Yeast culture is a kind of green feed additive. It has been researched and applied widely in the feed industry. In this paper, the functions of yeast culture and its application in the actual production were discussed...Yeast culture is a kind of green feed additive. It has been researched and applied widely in the feed industry. In this paper, the functions of yeast culture and its application in the actual production were discussed. It can be concluded that yeast culture has a great application prospect.展开更多
In this paper, the Sb2O3 nanoparticles prepared with SbCl3 by the alky hydrolysis, processed with the surfactants, were assembled on mica substrates. The morphology and the assembled behavior of the nano-Sb2O3 on the ...In this paper, the Sb2O3 nanoparticles prepared with SbCl3 by the alky hydrolysis, processed with the surfactants, were assembled on mica substrates. The morphology and the assembled behavior of the nano-Sb2O3 on the mica were analyzed by means of TEM. The flame retardant properties of nano-Sb2O3 and Sb2O3/mica complex were studied by combustion test and thermal analysis. The results show that the Sb2O3 nanoparticles are assembled uniformly on the mica substrates. The nano-Sb2O3 was characterized with small size, narrow size distribution, uniform crystal and monodispersed particles. Compared with nano-Sb2O3, the Sb2O3/mica complexes have been achieved the same coordinated effects with Chlorinated Paraffin(CP) and excellent flame retardant properties.展开更多
High-level expression ofβ-mannanase has been reported in Pichia pastoris under control of the GAP promoter.Two factors that strongly influence protein production and fermentation process development in Pichia pastori...High-level expression ofβ-mannanase has been reported in Pichia pastoris under control of the GAP promoter.Two factors that strongly influence protein production and fermentation process development in Pichia pastoris protein expression system are gene dosage and cultivation temperature.The aim of this research was to improve the expression level ofβ-mannanase in Pichia pastoris by proper increasing the gene dosage and decreasing the culture temperature.To this end,a panel of strains harboring different copy numbers ofβ-mannanase gene were obtained by multiple zeocin concentration gradients screening,the influence of gene copy number on the expression ofβ-mannanase in Pichia pastoris X33 was investigated.With the constitutive GAP promoter,the four copies strain exhibited a 4.04-fold higherβ-mannanase yield and a 1.83-fold higher total secretion proteins than the one copy strain,but an increase of the copy number above four resulted in a decrease of expression.Furthermore,the effects of culture temperature were studied in flask.The decreased culture temperature of four copies strain resulted in a 1.8-fold(26℃)and 3.5-fold(22℃)higherβ-mannanase activity compared to that at 30℃.A fed-batch strategy was successfully used for high cell-density fermentation andβ-mannanase activity reached 2124 U/mL after cultivation for 72 h in a 5 L fermenter.展开更多
The stability of Candida rugosa lipase coated with glutamic acid didodecyl ester ribitol amide was investigated taking esterification of lauryl alcohol and lauric acid in isooctane as a model reaction. At 30C, the hal...The stability of Candida rugosa lipase coated with glutamic acid didodecyl ester ribitol amide was investigated taking esterification of lauryl alcohol and lauric acid in isooctane as a model reaction. At 30C, the half-life of the activity of the coated lipase was ca 10 h, the enzyme activity became less changed after 12 h and the residual activity was 39% of the initial value. The coated lipase obeyed a first-order deactivation model with a deactivation energy of 29.9J.mol-1.展开更多
In this study, X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) together with Scanning probe microscopy (SPM) were used to characterize the structure and morphology of the complexes, where...In this study, X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) together with Scanning probe microscopy (SPM) were used to characterize the structure and morphology of the complexes, where the hydrobiotites (Xinfiang) were modified by single-chain surfactants octyltrimethylammonium bromide (OTMA) and octadecyltrimethylammonium bromide (ODTMA). XRD patterns showed that the structure of complexes was significantly influenced by the surfactant concentration and the alkyl chain length, because obvious changes took place in the basal spacing. Furthermore, according to the XRD results, several arrangements of surfactant molecules within the hydrobiotite interlayer space were deduced. The FTIR spectrum indicated that the surfactant contents in complexes dramatically increased with the alkyl chain length. The SPM micrographs demonstrated that the surfaces of complexes prepared at lower surfactant concentration were relatively flat compared with that prepared at higher concentration, while those with higher surfactant concentration had much steeper surface due to the alkyl chain length. It was concluded that structure and morphology of surfactant/hydrobiotite complexes depend not only on the surfactant concentration, but also strongly on the surfactant species.展开更多
