No abstract

The partial nucleotide sequence of a Lactococcus lactis subsp. lactis ADRIA 85L030 bacteriocin-producing operon was determined. The first two open reading frames of the operon are necessary to get bacteriocin expression in L. lactis IL1403R.

The problem of the incomplete assimilation of prolineby brewing yeasts has been approached by studying growth on synthetic media under various conditions, by examining a catabolic reaction which could explain non-degradation under anaerobic conditions and by following the penetration of L-"C proline into the yeast cells.Demonstrations have been made that proline oxidase, the enzyme responsible for the first catabolic reaction of L-proline, requires the participation of cytochrome c to operate and therefore needs the presence of molecular oxygen, and that the permease responsible for the transport of proline is, under normal brewery condi tions, repressed by other amino acids of wort. Permease derepression, which should normally occur after the complete consumption of the other amino acids, is made impossible because of the strong anaerobic conditions achieved at that stage.

The chromosomal DNA of a number of strains of the lactic acid bacterium Streptococcus thermophilus was analysed with the aim of rapidly differentiating and assessing the characteristics of each strain. Pulsed‐field gel electrophoresis was used to separate large DNA fragments formed by the restriction enzymes SmaI, SfiI or ApaI. Hybridization with a non‐radioactive DNA probe confirmed the identification of strains as Strep. thermophilus and analysis of the electrophoretic patterns differentiated some strains from others. A more extensive study of the pulsed‐field electrophoresis restriction patterns of new isolates of Strep. thermophilus may facilitate assessment of their technological properties by comparison of their restriction patterns with those of reference strains.