Meat starters have individual requirements for Mn(2+).

The effect of different Mn(2+) concentrations on sausage fermentation was evaluated. A screening experiment was carried out with six lactobacilli starters in a sausage model. To further investigate the effects found, two selected lactobacilli strains were tested in pilot-scale sausage production. For all starters an increased fermentation rate was observed after Mn(2+) addition. Differences in the development of microbial, textural and sensory parameters were observed in the sausages. For one of the cultures these differences levelled out during sausage production yielding identical end products with and without Mn(2+), for the other strain the differences due to Mn(2+) addition in the sausages remained throughout the production process yielding sausages with different properties. Knowing a starter culture's requirements for Mn(2+) will allow optimisation of dry fermented sausage production in order to increase reliability and reproducibility of production decrease fermentation time and ensure microbial safety of the final product.

Accelerated production of dry fermented sausage.

The scope of this paper is to review work connected with accelerated ripening of dry fermented sausages by addition of proteolytic enzymes. An overview of the following topics is given: practical sausage experiments with addition of various proteinases of bacterial origin, including data from sensory, biochemical and gc/ms analyses; biochemical and genetic characterization of the enzyme shown to be most useful in these experiments, the serine proteinase from Lactobacillus paracasei subsp. paracasei NCDO 151; experiments to transform starter cultures with the genes for production of this proteinase and proposals for future work in this field.

Cloning, sequencing and expression of the gene encoding the cell-envelope-associated proteinase from Lactobacillus paracasei subsp. paracasei NCDO 151.

The gene encoding the cell-envelope-associated proteinase of Lactobacillus paracasei subsp. paracasei NCDO 151 (formerly Lactobacillus casei NCDO 151) was cloned and sequenced. The gene was located on the chromosome and encoded a polypeptide of 1902 amino acids. The proteinase is N-terminally cleaved upon maturation. It shows extensive homology to the Lactococcus lactis subsp. cremoris Wg2 proteinase. Similar to the situation in Lactococcus, a maturation gene was found upstream of the proteinase gene. The cloned proteinase gene was expressed in Lactobacillus plantarum. However, no expression was observed when the gene was cloned in Lactococcus lactis.

Purification and N-terminal amino acid sequence determination of the cell-wall-bound proteinase from Lactobacillus paracasei subsp. paracasei.

The cell-wall-bound proteinase from Lactobacillus paracasei subsp. paracasei NCDO 151 was purified to homogeneity by anion-exchange and hydrophobic-interaction chromatography, chromatofocusing and gel-filtration. The purification resulted in a 600-700-fold increase in specific activity of the proteinase and the final yield was approximately 20%. Upon chromatofocusing, two proteolytically active components, termed pro135 and pro110, were detected. pro135 had an isoelectric point of 4.2. It had an Mr of about 300,000 as determined by gel-filtration and 135,000 as judged by SDS-PAGE, indicating that it may exist as a dimer in its native state. pro110 had an isoelectric point of 4.4, and an Mr of about 150,000 as determined by gel-filtration and 110,000 as judged by SDS-PAGE. pro110 appears to be a degradation product of pro135 as they have the same N-terminal amino acid sequence. The first N-terminal amino acid was ambiguous for both components, whereas the sequence from the second to the ninth amino acid was Ala-Lys-Ala-Asn-Ser-Met-Ala-Asn. This is identical to the corresponding sequence of the lactococcal cell-wall-bound proteinases. Although the Lactobacillus proteinase was a little smaller than the lactococcal proteinase, their purification characteristics were very similar, suggesting that these proteinases are related.

Effect of Photon Fluence Rate and Specific Growth Rate on Geosmin Production of the Cyanobacterium Oscillatoria brevis (Kütz.) Gom.

The production of geosmin from the cyanobacterium Oscillatoria brevis was studied as a function of the photon fluence rate and appears to be related to the chlorophyll content.