Low temperature as an environmental stress on microbial enzymes

The production of industrial enzymes

This paper reviews the essential features and current techniques used on an industrial scale in the preparation of partly purified or ‘bulk’ enzymes, as opposed to highly purified enzymes for analytical or diagnostic use, which are covered elsewhere in this volume. Industrial enzymes may be derived from a wide variety of plant, animal or microbial sources, although most production processes rely on the last of these. Microbial enzymes are either extracellular, such as the proteases and carbohydrates, which account for a large proportion of total sales, or intracellular, such as glucose oxidase. Intracellular enzymes usually remain associated with the cell and therefore have to be released, unless the microorganism itself is used as the catalyst. Although specific fermentation procedures adopted by manufacturers vary to a degree, there remain only two principal methods of cultivation, i.e. solid-state and submerged fermentation. Most microbial enzymes are produced by aerobic submerged fermentation, which allows greater control of growth factors than solid-state methods. The recovery and purification techniques discussed are typical of those used for fermentation enzymes, although they may be applied, generally, to most extraction and refining operations irrespective of whether the enzyme source is of plant, animal or microbial origin. In particular the following processes are covered; cell disruption, precipitation and solid-liquid separation including concentration by ultrafiltration. It is shown how, by using a combination of these techniques at different stages in the recovery process, it is possible to produce a complete range of product specifications.

Growth inhibition of oral streptococci in saliva by anionic proteins from two caries-free individuals

Mixed saliva from two caries-free individuals possessed antimicrobial activity toward Streptococcus mutans and S. sanguis. This inhibitory activity was attributed to the presence of a group of four anionic proteins each of which strongly inhibited the growth of the oral streptococci in a saliva protein-based medium but not in a medium containing amino acids as a nitrogen source. These proteins, with isoelectric points of 4.70, 4.90, 4.98, and 5.05, respectively, neither reacted with antisera to immunoglobulin A, G, or M nor appeared to be functionally related to a number of salivary peroxidases, lactoferrin, or lysozyme. On this basis, they may represent a previously unreported group of growth-inhibitory antimicrobial factors occurring in the saliva of some individuals.

Hydrolysis of α s, 1 -Casein B by Streptococcus lactis Membrane Proteinase

The membrane-associated proteinase of Streptococcus lactis strain 3 hydrolyzed α s, 1 -casein B into 11 peptide fragments. Eight of the 11 peptides were purified and partially characterized. Each peptide contained several, but not all six, essential amino acids required for growth. The culture was able to utilize one peptide as the sole source for the essential amino acid leucine. Leucine, serine, valine, and glycine were found to be NH 2 -terminal residues. Two of the peptides were phosphopeptides. The data support the functional role of the membrane-associated proteinase as being involved in the initial breakdown of proteins to peptides.