Industrial important enzymes have traditionally been obtained by using submerged fermentation technology. Many organisms are able to produce these enzymes, but only a few of them exhibit satisfactory characteristics for industrial application. The ability of bacterial strains from the genus Bacillus to secrete large amounts of extracellular a-amylase has made them well suited for commercial production. Amylase production using Bacillus subtilis SY134D strain was conducted in flasks and bioreactor. In flasks, our results showed that soybean cake, beet pomace and tomato pomace were the best carbon source used in submerged fermentation (SmF) after 72 h of incubation. In bioreactor, the rates of air flow and agitation speed are important factors that affect oxygen transfer rate which influence on product formation. When the aeration rate was increased from 0.25 to 0.75 vvm, amylase production increased at the speed of agitation 100 and 200 rpm. The best enzyme yield 127 IU/mL was obtained at 0.25 vvm an aeration rate and 300 rpm agitation speed in a 3L Electro-lab bio-reactor.
Enhancement of the amylase productivity by Aspergillus flavus was investigated. Spores ofstrain were exposed to ultraviolet (UVC) radiation and 10 different mutants were selected and isolatedfrom starch plate agar on the basis of the visible clearance zone around the colonies. The amylase productionby selected mutants was evaluated under solid state fermentation. One mutant of A. flavus FSS63UV8showed higher biosynthesis level of amylase (733 IU/g), which was 3.35 fold higher than that detectedin the parental strain. Physical parameters optimisation revealed that the optimum pH and temperature foramylase production obtained by mutant are 7.0 and 35°C, respectively. Among several tested agriculturalwastes , wheat bran was found to support the highest yield of amylase after 5 days of incubation. A. flavusFSS63UV8 strain proved to be a promising microorganism for a high amylase production in a simplemedium.
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