Abstract: A flow passage joint structure includes: a first external thread portion formed, at an end portion of first piping block, radially outward of flow passage hole; a second external thread portion formed, at an end portion of second piping block, radially outward of flow passage hole; a union nut having a first internal thread portion to be screwed to the first external thread portion, on one side in an axial direction thereof, and having a second internal thread portion to be screwed to the second external thread portion, on another side in the axial direction thereof; and a gasket configured to seal a connection portion between the flow passage holes on a radially inner side of the union nut. The first external thread portion and the first internal thread portion are right-hand threads, and the second external thread portion and the second internal thread portion are left-hand threads.

Abstract: It is to provide a method for producing hyaluronic acid or a hyaluronic acid derivative which is a simple preparation method as compared with a cockscomb extraction method or a fermentation method which has conventionally been employed industrially, and with which isolation and purification of the product from the reaction liquid is easy. It is a method for producing hyaluronic acid or a hyaluronic acid derivative, which comprises acting a hyaluronidase on an oxazoline derivative.

Abstract: It is to provide a method for producing hyaluronic acid or a hyaluronic acid derivative which is a simple preparation method as compared with a cockscomb extraction method or a fermentation method which has conventionally been employed industrially, and with which isolation and purification of the product from the reaction liquid is easy. It is a method for producing hyaluronic acid or a hyaluronic acid derivative, which comprises acting a hyaluronidase on an oxazoline derivative.