The surfactant-coated Candida rugosa lipase was used as catalyst for hydrolysis of olive oil in two-phase system consisting of olive oil and phosphate buffer without organic solvent. For both the coated and native lip...The surfactant-coated Candida rugosa lipase was used as catalyst for hydrolysis of olive oil in two-phase system consisting of olive oil and phosphate buffer without organic solvent. For both the coated and native lipases,the optimal buffer/oil volume ratio of 1.0, aqueous pH 6.8 and reaction temperature 30℃ were determined. The maximum activity of the coated lipase was ca 1.3 times than that of the native lipase. The half-life of the coated lipase in olive oil and the native lipase in phosphate buffer was ca 9 h and 12 h, and the final residual activity was 27% and 20% of their initial values, respectively. The final substrate conversion by the coated lipase was ca 20% higher than that of the native lipase.展开更多
[Objective] The aim was to explore the effect of eliminated the breeding pigs with unqualified CSFV antibody on sow's reproductive performance and pig's growth performance so as to provide a scientific basis f...[Objective] The aim was to explore the effect of eliminated the breeding pigs with unqualified CSFV antibody on sow's reproductive performance and pig's growth performance so as to provide a scientific basis for the eliminating of the breeding pigs with unqualified CSFV antibody in large-scale pig farms.[Method] Serum samples from three scale pig farms were collected and tested with HerdChek CSFV-ELISA kit,then provided a certain scientific basis for scale pig farm to eliminate the unqualified(antibody blocking rate<50%)breeders after booster immunization.[Result ] After eliminating the breeding pigs with unqualified CSFV antibody,the average litter number of piglet in three pig farms(A,B,C)were increased by 0.29(P<0.05),0.40(P<0.01),0.39(P<0.01)respectively;the average number of survival piglets were increased by 0.54(P<0.01),0.35(P<0.01),0.62(P<0.01)respectively;the average litter number of weaned piglets were increased by 0.65(P<0.01),0.71(P<0.01),0.81(P<0.01)respectively.The difference in weight gain of piglet at 30-60 d of age was extremely significant(P<0.01),but inconspicuousness for the swine pregnancy rate,the survival rate of weaned piglet and piglet at 30-60 d of age.[Conclusion] The eliminating the breeding pigs with unqualified CSFV antibody can significantly improve the performance of breeder and piglets.展开更多
Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent,...Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.展开更多
Selenium protects cells from oxidative damage and reduces lipopolysaccharide (LPS)-induced expression of inflammatory cytokines. Because inflammatory cytokines induce growth depression, we hypothesized that selenium...Selenium protects cells from oxidative damage and reduces lipopolysaccharide (LPS)-induced expression of inflammatory cytokines. Because inflammatory cytokines induce growth depression, we hypothesized that selenium-rich yeast (SeY) would inhibit growth depression caused by LPS. Twenty Meishan weanling pigs [28 (s.d. 2 d), 7.6 (s.d. 0.3 kg) body weight (BW)] were used in a 2×2 factorial design (n=5). The main factors were dietary Se sources [selenium-rich yeast (SeY) vs. sodium selenite (SSe)] with supplement level at 0.3 mg Se/kg, and immunological stress (LPS vs. saline). The experiment lasted for 28 d. On d 14 and d 21, half of pigs in each dietary treatment were intramuscularly injected with either 50 μg/kg BW LPS or an equivalent amount of sterile saline. Blood samples were collected at 3 h post-injection. There were no interactions between dietary Se sources and immunological stress on growth performance. LPS depressed average daily gain (ADG) (d 14-21, P〈0.05; d 21-28, P〈 0.01), and elevated feed to gain ratio (F/G) (d 21-28, P〈0.05), while SeY elevated ADG (d 0-14, P〈0.05; d 21-28 and d 0-28, P〈0.01), and decreased F/G (P〈0.01). Interactions were observed on interleukin-1β(IL-1β) and interleukin-6 (IL-6) from serum samples of d 14 and d 21 (P〈0.01), as well as superoxide dismutase (SOD) and insulin like growth factor (IGF-1) of d 21 (P〈0.05). In conclusion, SeY relieved the growth depression of piglets immunologically stressed by LPS, which maybe resulted from the decreased externalization of inflammatory cytokines and improved antioxidant status.展开更多
