title: Synthesis of Extracellular Proteinase by Pseudomonas fluorescens Under Conditions of Limiting Carbon, Nitrogen, and Phosphate.
abstract: The influence of carbon, nitrogen, and phosphate concentrations on growth and proteinase production by Pseudomonas fluorescens 32A was examined. In mineral salts medium containing dialyzed skim milk supernatant as an inducer, maximum growth was obtained at 1.0 and 2.5 mM orthophosphate at 20 and 5 degrees C, respectively. At both temperatures, 5 mM orthophosphate was required for maximum proteinase production, whereas significant inhibition was found at 10 mM. Orthophosphate was the only phosphate compound able to support growth. With sodium pyruvate as the carbon source, maximum enzyme synthesis was at 100 mM carbon at both temperatures. At both 20 and 5 degrees C maximum growth and enzyme production was found with 10 mM NH(4)Cl. A bioassay for available phosphate based on the growth of P. fluorescens 32A in phosphate-limited mineral salts medium showed that skim milk and skim milk supernatant contained 50 and 10 mM orthophosphate, respectively. Proteinase production in skim milk was 2.6- and 12-fold greater than that in optimal mineral salts medium at 20 and 5 degrees C, respectively. These results suggest that proteinase production in milk does not occur as a result of nutrient limitation and may be regulated in part by milk phosphates.
authors.affiliation: Food Research Institute, Agriculture Canada, Research Branch, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6.
authors.forename: R C
authors.initials: RC
authors.lastname: McKellar
authors.forename: H
authors.initials: H
authors.lastname: Cholette