This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Birkeland, S E Articles by Sørhaug, T Search for Related Content PubMed PubMed Citation Articles by Birkeland, S E Articles by Sørhaug, T Agricola Articles by Birkeland, S E Articles by Sørhaug, T

 Previous Article  |  Next Article 

Appl Environ Microbiol. 1985 February; 49(2): 382-387

Quantitative studies of heat-stable proteinase from Pseudomonas fluorescens P1 by the enzyme-linked immunosorbent assay.

S E Birkeland, L Stepaniak and T Sørhaug

ABSTRACT

Pseudomonas fluorescens P1 is a psychrotrophic bacterium isolated from milk. Proteinase P1, the main extracellular heat-stable proteinase fraction of P. fluorescens P1, has been purified to homogeneity. A procedure with a sandwich enzyme-linked immunosorbent assay, using microplates and alkaline phosphatase conjugate was shown to detect 0.25 ng of proteinase P1 in 1 ml of reconstituted skim milk or defatted cream. The method offers the combination of sensitivity and specificity for the detection of these enzymes in milk and dairy products. In reconstituted skim milk cultures proteinase P1 was detectable when the CFU approached 10(7)/ml. Cultures in milk diluted 1:10, 1:30, or 1:100 with water showed detectable proteinase at population densities close to 10(6) CFU/ml. Aeration stimulated proteinase production; thus, a skim milk culture with shaking at 5 degrees C had a proteinase level of 36,000 ng/ml after 7 days as compared to 80 ng/ml in a stationary culture. The rate of inactivation of proteinase P1 at 150 and 55 degrees C as expressed by residual antigenic activity determined by the enzyme-linked immunosorbent assay was somewhat different from the rate determined on the basis of residual proteolytic activity. The specificity of the enzyme-linked immunosorbent assay with proteinase P1 antibodies was identical for proteinase P1 and for enzymes from six other strains of P. fluorescens, one Chromobacterium strain, and one Flavobacterium strain. Some psychrotrophic strains produced immunologically unrelated proteinase(s). These preliminary observations indicate that proteinase P1-related enzymes are common among psychrotrophs appearing as spoilage bacteria in milk.

---

Appl Environ Microbiol. 1985 February; 49(2): 382-387

This article has been cited by other articles:

• Lopez-Fandino, R., Olano, A. (1999). Review: Selected indicators of the quality of thermal processed milk / Revision: Indicadores seleccionados para el control de calidad de la leche tratada termicamente. Food Science and Technology International 5: 121-137 [Abstract]