A temperature-sensitive poly(N-isopropylacrylamide) hydrogel was used to concentrate cellulases from the fermentation broth of Trichoderma reesei. The steady-state gel volume was less and the gel collapse temperature was lower in fermented broth compared to those in water. Upon a long (24 h) temperature swing for gel swelling, a gel with lower monomer and cross-linker content showed a larger volume increase, and it took longer to reach a constant volume which was smaller than the steady-state volume. Upon a long (24 h) temperature swing for gel collapsing, different gels reached the same collapsed volume in a short period of time. The largest volume increase per unit temperature decrease was obtained for a temperature swing between 28 and 33-degrees-C. For short temperature swings (1-5 h), swollen and collapsed gel volumes were reproducible and were approximately the same as the final volumes during long (24 h) swings. Separation efficiency was higher for the gel with a smaller volume change because of higher concentrations of monomer or cross-linking agent. When the gels were reused, separation efficiency was improved.
