6-24: Influence of different substrates on the production of a mutant glucoamylase in submerged fermentation

Glucoamylase (GA) has a great importance for starch and other related oligosaccharides saccharification in fermentation and food industries. GA hydrolyzes α-1,4 and α-1,6 glycosidic bonds from starch resulting in glucose production. The main use of GA is related to glucose production, which is applied as a feedstock in biological fermentations for ethanol or high fructose syrups production. This enzyme has been used in many researches about molecular biology, mainly regarding to stability improvement. However, there are very few studies about the influence of the kind of starchy substrate on the enzyme production.  The aim of this study was to produce a mutant thermostable GA of Aspergillus awamori expressed by Saccharomyces cerevisiae, using different sources of starch as cassava, potato and corn. The best substrate for GA production was the cassava starch, that shown an enzymatic activity of 6.0 U/mL. The commercial soluble starch (control) displayed an enzymatic activity of 5.8 U/mL. Activities with potato starch and corn starch were 3.6 and 3.0 U/mL, respectively. So, these results show a significant difference on GA production regarding to the carbon source employed. The culture supernatant containing GA from cassava starch was concentrated and diafiltrated against a buffer of 0.5 M NaCl/ 0.1 M NaOAc, pH 4.5, using Amicon S1 spiral ultrafiltration cartridge, and purified by acarbose-Sepharose affinity chromatography. The molecular mass of the enzyme was estimated in100 KDa. The mutant GA exhibited optimum activity at pH 4.5, and optimum temperature of 65 °C.

 Financial support: FAPESP and CNPq.