Viability of the R, S and M variants of Mycobacterium lacticolum under various preservation conditions

The survival rate of Mycobacterium lacticolum and the proportion between its R, S and M variants were studied in the course of 12 months under different conditions of storage (freeze-drying, under vaseline oil, in 0.85% NaCl solution and in distilled water). A high survival rate of the variants was found in cells freeze-dried in a protective medium containing 10% of sucrose +1% of gelatin as well as in a 0.85% solution of NaCl.The survival rate of te variants differed by 2--3 orders of magnitude in cells freeze-dried with sodium glutamate or suspended in distilled water. The proportion between the R, S and M variants in the population noticeable changed after storage under these conditions.     

Spore formation by Bacillus polymyxa during the inhibition of polymyxin biosynthesis

When amino acids are added to the culture of Bacillus polymyxa growing under the conditions of active spore formation, the rate of polymyxin biosynthesis and the quantity of spores being formed decrease. All cells in the population start to produce spores under these conditions, but only some of them pass through all of the differentiation stages. Most of the cells remain in the state of prospores. Some cells which have started to differentiate are characterized by ultrastructural anomalies, do not form prospores and undergo early lysis.     

Nisin adsorption on silica adsorbents

It has been shown that silica adsorbents can be used for adsorption of nizin from solutions obtained after centrifugation of the fermentation broth. The optimal structure of the adsorbent pores has been determined. Silica with pores 50 to 75 nm in size provided the highest adsorption rates. The value of silica adsorption of nizin depended on the medium pH. The maximum adsorption rates were observed at pH 6.5--7. At pH 3.5 the level of nizin adsorption was low.     

Detoxification of ochratoxin A,a food contaminant: Prevention of growth of Aspergillus ochraceus and its production of ochratoxin A

The toxicity of ochratoxin A (OTA), a mycotoxin produced by fungi ofAspergillus orPenicillium genera is now well documented. Its nephrotoxicity, immunosuppression, teratogenicity, and carcinogenicity have been widely studied. Physical and biochemical methods have been studied to prevent these toxinogenicAspergillus andPenicillium from producing OTA, and/or to destroy the mycotoxin when already produced in a liquid or a solid medium. Repeated freezing at ? 20?C and thawing at + 26?C aleatory reduce OTA production in a liquid medium. Exposure to UV B for different periods of time is efficient in preventing OTA production in a liquid medium. Gamma-irradiation from 2 to 5 kGy gives good results in preventing the production of OTA or destroying it when already produced. Carboxypeptidase is very efficient at 5 units/50 ml in a liquid medium for cleaving the OTA already produced.     

Use of adsorbents for optimizing the process of isolating nisin from the culture broth

The results of the study on optimization of the process of nisin isolation from the cultural liquid are presented. Different adsorbents, streptococcal cells, medium solid particles (biomass fermentalysates) and silica gel, were used for antibiotic adsorption.     

Molecular complexes of amino acids with porphyrins as possible precursors of pigment-protein systems

The present communication gives experimental results of the studies of catalytic and photochemical properties of peptide-like compounds containing metalloporphyrins (hemoproteinoids and molecular complexes obtained through adsorption of porphyrins and amino acids on volcanic ash). The data suggest that molecular complexes of amino acids with porphyrins could have evolved in the course of chemical evolution and were intermediated between abiogenically synthesized molecules of amino acids and porphyrins and pigment-protein systems of living organisms.