W. H. BARTHOLOMEW and DAVE KOZLOW Pabsf Laboratories, Division of Pabst Brewing Co., Milwaukee, Wis.
Automatic Antifoam and Nutrient Feed Control for Bench Scale Fermentation An automatic system provides uniform control and economical and positive operation of submerged laboratory fermentations
SUBMERGED
laboratory fermentations are frequently performed in batteries of aerated, mechanically agitated, borosilicate glass jars. A means for sterile introduction of antifoam is usually needed to control foaming-often a serious problem. The control systems can be manual or automatic. A reliable automatic system facilitates uniform control. Often fermentations are enhanced by serial nutrient addition during fermentation. In these laboratories such a technique formerly required manual operation. At the time it was decided to install automatic antifoam control for the battery of 27 agitated bench scale fermentors, it was apparent that only a satisfactory automatic nutrient feed system would give full benefit in labor saving and flexible operation. Thus the installation was designed to incorporate both features. Antifoam control devices of various design for laboratory fermentors have been used. Anderson and others (7), Brown and Peterson (Z), Chain and others ( 3 ) , and Dworschack, Lagoda, and Jackson ( 4 ) , describe useful antifoam control units. I t was decided to fabricate the antifoam and automatic feed device for this laboratory, using commercial control units for the component parts.
Apparatus The fermentors were set up in groups of six in constant temperature baths on both sides of a central drive shaft. The control panel for each group of six is located above the fermentors. As there is a set of antifoam and nutrient feed controls for every three fermentors, there are duplicate sets of such controls. The companion installation for six more tanks is located back to back to the one described. The antifoam and serial feed reservoirs are above the fermentors. The antifoam and nutrient feed control panel has three Lumenite electronic relays which are connected to the electrodes of each of three fermentors and activate the solenoid valves to dispense
antifoam. A General Electric timer connected in the circuit provides the timing for antifoam shots to three fermentors. Next to this is the Zenith clock and timer, which can be set to activate the other solenoid valves for automatic nutrient feed. A separate fused circuit provides power for the system; no other operation in the pilot plant can affect the 24-hour operation of the controls. The diagram of the system shows the external connections. The Lumenite
electronic level control F1-101I-KlO is supplied with one normally open and one normally closed circuit. This standard unit has been adapted to the desired operation by addition of another open circuit; a two-pole flapper and normally open contact are added to the left side of the relay. 'The normally closed circuit wire was removed from the No. 3 connector and the second normally open circuit was soldered to this connector in its place. The General Electric time switch
Laboratory fermentors and wiring diagram for antifoam and nutrient feed controls A . Lumenite electronic level control F1-1011-K-10 modified to provide two open circuits
i
B.
General Electric 60-second time switch
C.
Combination 24-hour clock and 14-second timer
D. TPIG signal light E.
Warrick TIBI electrode, 3/&ch Teflon insulation
pipe thread,
F. ASCO '/s-inch normally closed solenoid valve with l/ls-inch port supplied with Luxolene coil without housing in place of regular coil VOL. 49,
Lumenite Electronic Co. 407 South Dearborn St. Chicago 5, Ill. General Electric Co. 840 South Canal St. Chicago 80, 111. Zenith Electric Co. 152 West Walton St. Chicago 10, Ill. Square D. Co. 4041 North Richards St. Milwaukee, Wis. Charles F. Warrick Co. 1964 West Eleven Mile Road Berkley, Mich. Automatic Switch Co. 391 Lakeside Ave. Orange, N. J.
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AUGUST 1957
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has two open circuits, to provide for 10070 timing control. This timer makes one revolution in 60 seconds. Only one of the circuits is used in this case as the operation is to permit a variable 0- to 5second control of “on” cycle for opening the solenoid valve. The balance of the 60-second cycle is “off,” to allow time for the contact to break after antifoam is added. This prevents further antifoam addition, even though the electrode may still be in contact with the foam. The black (BK) wire is the outlet for the 0- to 30-second circuit and the green wire (G) is the outlet for the 30- to 60-second circuit, which is not used. One General Electric time switch is used for a set of three fermentors hooked into three Lumenite controls. The Zenith Electric Co. combination clock and timer, used for nutrient feed addition, is mounted on the same panel with the antifoam control. Each clock controls three fermentors. Usually fermentation variables are run in triplicate. The 24-hour clock has tabs located at 15-minute intervals, to allow operation of the feed device at 30minute minimum intervals. The clock operates a 0- to 14-second reset timer which closes the circuit to open the solenoid valve for a preset time interval The ASCO solenoid valves (brass for antifoam feed and stainless steel for nutrient feed) are operated by a waterproof Luxolene coil. The coil slips over the solenoid and is held in place with a short section of rubber tubing. No housing is required, so the setup for operation is very simple. The valves are welded to the inlet lines at the top of the fermentor and can be sterilized with the fermentor unit, completely separated from all electric leads and parts. Heat-resistant and resilient valve disks seat against the valve seats. This valve is a key to successful op. eration. The closure disk is resistant to prolonged sterilization in the presence of antifoam oil, giving long life and trouble-free service. The body of the valve is easily cleaned-important for successful sterile operation. The electrode lead for the antifoam control can be attached to a Warrick TIBI electrode fitting after sterilization, when the fermentor is placed in the bath. A stainless steel rod, threaded to the fitting. serves as the electrode. It is cut to a suitable length for the service required. For antifoam control, three wire leads connect the control boxes to the individual fermentors and can reach individual tanks only. The leads to solenoid valves for nutrient feed can reach all 1 2 fermentors, allowing random spacing of variables in the tanks. A sterile air pressure line, adjustable from 1 to 4 pounds per square inch gage, is provided to each fermentor for use with antifoam or nutrients too vis-
