The biodegradations of phenol and 4-chlorophenol （4-cp） were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis. The results showed that the capacity of the...The biodegradations of phenol and 4-chlorophenol （4-cp） were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis. The results showed that the capacity of the CTM 2 to biodegrade 4-cp was increased up to 400 mg·L^-1 within 59.5 h. In the dual-substrate biodegradation both velocity and capacity of the CTM 2 to degrade 4-cp increased with low-concentration phenol. A totalof 400 mg·L^-1 4-cp was completely degraded within 50.＇5 h in thepresence of 300 mg·L^-1 phenol. The maximum 4：cp biodegegradation could reach 440 mg·L^1 with 120 mg·L^1 phenol. Low-concentration 4-cp caused great inhibition on the CTM 2 to degrade phenol. In addition, the kinetic behaviors were described using the kinetic model proposed in this lab.展开更多
Bacillus pumilus X-6-9 isolated from soil and subsequently identified, produced xylooligosaccharides with long chains from xylan and accumulated them in the culture. By improving the culture conditions and mutating th...Bacillus pumilus X-6-9 isolated from soil and subsequently identified, produced xylooligosaccharides with long chains from xylan and accumulated them in the culture. By improving the culture conditions and mutating the bacterium, a 3.2-fold increase in the production of the xylooligosaccharides was established, when compared to the original culture conditions of B. pumilus X-6-19. The addition of D-glucose to the culture of the mutant strain U-3 of B. pumilus X-6-9 repressed the synthesis of β-xylosidase, but not xylanase. Thus, it was revealed that strain U-3 was a good organism for the production and accumulation of xylooligosaccharides with long chains from xylan by a microbial culture. Xylanase produced by strain U-3 was purified to homogeneity and characterized. The hydrolyzates generated by the purified xylanase contained xylobiose, xylotriose, xylotetraose, and xylopentaose, but not xylose.展开更多
Amplified inter simple sequence repeats （ISSR） markers were used to determine genetic relationships among mutant silkworm strains of Bombyx mori. Fifteen ISSR primers containing simple sequence repeat （SSR） motifs...Amplified inter simple sequence repeats （ISSR） markers were used to determine genetic relationships among mutant silkworm strains of Bombyx mori. Fifteen ISSR primers containing simple sequence repeat （SSR） motifs were used in this study. A total of 113 markers were produced among 20 mutant strains, of which 73.45% were found to be polymorphic. In selected mutant genetic stocks, the average number of observed allele was （1.7080 ± 0.4567）, effective alleles （1.5194 ± 0.3950） and genetic diversity （Ht） （0.2901 ± 0.0415）. The dendrogram produced using the unweighted pair group method with arithmetic means （UPGMA） and cluster analysis made using Nei＇s genetic distance resulted in the formation of one major group containing 6 groups separated 20 mutant silkworm strains. Therefore, ISSR amplification is a valuable method for determining the genetic variability among mutant silkworm strains. This efficient molecular marker would be useful for characterizing a considerable number of silkworm strains maintained at the germplasm center.展开更多
[Objective] The aim of this study was to screen Saccharomyces for glutathione over-production. [Method] Ethionine-resistant mutants were obtained through UV mutagenesis and rational screening. [Result] A high GSH-prod...[Objective] The aim of this study was to screen Saccharomyces for glutathione over-production. [Method] Ethionine-resistant mutants were obtained through UV mutagenesis and rational screening. [Result] A high GSH-producing strain HSJB1 was isolated from soil, and the biomass for this strain by flask shaking fermentation was 3.87 g/L while the GSH yield was 91.87 mg/L. According to the morphological, physiological and biochemical characteristics of cells, this strain was primarily identified as Saccharomyces cerevisiae. An ethionine-resistant mutant YBS77 was obtained through UV mutagenesis of the original strain HSJB1, and the biomass for this strain by flask shaking fermentation was 7.60 g dry cell weight/L while the GSH yield was 211.96 mg/L. [Conclusion] The biomass of the mutant obtained by breeding is increased by 96.38% than that of the original strain, and the GSH yield of the mutant obtained by breeding is increased by 130.72% than that from the original strain, which indicates that the breeding method is feasible.展开更多
