The wild type, Penicillium occitanis, was chosen for a programme of genetic improvement. After a single round of nitrous acid mutagenesis. a hyperpectinolytic mutant was selected. It secretes about fifty times more of endo and exopectinases activities than the wild type one. Most interestingly, this mutant is fully constitutive since it produces all pectinases on glucose and glycerol, known as repressors of pectinolytic genes. It does not hyper-produce other hydrolytic enzymes such as cellulase. IEF analysis confirmed these results and showed that, al pectinases are over expressed in Our mutant,