TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method (M1) further involves adding a microorganism to the vessel and fermenting the saccharified feedstock, where during at least part of fermentation all of the jet-flow agitators are operated in the first mode; monitoring a glucose level of a mixture of the feedstock, the fluid medium and the saccharifying agent during operation of the jet mixer; adding additional feedstock and saccharifying agent to the vessel during saccharification; adding an emulsifier or surfactant to the mixture in the vessel; and adding a microorganism to the vessel and fermenting the saccharified feedstock. In the method (M1), saccharifying the feedstock involves agitating the feedstock with the jet-flow agitator. In the method (M1), during at least part of mixing all of the jet-flow agitators are operated in the first mode. In the method (M1), during at least part of mixing some of the jet-flow agitators are operated in the first mode and, at the same time, others are operated in the second mode. The jet mixer comprises a jet aeration type mixer having a delivery nozzle, and where saccharifying the feedstock involves delivering a jet through the delivery nozzle. The jet mixer is operated without injecting air through the delivery nozzle. The saccharifying involves supplying a liquid to two inlet lines of the jet aeration type mixer. In the method (M1), saccharifying involves adding the feedstock to the fluid medium in discrete increments; and mixing each discrete increment of feedstock into the fluid medium with the jet mixer before adding another increment of feedstock. In the method (M1), the saccharification takes place partially or completely during transport of the mixture of feedstock, fluid medium and saccharifying agent. In the method (M2), the mixer is configured to limit any increase in the overall temperature of the fluid medium to less than 5 degrees C over the course of mixing. In the method (M3), converting involves agitating the feedstock with the jet-flow agitator. The method (M4) further involves during fermentation, transferring the contents of the vessel to a transport vessel and allowing fermentation to continue in the transport vessel; agitating the contents of the vessel with a jet mixer during saccharification and fermentation; and monitoring the oxygen content and ethanol and/or sugar content of the fermenting mixture. Preferred Components: The feedstock has a bulk density of less than 0.5 g/cm3. The fluid medium comprises water. The saccharifying agent comprises an enzyme. The microorganism comprises yeast. The vessel comprises a tank (preferably a tank of a rail car or a tanker truck). The vessel has an arcuate bottom surface. The jet mixer comprises a jet-flow agitator (preferably an impeller mounted at a distal end of a shaft, and a shroud surrounding the impeller), each jet-flow agitator is configured to operate reversibly, pumping fluid towards the top of the vessel in a first mode, and towards the bottom of the vessel in a second mode. The jet mixer comprises a suction chamber jet mixer. The jet mixer comprises a nozzle in fluid communication with a first end of an ejector pipe, the first end of the ejector pipe being spaced from the nozzle, and the ejector pipe having a second end that is configured to emit a fluid jet. Preferred Apparatus: The apparatus further comprises a torque monitor that monitors torque of the motor during mixing, and/or an amp monitor that monitors the full load amperage of the motor; a controller that adjusts the operation of the feedstock delivery device and/or the saccharifying agent delivery device based on input from the torque monitor; and a variable frequency drive configured to adjust the speed of the motor. The jet mixer further comprises a motor. The tank has an arcuate bottom surface. Preferred System: The fermentation system further comprises a fermentation monitor configured to monitor the sugar concentration and/or ethanol concentration of the liquid in the vessel; and a controller configured to stop fermentation based on input received from the fermentation monitor. The fermentation system further comprises a fermentation stopping module configured to stop fermentation in response to a signal received from the controller. In the system, the controller is configured to oxygenate the vessel at a rate of less than 0.2 volumes versus mass (vvm). EXAMPLE - No suitable example is given.