A new protein, an approximately 59-kDa monomer containing iron atoms, was first isolated from the mutant strain DJ35 of Azotobacter vinelandii Llpmann. After analysis by matrix-assisted laser desorptlon ionization tim...A new protein, an approximately 59-kDa monomer containing iron atoms, was first isolated from the mutant strain DJ35 of Azotobacter vinelandii Llpmann. After analysis by matrix-assisted laser desorptlon ionization time-of-flight mass spectrometry, the protein was Identified as the product of a predicted gene. Thus, the protein was tentatively called HBP59. Its absorption spectra （ABS） In the reduced state exhibited three peaks at 421,517, and 556 nm and the maximal peak was shifted from 421 to 413 nm after exposure of HBP59 to air. The Soret circular dichrolsm （CD） spectrum of HBP59 In the reduced state displayed four positive peaks at 364, 382, 406, and 418 nm and two negative peaks at 398 and 433 nm; the △ε （CD extinction coefficient） values of these peaks were found to be 0.92, 0.58, 0.87, 0.72, -0.65 and -1.12 L/mol per cm, respectively. Titration with heme showed that the protein has 0.1 heme molecules/protein molecule. After HBP59 had fully Interacted with heme, Its maximal ABS value and Soret CD Intensity were increased by approximately 10-fold compared with values before Interaction. Therefore, It seems that one molecule of HBP59 can be interacted with only one heme. These results indicate that HBP59 contains heme with low spin and may be Involved In heme utilization or adhesion.展开更多
Probiotic fermented milk has emerged as a prominent functional food for its substantial role in promoting in-testinal health and overall wellness.However,a persistent challenge in the industry is post-acidification,a ...Probiotic fermented milk has emerged as a prominent functional food for its substantial role in promoting in-testinal health and overall wellness.However,a persistent challenge in the industry is post-acidification,a process where lactic acid bacteria continue fermenting during storage,leading to excessive acidity,textural degradation,and flavor alterations.This study focuses on the identification and characterization of a naturally mutated strain of Lacticaseibacillus paracasei capable of significantly attenuating post-acidification in fermented milk.A novel mutation was discovered in theα-glucosidase gene(AF91_03255),wherein the substitution of arginine at position 477 with glycine altered the enzyme’s binding dynamics.This mutation enhanced binding stability between the enzyme and its substrate by approximately 16.8%,indirectly modulating acid production without directly limiting glucose metabolism.Through a combination of multi-omics techniques,including metabolomics and genomic sequencing,this study revealed significant shifts in the glycerophospholipid meta-bolic pathway,suggesting alterations in cell membrane composition as a core mechanism.Additionally,comparative analyses between the wild-type and mutant strains demonstrated notable differences in acid pro-duction,viable cell counts,and storage stability.The mutant strain maintained a higher pH and reduced titratable acidity during extended storage while preserving bacterial viability,distinguishing it from traditional approaches reliant on additives or processing modifications.The findings underscore the potential ofα-gluco-sidase as a pivotal target for post-acidification regulation in fermented milk products.Furthermore,this work contributes valuable insights into the strain improvement strategies essential for advancing the stability and sensory qualities of fermented milk.展开更多
Using pseudorabies virus Ea strain as material,we inserted LacZ gene expression cassette into gE gene.After blue plaque and plaque purification,a recombinant virus PRVEa TK+-/gE+-/LacZ++ generated.Utilizing EcoR I sit...Using pseudorabies virus Ea strain as material,we inserted LacZ gene expression cassette into gE gene.After blue plaque and plaque purification,a recombinant virus PRVEa TK+-/gE+-/LacZ++ generated.Utilizing EcoR I site in LacZ gene, digested PRVEa TK+-/gE+-/LacZ++ genome DNA was cotransfected into PK-15 cells with plasmid pFBBS,then PRVEa TK+-/gE+-/gp63+- generated after plaque purification.Four pairs of primers amplification demonstrated the virus was pure TK+-/gE+-/gp63+- mutant virus.PCR product sequence indicates there were 205bp deletion in TK gene;1247bp deletion in gE,gp63 and intergenic region of PRVEa TK+-/gE+-/gp63+- mutant virus genome DNA.Inoculation to Balb/C mice with PRVEa TK+-/gE+-/gp63+- indicates the virulence is reduced greatly.展开更多
基金Supported by the science and Technology Innovative Talents Foundation of China （2006RFQXS070）, the Youth Academic Cadreman Project of Heilongjiang Province （1152G068）, Scientific Research Fund of Heilongjiang Province （11523063） and the Science Foundation for Post Doctorate of China （20070410268）.
