Mathematical modeling of lipase and protease production by Penicillium restrictum in a batch fermenter

This work presents a mathematical model that describes time course variatio ns of extracellular lipase and protease activities for the batch fermentati on of the fungus Penicillium restrictum, a new and promising strain isolate d from soil and wastes of a Brazilian babassu coconut oil industry. The fer mentation process was modeled by an unstructured model, which considered th e following dependent variables: cells, fat acid, dissolved oxygen concentr ations, lipase and protease activities, and cell lysate concentration. The last variable represents the amount of cells that has been lysed by the she ar stress and natural cell death. Proteases released to the medium, as cons equence of this process, enhance lipase inactivation. The model is able to predict the effects of some operation variables such as air flow rate and a gitation speed. The mathematical model was validated against batch-fermenta tion data obtained under several operating conditions. Because substrate co ncentration has antagonistic effects on lipase activity, a typical optimiza tion scheme should be developed in order to minimize these deleterious effe cts while maximizing lipase activity.