Hydrogen peroxide bacterial culture

Small amounts of hydrogen peroxide in raw milk can activate the lactoperoxidase-catalyzed oxidation of thiocyanate to produce a bacterial inhibitor (Hogg and Jago 1970). Inhibitory compounds resulting from oxygen metabolism can produce initially slow starter culture growth in industrial dairy fermentations if the milk has been excessively agitated. 

Detoxification. The process by which bacterial toxins are converted to harmless toxoids. Formaldehyde is used to detoxify the toxins of Corynebacterium diphtheriae, Clostridium botu-linum and Cl. tetani. The detoxification may be performed either on the whole culture in the fermenter or on the purified toxin after fractionation. Traditionally the former approach has been adopted, as it is much safer for the operator. However, the latter gives a purer product. The pertussis toxin used in acellular vaccines may be detoxified with formaldehyde, glutaraldehyde, or both, hydrogen peroxide or tetranitromethane. In the case of genetically detoxified pertussis toxin, a treatment with a low concentration of formaldehyde is still performed to stabilize the protein. 

Suflita, J. M., L. N. Liang, and A. Saxena. 1989. The anaerobic biodegradation of o-, m-, and p-cresol by sulfate-reducing bacterial enrichment cultures obtained from a shallow anoxic aquifer. J. Ind. Microbiol. 4(4) 255-66. Sundstrom, D. W., B. A. Weir, and H. E. Klei. 1989. Destruction of aromatic pollutants by UV light catalyzed oxidation with hydrogen peroxide. Environ. Prog. S(l) 6-11. 

The SCEM technique was proved applicable for investigating the interaction of different bacteria strains in mixed culture biofilms. In a recent study of Bard s group [146] the distribution of bacterial produced hydrogen peroxide concentration was determined using SECM line scans over specially grown biofilms. In these experiments gold disc electrode with 25 pm diameter was used as measuring tip. 

For the experiments biofilm from separately grown Sp and Aa strains was made on polycarbonate membrane. First the Sp biofilm was spread on the membrane and after a spot of the Aa culture was added. In this way a 25 pm diameter bacterial biofilm of Sg with a spot of 5-7 pm Aa in the middle was obtained as substrate for SECM studies. Two different strains of Aa were used - the Y4 and the Y4-katA -containing an insertion mutant of the catalase-encoding gene katA. It is Aa with higher tolerance to hydrogen peroxide toxicity. 

---