Catabolism of arginine byCarnobacterium spp. isolated from vacuum-packed sugar-salted fish

The ability ofCarnobacterium spp. originally isolated from vacuum-packed, sugar-salted fish to catabolize arginine was examined. All strains were able to produce citrulline, ornithine, and NH₃ from arginine, presumably by the arginine deiminase pathway. The metabolism of arginine was concurrent with acid production from glucose for one strain ofCarnobacterium sp. but delayed for one strain ofCarnobacterium piscicola. The arginine catabolism was not inhibited in the presence of 2% glucose for three strains of carnobacteria during growth in test broth and/or shrimp extract. Growth as well as arginine catabolism was delayed for two strains of carnobacteria by lowering the temperature from 9°C to 4°C. A similar result was obtained by incubating one strain ofC. piscicola in CO₂. None of the compoundsl-citrulline,l-ornithine hydrochloride, and (NH₄)₂SO₄ had any effect on growth or arginine catabolism of this strain. Neither did pH of the medium affect the time for initiation of arginine catabolism.     

Production of a heterologous proteinase A by Saccharomyces kluyveri

In order to evaluate the potential of Saccharomyces kluyveri for heterologous protein production, S. kluyveri Y159 was transformed with a S. cerevisiae-based multi-copy plasmid containing the S. cerevisiae PEP4 gene, which encodes proteinase A, under the control of its native promoter. As a reference, S. cerevisiae CEN.PK 113-5D was transformed with the same plasmid and the two strains were characterised in batch cultivations on glucose. The glucose metabolism was found to be less fermentative in S. kluyveri than in S. cerevisiae. The yield of ethanol on glucose was 0.11 g/g in S. kluyveri, compared to a yield of 0.40 g/g in S. cerevisiae. Overexpression of PEP4 led to the secretion of active proteinase A in both S. kluyveri and S. cerevisiae. The yield of active proteinase A during growth on glucose was found to be 3.6-fold higher in S. kluyveri than in the S. cerevisiae reference strain.