CHAPTER 3 – Theoretical Analysis of Continuous Culture Systems

INTRODUCTION............................................................ 1 DESIGN AND APPARATUS .................................................. 2 Membrane Dialysis Culture................................................... 2 Interface Dialysis Culture ............... ..................................... 6 Colonial Growth with Dialysis ................................................ 8 Methods of Operation ....................................................... 9 Types of Membranes........................................................ 10 Membrane Permeability and Solute Sieving ........ ............................. 11 Membrane Penetrability by Microorganisms .................................... 12 THEORY................................................................. 14 Principles of Dialysis........................................................ 14 Membrane characteristics................................................... 14 Measurement of permeability............................................... 15 Porosity................................................................. 15 Hydrodynamics............................................................ 17 Osmosis................................................................. 18 Growth in Dialysis Culture................................................... 19 Basic considerations ....................................................... 19 Completely continuous operation............................................. 20 Completely batch operation................................................. 25 Batch fermentor, continuous reservoir operation.............................. 28 Continuous fermentor, batch reservoir operation................................ 29 Product Formation in Dialysis Culture.......................................... 29 Basic considerations ....................................................... 29 Completely continuous operation............................................. 30 Batch operations.......................................................... 31 Implications of Theory....................................................... 31 Summary of Mathematical Abbreviations ......... .............................. 32 Analogue Computer Program................................................. 32 RESULTS AND APPLICATIONS............................................. 34 In Vitro Systems............................................................ 34 Growth response and variables.............................................. 34 Cell production........................................................... 37 Formation of nondiffusible products.......................................... 38 Production of diffusible compounds .......... ................................ 39 Interbiosis................................................................ 40 Gas exchange............................................................. 40 In Vivo Systems................................ ''I ....... 41 Peritoneal dialysis......................................................... 41 Hemodialysis............................................................. 43 Solid tissue implants....................................................... 43 Embryonated egg ......................................................... 43 Rumen symbiodialysis ................ ..................................... 43 LITERATURE CITED........................................................ 44

Dialysis culture of microorganisms: design, theory, and results.

SUMMARY: The amounts of three catabolite repressible enzymes, alkaline protease, neutral protease and α-amylase, produced by Bacillus subtilis NRRL-B3411 growing in a chemostat, depended on the growth-limiting substrate. Limiting growth with glucose was advantageous for α-amylase synthesis while nitrogen-limited growth was advantageous for synthesis of the two proteases. Under the conditions used, continuous cultures were unsuitable for large-scale production of the three enzymes since spontaneous mutations to less productive strains occurred in the long term.

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Continuous culture studies on the biosynthesis of alkaline protease, neutral protease and -amylase by Bacillus subtilis NRRL-B3411.

The feasibility of producing ethanol in a continuous system from cellulose using Clostridirrrn thermocellum was investigated. This anaerobic and therniophilic bacterium was able to degrade cellulose directly into ethanol with acetic acid, hydrogen. and carbon dioxide as by-products of this fermentation. The fermentation was first carried out in a batch mode to study the effects of buffers, temperature, and agitation on microbial growth and ethanol production. From the compounds used to control pH. sodium bicarbonate had the most preferred effects on generation time and ethanol production. As expected, there was a positive relationship between temperature and growth rate. On the other hand, agitation did not benefit from ethanol production or microbial growth. The possibility of noncompetitive inhibition within such a system was deduced from the calculation of the kinetic constants K(m) and V(max). Continuous fermentations were carried out at 60 degrees C and pH 7.0 using 1.5 and 3% pure cellulose as a limiting substrate. The maximum ethanol concentration reached during the 1.5% cellulose fermentation was 0.3%. and 0.9% during the 3% cellulose fermentation. The yield of ethanol was about 0.3 grams per gram of consumed cellulose. The overall yield in both schemes was around 0.45 and 0.75 grams per gram of cellulose degraded. It was concluded that cellulose could be degraded continuously in a system with C. thermocellum for production of ethanol. While the continuous system like the batch method is feasible, it may not be promising as yet because of the slow generation time of this microorganism.

A study of producing ethanol from cellulose using Clostridium thermocellum.

The control and measurement of ‘CO2’ during fermentations

SUMMARY: The report reviews methods of continuous infrared absorption analysis and gives the description and performance of a commercial infrared CO2 analyser. Examples are given of the use of an infrared analyser recorder to measure CO2 in effluent air from deep cultures. This measure of metabolic activity can be used to estimate growth rate. It is particularly useful because results are obtained with little or no measurement lag and without the need to sample the culture fluid itself.

A continuous infrared analyser for measurement of co2 in effluent air from bacterial cultures

SUMMARY: Comparisons are given of the output of sorbose from 3 litre cultures of Acetobacter suboxydans grown in a sorbitol medium in batch and continuous culture. An estimate is given of the investment value of a continuous process of sorbose production relative to the batch process.

R. C. Telling

Papers

A continuous infrared analyser for measurement of co2 in effluent air from bacterial cultures

The investment value of continuous culture