文摘The biodegradations of phenol and 4-chlorophenol （4-cp） were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis. The results showed that the capacity of the CTM 2 to biodegrade 4-cp was increased up to 400 mg·L^-1 within 59.5 h. In the dual-substrate biodegradation both velocity and capacity of the CTM 2 to degrade 4-cp increased with low-concentration phenol. A totalof 400 mg·L^-1 4-cp was completely degraded within 50.＇5 h in thepresence of 300 mg·L^-1 phenol. The maximum 4：cp biodegegradation could reach 440 mg·L^1 with 120 mg·L^1 phenol. Low-concentration 4-cp caused great inhibition on the CTM 2 to degrade phenol. In addition, the kinetic behaviors were described using the kinetic model proposed in this lab.
文摘Bacillus pumilus X-6-9 isolated from soil and subsequently identified, produced xylooligosaccharides with long chains from xylan and accumulated them in the culture. By improving the culture conditions and mutating the bacterium, a 3.2-fold increase in the production of the xylooligosaccharides was established, when compared to the original culture conditions of B. pumilus X-6-19. The addition of D-glucose to the culture of the mutant strain U-3 of B. pumilus X-6-9 repressed the synthesis of β-xylosidase, but not xylanase. Thus, it was revealed that strain U-3 was a good organism for the production and accumulation of xylooligosaccharides with long chains from xylan by a microbial culture. Xylanase produced by strain U-3 was purified to homogeneity and characterized. The hydrolyzates generated by the purified xylanase contained xylobiose, xylotriose, xylotetraose, and xylopentaose, but not xylose.
文摘Amplified inter simple sequence repeats （ISSR） markers were used to determine genetic relationships among mutant silkworm strains of Bombyx mori. Fifteen ISSR primers containing simple sequence repeat （SSR） motifs were used in this study. A total of 113 markers were produced among 20 mutant strains, of which 73.45% were found to be polymorphic. In selected mutant genetic stocks, the average number of observed allele was （1.7080 ± 0.4567）, effective alleles （1.5194 ± 0.3950） and genetic diversity （Ht） （0.2901 ± 0.0415）. The dendrogram produced using the unweighted pair group method with arithmetic means （UPGMA） and cluster analysis made using Nei＇s genetic distance resulted in the formation of one major group containing 6 groups separated 20 mutant silkworm strains. Therefore, ISSR amplification is a valuable method for determining the genetic variability among mutant silkworm strains. This efficient molecular marker would be useful for characterizing a considerable number of silkworm strains maintained at the germplasm center.
基金Supported by Scientific Research Project of Liaoning Educational Department(20060154)Initial Funds for Doctors in Dalian Nationalities University(20066206)~~
文摘[Objective] The aim of this study was to screen Saccharomyces for glutathione over-production. [Method] Ethionine-resistant mutants were obtained through UV mutagenesis and rational screening. [Result] A high GSH-producing strain HSJB1 was isolated from soil, and the biomass for this strain by flask shaking fermentation was 3.87 g/L while the GSH yield was 91.87 mg/L. According to the morphological, physiological and biochemical characteristics of cells, this strain was primarily identified as Saccharomyces cerevisiae. An ethionine-resistant mutant YBS77 was obtained through UV mutagenesis of the original strain HSJB1, and the biomass for this strain by flask shaking fermentation was 7.60 g dry cell weight/L while the GSH yield was 211.96 mg/L. [Conclusion] The biomass of the mutant obtained by breeding is increased by 96.38% than that of the original strain, and the GSH yield of the mutant obtained by breeding is increased by 130.72% than that from the original strain, which indicates that the breeding method is feasible.
基金Supported by the State Key Basic Research and Development Plan of China （001CB1089-06） and the National Natural Science Foundation of China （30270296）.Acknowledgements The authors thank Professors YX Jing and JG Li for their valuable advice.
