Proteolytic Activity of Microorganisms Isolated from Freshwater Fish

Abstract

A raw fish-juice was prepared and sterilized through the use of ttCo y-irradiation. It was evaluated for suitability in an agar medium for testing the proteolytic activity of bacteria isolated from fish. Microorganism proteolytic activity was also detected by conventional methods with skim milk-agar. We tested 1,145 isolates from fresh and spoiling irradiated (0.0, 0.3, and 0.6 Mrad) yellow perch fillets for proteolytic activity, by the use of both media. Most isolates that showed proteolytic activity exhibited this activity in both media. A few isolates showed proteolytic activity only in one medium or the other. Proteolysis was found mainly among bacteria isolated from nonirradiated perch fillets. Nonproteolytic organisms were slightly more abundant than were proteolytic ones throughout refrigerated storage (6 days); the latter constituted 48% of the total organisms. Irradiation eliminated essentially all proteolytic bacteria when the fillets were stored at 1 C. However, some proteolytic bacteria survived for a few days after irradiation when the fillets were stored at 5 C.

Phylogenetic and Functional Characterization of Culturable Endophytic Actinobacteria Associated With Camellia spp. for Growth Promotion in Commercial Tea Cultivars

“…For detection of proteolytic activity, the actinobacteria isolates were spot inoculated on skim milk agar media plates comprising of (per liter) 2.5 g yeast extract, 1 g glucose, 5 g pancreatic digest of casein, 28 g skim milk powder and 15 g agar, followed by incubation at 28 • C for 7 days. Positive isolates were confirmed by the presence of clear areas around the actinobacteria colony (Kazanas, 1968). Cellulase and pectinase activity was tested by spot inoculation of actinobacteria isolates on M9 minimal salt medium consisting of (per liter) 33.9 g Na 2 HPO 4 , 15 g KH 2 PO 4 , 2.5 g NaCl, 5 g NH 4 Cl, 15 g agar, 1.2 g yeast extract.…”

Variations in the microbial log reduction curves of irradiated cod fillets, shrimp, and their respective homogenates

“…The relatively high radiation susceptibility of pseudomonads is adequately documented (6, 7, 10, 11). Additionally, the role of pseudomonads as the principal spoilage microorganisms in fresh fish has also been adequately documented (1,6,10). It might then be concluded from Fig.…”

Combination of rosemary extract and buffered vinegar inhibits Pseudomonas and Shewanella growth in common carp (Cyprinus carpio)

“…24 Proteolytic activity was seen as a clearance halo around bacterial growth on milk agar. 25 Production of H 2 S was evaluated as colony blackening on iron agar. 26 To assess inhibitory effect on spoilage potential, these agar plates with additives at the selected concentrations were prepared.…”