定向进化提高来源于Arthrobacter ramosus的MTHase的热稳定性

麦芽寡糖基海藻糖水解酶(maltosyltrehalose hydrolase,MTHase)是以淀粉或麦芽糊精为底物制备海藻糖的关键酶之一。来源于Arthrobacter ramosus的MTHase,表达量好,比活高,但热稳定性差,限制了其工业化应用。采用定向进化技术,筛选得到L137M和A216T两个突变体,在60℃下,野生型和两个突变体的半衰期(t1/2)分别为15.5、20.5和23.3 min,L137M和A216T的t1/2分别比野生型提高1.3和1.5倍。进一步考察了L137M、A216T和野生型酶在60℃分别和同样来源于Arthrobacter ramosus的麦芽寡糖基海藻糖合成酶(maltosyltrehalose synthase,MTSase)复配制备海藻糖,在相同的加酶量下,野生型、L137M和A216T的海藻糖转化率分别为51.3%,52.6%和55.7%,两个突变体的转化率都比野生型提高,说明突变体提高的热稳定性有利于海藻糖的转化率。

Screening of antibacterial drugs from marine gastropod Chicoreus ramosus(Linnaeus,1758)

Objective:To screen the antibacterial drugs from different solvent extracts of tissue and egg of marine gastropods Chicoreus ramosus against clinically isolated human pathogenic bacteria.Methods:Vibrio parehaemolyticus(J13300),Aeromonus hydrophilla(IDH1585),Salmonella typhi(C6953),Salmonella paratyphi A(C6915),Vibrio cholerae(IDH5439)and Escherichia coli(H10407)using standard well diffusion method and its minimum inhibitory concentration.Results:Different solvent extracts of Chicoreus ramosus was screened for their activity against egg inhibited the growth of the tested pathogenic bacterial strains.The minimum inhibitory concentration of both the extract ranged from 4 to 12 mg/mL.The study revealed that the acetone and chloroform extract of both the tissues and Conclusions:These results suggest that marine gastropods tissue and egg extract contains comparatively good antibacterial activity.