For further practical application, the phylogenetic analysis and de-emulsification properties study of strain XH1 with high de-emulsification efficiency isolated from crude oil contaminated soil in Daqing oil field we...For further practical application, the phylogenetic analysis and de-emulsification properties study of strain XH1 with high de-emulsification efficiency isolated from crude oil contaminated soil in Daqing oil field were conducted with a surfactant-stabilized water-kerosene model emulsion. The factors influencing the de-emulsification efficiency and the generation site of de-emulsification active component of the strain were also investigated. The similarity of 16SrDNA sequences between strain XH1 and Bacillus mojavensis （DQ993678）was 99%. According to the physiological biochemical test, strain XH1 was preliminarily identified as Bacillus mojavensis. The logarithmic growth, stable phase and decline phase of strain XHI were determined as 14, 18 and 28 h, respectively. The best de-emulsification activity emerged after cultivating for 18h, and the complete de-emulsification was achieved at 24 h. The most favorable incubation conditions for de-emulsification occurred with pH of 6. 0 at 30 ℃. The de-emulsification capability of strain XH1 was mainly resulted from extracellular metabolites. The above results indicate that strain XH1 has high de-emulsification efficiency and is potential as a commercial de-emulsifier.展开更多
The aim of this study was to elucidate the mode of action of two antimicrobial compounds, nisin, which is hydrophilic, and the lipophilic compound carvacrol. For that purpose, both antimicrobials were loaded into Oil-...The aim of this study was to elucidate the mode of action of two antimicrobial compounds, nisin, which is hydrophilic, and the lipophilic compound carvacrol. For that purpose, both antimicrobials were loaded into Oil-in-/Water nanoemulsions, and their antimicrobial activity against Bacillus subtilis was investigated. The experimental results indicated that the O/W nanoemulsions loaded with both, nisin and carvacrol, having Sauter mean diameter （d3,2） of around 120 nm, were considerably stable under the conditions investigated （up to 1 week storage at room temperature）. The interfacial tension between nisin aqueous solutions and soybean oil could be reduced up to 12 mN/m, as compared to that of pure water and soybean oil （21 mN/m）, so that demonstrating the potential of nisin to be used as emulsifier. The results obtained for O/W nanoemulsions loaded with both antimicrobial compounds indicated a reduction of nearly two log cycles （around 100 times） on B. subtilis population upon incubation for 24 h, compared to the blank （10 mM phosphate buffer）.展开更多
The enzyme β-galactosidase （lactase; EC 3.2.1.23） is a commercially important enzyme due to its various applications in dairy and food industries, which are based on the β-galactosidase-catalysed hydrolysis of lac...The enzyme β-galactosidase （lactase; EC 3.2.1.23） is a commercially important enzyme due to its various applications in dairy and food industries, which are based on the β-galactosidase-catalysed hydrolysis of lactose into glucose and galactose. The objectives of this work were to identify novel and attractive sources of this industrially relevant enzyme, and to study the effect of selected growth parameters （carbon source, lactose concentration, nitrogen source, peptone concentration, initial pH and temperature） on the formation of β-galactosidase. Based on a screening of isolates from Tha Pai hot spring, Mae Hong Son Province, Thailand, strain BI.1 was selected for further studies. Strain BI.1 is a Gram-positive, rod-shaped, catalase-positive bacterium that forms endospores. Based on the sequence of the 16S rDNA determined, this isolate is most closely related to Anoxybacillus sp. and Bacillus sp., and hence the strain is designated as Bacillus sp. B 1. I.β-Galactosidase was produced by this strain with lactose and peptone as carbon and nitrogen sources, respectively. Optimal enzyme production occurred at an initial culture pH of 8.5 and at 45 ℃. Under these optimum culture conditions, maximal volumetric and specific β-galactosidase activity of 0.478 U mL^-1 and 0.338 U mg^-1 protein, respectively, were obtained after 13 h of cultivation in a medium contain 2.5% lactose, 2.0% peptone, 0.3% K2HPO4, 0.1% KH2PO4 and 0.05% MgSOa·7H2O.展开更多
The aim of this work was to construct a novel food-grade industrial arming yeast displaying β-1,3-1,4-glucanase and to evaluate the thermal stability of the glucanase for practical application. For this purpose, a bi...The aim of this work was to construct a novel food-grade industrial arming yeast displaying β-1,3-1,4-glucanase and to evaluate the thermal stability of the glucanase for practical application. For this purpose, a bi-directional vector containing galactokinase （GALl） and phosphoglycerate kinase 1 （PGK1） promoters in different orientations was constructed. The β-1,3-1,4-glucanase gene from Bacillus subtilis was fused to α-agglutinin and ex- pressed under the control of the GALl promoter, α-galactosidase induced by the constitutive PGK1 promoter was used as a food-grade selection marker. The feasibility of the α-galactosidase marker was confirmed by the growth of transformants harboring the constructed vector on a medium containing melibiose as a sole carbon source, and by the clear halo around the transformants in Congo-red plates owing to the expression of β-1,3-1,4-glucanase. The analysis of β-1,3-1,4-glucanase activity in cell pellets and in the supernatant of the recombinant yeast strain revealed that β-1,3-1,4-glucanase was successfully displayed on the cell surface of the yeast. The displayed β-1,3-1,4-glucanase activity in the recombinant yeast cells increased immediately after the addition of galactose and reached 45.1 U/ml after 32-h induction. The thermal stability of β-1,3-1,4-glucanase displayed in the recombinant yeast cells was en- hanced compared with the free enzyme. These results suggest that the constructed food-grade yeast has the potential to improve the brewing properties of beer.展开更多
