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The marine yeast strain W6b isolated from sediment of the South China Sea was found to produce a cell-bound acid protease.
The crude acid protease produced by this marine yeast showed the highest activity at pH 3.5 and 40 °C. The optimal pH and
temperature for the crude acid protease were in agreement with those for acid protease produced by the terrestrial yeasts.
The optimal medium of the acid protease production was seawater containing 1.0% glucose, 1.5% casein, and 0.5% yeast extract,
and the optimal cultivation conditions of the acid protease production were pH 4.0, a temperature of 25 °C and a shaking speed
of 140 rmin−1. Under the optimal conditions, 72.5 UmL−1 of acid protease activity could be obtained in cell suspension within 48 h of fermentation at shake flask level. The acid
protease production was induced by high-molecular-weight nitrogen sources and repressed by low-molecular-weight nitrogen sources.
Skimmed-milk-clotting test showed that the crude acid protease from the cell suspension of the yeast W6b had high skimmed
milk coagulability. The acid protease produced by M. reukaufii W6b may have highly potential applications in cheese, food and fermentation industries. 相似文献
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Viable cell count was used to determine whether Metschnikowia sp.C14 can colonize the intestine of juvenile sea cucumber Apostichopus japonicus.Sea cucumber individuals were divided into two groups,which were fed the control diet for 38 days or the C14-supplemented diet at 105 cells g−1 diet for 28 days,then the control diet from day 29 to day 38.The number of C14 cells in the intestine of sea cucumber fed the C14-supplemented diet significantly increased from day 7 to day 28,and decreased from day 29 to day 38.Sea cucumber fed with the diet containing C14 showed a significant increase in trypsin activity and lipase activity from day 21 to day 33 compared with the control.Feeding C14 significantly improved the phagocytic activity and respiratory burst in coelomocytes from day 21 to day 35 and from day 14 to day 38,respectively.In addition,there was an obvious enhancement in lysozyme activity(from day 21 to day 38 or day 33),phenoloxidase activity(from day 21 to day 28)and total nitric oxide synthase activity(from day 14 to day 38)in coelomic fluid supernatant and/or coelomocyte cell lysate supernatant compared with the control.There were significant positive correlations between the number of C14 cells colonizing the intestine and trypsin activity of the intestine,lysozyme activity of the coelomic fluid supernatant and coelomocyte lysate supernatant from sea cucumber.These data suggested that the number of C14 cells should be maintained at 105 cfu(colony-forming units)g−1 intestine material for the maximum benefit. 相似文献
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