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cous to feed by gravity. Each line can be attached to the top of a feed container, but this setup is seldom required, as gravity feed is satisfactory. The glass fermentors are operated a t atmospheric pressure. Operation
The defoamer control is operated by setting the General Electric time switch for the desired volume of antifoam, predetermined in a duplicate laboratory solenoid setup using a stop watch to time the flow. With the defoamers used in this laboratory a 0.5-second “on” time delivers 1 or 2 drops, and this is usually sufficient to break the foam. The quantity delivered is less than can normally be delivered manually. The general level of antifoam consumption has been lower since the switch from manual control. When foam establishes contact with the electrode, the relay closes both open circuits in the Lumenite control The signal light turns on, showing antifoam is called for, and the lead to the solenoid is energized, When the General Electric 60-second timer reaches the “on” cycle, the solenoid circuit is completed for the set interval and the valve opens to allow addition of antifoam. If the foam disperses, all circuits open again as contact is broken. If the foam does not drop, another shot is added after 60 seconds, when the timer again reaches the “on” cycle. Once in operation, no attention is required as the operation is fully automatic. Each tank can operate independentlv. However, if two or three in the same circuit call simultaneously for antifoam, they receive their shots a t the same time. Nutrient feed addition is regulated bv first setting the 24-hour clock to the correcr time. Then the tabs located at 15-minute intervals are depressed, corresponding to the exact time feeding is desired. A microswitch is activated by the depressed tab to dose the two open circuits, activating the three solenoid valves. Simultaneously, the clock operates the 0- to 14-second reset timer. After traveling the predetermined set time, the timer remains at the zero rest point, reopening the one timer circuit. This closes the solenoid valves. The reset timer stays at the zero rest until the microswitch breaks contact with the depressed tab a t the end of the 15-minute interval, where it reaches the open tab space for the next 15-minute interval. This opens the circuit which supplies power to the reset timer. The timer then is reset by a spring and is ready for a subsequent feed signal from a depressed tab. Whenever two adjacent 15-minute tabs are depressed, the timer cannot reset. Thus, this svstem can repeat feed a t a minimum of 30 minutes.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
The operator can predetermine the time setting required for delivery of the quantity of nutrient desired, by calibrating the flow a t the desired concentration in a duplicate laboratory setup. A homogeneous feed is necessary for satisfactory operation. The quantities of nutrient can be determined by previous experience coupled with control tests on samples taken at intervals during the fermentation. The settings can be changed a t will during the fermentation, depending on a control test such as pH, which is frequently a criterion. Summary The antifoam and nutrient feed devices for 27 laboratory fermentors were installed for a total cost of $2900. There has been considerable labor saving, in addition to the closer control made possible by the automatic system. Weekend labor is reduced to the minimum required for taking regular samples at 8- to 12-hour intervals. As the pilot plant fermentation operation is run 7 days a week, and setting tanks only during week days, elimination of full week-end coverage has saved about $4000 to $5000 per year. The operators assigned to fermentor operation had to devote all their time to this work during the regular work week. They are now free to run other pilot plant operations, except for fermentor sampling and a minimum of recording time. This has proirided greater flexibility and increased work output per man in the pilot plant. The automatic feed systems have operated in a sterile and trouble-free manner, with negligible contamination. The equipment has operated excellently with several types of defoamer used for many different fermentations-riboflavin, vitamin B11, bacitracin, bacterial amylase and protease, fungal amylase and protease, and numerous antibiotics originating from a screening program. Literature Cited
(1) Anderson, R. F., Whitmore, L. M., Brown. W. E., Peterson, W. H., Churchill, B. W., Roegner, F. R., Campbell, T. H., Backus, M. P.. Stauffer, J. F., IND.ENG.CHEW45, 768 11953).
Brown,‘ W. E., Peterson, W. H., Ibid., 42, 1769 (1950). Chain, E. B., Paladino, S., Ugolini, F., Callow, D. S.,Van der Sluis, J.. Rend.
ist.
supeiiore sanitd
17, 61
(1954) (English ed.). Dworschack, R. G., Lagoda, A. A., Jackson, R. W., Appl. hficrobiol. 2, 190 (1954). RECEIVED for review November 20, 1956 ACCEPTED February 28, 1957 Division of Agricultural and Food Chemistry, Symposium on Fermentation Process and Equipment Design, 130th Meeting, ACS, Atlantic City, N. J., September 1956.
