Use of a growth-associated control algorithm for efficient production of a heterologous laccase in Trichoderma reesei in fed-batch and continuous cultivation

In this work, a thermostable laccase from the fungus Melanocarpus albomyces was produced in the efficient protein producer Trichoderma reesei in batch, fed-batch and continuous cultivations on lactose medium in a laboratory fermenter. The rate of consumption of base for pH control (DELTABAS) was measured in all the cultivations and was used as a control parameter in one fed-batch run and in a 1000 h continuous cultivation. The dynamic DELTABAS control parameter can be used to maintain optimal production of secreted protein by fitting the rate of substrate feeding to the amount of substrate available to the growing fungus in the fermenter, thus maintaining growth limitation due to availability of carbon source while avoiding total carbon source depletion. The use of this parameter, capable of maintaining the biomass in a physiological state of imminent but not actual exhaustion of carbon source, was successful in both the fed-batch and continuous production of heterologous laccase. Laccase production in fed-batch and continuous runs was considerably improved in comparison to the batch cultivation, both in terms of volumetric productivity and yield on lactose. The DELTABAS-control algorithm was shown to be a useful research tool for process optimization.