Influence of Different Substrates on the Production of a Mutant Thermostable Glucoamylase in Submerged Fermentation

Abstract

Three mutations, Ser54→Pro, Thr314→Ala, and His415→Tyr, were identified in Aspergillus awamori glucoamylase gene expressed by Saccharomyces cerevisiae. The mutant glucoamylase (GA) was substantially more thermostable than a wild-type GA at 70 °C, with a 3.0 KJ mol(-1) increase in the free energy of thermo-inactivation. The effect of starch from different botanical sources on the production of this GA was measured in liquid fermentation using commercial soluble starch, cassava, potato, and corn as the carbon source. The best substrate for GA production was the potato starch showing an enzymatic activity of 6.6 U/mL. The commercial soluble starch was also a good substrate for the enzyme production with 6.3 U/mL, followed by cassava starch and corn starch with 5.9 and 3.0 U/mL, respectively. These results showed a significant difference on GA production related to the carbon source employed. The mutant GA was purified by acarbose-Sepharose affinity chromatography; the estimated molecular mass was 100 kDa. The mutant GA exhibited optimum activity at pH 4.5 and an optimum temperature of 65 °C.

A Novel β‐Glucosidase from Sporidiobolus pararoseus: Characterization and Application in Winemaking

“…The Sp‐β‐gl activity toward cellobiose was determined by assaying the amount of glucose released by the glucose oxidase/peroxidase method (Pavezzi and others 2010). The cellobiase activity was determined using different concentrations of cellobiose (5, 10, and 20 g/L) and 100 mM citrate phosphate buffer at the optimum pH and also at the wine pH (pH 3.5), at the optimum temperature.…”

Comparative genomics of the aconidial Aspergillus niger strain LDM3 predicts genes associated with its high protein secretion capacity

“…In general, sporulation-deficient Aspergillus strains are known to be defective in many regulators, including the transcription factors (TFs) BrlA and FlbA. The functions of both these 2 proteins have been well documented in A. niger, Aspergillus nidulans, Aspergillus fumigatus, and Aspergillus oryzae (Adams et al 1988;Krijgsheld et al 2013;Lee and Adams 1996;Mah and Yu 2006;Pavezzi et al 2011;van Munster et al 2015;Yamada et al 1999). BrlA is the central regulator of conidiophore development which becomes activated by FlbA (Krijgsheld et al 2013).…”

Effects of Temperature and Additives on the Thermal Stability of Glucoamylase from Aspergillus niger

“…The major application of glucoamylase is to catalyze starch saccharification to produce glucose for food and fermentation industries. The enzymes, the majority produced by the filamentous fungi Aspergillus and Rhizopus, display low transglycosylation activity and near 100% glucose is obtained from starch hydrolysis [19,20,25].…”