Production of thermostable glucoamylase by newly isolated Aspergillus flavus A 1.1 and Thermomyces lanuginosus A 13.37

Abstract

Thirteen thermophilic fungal strains were isolated from agricultural soil, tubers and compost samples in tropical Brazil. Two strains were selected based on of their ability to produce considerable glucoamylase activity while growing in liquid medium at 45ºC with starch as the only carbon source. They were identified as Aspergillus flavus A1.1 and Thermomyces lanuginosus A 13.37 Tsiklinsky. The experiment to evaluate the effect of carbon source, temperature and initial pH of the medium on enzyme production was developed in a full factorial design (2x2x3). Enzyme productivity was influenced by the type of starch used as carbon source. Cassava starch showed to be a better substrate than corn starch for glucoamylase production by A. flavus but for T. lanuginosus the difference was not significant. Enzyme activities were determined using as substrates 0.3% soluble starch, 0.3% maltose or 0.3% of starch plus 0.1% maltose. The enzymes from A. flavus A1.1 hydrolyzed soluble starch preferentially but also exhibited a significant maltase activity. Moreover higher quantities of glucose were released when the substrate used was a mixture of starch and maltose, suggesting that this fungus produced two types of enzyme. In the case T. lanuginosus A 13.37, the substrate specificity test indicated that the enzyme released also hydrolyzed starch more efficiently than maltose, but there was no increase in the liberation of glucose when a mixture of starch and maltose was used as substrate, suggesting that only one type of enzyme was secreted. Glucoamylases produced from A. flavus A1.1 and T. lanuginous A.13-37 have high optimum temperature (65ºC and 70ºC) and good thermostability in the absence of substrate (maintaining 50% of activity for 5 and 8 hours, respectively, at 60ºC) and are stable over in a wide pH range. These new strains offer an attractive alternative source of enzymes for industrial starch processing.

Optimization of Culture Conditions Using One-Factor-at-Time Methodology and Partial Purification of Amylase from Aspergillus niger of DTO: H5 under Solid State Fermentation

“…Fungal enzymes are more preferable to enzymes from other microorganisms because of their Generally Regarded as Safe (GRAS) status (Sindhu et al, 2009). Studies on fungal amylase especially in the developing countries have concentrated mainly on Aspergillus species probably because of ubiquitous nature and non-fastidious nutritional requirement of this organism (Abu et al, 2005;Gomes et al, 2005;Okolo et al, 2000).…”

Bioprospecting of yeasts for amylase production in solid state fermentation and evaluation of the catalytic properties of enzymatic extracts

“…In the same study, the authors reported that the enzymes exhibited about 60% of residual activity after 1 h at 50°C. Gomes et al (2005) reported a decrease of approximately 30% in the catalytic activity of amylase produced by the fungus Thermomyces lanuginosus when incubated for 24 h at pH 4.0 and 10.0. However, the enzyme remained stable after 1 h at 60°C.…”

Partitioning of thermostable glucoamylase in polyethyleneglycol/salt aqueous two-phase system

“…A lot of focus is currently made on the high thermostability of glucoamylase used in the starch processing. Hence, a highly thermostable and environmentally compatible glucoamylase is very essential for industrial purposes [4]. The main benefits of using thermostable enzymes in the starch processing industry include increased reaction rates, decreased contamination risk and cost-reduction in terms of cooling system [5,6].…”