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...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 ℃.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 ℃ 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-molecu-lar-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.展开更多
This research focused using novel substrate, longan Lactobacillus casei subsp, rhamnosus TISTR 108. The optimum juice as carbon source for continuous lactic acid production by medium for lactic acid production was pur...This research focused using novel substrate, longan Lactobacillus casei subsp, rhamnosus TISTR 108. The optimum juice as carbon source for continuous lactic acid production by medium for lactic acid production was pure longan juice with 120 g/L sugar concentration and among the different nitrogen sources were added to the longan juice （yeast extract, tryptic soy, urea, （NH4）2SO4 and NaNO3）, yeast extract had the most efficiency. Yeast extract （10 g/L） without adding minerals to longan juice could produced the maximum lactic acid concentration of 38.91 ± 0.190 g/L in 60 h and the yield of 0.460± 0.122 g/g with the productivity of 0.649± 0.002 g/Lh in 2 liters flask. Batch fermentation was conducted in 2 liters fermentor and 41.38± 0.030 g/L lactic acid was produced in 48 h with the yield of 0.398 ± 0.215 g/g and the productivity was 0.862 ± 0.001 g/L h. The continuous fermentation using 2 liters fermentor as a high productivity for lactic acid （1.091 ± 0.001 g/L h） was achieved at dilution rate （D） of 0.0685 h-1.展开更多
基金supported by the National High Technology Research and Development Program of China (2006AA09Z403)the National Natural Science Foundation of China (30771645)
文摘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 ℃.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 ℃ 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-molecu-lar-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.
文摘This research focused using novel substrate, longan Lactobacillus casei subsp, rhamnosus TISTR 108. The optimum juice as carbon source for continuous lactic acid production by medium for lactic acid production was pure longan juice with 120 g/L sugar concentration and among the different nitrogen sources were added to the longan juice （yeast extract, tryptic soy, urea, （NH4）2SO4 and NaNO3）, yeast extract had the most efficiency. Yeast extract （10 g/L） without adding minerals to longan juice could produced the maximum lactic acid concentration of 38.91 ± 0.190 g/L in 60 h and the yield of 0.460± 0.122 g/g with the productivity of 0.649± 0.002 g/Lh in 2 liters flask. Batch fermentation was conducted in 2 liters fermentor and 41.38± 0.030 g/L lactic acid was produced in 48 h with the yield of 0.398 ± 0.215 g/g and the productivity was 0.862 ± 0.001 g/L h. The continuous fermentation using 2 liters fermentor as a high productivity for lactic acid （1.091 ± 0.001 g/L h） was achieved at dilution rate （D） of 0.0685 h-1.
