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161.
Kwang Kim A. Louise Creagh Charles A. Haynes 《Biotechnology and Bioprocess Engineering》1998,3(2):71-77
The strain ofSerratia marcescens QM B1466 produces selectively large amount of chitinolytic enzymes (about 1mg/L medium). Enzymatic hydrolysis of chitin to
N-acetyl-β-D-glucosamine (NAG) was performed with a system consisting of two hydrolases (chitinase and chitobiase) produced
by optimization of a microbial host consuming chitin particles. For the development of Large-scale biological process for
the production of NAG from chitinaceous waste, the selection and optimization of a microbial host, particle size of chitin
and pretreatment of chitin source were investigated. Also, the effect of crab/shrimp chitin sources and initial induction
time using chitin as a sole carbon source on chitinase/chitobiase production and NAG production were examined. Crab-shell
chitin(1.5%) treated by dilute acid and, ball-milled with a nominal diameter less than 250m gave the highest chitinase activity
over a 7 days culture. Crude chitinase/chitobiase solution obtained in a 10 L fed-batch fermentation showed a maximum activities
of 23.6 U/mL and 5.1 U/mL, respectively with a feeding time of 3 hrs, near pH 8.5 at 30°C. 相似文献
162.
Fungi isolated from soil in Timna Park (Israel) were found to belong to a new species of Exserohilum for which the name Exserohilum israeli sp. nov. is proposed. The main physiological properties of members of this species are discussed and the influence of temperature and copper concentrations on the growth and morphology of the fungus were investigated. 相似文献
163.
M. A. Zenkova N. L. Chumakova A. V. Vlassov N. I. Komarova A. G. Venyaminova V. V. Vlassov V. N. Silnikov 《Molecular Biology》2000,34(3):390-394
The mechanism of hydrolysis of RNA substrates—diribonucleoside monophosphate CpA and decaribonucleotide UUCAUGUAAA—by chemical
constructs functionally mimicking ribonuclease A was studied. It is shown that RNA cleavage by chemical RNases 2L2 and 2D3
proceeds similar to the RNase A-induced RNA hydrolysis through 2′,3′-cyclophosphate as an intermediate product. A comparison
of hydrolyses of CpA in water and D2O revealed an isotope effect (K
H/K
D=2.28), which implies acid-base catalysis at the limiting stage of the reaction. Two feasible mechanisms of RNA hydrolysis
by chemical RNases (linear and adjacent) are discussed. 相似文献
164.
双酶法制备玉米皮膳食纤维的研究 总被引:1,自引:0,他引:1
采用蛋白酶和淀粉酶结合水解制备玉米皮膳食纤维,通过正交试验确立了玉米皮膳食纤维的双酶法制备工艺。双酶法制备的玉米皮膳食纤维的产率为59.4%,膳食纤维的蛋白质量分数为0.82%,淀粉质量分数为1.42%,灰分为0.4%,水分质量分数为8.6%,持水力为5.9±0.4 g.g-1。 相似文献
165.
Aspergillus sp.脂肪酶发酵条件优化及酶学性质的研究 总被引:2,自引:0,他引:2
作者为了得到一种热稳定性较好的脂肪酶新酶种,通过研究分离白极端环境的Aspergillus sp.的最佳产酶条件及其所产脂肪酶的酶学性质,得出了该菌产酶的最佳发酵条件为:以1%黄豆饼粉为氮源、0.2%玉米淀粉为碳源,1.5%橄榄油为诱导物,起始pH6.0左右。装量10mL(250mL三角瓶。摇瓶转速180r/min)、发酵时间为96h。在最佳发酵条件下可得最大发酵酶活36U/mL。Aspergillus sp.所产的脂肪酶的酶学性质是:最适pH为9.0,在pH5.0—10.0于20℃下放置24h后,残余酶活仍保持在起始酶活的90%以上;该酶的最适温度为50℃,50℃保温60min后仍保留70%以上的酶活。Aspergillus sp.所产脂肪酶的热稳定性较好。 相似文献
166.
