SOME RELATIONSHIPS BETWEEN THE PROTEIN NITROGEN OF BARLEY AND THE PRODUCTION OF AMYLOLYTIC ENZYMES DURING MALTING

Barleys studied (Chariot and Delibes) contained different levels of extractable β-amylase enzymes. The potential levels of β-amylase enzymes of the two varieties studied were similar at 1.4 to 1.7% total nitrogen. Higher values of potential β-amylase enzyme were observed in the Delibes barley of higher total nitrogen of 1.9%. The higher level of β-amylase found in the barleys with the highest total nitrogen was not reflected in the protein banding patterns as revealed by SDS-PAGE protein fractionation. Extraction of barley proteins was largely influenced by the different extractants used. The alcohol soluble proteins, M_r 97 kDa (D-hordeins), were only extracted when mercaptoethanol was included in the extracting solution. Although barleys with the highest nitrogen (1.9%) had the highest apparent potential to develop β-amylase enzymes, the better modified low nitrogen barleys produced higher levels of β-amylase and α-amylase when malted. Dehusking revealed that the high nitrogen barleys contained more steely grains. In contrast, the low nitrogen barleys contained more mealy grains. Steely grains contained more nitrogen than mealy grains and had the greater potential to develop β-amylase. Notwithstanding, the results of this study suggested that the proteins of the lower nitrogen barleys (1.4–1.7%) were capable of producing higher levels of β-amylase and α-amylase than the higher nitrogen barleys (1.9%) over comparable periods of malting. The high apparent β-amylase potential of the barley was linked to high nitrogen levels and associated high levels of steeliness, whilst the corresponding high β-amylase levels of malt were linked to the efficiency of endosperm modification of the malted grain.     

The flow‐through diffusion cell (FTDC) method: a novel approach to in vitro drug release studies

A terpolymeric semi‐interpenetrating network (IPN) has been synthesized by carrying out the aqueous polymerization of methacrylamide in the presence of poly(ethylene glycol) (PEG) and natural polysaccharide starch, and its enzymatic degradation has been studied by a newly developed technique, known as the ‘flow‐through diffusion cell’ (FTDC) method, in a phosphate buffer medium of pH 6.8 at the physiological temperature, 37 °C. The hydrogel exhibits different degradation behaviors when studied by the ‘traditional degradation/dissolution test’ (TDT) or the FTDC method. The degradability is suppressed in the FTDC method, owing to the adsorption of amylase molecules onto the filler particles. The nature of the filler particles also affects the degradation behavior of the hydrogels. Finally, the release of the model drug, vitamin B₁₂, from the degrading hydrogels has also been studied by the FTDC method. The results obtained indicated that the release behavior also depends on α‐amylase‐induced degradability. Copyright © 2006 Society of Chemical Industry     

In vitro enzymatic degradation kinetics of polymeric blends of crosslinked starch and carboxymethyl cellulose

Hydrophilic blend matrices of crosslinked starch and carboxymethyl cellulose were synthesized and their susceptibilities to enzymatic degradation were assessed by taking α‐amylase as a model enzyme. The polymeric blends were characterized by FT‐IR spectroscopy, differential scanning calorimetry and scanning electron microscopy. The influence of the chemical compositions of the blends, and the pH values and temperatures of the α‐amylase solutions was investigated by studying the swelling and degradation kinetics of the blends. The impact of the concentrations of the enzyme solutions on the degradation profiles was also examined. The blends were found to exhibit a mixed type of degradation mechanism, ie both diffusion and surface erosion. Copyright © 2005 Society of Chemical Industry     

Cationic polyacrylamides increase the rate of liquefaction and hydrolysis of cornstarch

Cationic polyacrylamides (c‐PAMs) bind to starch granules and decrease the temperature for the onset of gelatinization by 8^°C. c‐PAM increases the binding of α‐amylase to cornstarch; the rate of cornstarch hydrolysis also increases. By analogy to previous work on the c‐PAM promoted hydrolysis of cellulose, it is proposed that the polymer reduces the charge on the surface of starch through a charge‐patch mechanism. Because both enzyme and substrate are negatively charged, the bound c‐PAM reduces the charge repulsion experienced by the approaching enzyme, which leads to stronger enzyme‐substrate binding and faster hydrolysis. Overall, the c‐PAM reduces enzyme dose by up to 62% under the conditions used. There is a mirror image relationship between the viscosity of the medium and the hydrolysis rate, which allows optimization of these parameters with enzyme and c‐PAM dosage. Low c‐PAM levels increase viscosity by agglomerating the substrate, but the viscosity drops at higher c‐PAM concentration. © 2012 American Institute of Chemical Engineers AIChE J, 59: 79–83, 2013     

Soybean oil based resin: A new tool for improved immobilization of α‐amylase

Acrylated epoxidized soybean resin has been utilized to immobilize the α‐amylase via UV‐curing technique. Among the numerous methods that exist for enzyme immobilization, entrapment and covalent binding are the focus of this study. The properties of immobilized enzyme were investigated and compared with those of the free enzyme. Upon immobilization by the two methods, the catalytic properties of the enzyme were not considerably changed as compared with that of nonimmobilized form; only the pH profile was broadened for the immobilized enzyme. The free enzyme lost its activity completely in 20 days, where as storage and repeated usage capability experiments demonstrated higher stability for the immobilized form. Immobilized enzyme prepared by attachment method possesses relatively higher activity compared with the activity of those obtained by entrapment method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4757–4761, 2006     

淀粉酶在面包烘焙中的作用及机理

综述了淀粉酶在面包烘焙过程中对面包的体积和重量、面包心的质地、表皮色泽和风味以及防止面包老化等方面的作用和机理。并对不同来源的淀粉酶特性及作用进行了一定的比较。     

Production of α‐amylase by Aspergillus oryzae As 3951 in solid state fermentation using spent brewing grains as substrate

BACKGROUND: The optimisation of nutrient levels for the production of α‐amylase by Aspergillus oryzae As 3951 in solid state fermentation (SSF) with spent brewing grains (SBG), an inexpensive substrate and solid support, was carried out using response surface methodology (RSM) based on Plackett–Burman design (PBD) and Box–Behnken design (BBD). RESULTS: In the first optimisation step a PBD was used to evaluate the influences of related factors. Corn steep liquor, CaCl₂ and MgSO₄ were found to be the most compatible supplements to the substrate of SBG and influenced α‐amylase activity positively. In the second step the concentrations of these three nutrients were optimised using a BBD. The final concentrations (g/g dry substrate basis) in the medium optimised with RSM were 1.8% corn steep liquor, 0.22% CaCl₂ and 0.2% MgSO₄ · 7H₂O using SBG as the solid substrate. The average α‐amylase activity reached 6186 U g^?1 dry substrate under the optimised conditions at 30 °C after 96 h. Under the optimised conditions of SSF an approximately 17.5% increase in enzyme yield was observed. CONCLUSION: SBG was found to be a good substrate for the production of α‐amylase by A. oryzae As 3951 under SSF. Copyright © 2007 Society of Chemical Industry     

防止粒子性污垢附着的淀粉酶

介绍了洗涤用低温酶的发展状况。试验证明，淀粉酶对防止棉布上粒子污物的附着是有效的。