Isolation And Identification Of Amylase-Producing Marine Yeasts And Partial Characterization Of Their Crude Amylases

Over three hundreds of marine yeast strains were isolated from marine environments. Eight marine yeast strains N13d, DMC, W13a, G7b, Ba, H, M and W1a were found to produce a larfe amount of amylase. N13d was screened from the samples collected in the South Pole, DMC from sediments of coastal water of Fujian Province of China, W13a and G7b from the sediments of South China Sea, Ba and M from Guts of Curier collected from Coastal water, Changdao of Yantai, H from Guts of Mackerel which was collected from Coastal water Changdao of Yantai, and W1a was screened from algae, which was collected from Changdao of Yantai.Influences of pH on amylase activity were measured under the standard condition of pH 3.0-10.0. Influences of temperature on amylase activity were measured at temperature ranges from 20℃to 80℃. Optimum pH and temperature of the crude amylases produced by DMC, W13a, G7b, Ba, H, M and W1a were 5.0 and 50℃, respectively; while optimum pH and temperature of the crude amylases produced by N13d were 4.5 and 60℃. Specific amylase activity in supernatant of the cultures was measured under the optimal conditions mentioned above, The results show that specific amylase activity from strain Ba was 96.0 U/mg,strain DMC 80.9 U/mg,strain H 256.0 U/mg,strain M 314.5 U/mg,strain W1a 189.0 U/mg,strain W13a 707.0 U/mg,strain G7b 984.0 U/mg, strain N13d 1282.0 U/mg.According to results of carbon assimilation, fermentation and molecular identification, it was found that strains Ba,H,M and W1a belonged to Yarrowia lipolytica, strain DMC belonged to Candida parapsilosis, strains W13a,G7b and N13d belonged to Aureobasidium pullulans.After starch hydrolysis by using the crude amylases, the results show that only glucose was released from raw potato starch, gelatinized potato starch and gelatinized soluble starch. These results strongly suggest that the amylases produced by the marine yeasts was glucoamylase with cleavage activity on bothα-1,4 andα-1,6-glycoside linkages in starch molecules.To date, it has been noticed that the terrestrial yeasts which can produce extracellular amylolytic enzymes include Arxula adeninivorans, Lipomyces, Saccharomycopsis, Schwanniomyces, Candida japonica and Filobasidium capsuligenum. This research found Yarrowia lipolytica, Candida parapsilosis and Aureobasidium pullulans of marine yeasts are amylae-producing yeasts.