING MECHANISM OF SODIUM-BICARBONATE ON SPORE GERMINATION OF BACILLUS-STEAROTHERMOPHILUS

Spore germination of Bacillus stearothermophilus was progressively inh ibited as the concentrations of sodium bicarbonate (NaHCO3) in the ger mination media increased from 0% to 1.0% (w/v). The inhibitory effect of NaHCO3 was attributed to the release of HCO3- and its alkaline prop erties, each of which played a different role. At low concentrations ( < 0.3%), the inhibitory effect of NaHCO3 was mainly due to bicarbonate . As NaHCO3 increased from 0.3% to higher concentrations, the effect o f HCO3- reached a plateau while the alkalinating effect became the mor e dominant inhibitory factor. Fourier transform infrared (FTIR) analys is reveals that sodium bicarbonate reacted with the carboxyl group (15 70 cm(-1)) of some acidic amino-acid residues of protein in the spore, leading to a less orientated structure. A shift of two units towards the longer frequency for carboxyl groups indicates that a stronger int eraction was formed between the carboxyl group and the Na+ ion. The la rgest ratio of peak height between the absorbance of carboxylate (1570 cm(-1)) and of amide II (1546 cm(-1)) of spores after pretreatment wi th 0.3% sodium bicarbonate reflects the biggest structural alterations of keratin-like proteins in the spore. The role of NaHCO3 in enhancin g the sporicidal effect of glutaraldehyde is discussed.