Production and partial characterization of polygalacturonases produced by thermophilic Monascus sp N8 and by thermotolerant Aspergillus sp N12 on solid-state fermentation

Abstract

Polygalacturonases production by newly isolated Monascus sp N8 and Aspergillus sp N12 strains was carried out in solid-state fermentation using mixtures of wheat bran, sugar cane bagasse and orange bagasse as carbon sources. The maximal activity values of exo-polygalacturonases (exo-Pg) from Monascus sp and Aspergillus sp were obtained using wheat bran/sugar cane bagasse/orange bagasse mixture (6.6 U/mL) and wheat bran/orange bagasse mixture (10 U/mL), respectively. Enzyme production by both strains was higher at 45oC after 72 h and 1.6 U/mL at 50oC after 120 h. Endo-polygalacturonase (endo-Pg) production was higher in wheat bran/orange bagasse mixture and was not affected by temperature of incubation for both fungi. Endo-Pg production by Monascus was 1.8 U/mL at 45oC and 50oC, after 72. Similar values were obtained in Aspergillus sp culture, 1.9 U/mL at 45oC and 1.8 U/mL at 50oC. Exo-Pg from both strains showed optimum activity at pH 5.5. Maximal activity was determined at 60oC for enzyme from Monascus sp and 50oC for that produced by Aspergillus sp. Exo-Pg from Monascus sp was stable at pH range 4.5-6.0 whereas that from Aspergillus sp enzyme was stable at pH 4.0. Both enzymes showed stability when incubated at 50oC for 1 h, in absence of substrate.