Genetic engineering of Penicillium chrysogenum for the reactivation of biosynthetic pathways with potential pharmaceutical value

Since the discovery of penicillin by Alexander Fleming, the filamentous fungus Penicillium chrysogenum has been extensively exploited as a β-lactam producer at an industrial scale. Although this fungus also possesses the ability to produce other possibly useful bioactive compounds, the process of classical strain improvement (CSI) of P. chrysogenum that has led to a major boost of the β-lactam production capacity at the same time led to a major reduction of the production of other bioactive compounds. In the CSI programme, random mutagenesis induced by ultra-violet light and mutagenic chemical agents was used and this silenced biosynthetic pathways of metabolites that were considered as contaminants of β-lactam at that time. One of these molecules are the sorbicillinoids that have gained renewed pharmaceutical interest because of its anti-HIV activities. To restore the sorbicillinoids production in current industrial strains, a critical point mutation in the sorbicillinoids biosynthetic gene cluster (BGC) was repaired via homologous recombination. This restored strain produced high levels of sorbicillinoids and was used to elucidate the mechanism of sorbicillinoids biosynthesis. At the same time, it was discovered that sorbicillinoids biosynthesis is controlled by two transcriptional regulators involving an auto-induction mechanism wherein sorbicillinoids stimulate the expression of the pathway genes. Overall, the programme has yielded a host for the high-level production of sorbicillinoids and will be used in future studies for the production of advanced sorbicillinoids derivatives of pharmaceutical value.