Accordion bioreactor

A bioreactor comprising:

• (a) a first sheet and a second sheet, wherein the second sheet is disposed adjacent to the first sheet and the first and second sheets are sealed along a first longitudinal edge, a second longitudinal edge, a first horizontal edge, and a second horizontal edge, and comprising at least one intermediate horizontal seal between the first horizontal edge and the second horizontal edge, thereby forming at least two chambers for holding fluid in series along a vertical axis, wherein each of the two or more chambers is oriented at an angle relative to the vertical axis, wherein the angle is about 0° to about 90° and at least one of the chambers is oriented at an angle greater than 0° and at least one of the chambers is oriented at an angle of about 0° relative to the vertical axis, wherein the at least two chambers alternate between a chamber oriented at an angle greater than 0° and a chamber oriented at an angle of about 0° relative to the vertical axis, and wherein there is at least one opening in each of the first horizontal edge, the second horizontal edge, and the at least one intermediate horizontal seal;
• (b) a support structure comprising at least one horizontal support, wherein the horizontal support is located at or near the position of the intermediate horizontal seal;
• (c) a reservoir below the second horizontal edge of the first and second sheets;
• and
• (d) means for pumping fluid from the reservoir to the first horizontal edge of the first and second sheets.