文摘A new protein, an approximately 59-kDa monomer containing iron atoms, was first isolated from the mutant strain DJ35 of Azotobacter vinelandii Llpmann. After analysis by matrix-assisted laser desorptlon ionization time-of-flight mass spectrometry, the protein was Identified as the product of a predicted gene. Thus, the protein was tentatively called HBP59. Its absorption spectra （ABS） In the reduced state exhibited three peaks at 421,517, and 556 nm and the maximal peak was shifted from 421 to 413 nm after exposure of HBP59 to air. The Soret circular dichrolsm （CD） spectrum of HBP59 In the reduced state displayed four positive peaks at 364, 382, 406, and 418 nm and two negative peaks at 398 and 433 nm; the △ε （CD extinction coefficient） values of these peaks were found to be 0.92, 0.58, 0.87, 0.72, -0.65 and -1.12 L/mol per cm, respectively. Titration with heme showed that the protein has 0.1 heme molecules/protein molecule. After HBP59 had fully Interacted with heme, Its maximal ABS value and Soret CD Intensity were increased by approximately 10-fold compared with values before Interaction. Therefore, It seems that one molecule of HBP59 can be interacted with only one heme. These results indicate that HBP59 contains heme with low spin and may be Involved In heme utilization or adhesion.
基金financial interests/personal relationships which may be considered as potential competing interests:Shijie Wang reports financial support was provided by National Natural Science Foundation of China(Grant No.3207161439)Shijie Wang reports financial support was provided by Shijiazhuang Science and Technology Bureau(Grant No.237790579A)+1 种基金Han Lu reports financial support was provided by Hebei Provincial Department of Science and Technology(Grant No.236Z2804G)Shijie Wang reports financial support was provided by National Center of Technology Innovation for Dairy(Grant No.2022-Scientific research-14).
文摘Probiotic fermented milk has emerged as a prominent functional food for its substantial role in promoting in-testinal health and overall wellness.However,a persistent challenge in the industry is post-acidification,a process where lactic acid bacteria continue fermenting during storage,leading to excessive acidity,textural degradation,and flavor alterations.This study focuses on the identification and characterization of a naturally mutated strain of Lacticaseibacillus paracasei capable of significantly attenuating post-acidification in fermented milk.A novel mutation was discovered in theα-glucosidase gene(AF91_03255),wherein the substitution of arginine at position 477 with glycine altered the enzyme’s binding dynamics.This mutation enhanced binding stability between the enzyme and its substrate by approximately 16.8%,indirectly modulating acid production without directly limiting glucose metabolism.Through a combination of multi-omics techniques,including metabolomics and genomic sequencing,this study revealed significant shifts in the glycerophospholipid meta-bolic pathway,suggesting alterations in cell membrane composition as a core mechanism.Additionally,comparative analyses between the wild-type and mutant strains demonstrated notable differences in acid pro-duction,viable cell counts,and storage stability.The mutant strain maintained a higher pH and reduced titratable acidity during extended storage while preserving bacterial viability,distinguishing it from traditional approaches reliant on additives or processing modifications.The findings underscore the potential ofα-gluco-sidase as a pivotal target for post-acidification regulation in fermented milk products.Furthermore,this work contributes valuable insights into the strain improvement strategies essential for advancing the stability and sensory qualities of fermented milk.
文摘Using pseudorabies virus Ea strain as material,we inserted LacZ gene expression cassette into gE gene.After blue plaque and plaque purification,a recombinant virus PRVEa TK+-/gE+-/LacZ++ generated.Utilizing EcoR I site in LacZ gene, digested PRVEa TK+-/gE+-/LacZ++ genome DNA was cotransfected into PK-15 cells with plasmid pFBBS,then PRVEa TK+-/gE+-/gp63+- generated after plaque purification.Four pairs of primers amplification demonstrated the virus was pure TK+-/gE+-/gp63+- mutant virus.PCR product sequence indicates there were 205bp deletion in TK gene;1247bp deletion in gE,gp63 and intergenic region of PRVEa TK+-/gE+-/gp63+- mutant virus genome DNA.Inoculation to Balb/C mice with PRVEa TK+-/gE+-/gp63+- indicates the virulence is reduced greatly.
