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
Traditionally, coconut dregs will be used as animal feed after the extraction of coconut oil and coconut milk from the copra. This study was carried out to discover the commercial value of coconut dregs as a solid sub...Traditionally, coconut dregs will be used as animal feed after the extraction of coconut oil and coconut milk from the copra. This study was carried out to discover the commercial value of coconut dregs as a solid substrate in the production of amylase through solid state fermentation （SSF） since this agro-waste is fairly rich in nutrients, providing the necessary nutrients supplementation for better microbial activity to produce enzymes. In this study, amylase is to be produced from coconut dregs by Aspergillus niger through solid state fermentation （SSF）. Three parameters were covered, which are incubation time, initial moisture content of substrate and inoculum sizes. SSF was carried out by using incubator at 37 ~C to test for enzyme activity at these following parameters： incubation time： 24, 48, 72, 96 and 120 hours; substrate moisture content： 64, 66, 68, 70 and 72% （w/w）; inoculum sizes： 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mL spore suspension （5.5 × 10^6 spores/mL）. Enzyme activities were measured through the estimation of liberated reducing sugars after the assay of amylase enzyme by using DNS （3, 5 dinitrosalicylic acid） method. Highest enzyme activities were obtained at these following parameters： incubation time： 72 hours （31.76 U/gds）; initial moisture content ofsubstrate： 66% （26.66 U / gds） and inoculum sizes： 2.0 mL （30.56 U/gds）.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Traditionally, coconut dregs will be used as animal feed after the extraction of coconut oil and coconut milk from the copra. This study was carried out to discover the commercial value of coconut dregs as a solid substrate in the production of amylase through solid state fermentation （SSF） since this agro-waste is fairly rich in nutrients, providing the necessary nutrients supplementation for better microbial activity to produce enzymes. In this study, amylase is to be produced from coconut dregs by Aspergillus niger through solid state fermentation （SSF）. Three parameters were covered, which are incubation time, initial moisture content of substrate and inoculum sizes. SSF was carried out by using incubator at 37 ~C to test for enzyme activity at these following parameters： incubation time： 24, 48, 72, 96 and 120 hours; substrate moisture content： 64, 66, 68, 70 and 72% （w/w）; inoculum sizes： 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mL spore suspension （5.5 × 10^6 spores/mL）. Enzyme activities were measured through the estimation of liberated reducing sugars after the assay of amylase enzyme by using DNS （3, 5 dinitrosalicylic acid） method. Highest enzyme activities were obtained at these following parameters： incubation time： 72 hours （31.76 U/gds）; initial moisture content ofsubstrate： 66% （26.66 U / gds） and inoculum sizes： 2.0 mL （30.56 U/gds）.
