Abstract: A fermentor system for cultivation of microorganisms dependent on gas supply for growth includes an inlet pipe feeding growth medium and gas connected with one or more adjustable inlet pump members allowing a given velocity of growth medium and gas through the inlet pipe; a fermentor tank having a cylindrical volume, the fermentor tank including liquid media with a microorganism to be cultivated and a plurality of upper feeding nozzles that receive and distribute growth medium and gas from the inlet pipe into the fermentor tank; an inner cylindrical outlet pipe, extending from the bottom to the top of the fermentor tank, and being encircled by the plurality of upper feeding nozzles at the top of the fermentor tank; and a transport pipe transporting liquid media from the outlet pipe to a dewatering separator, thereby obtaining concentrated living microorganism material for further processing and liquid separated from concentrated living microorganism material.