The present study was conducted to evaluate the effect of baker yeast, Saccharomyces cerevisiae (SC) and exogenous digestive enzymes (pepsin, papain and a-amylase, EDE) dietary supplementation on growth performanc...The present study was conducted to evaluate the effect of baker yeast, Saccharomyces cerevisiae (SC) and exogenous digestive enzymes (pepsin, papain and a-amylase, EDE) dietary supplementation on growth performance, feed utilization and hematological indices of Nile tilapia, Oreochromis niloticus fingerlings. A total of 630 Nile tilapia fingerlings with an average body weight of 26.4 ± 0.2 g were divided in the seven experimental net-pen treatments (three replicates each). The experiment was conducted for 119 days. Seven isonitrogenous (26.50%) digestible protein and isocaloric (13.40 MJ kgl) digestible energy experimental diets were formulated. The control diet had no SC and EDE added. Diets 2-3 each contained SC at levels of 2 and 4 g 100 g diet-t, respectively, while diets 4-5 each contained EDE at levels of (0.64, 1.28, 0.16) and (1.28, 2.56, 0.32) g 100 gdiefI of pepsin, papain and a-amylase, respectively. Diet 6 contained mixture of SC and EDE at levels of 1 g yeast and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet1 and diet D7 contained 2 g yeast and 0.64, 1.28, 0.16 g of pepsin, papain and a-amylase, respectively 100 g dietl. Growth performance and feed utilization efficiency of Nile tilapia were significantly (P 〈 0.05) higher in all treatments receiving SC and/or EDE supplemented-diets than the control diet which suggests that the addition of SC and EDE enhanced the growth performance. Red blood cells counts, hematocrit and hemoglobin were significantly (P 〈 0.05) highest in all treatments receiving mixture of SC and EDE supplemented-diets (D6 + D7). The same trend was observed for total plasma protein and total plasma globulin levels. The results of present study suggested that Nile tilapia fingerlings fed diets containing the mixture of I g yeast, SC and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet^-1, for 119 days had enhanced growth performance, diet utilization efficiency and hematological indices.展开更多
method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the ...method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the concentration of HCl was 0.4 mol.L^-1, the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control. Acetone or benzene as single polar or non-polar solvent was the most ef- fective solvent in our research. With a combination of isopropanol and n-hexane (volume ratio of 2 : 1), the maxi- mal extraction efficiency was achieved, approximately 60% higher than that obtained with a single solvent. The liquid-solid ratio and the extracting time were also optimized. Under the optimum extraction conditions, the extraction yield of astaxanthin exceeded 98%.展开更多
According literature, the induction of Yarrowia lipolytica alkaline protease promoter (PXPR2) is efficient in pH 〉 6.0 and with high peptone dose. To establish optimal pH and peptone concentration for induction of ...According literature, the induction of Yarrowia lipolytica alkaline protease promoter (PXPR2) is efficient in pH 〉 6.0 and with high peptone dose. To establish optimal pH and peptone concentration for induction of invertase gene (suc2 of Saccharomyces cerevisaie) under PXPR2 in new Y. lipolytica A-101 invertase positive (Suc+) transformants their growth on Bioscreen C was analyzed. Minimal mineral medium with thiamine (MMT) and sucrose (1%), adjusted to pH from 5.8 to 7.6 and supplemented by 0-0.1% of peptone was used. Biomass (OD), maximal specific growth rate (μmax) and consumed sucrose were measured. Maximal yeasts growth, resulting from the optimal PXPR2 induction, was observed at pH 7.2 and with very low peptone doses (0.0025% and 0.01%). For five clones (A-101 1356-5; A-101 B54-6; A-101 B57-4; A-101 A18 and W29 ura3-302) only 0.005% of peptone was needed. Amount of hydrolyzed sucrose varied from 24% to 83% and μmax from 0.06 to 0.28 hl. Suc^+ clones differ in growth parameters, so the site of yeast cassette integration into genome influences expression level of suc2 under PXPR2. Designing large scale processes with Y. lipolytica Suc^+ clones peptone concentration has to be 100 times smaller than recommended so far.展开更多
文摘Yeast culture is a kind of green feed additive. It has been researched and applied widely in the feed industry. In this paper, the functions of yeast culture and its application in the actual production were discussed. It can be concluded that yeast culture has a great application prospect.
