The Construction And Selection Of Surface Display CALB Lipase On Aspergillus Niger SH-1

Filamentous fungi has unique characteristics and advantages because of very strong capacity of protein secretion comparing to the prokaryotic expression system such as E.coli and yeast.To be a special host,Aspergillus Niger expressing heterologous protein has a lot of advantages such as high rate of exocytosis and protein expression,modification of protein closing to a higher eukaryotes model.Aspergillus Niger as cell factories,which are widely used in enzyme preparation,heterologous proteins,organic acids and other areas of the production.Aspergillus Niger was generally regarded as safe(GRAS)organisms by the FDA and the world health organization.Lipase is the most important enzymes in non-aqueous enzymatic and it is significantly different from aqueous enzymatic system.Lipase is using in most reaction for example esterification,transesterification,alcoholysis and so on.These features make the lipase can be widely used in biological energy(biodiesel),synthetic drugs,and other prospect wide area.As a result,the research of lipase is very meaningful.Surface display technology has become a very important item today,such as the protein screening,directed evolution of protein,high-affinity antibodies,sorting,antigen/antibody construction,affinity maturation,vaccine production,immunobiological catalytic and biological sensors,and other fields have been developed and applied.Now,with the yeast surface display technology improving,the technology has developed rapidly in the last ten years in many fields.However,Aspergillus niger surface display technology is still exploring.Improving the unit activity of the surface display of Aspergillus niger with the way of fermentation laid the foundation of surface display technology.Our laboratory make an innovation on aspergillus Niger surface display technology.Aspergillus Niger surface display lipase as a potential efficient food-grade whole-cell catalyst is used in the production of the oil,essence and so on.This paper tell us some specific studies are as follows,(1)Using a constitutive promoter took the place of an inducible promoter.In this way,the enzyme activity,the ratio of displaying and secretion,Unit volume of enzyme were higher than before in the nonspore aspergillus Niger display system.(2)Contrasting at glucose some nonglucose carbon sources,such as xylose,can be used in this system to improve enzyme activity and biomass without oxalic acid which was bad to Aspergillus niger.The peak cell wall activity is 1100U/g dry cell and the highest point of biomass is 22g/L.(3)Lignocellulosic hydrolysate also is a kind of carbon source in this fermentation process.The nonspore aspergillus Niger can using lignocellulosic hydrolysate without detoxication to display lipase CALB.The peak cell wall activity is 600U/g dry cell and the highest point of biomass is 35g/L.Meanwhile the peak ability of producing is 36U/ml.Whole-cell catalyst made from can be used in the way of phospholipid modification with 92.8% productivity.