The present work is aimed to show the effects of environmental parameters such as temperature, pH, ionic strength, and sodium nitrate on enzyme activity of a LiP Isoenzymes Mixture (LIM) obtained from an immobilized culture of Phanerochaete chrysosporium. LIM enzyme stability was also evaluated. The results are discussed in detail and a comparison with literature data is carried out. LIM showed high activity at pH 3.0 in the temperature range 30 to 40°C, it is able to catalyze oxidation reactions at acid pH (2.5 < pH < 6) and over a wide range of temperatures (25 to 60°C). Ionic strength below 0.2 M had no effect on enzyme activity at pH 4.7 and 39°C. An evaluation of the time decay constant of LIM activity under a specific combination of parameters was also conducted. Finally, an LIM activity and durability map shows the optimal working conditions that might be suitable for its practical application in waste bioremediation processes.

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The effect of different lyoprotectants (sucrose, dimethyl-succinate buffer (DMS), bovine serum albumin (BSA), mannitol and dextran, mw 60 kDa) on the stability of the enzyme lignin peroxidase (LiP, EC number: 1.11.1.-), both during the freeze-drying process and storage were investigated. The shelf stability tests were performed at 4°C and 27°C. Both DMS buffer and sucrose showed a good protective action: the former was particularly effective during the process, while the latter improved the stability during storage. In contrast, mannitol and dextran had negative effects, reducing the activity also in the lignin peroxidase solution. BSA was discarded because, in the range of compatible concentrations with LiP, it does not confer a consistent structure to the freeze-dried product.

The aim of this paper is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze-drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory scale apparatus which allowed monitoring the temperature as well as the weight of the samples; the technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed.

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