Abstract
Thermostable α-amylases hold a very important place in commercial industrial applications in Sri Lanka. Therefore, the main aim of this study was to identify superior Bacillus strain and optimize growth conditions that could yield high α-amylase production. Three Bacillus strains, B. amyloliquefaciens ATCC 23350, B. licheniformis ATCC 14580 and B. megaterium ATCC 14581 were used for the study. Shake flask culture experiments were conducted to identify the effect of various fermentation conditions such as growth temperature, incubation period, carbon source, nitrogen source, initial pH and carbon concentration on extracellular α-amylase production. DNSA assay was carried out to determine the enzyme activity. The highest temperature for enzyme activity was reported by B. licheniformis at 85°C, followed by B. amyloliquefaciens at 75°C and B. megaterium at 45°C. Both B. amyloliquefaciens and B. licheniformis were able to give their optimum enzyme production at 37°C, while B. megaterium at 30°C in 150 rpm with initial pH of 7. B. licheniformis and B. amyloliquefaciens gave their optimum yield of the enzyme after 48 h of incubation while B. megaterium gave after 24 h of incubation. Among the carbon sources tested cassava starch was able to give the highest enzyme production. For B. amyloliquefaciens, the highest yield of the enzyme was obtained with 2% of starch, tryptone as a nitrogen source and initial pH of 7. Maximum enzyme production for B. licheniformis was obtained with 1.5% of starch, KNO3 as a nitrogen source and initial pH of 6. For B. megaterium 1% of starch, tryptone and pH 7.5 induced the optimum α-amylase production. According to the results obtained, B. amyloliquefaciens is the highest thermostable alpha amylase producer. However, according to the industrial requirement, B. licheniformis can also be used as an enzyme producer due to its stability in higher temperatures.
Highlights
Enzymes act as catalysts for biological processes that regulate specific biochemical reactions
The fermentation conditions and composition of the media for optimal production of thermostable extracellular α-amylases by B. amyloliquefaciens strain American Type Culture Collection (ATCC) 23350, B. licheniformis strain ATCC 14580 and B. megaterium strain ATCC 14581 have been developed in this study
It can be concluded that enzyme synthesis can be affected by conditions of fermentation such as growth temperature, incubation period and components of media such as carbon source, carbon concentration, nitrogen source and initial pH of the growth medium
Summary
Enzymes act as catalysts for biological processes that regulate specific biochemical reactions. The main constituents of enzymes are proteins. Almost all pathways in a biological cell required enzymes to bring the reaction to its equilibrium position more rapidly and maintain the reaction at a significant rate. Enzymes are selective for their substrates and have the ability to determine which metabolic pathways take place in the cell [1]. Amylases are among the most valuable enzymes and hold great significance in biotechnology [2]. Α-Amylases (E.C.3.2.1.1) have the ability to catalyze the hydrolysis of internal α-1,4-glycosidic linkages in starch into reducing sugars, such as glucose, maltose and maltotriose units [3]. Alpha amylases are members of a class of enzymes called glucosidases. The starch degrading enzymes are among the most important enzymes widely used industrially [4]
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