(eng): Since their discovery, fermentation processes have gone along not only with the industrial beverages production and breweries but since the times of Alexander Fleming they have become a crucial part of the health care due to antibiotics production (from which the overwhelming majority of 90% is produced during a fermentation process). However, complicated dynamics and strong nonlinearities cause that the production with the use of linear control methods achieves only suboptimal yields. From the variety of nonlinear approaches, gradient method has proved the ability to handle these issues - nevertheless, its potential in the field of fermentation processes has not been revealed completely. In this paper, two fresh control strategies are introduced and compared - both of them are based on a double-input optimization approach, yet a successful reduction to a single-input optimization task is proposed.