Production of polygalacturonases by Aspergillus section Nigri strains in a fixed bed reactor.
Polygalacturonases (PG) are pectinolytic enzymes that have technological, functional and biological applications in food processing, fruit ripening and plant-fungus interactions, respectively. In the present, a microtitre plate methodology was used for rapid screening of 61 isolates of fungi from Aspergillus section Nigri to assess production of endo- and exo-PG. Studies of scale-up were carried out in a fixed bed reactor operated under different parameters using the best producer strain immobilised in orange peels. Four experiments were conducted under the following conditions: the immobilised cells without aeration; immobilised cells with aeration; immobilised cells with aeration and added pectin; and free cells with aeration. The fermentation was performed for 168 h with removal of sample every 24 h. Aspergillus niger strain URM 5162 showed the highest PG production. The results obtained indicated that the maximum endo- and exo-PG activities (1.18 U · mL-1 and 4.11 U · mL-1, respectively) were obtained when the reactor was operating without aeration. The microtitre plate method is a simple way to screen fungal isolates for PG activity detection. The fixed bed reactor with orange peel support and using A. niger URM 5162 is a promising process for PG production at the industrial level.
Mycology Department, Federal University of Pernambuco, Cidade Universitária, Recife 50670-420, Pernambuco, Brazil. lilomaciel@hotmail.com
Marília
M
Maciel
Cristiane
C
Ottoni
Cledir
C
Santos
Nelson
N
Lima
Keila
K
Moreira
Cristina
C
Souza-Motta
D001230:Aspergillus / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D032084:Citrus sinensis; D057075:Enzyme Assays; D005285:Fermentation; D011096:Polygalacturonase / Q000096:biosynthesis*
D011096:Polygalacturonase