Optimum production and characterization of an acid protease from marine yeast <Emphasis Type="Italic">Metschnikowia reukaufii</Emphasis> W6b |
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| Authors: | Jing Li Ying Peng Xianghong Wang Zhenming Chi |
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| Institution: | UNESCO Chinese Center of Marine Biotechnology,Ocean University of China,Qingdao 266003,P.R.China |
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| Abstract: | 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. |
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| Keywords: | acid protease marine yeasts Metschnikowia reukaufii milk coagulability |
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