A polyelectrolyte complex gel was prepared by mixing chitosan and K-carrageenan solutions in the presence of NaCl. To study the effect of ambient pH on the swelling behavior, the diameter of the cylindrical gel ( 4 mm X 8 mm) immersed in aqueous NaOH, KOH, or HC1 solution was measured. In the range of pH 10-12, the diameter increased with time, and the gel reached swelling equilibrium within 6 days. In an NaOH solution of pH 10.5, the maximum swelling occurred, and the volume of the gel at equilibrium was 10.2 times as large as the initial one. At pH below 9 and at pH 13, no swelling was observed. Thus, the swelling of the complex gel prepared in this study was sensitive to a rather narrow range of pH. The swelling equilibrium in the presence of NaCl was also investigated at various pH.

SummaryA theoretical study was made on the dynamic behavior of a single-vessel continuous fermentation subject to a growth inhibition a t high concentration of the rate limiting substrate. Phase plane plotting and stability analysis showed three steady states to exist; namely, a "washout" state, a nontrivial stable state, and an unstable state. Whether the system attains a nontrivial steady state or is to be washed-out depends upon the initial values of the cell and/or substrate concentration(s). Since this property is a characteristic feature of the present system, an experimental procedure was suggested to insure a stable operation in practice.

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