0-amylase conversion

By /3-amylase conversion studies, R. W. Kerr of this laboratory has reached similar conclusions regarding the effectiveness of aqueous leaching methods. 

Hirata, A., M. Adachi, S. Utsumi, and B. Mikami. 2004. Engineering of the pH Optimum of Bacillus Cereus Beta-Amylase Conversion of the pH Optimum from a Bacterial Type to a Higher-Plant Type. Biochemistry 43 (39) 12523-12531. 

P-amylase, and debranching enzymes. Conversion of D-glucose to D-fmctose is mediated by glucose isomerase, mosdy in its immobilized form in columns. Enzymic degradation of starch to symps has been well reviewed (116—118), and enzymic isomerization, especially by immobilized glucose isomerase, has been fiiUy described (119) (see Syrups). 

After 30 hours, the maximum and critical fermentation is underway and the pH must remain above 4.0 for optimal fermentation. However, accompanying bacterial contamination from various sources such as yeast contamination, improper cleaning procedures, slow yeast growth, or excessive temperatures can result in a pH below 4.0. The remaining amylase enzymes, referred to as secondary conversion agents, are inactivated and can no longer convert the dextrins to maltose. Under these circumstances, the fermentor pH continues to drop because of acid production of the bacteria, and the pH can drop to as low as 3.0. The obvious result is a low ethanol yield and quaUty deterioration. 

Malted barley contains a- and P-amylases along with proteases and phytases. Most standardi2ed microbial en2yme preparations for industrial starch conversion contain approximately 100 times more amylase activity than malt. In beermaking, malt is not just valuable for its en2ymes but also for flavor compounds. 

Obviously, more work on this subject is necessary, but the problem is complicated by the fact that some authors have reported that the conversion of amylose to maltose by the action of /3-amylase is incomplete. Limits of from 70 to 97 % have been recorded. Apparently, variations depend on the actual D. P. of the amylose and on the concentration of enzyme. Meyer and coworkers19-214 maintain that these lower limits may be due to retro-gradation phenomena, which is not unreasonable in view of the fact that... 

The marked changes in the ratios of dextrinogenic to saccharogenic activities found when crude extracts of malted barley are heated or acidified, led to the recognition of two amylases in these extracts. Conversely, relatively small changes in these ratios in amylase solutions before and after various procedures are often taken as proof that only one amylase is present. 

Contacts with the catalytic residues, in combination with hydrophobic interactions, are also observed in the complex of an insect a-amylase with the Ragi bifunctional a-amylase/trypsin inhibitor (RBI) [174]. Conversely, the mechanism of inhibition of barley a-amylase by the barley a-amylase/subtilisin inhibitor (BASI) did not involve direct contact between inhibitor residues and the catalytic site [175]. The inhibitor sterically blocks the catalytic site, but does not extend into it. A cavity is created, which is occupied by a calcium ion coordinated by water-mediated interactions with the catalytic residues. 

Suppose we start with a starch-rich meal, say one containing a lot of pasta or bread. The digestion of starches begins in the mouth. Saliva contains an enzyme, salivary amylase (aka ptyalin), which catalyzes the conversion of starch to simple sugars such as glucose. This process is completed in the small intestine under the influence of other enzymes in the amylase class. This completes the first phase of carbohydrate catabolism the conversion of complex, polymeric carbohydrates (e.g., starches) to their simple monomeric units, the sugars. 

Moebus, O. and Teuber, M., Direkte Umwandlung von Starke in Ethanol in einem Gas-Festhoff-Wirbelschichtfermenter mit technischen Amylasen und Backerhefe [Direct conversion of starch into ethanol in a gas-solid fluidized bed fermenter with technical amylases and baker s yeast], Wissenschaft und Umwelt, 1 (1985) 80-84. 

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