Abstract: An apparatus for providing an enhanced liquid/gas exchange surface such as during call culturing has an enclosed housing, a set of trays arranged in parallel inside the housing with a regular spacing between them, each of the trays being formed with a planar base, first rims on longitudinal sides and second rims on transverse sides of the trays projecting on both sides of the base so as to form retaining basins for retaining reaction liquid on both sides of the base as the trays are rotated through horizontal positions. In a preferred embodiment, the trays are stacked and have their first rims welded together to form the housing walls, while the second rims have a height lower than the first rims to create apertures between trays for fluid flow among the trays when they are rotated. The bases of the trays can have cutout portions on opposing transverse sides for the flow of reaction liquid from one side to the other.

Abstract: Adherent or non-adherent microorganisms with or without microcarriers are cultured in an apparatus having rotatable planar trays that dip in and out of culture medium and momentarily retain culture medium due to rims along edges of the trays on both sides. The trays are in a housing that is substantially cylindrical and elongated along a longitudinal axis. The trays are arranged longitudinally to the longitudinal axis with spacing between the trays. The trays can be attached substantially radially to and around a shaft extending coaxially inside the housing, attached to both the shaft and the housing or attached to the housing without a shaft. Attachment is at one or two longitudinal edges of the trays. The shaft can be hollow and have a wall with openings. During culturing, the trays can be rotated in one direction 180.degree. and then rotated through 180.degree. in an opposite direction.