A bioreactor apparatus for performing biological and biochemical reactions comprising: a vessel comprising a mixing port, a reaction port, and a harvesting port; an agitator extending through the mixing port into the vessel; a reaction assembly extending through the reaction port into the vessel, the reaction assembly comprising: (a) a gas conduit adapted to introduce gas into a reaction medium in the vessel; (b) a sampling device adapted to remove a portion of the reaction medium from the vessel without contamination of the remaining reaction medium remaining in the vessel, wherein the sampling device comprises: (i) a collection conduit extending into the vessel; (ii) a sampling valve positioned in the collection conduit and disposed outside the vessel; and (iii) an extractor associated with the collection conduit and disposed outside the vessel and adapted to remove a sample portion of the reaction medium through the collection conduit; and (c) an introduction conduit permitting the introduction of at least the reaction medium into the vessel; and (d) a sealing cover adapted to enclose and substantially seal the reaction port; wherein the sealing cover includes openings for passage of the gas conduit, the introduction conduit, and the collection conduit each disposed in respective openings of the cover in a fluid-tight manner; wherein the harvesting port comprises a harvesting outlet extending therethrough for the withdrawal of the reaction medium from the vessel to another vessel. a vessel comprising a mixing port, a reaction port, and a harvesting port; an agitator extending through the mixing port into the vessel; a reaction assembly extending through the reaction port into the vessel, the reaction assembly comprising: (a) a gas conduit adapted to introduce gas into a reaction medium in the vessel; (b) a sampling device adapted to remove a portion of the reaction medium from the vessel without contamination of the remaining reaction medium remaining in the vessel, wherein the sampling device comprises: (i) a collection conduit extending into the vessel; (ii) a sampling valve positioned in the collection conduit and disposed outside the vessel; and (iii) an extractor associated with the collection conduit and disposed outside the vessel and adapted to remove a sample portion of the reaction medium through the collection conduit; and (c) an introduction conduit permitting the introduction of at least the reaction medium into the vessel; and (d) a sealing cover adapted to enclose and substantially seal the reaction port; wherein the sealing cover includes openings for passage of the gas conduit, the introduction conduit, and the collection conduit each disposed in respective openings of the cover in a fluid-tight manner; wherein the harvesting port comprises a harvesting outlet extending therethrough for the withdrawal of the reaction medium from the vessel to another vessel. (a) a gas conduit adapted to introduce gas into a reaction medium in the vessel; (b) a sampling device adapted to remove a portion of the reaction medium from the vessel without contamination of the remaining reaction medium remaining in the vessel, wherein the sampling device comprises: (i) a collection conduit extending into the vessel; (ii) a sampling valve positioned in the collection conduit and disposed outside the vessel; and (iii) an extractor associated with the collection conduit and disposed outside the vessel and adapted to remove a sample portion of the reaction medium through the collection conduit; and (i) a collection conduit extending into the vessel; (ii) a sampling valve positioned in the collection conduit and disposed outside the vessel; and (iii) an extractor associated with the collection conduit and disposed outside the vessel and adapted to remove a sample portion of the reaction medium through the collection conduit; and (c) an introduction conduit permitting the introduction of at least the reaction medium into the vessel; and (d) a sealing cover adapted to enclose and substantially seal the reaction port; wherein the sealing cover includes openings for passage of the gas conduit, the introduction conduit, and the collection conduit each disposed in respective openings of the cover in a fluid-tight manner; wherein the harvesting port comprises a harvesting outlet extending therethrough for the withdrawal of the reaction medium from the vessel to another vessel.