title: Comparison of the growth kinetics and proteolytic activities of Chryseobacterium species and Pseudomonas fluorescens.
abstract: The effect of temperature on the growth kinetics and proteolytic activity of Chryseobacterium joostei and Chryseobacterium bovis was determined during this study. The results were compared with the activities of Pseudomonas fluorescens, which is regarded to be a major food spoilage psychrotolerant microorganism. For the growth studies, cultures were incubated in nutrient broth in a temperature gradient incubator (from 9 to 50 °C) and separately at 4 °C, and the optical density was measured at different time intervals. Growth temperature profiles for each organism were constructed. For determination of proteolytic activity, the cultures were incubated in fat-free ultra-high temperature processed milk in the temperature gradient incubator for 72 h (temperature range as above). Cell-free extracts were used to determine the proteolytic activity using the azocasein method. Results of the growth studies showed that C. joostei had the ability to grow over a wider temperature range than C. bovis and P. fluorescens without being affected by changes in the temperature. For the proteolytic activity, C. joostei had significantly (p < 0.001) higher activity per milligram of protein at 15.5 °C, followed by C. bovis and P. fluorescens. The results showed that C. joostei potentially has an even greater spoilage capacity in milk on the basis of growth rate and proteolytic activity than did P. fluorescens.
authors.affiliation: a Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Bekker
authors.affiliation: a Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: L
authors.initials: L
authors.lastname: Steyn
authors.affiliation: a Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: G
authors.initials: G
authors.lastname: Charimba
authors.affiliation: b Department of Biotechnology and Food Technology, Tshwane University of Technology, Pretoria, South Africa.
authors.forename: P
authors.initials: P
authors.lastname: Jooste
authors.affiliation: a Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: C
authors.initials: C
authors.lastname: Hugo
mesh_terms: D000818:Animals; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D045247:Chryseobacterium / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D007700:Kinetics; D008892:Milk / Q000378:metabolism / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D013696:Temperature
chemical_list: D002364:Caseins; C026018:azocasein
keywords: Chryseobacterium; Pseudomonas; activité protéolytique; cinétique de croissance; growth kinetics; proteolytic activity; temperature; température