Influence of pectin and glucose on growth and polygalacturonase production by Aspergillus niger in solid-state cultivation.
The solid-state production of endo- and exo-polygalacturonases (PG) by Aspergillus niger was studied in a media containing wheat bran, salts, and different citric pectin and/or glucose concentrations. Kinetic analysis of the process indicated that the formation of PG and the growth of A. niger are associated processes. By increasing citric pectin from 0 to 16% (w/w), the maximum A. niger concentration (X (m)) was raised from 94 to 121 mg/g dry medium suggesting that pectin can be used by A. niger as a growth substrate besides its role as an inducer. With 16% (w/w) pectin, 281 U exo-PG/gdm and 152 U endo-PG/gdm were obtained. Otherwise, pectin concentrations from 20 to 30% (w/w) hindered both production and growth. A. niger concentrations of 108-113 mg/gdm were achieved in runs with glucose from 5 to 12% (w/w), whereas at 16 and 20% (w/w) glucose, lower X (m) values (ca. 100 mg/gdm) were measured. The addition of glucose to the wheat bran medium, up to 10% (w/w) led to maximum endo-PG titers slightly lower than those found in the absence of glucose. Nevertheless, exo-PG formation in these media was strongly increased and activities over 370 U/gdm were achieved. The results suggest that in experiments with pectin concentrations until 16% (w/w), exo-PG production was repressed by pectin-degradation products although these same substances had favored biomass growth. When glucose concentrations over 10% (w/w) were added to the media, the maximum activities of both enzymes decreased drastically, suggesting that glucose at high concentrations also exerts a repressive effect on PG production.
Fontana
Roselei Claudete
RC
Instituto de Biotecnologia, Universidade de Caxias do Sul, Caixa Postal 1352, 95001-970 Caxias do Sul, RS, Brazil.
Salvador
Suzielle
S
Silveira
Mauricio Moura da
MM
D001234:Aspergillus niger / Q000201:enzymology* / Q000254:growth & development* / Q000502:physiology; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D010368:Pectins / Q000378:metabolism*; D011096:Polygalacturonase / Q000096:biosynthesis*
D010368:Pectins; D011096:Polygalacturonase; D005947:Glucose