文摘以菊糖芽孢乳杆菌(Sporolactobacillus inulinus)为出发菌株,经紫外线、硫酸二乙酯的诱变处理,采用碳酸钙平板初筛及摇瓶复筛得到1株高产D-乳酸的正向突变株D11。通过单因素试验研究D11菌株发酵产D-乳酸的条件。结果表明,当发酵温度37℃,初始p H 6.5,转速160 r/min,接种量5%,装液量50m L/250 m L,发酵68 h,该菌株D-乳酸产量达到56.18 g/L,比出发菌种提高49.53%。
基金Sponsored by the National Basic Research Program of China (973 Program) (Grant No. GA06C2021)the Major Scientific and Technology Project of Heilongjiang (Grant No. GA06C202)
文摘For further practical application, the phylogenetic analysis and de-emulsification properties study of strain XH1 with high de-emulsification efficiency isolated from crude oil contaminated soil in Daqing oil field were conducted with a surfactant-stabilized water-kerosene model emulsion. The factors influencing the de-emulsification efficiency and the generation site of de-emulsification active component of the strain were also investigated. The similarity of 16SrDNA sequences between strain XH1 and Bacillus mojavensis （DQ993678）was 99%. According to the physiological biochemical test, strain XH1 was preliminarily identified as Bacillus mojavensis. The logarithmic growth, stable phase and decline phase of strain XHI were determined as 14, 18 and 28 h, respectively. The best de-emulsification activity emerged after cultivating for 18h, and the complete de-emulsification was achieved at 24 h. The most favorable incubation conditions for de-emulsification occurred with pH of 6. 0 at 30 ℃. The de-emulsification capability of strain XH1 was mainly resulted from extracellular metabolites. The above results indicate that strain XH1 has high de-emulsification efficiency and is potential as a commercial de-emulsifier.
文摘The aim of this study was to elucidate the mode of action of two antimicrobial compounds, nisin, which is hydrophilic, and the lipophilic compound carvacrol. For that purpose, both antimicrobials were loaded into Oil-in-/Water nanoemulsions, and their antimicrobial activity against Bacillus subtilis was investigated. The experimental results indicated that the O/W nanoemulsions loaded with both, nisin and carvacrol, having Sauter mean diameter （d3,2） of around 120 nm, were considerably stable under the conditions investigated （up to 1 week storage at room temperature）. The interfacial tension between nisin aqueous solutions and soybean oil could be reduced up to 12 mN/m, as compared to that of pure water and soybean oil （21 mN/m）, so that demonstrating the potential of nisin to be used as emulsifier. The results obtained for O/W nanoemulsions loaded with both antimicrobial compounds indicated a reduction of nearly two log cycles （around 100 times） on B. subtilis population upon incubation for 24 h, compared to the blank （10 mM phosphate buffer）.
文摘The enzyme β-galactosidase （lactase; EC 3.2.1.23） is a commercially important enzyme due to its various applications in dairy and food industries, which are based on the β-galactosidase-catalysed hydrolysis of lactose into glucose and galactose. The objectives of this work were to identify novel and attractive sources of this industrially relevant enzyme, and to study the effect of selected growth parameters （carbon source, lactose concentration, nitrogen source, peptone concentration, initial pH and temperature） on the formation of β-galactosidase. Based on a screening of isolates from Tha Pai hot spring, Mae Hong Son Province, Thailand, strain BI.1 was selected for further studies. Strain BI.1 is a Gram-positive, rod-shaped, catalase-positive bacterium that forms endospores. Based on the sequence of the 16S rDNA determined, this isolate is most closely related to Anoxybacillus sp. and Bacillus sp., and hence the strain is designated as Bacillus sp. B 1. I.β-Galactosidase was produced by this strain with lactose and peptone as carbon and nitrogen sources, respectively. Optimal enzyme production occurred at an initial culture pH of 8.5 and at 45 ℃. Under these optimum culture conditions, maximal volumetric and specific β-galactosidase activity of 0.478 U mL^-1 and 0.338 U mg^-1 protein, respectively, were obtained after 13 h of cultivation in a medium contain 2.5% lactose, 2.0% peptone, 0.3% K2HPO4, 0.1% KH2PO4 and 0.05% MgSOa·7H2O.
基金Project (No.2006AA10Z316) supported by the Hi-Tech Research and Development Program (863) of China
文摘The aim of this work was to construct a novel food-grade industrial arming yeast displaying β-1,3-1,4-glucanase and to evaluate the thermal stability of the glucanase for practical application. For this purpose, a bi-directional vector containing galactokinase （GALl） and phosphoglycerate kinase 1 （PGK1） promoters in different orientations was constructed. The β-1,3-1,4-glucanase gene from Bacillus subtilis was fused to α-agglutinin and ex- pressed under the control of the GALl promoter, α-galactosidase induced by the constitutive PGK1 promoter was used as a food-grade selection marker. The feasibility of the α-galactosidase marker was confirmed by the growth of transformants harboring the constructed vector on a medium containing melibiose as a sole carbon source, and by the clear halo around the transformants in Congo-red plates owing to the expression of β-1,3-1,4-glucanase. The analysis of β-1,3-1,4-glucanase activity in cell pellets and in the supernatant of the recombinant yeast strain revealed that β-1,3-1,4-glucanase was successfully displayed on the cell surface of the yeast. The displayed β-1,3-1,4-glucanase activity in the recombinant yeast cells increased immediately after the addition of galactose and reached 45.1 U/ml after 32-h induction. The thermal stability of β-1,3-1,4-glucanase displayed in the recombinant yeast cells was en- hanced compared with the free enzyme. These results suggest that the constructed food-grade yeast has the potential to improve the brewing properties of beer.
