Screening of fungi from the genus Penicillium for production of β- fructofuranosidase and enzymatic synthesis of fructooligosaccharides

Eight new isolated fungi of the genus Penicillium were evaluated for β- fructofuranosidase (FFase) production. From these, Penicillium citreonigrum was selected for FFase and fructooligosaccharides (FOS) production. The influence of temperature, yeast extract concentration, pH and fermentation time on the FFase activity when using the whole microorganism was evaluated by 2⁴ and 2³ designs. The pH was set at 6.5 and no yeast extract was used in the optimization experiments since both shown low significant effects on FFase activity. After optimization, temperature and fermentation time, were set to 25.5 °C and 67.8 h. Under these conditions, the model predicted a FFase production of 301.84 U/mL. The scaled-up process in a 2 L bioreactor enhanced the enzyme productivity up to 1.5 times (6.11 U/mL h). A concentration of 58.7 g/L of FOS was obtained, where kestose was the main product. Assays performed for enzyme characterization showed that 50 °C and a pH 5.0 are the optimal conditions for FFase activity. FFase showed to be stable at temperatures between 25 and 30 °C and pH 4.0–10.0 and its activity increased in the presence of ions, especially Cu⁴⁺. Results obtained in this primary report are a clear indication on the interest of using P. citreonigrum as a source of FFase for further FOS production.