Zhen Xu — Page 3 | PubMed Health

PubMed2002

[Cloning, sequencing and high expression in Escherichia coli of D-hydantoinase gene from Burkholderia pickettii].

A strain, MMR003, used for D-p-HPG production in industry was classified as Burkholderia pickettii by morphological observation and biochemical characterization. The gene encoding the D-hydantoinase enzyme was cloned, sequenced and expressed in Escherichia coli. The nucleotide sequence of the 5.0 kb insert of subclone pXZ-total was determined. One open reading frame of 1374 bp was found and predicted to encode a polypeptide consisting of 458 amino acids in size of 50 kD. The amino acid sequence alignment of D-hydantoinase from Burkholderia pickettii shows the 85% homologous with the corresponding enzyme from Agrobacterium radiobacter NRRL B11291. The D-hydantoinase gene (dha) harboured in the plasmid pXZPH2 in E. coli BL21(DE3) was highly expressed by IPTG induction. The D-hydantoinase activity for D, L-p-hydroxyphenylhydantion is 0.66 u/mL broth, which is 2-fold increase compared to the parent strain Burkholderia pickettii.

Amidohydrolases↗

PubMed2002

[Regrowth of different plant populations in mixed pasture].

The number of tillers and leaf regrowth of perennial ryegrass (Lolium perenne) and that of branches and stolon growth of white clover (Trifolium repens) in mixed ryegrass/white clover pastures under different cutting frequency were monitored from 1998 to 2000, and the herbage yields and the proportion of each component in total yields were also determined. The results showed that cutting could stimulate perennial ryegrass leaf regrowth and white clover branching, maintain proper proportions of perennial ryegrass and white clover in the mixed pasture, and create the environments for the coexistence of the two species. Therefore, the total annual dry matter yields of the pasture was increased. However, cutting frequency had no significant effects on herbage yields and vegetative composition (P > 0.05). More leaf regrowth of perennial ryegrass was found in the plots cut in June than in August, whereas white clover exhibited an inverse trend. The herbage yield of perennial ryegrass depended on its leaf regrowth, while the dry matter accumulation of white clover relied on its stolon branching numbers. During the period of three year experiment, the proportion of perennial ryegrass and white clover in total herbage yields obtained from the plots under cutting was 50% and 15%, respectively, approximately 10% or 5% lower than its initial value, while CK was 39% and 6%, respectively.

Agriculture↗