Lipolytic and proteolytic activity of yeasts isolated from fish

Abstract EN

This study was undertaken to determine lipolytic and proteolytic yeast count in 50 random samples of fish collected from different places at sharkia governorate.

proteolytic activity was determined by using caseinate agar and lipolytic activity was determined by using plate count agar accompanied with tributyrin.

the identification of the isolated yeasts was performed by a procedure which included two phases involved in the master key of simplified identification method (SIM).

the mean values of total yeast count of fresh tilapia nilotica and frozen fishes of Pagellus acarne, Trachurus indicus, Lutjanus and Atherina, were 3.76 ± 0.18, 4.19 ± 0.19, 2.49 ± 0.30, 4.67 ± 0.25 and 5.62 ± .016 log10cfu / g, respectively.

the mean values of proteolytic yeast counts of fresh tilapia nilotica and frozen fishes of pagellus acarne, trachurus indicus, lutjanus and atherina, were 3.73 ± 0.31, 4.20 ± 0.01, 2.51 ± 0.34, 4.59 ± 0.22 and 4.59 ± 0.24 log10cfu /g, respectively.

the mean values of lipolytic log yeast counts of fresh Tilapia nilotica and frozen fishes of Pagellus acarne, Trachurus indicus, Lutjanus and Atherina, were 4.44 ± 0.13, 4.20 ± 0.01, 2.96 ± 0.21, 5.03 ± 0.11 and 4.92 ± 0.23 log10cfu / g, respectively.

four yeast genera could be identified including candida, cryptococcus, trichosporon, rhodotorula.

the results determined that C.glabrata showed both proteolytic and lipolytic activities while C.tropicalis and rhodotorula glutinis showed lipolytic activity and Cryptococcus and trichosporon showed proteolytic activity.

from the results of the present study, it can be concluded that yeast contamination of fish can lead to fish spoilage due to their lipolytic and proteolytic activities which characterized by off-odors, off-flavors and slime formation so consequently control of yeast growth in fish is necessary.