NITRITE FORMATION IN THE THIN JUICE BY TH ERMUS SPECIES

High concentrations of nitrite in molasses of an Austrian sugar factor y gave a rise to a systematic survey in order to identify location and cause of the formation of nitrite. The high levels could only partial ly be explained by microbial reduction of nitrate in the diffusion pla nt. It turned out that the critical rise of nitrite occurred during th e passage of thin juice through a newly installed softening plant. Car eful inspection of the plant revealed massive bacterial films on the g ravel bed of the ion exchange columns, although the temperature of the thin juice in the exchange columns had been kept at 80 degrees C, thu s exceeding the temperature tolerance limit of thermophilic, sporulati ng bacteria. However, cultivation of the mixed population of isolated bacteria in the laboratory confirmed their ability to reduce nitrate a t 80 degrees C. Upon growth in single cell colonies and both physiolog ical and microscopical examination their affiliation to the genus Ther mus was shown, which represents an extremely thermophilic, non-sporula ting group of Gram-negative bacteria. These results mean that in sugar factories bacterial activity has to be taken into account also in suc h sectors which hitherto have been regarded as non-critical.