Xiang-Zhong Huang Ying Xu Yi-Fan Zhang Yu Zhang Yue Him Wong Zhuang Han 《Biofouling》2014,30(4):473-481
Bioassay-guided isolation of an acetone extract from a terrestrial plant Piper betle produced four known piperamides with potent antifouling (AF) activities, as evidenced by inhibition of settlement of barnacle cypris larvae. The AF activities of the four piperamides and 15 synthesized analogues were compared and their structure–activity relationships were probed. Among the compounds, piperoleine B and 1-[1-oxo-7-(3′,4′-methylenedioxyphenyl)-6E-heptenyl]-piperidine (MPHP) showed strong activity against settlement of cyprids of the barnacle Balanus amphitrite, having EC50 values of 1.1?±?0.3 and 0.5?±?0.2?μg?ml?1, respectively. No toxicity against zebra fish was observed following incubation with these two compounds. Besides being non-toxic, 91% of piperoleine B-treated cyprids and 84% of MPHP-treated cyprids at a concentration of 100?μM completed normal metamorphosis in recovery bioassays, indicating that the anti-settlement effect of these two compounds was reversible. Hydrolysis and photolysis experiments indicated that MPHP could be decomposed in the marine environment. It is concluded that piperamides are promising compounds for use in marine AF coatings. 相似文献
167.
Summary It was previously shown that nuclei of-sheets surrounded by unordered segments are formed in polypeptide chains built up with alternating hydrophobic and hydrophilic residues and containing both L- and D-enantiomers. It was also established that segments of residues having the same configuration tend to segregate in these nuclei when the starting composition of stereomonomers departs from the racemic mixture.Soft acidic hydrolysis of these polymers has been studied. Kinetic measurements show two pseudo first order rate constants, in agreement with the existence of two conformational species. The unordered part of the chains is hydrolyzed more rapidly, allowing the isolation of a-fraction enriched in one enantiomer. Thus, a plausible process of enrichment in enantiomer during prebiotic evolution has been described, which however does not explain the preference of one enantiomer over the other one. 相似文献
168.
169.
Modeling and optimization of phospholipase A1‐catalyzed hydrolysis of phosphatidylcholine using response surface methodology for lysophosphatidylcholine production 下载免费PDF全文
Modeling the phospholipase A1 (PLA1)‐catalyzed partial hydrolysis of soy phosphatidylcholine (PC) in hexane for the production of lysophosphatidylcholine (LPC) and optimizing the reaction conditions using response surface methodology were described. The reaction was performed with 4 g of PC in a stirred batch reactor using a commercial PLA1 (Lecitase Ultra) as the biocatalyst. The effects of temperature, reaction time, water content, and enzyme loading on LPC and glycerylphosphorylcholine (GPC) content in the reaction products were elucidated using the models established. Optimal reaction conditions for maximizing the LPC content while suppressing acyl migration, which causes GPC formation, were as follows: temperature, 60°C; reaction time, 3 h; water content, 10% of PC; and enzyme loading, 1% of PC. When the reaction was conducted with 40 g of PC under these conditions, the reaction products contained 83.7 mol % LPC and were free of GPC. LPC had a higher total unsaturated fatty acid content than original PC had and was mainly composed of linoleic acid (78.0 mol % of the total fatty acids). © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:35–41, 2015 相似文献
170.
Effects of different physical pretreatments on water hyacinth for dilute acid hydrolysis process (121 ± 3 °C, 5% H2SO4, 60 min) were comparatively investigated. Untreated sample had produced 24.69 mg sugar/g dry matter. Steaming (121 ± 3 °C) and boiling (100 ± 3 °C) for 30 min had provided 35.9% and 52.4% higher sugar yield than untreated sample, respectively. The highest sugar yield (132.96 mg sugar/g dry matter) in ultrasonication was obtained at 20 min irradiation using 100% power. The highest sugar production (155.13 mg sugar/g dry matter) was obtained from pulverized samples. Hydrolysis time was reduced when using samples pretreated by drying, mechanical comminution and ultrasonication. In most methods, prolonging the pretreatment period was ineffective and led to sugar degradations. Morphology inspection and thermal analysis had provided evidences of structure disruption that led to higher sugar recovery in hydrolysis process. 相似文献