基金Project 50574092 supported by National Natural Science Foundation of China OH 4508 Supported by Science Foundation of China University of Mining &Technology
文摘In this paper, the Sb2O3 nanoparticles prepared with SbCl3 by the alky hydrolysis, processed with the surfactants, were assembled on mica substrates. The morphology and the assembled behavior of the nano-Sb2O3 on the mica were analyzed by means of TEM. The flame retardant properties of nano-Sb2O3 and Sb2O3/mica complex were studied by combustion test and thermal analysis. The results show that the Sb2O3 nanoparticles are assembled uniformly on the mica substrates. The nano-Sb2O3 was characterized with small size, narrow size distribution, uniform crystal and monodispersed particles. Compared with nano-Sb2O3, the Sb2O3/mica complexes have been achieved the same coordinated effects with Chlorinated Paraffin(CP) and excellent flame retardant properties.
基金Project(31870115)supported by the National Natural Science Foundation of ChinaProject(2015JJ5006)supported by the Natural Science of Hunan Province&Changde City Joint Foundation,ChinaProjects(2015zzts268,ZY2015823)supported by the Fundamental Research Funds for the Central Universities,China
文摘High-level expression ofβ-mannanase has been reported in Pichia pastoris under control of the GAP promoter.Two factors that strongly influence protein production and fermentation process development in Pichia pastoris protein expression system are gene dosage and cultivation temperature.The aim of this research was to improve the expression level ofβ-mannanase in Pichia pastoris by proper increasing the gene dosage and decreasing the culture temperature.To this end,a panel of strains harboring different copy numbers ofβ-mannanase gene were obtained by multiple zeocin concentration gradients screening,the influence of gene copy number on the expression ofβ-mannanase in Pichia pastoris X33 was investigated.With the constitutive GAP promoter,the four copies strain exhibited a 4.04-fold higherβ-mannanase yield and a 1.83-fold higher total secretion proteins than the one copy strain,but an increase of the copy number above four resulted in a decrease of expression.Furthermore,the effects of culture temperature were studied in flask.The decreased culture temperature of four copies strain resulted in a 1.8-fold(26℃)and 3.5-fold(22℃)higherβ-mannanase activity compared to that at 30℃.A fed-batch strategy was successfully used for high cell-density fermentation andβ-mannanase activity reached 2124 U/mL after cultivation for 72 h in a 5 L fermenter.
基金Supported by the National Natural Science Foundation of China(No.29876031)
文摘The stability of Candida rugosa lipase coated with glutamic acid didodecyl ester ribitol amide was investigated taking esterification of lauryl alcohol and lauric acid in isooctane as a model reaction. At 30C, the half-life of the activity of the coated lipase was ca 10 h, the enzyme activity became less changed after 12 h and the residual activity was 39% of the initial value. The coated lipase obeyed a first-order deactivation model with a deactivation energy of 29.9J.mol-1.
基金NSFC (No. 40502008)Sichuan Province Application and Basic Research Project (No. 05JY029-008)
文摘In this study, X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) together with Scanning probe microscopy (SPM) were used to characterize the structure and morphology of the complexes, where the hydrobiotites (Xinfiang) were modified by single-chain surfactants octyltrimethylammonium bromide (OTMA) and octadecyltrimethylammonium bromide (ODTMA). XRD patterns showed that the structure of complexes was significantly influenced by the surfactant concentration and the alkyl chain length, because obvious changes took place in the basal spacing. Furthermore, according to the XRD results, several arrangements of surfactant molecules within the hydrobiotite interlayer space were deduced. The FTIR spectrum indicated that the surfactant contents in complexes dramatically increased with the alkyl chain length. The SPM micrographs demonstrated that the surfaces of complexes prepared at lower surfactant concentration were relatively flat compared with that prepared at higher concentration, while those with higher surfactant concentration had much steeper surface due to the alkyl chain length. It was concluded that structure and morphology of surfactant/hydrobiotite complexes depend not only on the surfactant concentration, but also strongly on the surfactant species.
