Abstract: Provided is a recombinant microorganism including at least two genes for producing itaconic acid and its derived monomers, and the at least two genes are located on the same expression vector. The at least two genes include one encoding cis-aconitic acid decarboxylase and the other one encoding aconitase, and the genome of the recombinant microorganism includes a gene encoding the molecular chaperone protein GroELS. Also provided is a method for producing itaconic acid by using the microorganism.

Abstract: A dental impression tray made of plastic is proposed to be used in a disposable manner. The dental impression tray includes a tray body for securely holding a mold material, and a handle which is separately prepared and adapted to be connected with the tray body when in use. The handle is separated from the frame body while in storage, so that they can be separately stacked with less bulkiness in storage. The tray body and the handle are provided with a locking means which can securely connect the tray body and the handle into one unit.