ABSTRACT
OBJECTIVE:To determine quality indexes of Hejiang Dendrobium nobile at different harvesting time and months,and to provide scientific reference for reasonable harvesting period of Hejiang D.nobile.METHODS:The stem of annual,biennial and triennial D.nobile were collected.The drying rate,the contents of polysaccharides (colorimetry),dendrobine (GC) and total alkaloids (colorimetry),effective component total rate (dendrobine×drying rate) were measured.Biennial D.nobile were collected in autumn and winter (Oct.of the second year-Mar.of the third year,15th day a month) to determine drying rate,the contents of polysaccharides and dendrobine.RESULTS:The drying rate,the contents of polysaccharides and effective component total rate were higher than annual and triennial D.nobile.The content of total alkaloids and dendrobine were in descending order:annual D.nobile (0.52％,0.48％) ＞biennial D.nobile(0.48％,0.44％) ＞triennial D.nobile (0.32％,0.22％).From Oct.of the second year to Mar.of the third year,the drying rate of biennial D.nobile was increasing month by month;the contents of polysaccharides and dendrobine increased firstly and then decreased;the content of polysaccharide was the highest in Feb.(17.32％),and the content of dendrobine reached the highest level in Dec.(0.51％).CONCLUSIONS:The optimal harvesting period is biennial Hejiang D.nobile in Dec.and Jan.(third years before flowering),considering flowering characteristics,drying rate,the contents of polysaccharide and dendrobine.
ABSTRACT
The experiment was conducted by directed evolution strategy (error-prone PCR) to improve the activity of aflatoxin detoxifzyme with the high-throughput horse radish peroxidas and recessive brilliant green (HRP-RBG) screening system. We built up a mutant library to the order of 10(4). Two rounds of EP-PCR and HRP-RBG screening were used to obtain three optimum mutant strains A1773, A1476 and A2863. We found that mutant A1773 had upper temperature tolerance of 70 degrees C and that its enzyme activity was 6.5 times higher than that of the parent strain. Mutant strains A1476 worked well at pH 4.0 and its enzyme activity was 21 times higher than that of the parent strain. Mutant A2863 worked well at pH 4.0 and pH 7.5, and its enzyme activity was 12.6 times higher than that of the parent strain. With DNA sequencing we found that mutant A1773 revealed two amino acid substitutions, Glu127Lys and Gln613Arg. Mutant A1476 revealed four amino acid substitutions: Ser46Pro, Lys221Gln, Ile307Leu and Asn471lle. Mutant A2863 revealed four amino acid substitutions: Gly73Ser, Ile307Leu, Va1596Ala and Gln613Arg. The results provided a useful illustration for the deep understanding of the relationship between the function and structure of aflatoxin detoxifzyme.
Subject(s)
Aflatoxin B1 , Chemistry , Amino Acid Substitution , Directed Molecular Evolution , Enzyme Activation , Enzyme Stability , Multienzyme Complexes , Genetics , Metabolism , Mutant Proteins , Genetics , Metabolism , Point Mutation , Polymerase Chain Reaction , Methods , Protein EngineeringABSTRACT
Firstly, We used error-prone PCR to induce mutations on Armillariella tabescens MAN47 beta-mannanase gene, Secondly, we cloned the mutated fragments into secreted expression vector pYCalpha, Then the recombinant plasmids were transformed into Saccharomyces cerevisiae BJ5465 after amplified and extracted in DH5alpha cells. Through three cycles of error-prone PCR we built a mutant database, Then we screened one optimum (named M262) from about 104 mutants. The evoluted MAN47 beta-mannanase displayed both higher thermal stability and activity than wide type. The evoluted enzyme M262 retained high activity after treatment at 80 degrees C for 30 min, whereas, the wild type nearly lost activity under this condition. Meanwhile, the activity of M262 can reach to 25 U/mL, which is 4.3 times as wide type under optimum temperature. In addition, pH stability and pH range of evoluted enzyme M262 were both improved compared with wild-type enzyme. The optimum pH was estimated to be similar to that of wild-type enzyme. The sequence comparison illustrated that there were three nucleotide substitutions (T343A/C827T/T1139C) which carried corresponding amino acid changes (Ser115Thr/Thr276Met/Val380Ala). According to homologous modeling by SWISS-MODEL Repository, three mutated amino acids located at the sixth amino acid of the fourth beta-sheet, the first amino acid of the sixth alpha-helix, the turn between the tenth and eleventh beta-sheet, respectively.
Subject(s)
Armillaria , Classification , Genetics , Directed Molecular Evolution , Enzyme Stability , Escherichia coli , Genetics , Hot Temperature , Mutant Proteins , Genetics , Metabolism , Point Mutation , Polymerase Chain Reaction , Methods , Protein Engineering , Recombinant Proteins , Genetics , Metabolism , Saccharomyces cerevisiae , Genetics , beta-Mannosidase , Chemistry , Genetics , MetabolismABSTRACT
pPIC9 was used as a template and ?-factor gene of Saccharomyces cerevisiae was amplified by PCR.The gene was cloned in the intracellular expression vector pYES2/CT for Saccharomyces cerevisiae and the secreting expression vector named pYES2/CT/?-factor(pYC?)was constructed.The gene of mannase(man)from recombinant vector of pKLAC1-man(pKLman) was cut by restriction enzymes and linked with pYC?.This recombinant vector pYC?-man was used to determine the secretory ability and stability of pYC?.The excellent secretory ability of pYC? was proved by two experiments.One showed that INVSc1/pYC?-man clones formed the clear rings around the clones on the medium contained trypan blue,while INVSc1/pYC? clones had no rings.Further analysis of mannase activity of extracellular supernatant and intracellular extracts showed that both extracellular and intracellular mannase activities of INVSc1/pYC? were not detected,while INVSc1/pYC?-man had evident extracellular mannase activities and no intracellular mannase activities.The stability of pYC? was also very good proved by continuous cultivation for about 150h.