Multiple-input cultivation model based optimization of penicillin production

Unlike prevailing contemporary approach considering the influx feed flow as the only crucial input influencing the final product concentration in bioprocess cultivation, the current paper considers other (non-nutritional) inputs as well. Among them, the volume withdrawal is an important option. Two types of control strategies employing this second input are considered here, each of them using it in a different way. First, the so-called quasi-double-input strategies exploit the broth withdrawal to follow a pre-determined volume profile. Second, the true-double-input strategies consider the second input as a completely independent optimization variable. Main analysis tool here is the gradient optimization numerical algorithm and its adaptations. All resulting strategies are summarized and formulated in the context of optimization, those introduced earlier (i.e., the quasi-double-input) are unified into a common general strategy. Practical complication (inadmissible volume decrease) related to withdrawal introduction is successfully addressed and the summary results show indisputable improvement gained by the non-nutrient input introduction.