Amylase Production by two Microbial Isolates: Isolation, Enzyme characterization, and optimization of Cultivation condition
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Date
2017-03
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Addis Ababa Universty
Abstract
Amylases are commercially important enzymes commonly used for the hydrolysis of starch to generate hydrolysates for different food and nonfood applications. Although Ethiopia has a huge potential for the production of starch, to date the starch industry is nonexistent and the country import large quantities of starch hydrolysates from abroad. The aim of this study was production of industrially important microbial amylases through solid state fermentation (SSF), optimize the cultivation condition, and characterize the enzymes. Screening using starch containing media one bacterial isolate producing α-amylase, designated as BI151, and one fungal isolate producing glucoamylase, designated as FI97, were isolated from soil. Both isolates grew well on SSF with wheat bran as a solid substrate. BI151 α-amylase produced 4,636 U/g of amylase after 96 h of incubation at 50% moisture. Isolate FI97 produced a maximum activity of 4,674 U/g after 72 h of incubation under SSF at a moisture content of 67%. For both isolates supplementation with organic or inorganic nitrogen source did not have any impact on enzyme production. This suggests that wheat bran supplemented with mineral salts and water has enough nutrients to support growth of the organisms and make the production process a lot cheaper. Amylase BI151was optimally active in the temperature range of 65-75°C with a peak at 70°C and in the PH range of 4.5 -5.5. On the other hand amylase of FI97 was optimally active at 65°C and at pH 6. These properties showed that both enzymes have properties that make them potentially suitable for starch hydrolysis, especially in the brewery industries. Under lab scale evaluation, both enzymes were able to efficiently hydrolyze high concentration of starch adjuncts (60% of the malt adjunct mixture) indicating their potential for application as malt enzyme supplements.
Key word: α-amylase, Glucoamylase, starch hydrolysate, relative activity, residual activity
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α-amylase,, Glucoamylase, Starch hydrolysate, Relative activity, Residual activity