Production of raw-starch-digesting α-amylase isoform from Bacillus sp. under solid-state fermentation and biochemical characterization

Abstract

α-Amylase production by solid-state fermentation of different Bacillus sp. was studied previously on different fermentation media. However, no study has been reported on the influence of selected media on expression of desired amylase isoforms such as raw-starch-digesting amylase (RSDA). In this paper, the influence of different inexpensive and available agro-resources as solid media (corn, wheat and triticale) on α-amylase isoform induction from three wild-type Bacillus sp., selected among one hundred strains tested, namely 9B, 12B and 24A was investigated. For all three strains, tested amylases were detected in the multiple forms; however, number and intensity of each form differed depending on the solid media used for growth. To determine which isoform from Bacillus sp. 12B was RSDA, the suspected isoform was purified. The optimum pH for the purified α-amylase isoform was 6.0-8.0, while the optimum temperature was 60-90 °C. Isoform was considerably thermostable and Ca(2+)-independent, and actually the only α-amylase active towards raw starch. Purification and characterization of RSDA showed that not all of the solid media tested induced RSDA. From an economic point of view, it might be significant to obtain pure isoenzyme for potential use in the raw-starch hydrolysis, since it was 5 times more efficient in raw corn starch hydrolysis than the crude amylase preparation.

Optimization and scale-up of α-amylase production by Aspergillus oryzae using solid-state fermentation of edible oil cakes

“…Previous studies on the optimization of α-amylase production have considered factors such as modifying nutritional parameters (C:N ratio, supplements, and other nutrients), physiological conditions (temperature, pH, inoculum load, and incubation time), the superiority of organisms (fungi and bacteria), and the method of fermentation (SSF and SmF) [1,12]. One factor at a time (OFAT) optimization was predominantly used to optimize α-amylase production [12,[20][21][22][23][24][25]. Because of the tedious nature of OFAT, statistical optimization tools are preferred for optimization studies, especially for α-amylase production, since the past decade [24,25].…”

A thin layer chromatographic comparison of raw and soluble starch hydrolysis patterns of some α-amylases from Bacillus sp. isolated in Serbia

“…In a previous study, it was found that only one isoform amongst several produced by SSF of strain 12B had the ability to hydrolyze raw starch. 15 It is very important to notice that the control strain in this study (BL3), B. licheniformis ATCC9945a, which was already shown to produce highly efficient α-amylase for the digestion of raw starch, 7 was less efficient than the tested wild type strains. Nevertheless, it is very important to emphasize that approximately 10-100 times lower enzyme doses were applied in the present study where 35 % of raw cornstarch was hydrolyzed after 6 h of incubation at 65 °C.…”

“…15 according to the methods described in Bergey's Manual of Systematic Bacteriology. 16 α-Amylase was produced from different strains of Bacillus using a submerged fermentation described previously.…”