基金National Natural Science Foundation of China(No.29876031)
文摘The surfactant-coated Candida rugosa lipase was used as catalyst for hydrolysis of olive oil in two-phase system consisting of olive oil and phosphate buffer without organic solvent. For both the coated and native lipases,the optimal buffer/oil volume ratio of 1.0, aqueous pH 6.8 and reaction temperature 30℃ were determined. The maximum activity of the coated lipase was ca 1.3 times than that of the native lipase. The half-life of the coated lipase in olive oil and the native lipase in phosphate buffer was ca 9 h and 12 h, and the final residual activity was 27% and 20% of their initial values, respectively. The final substrate conversion by the coated lipase was ca 20% higher than that of the native lipase.
基金Supported by Agricultural Scientific and Technologic Program of Fujian Province(2009-03)
文摘[Objective] The aim was to explore the effect of eliminated the breeding pigs with unqualified CSFV antibody on sow's reproductive performance and pig's growth performance so as to provide a scientific basis for the eliminating of the breeding pigs with unqualified CSFV antibody in large-scale pig farms.[Method] Serum samples from three scale pig farms were collected and tested with HerdChek CSFV-ELISA kit,then provided a certain scientific basis for scale pig farm to eliminate the unqualified(antibody blocking rate<50%)breeders after booster immunization.[Result ] After eliminating the breeding pigs with unqualified CSFV antibody,the average litter number of piglet in three pig farms(A,B,C)were increased by 0.29(P<0.05),0.40(P<0.01),0.39(P<0.01)respectively;the average number of survival piglets were increased by 0.54(P<0.01),0.35(P<0.01),0.62(P<0.01)respectively;the average litter number of weaned piglets were increased by 0.65(P<0.01),0.71(P<0.01),0.81(P<0.01)respectively.The difference in weight gain of piglet at 30-60 d of age was extremely significant(P<0.01),but inconspicuousness for the swine pregnancy rate,the survival rate of weaned piglet and piglet at 30-60 d of age.[Conclusion] The eliminating the breeding pigs with unqualified CSFV antibody can significantly improve the performance of breeder and piglets.
基金Supported by the National Natural Science Foundation of China(No.20076019)the Natural Science Foundation of Guang-dong Province(No.000444).
文摘Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.
文摘Selenium protects cells from oxidative damage and reduces lipopolysaccharide (LPS)-induced expression of inflammatory cytokines. Because inflammatory cytokines induce growth depression, we hypothesized that selenium-rich yeast (SeY) would inhibit growth depression caused by LPS. Twenty Meishan weanling pigs [28 (s.d. 2 d), 7.6 (s.d. 0.3 kg) body weight (BW)] were used in a 2×2 factorial design (n=5). The main factors were dietary Se sources [selenium-rich yeast (SeY) vs. sodium selenite (SSe)] with supplement level at 0.3 mg Se/kg, and immunological stress (LPS vs. saline). The experiment lasted for 28 d. On d 14 and d 21, half of pigs in each dietary treatment were intramuscularly injected with either 50 μg/kg BW LPS or an equivalent amount of sterile saline. Blood samples were collected at 3 h post-injection. There were no interactions between dietary Se sources and immunological stress on growth performance. LPS depressed average daily gain (ADG) (d 14-21, P〈0.05; d 21-28, P〈 0.01), and elevated feed to gain ratio (F/G) (d 21-28, P〈0.05), while SeY elevated ADG (d 0-14, P〈0.05; d 21-28 and d 0-28, P〈0.01), and decreased F/G (P〈0.01). Interactions were observed on interleukin-1β(IL-1β) and interleukin-6 (IL-6) from serum samples of d 14 and d 21 (P〈0.01), as well as superoxide dismutase (SOD) and insulin like growth factor (IGF-1) of d 21 (P〈0.05). In conclusion, SeY relieved the growth depression of piglets immunologically stressed by LPS, which maybe resulted from the decreased externalization of inflammatory cytokines and improved antioxidant status.
文摘The present study was conducted to evaluate the effect of baker yeast, Saccharomyces cerevisiae (SC) and exogenous digestive enzymes (pepsin, papain and a-amylase, EDE) dietary supplementation on growth performance, feed utilization and hematological indices of Nile tilapia, Oreochromis niloticus fingerlings. A total of 630 Nile tilapia fingerlings with an average body weight of 26.4 ± 0.2 g were divided in the seven experimental net-pen treatments (three replicates each). The experiment was conducted for 119 days. Seven isonitrogenous (26.50%) digestible protein and isocaloric (13.40 MJ kgl) digestible energy experimental diets were formulated. The control diet had no SC and EDE added. Diets 2-3 each contained SC at levels of 2 and 4 g 100 g diet-t, respectively, while diets 4-5 each contained EDE at levels of (0.64, 1.28, 0.16) and (1.28, 2.56, 0.32) g 100 gdiefI of pepsin, papain and a-amylase, respectively. Diet 6 contained mixture of SC and EDE at levels of 1 g yeast and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet1 and diet D7 contained 2 g yeast and 0.64, 1.28, 0.16 g of pepsin, papain and a-amylase, respectively 100 g dietl. Growth performance and feed utilization efficiency of Nile tilapia were significantly (P 〈 0.05) higher in all treatments receiving SC and/or EDE supplemented-diets than the control diet which suggests that the addition of SC and EDE enhanced the growth performance. Red blood cells counts, hematocrit and hemoglobin were significantly (P 〈 0.05) highest in all treatments receiving mixture of SC and EDE supplemented-diets (D6 + D7). The same trend was observed for total plasma protein and total plasma globulin levels. The results of present study suggested that Nile tilapia fingerlings fed diets containing the mixture of I g yeast, SC and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet^-1, for 119 days had enhanced growth performance, diet utilization efficiency and hematological indices.
基金Supported by the Fundamental Research Funds for the Central Universities (FRF-AS-10-001B) and the National Natural Science Foundation of China (11071013).
文摘method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the concentration of HCl was 0.4 mol.L^-1, the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control. Acetone or benzene as single polar or non-polar solvent was the most ef- fective solvent in our research. With a combination of isopropanol and n-hexane (volume ratio of 2 : 1), the maxi- mal extraction efficiency was achieved, approximately 60% higher than that obtained with a single solvent. The liquid-solid ratio and the extracting time were also optimized. Under the optimum extraction conditions, the extraction yield of astaxanthin exceeded 98%.
文摘According literature, the induction of Yarrowia lipolytica alkaline protease promoter (PXPR2) is efficient in pH 〉 6.0 and with high peptone dose. To establish optimal pH and peptone concentration for induction of invertase gene (suc2 of Saccharomyces cerevisaie) under PXPR2 in new Y. lipolytica A-101 invertase positive (Suc+) transformants their growth on Bioscreen C was analyzed. Minimal mineral medium with thiamine (MMT) and sucrose (1%), adjusted to pH from 5.8 to 7.6 and supplemented by 0-0.1% of peptone was used. Biomass (OD), maximal specific growth rate (μmax) and consumed sucrose were measured. Maximal yeasts growth, resulting from the optimal PXPR2 induction, was observed at pH 7.2 and with very low peptone doses (0.0025% and 0.01%). For five clones (A-101 1356-5; A-101 B54-6; A-101 B57-4; A-101 A18 and W29 ura3-302) only 0.005% of peptone was needed. Amount of hydrolyzed sucrose varied from 24% to 83% and μmax from 0.06 to 0.28 hl. Suc^+ clones differ in growth parameters, so the site of yeast cassette integration into genome influences expression level of suc2 under PXPR2. Designing large scale processes with Y. lipolytica Suc^+ clones peptone concentration has to be 100 times smaller than recommended so far.