首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
《Process Biochemistry》2014,49(8):1297-1303
The present work illustrates the incorporation of ultrasound and its improved impact in the lipase catalysed esterification. Synthesis of isoamyl butyrate from isoamyl alcohol and butyric acid using immobilised Novozym 435, has been carried out in the presence of ultrasound. The optimisation of various parameters affecting the synthesis of ester in presence of ultrasound was done. The systematic experimentation involves change of one working parameter at one time while keeping the others constant. For the maximum conversion, optimum parameters such as the ultrasound of 25 kHz frequency with power of 70 W, at the temperature of 60 °C with stirring speed of 80 rpm, mole ratio of alcohol:acid followed as 2:1, use of molecular sieves weighing 2 g, with immobilised enzyme loading of 2% (m/v) and duty cycle of 83%, were obtained. The optimum parameters collectively, gave 96% conversion of the product in 3 h as compared with 10 h in absence of ultrasound. The immobilised biocatalyst, Novozym 435 has an added benefit of reusability till 7 repetitive cycles. Besides, the synthesis is executed in the solvent free system that contributes the production of flavour in greener way.  相似文献   

2.
A series of naphthopyrans was synthesized employing silica supported fluoroboric acid under solvent free conditions in a microwave reactor. The catalytic influence of HBF4–SiO2 was investigated in detail to optimize the reaction conditions. The synthesised compounds were evaluated for in vitro xanthine oxidase inhibitory activity for the first time. Structure–activity relationship analyses have also been presented. Among the synthesised compounds, NP-17, NP-19, NP-20, NP-23, NP-24, NP-25 and NP-26 were the active inhibitors with an IC50 ranging from 4 to 17 μM. Compound NP-19 with a thiophenyl ring at position 1 emerged as the most potent xanthine oxidase inhibitor (IC50 = 4 μM) in comparison to allopurinol (IC50 = 11.10 μM) and febuxostat (IC50 = 0.025 μM). The basis of significant inhibition of xanthine oxidase by NP-19 was rationalized by its molecular docking at MTE binding site of xanthine oxidase.  相似文献   

3.
《Process Biochemistry》2014,49(9):1377-1382
Decalactones are interesting flavouring compounds that can be produced from ricinoleic acid. In this study, the production of lactones in biofilms using Yarrowia lipolytica is investigated. The hydrophobia of cells increased for increased aeration rates resulting in higher adhesion when the reactor wall was hydrophobic (plastic). To increase adhesion, sheets of methyl-polymethacrylate (PMMA) were added in the reactor and the production of lactones increased with the surface of plastic added, reaching 850 mg/L of 3-hydroxy-γ-decalactone for 60 cm2. In an Airlift bioreactor made of PMMA, biofilms were present at the top of the reactor for increased aeration. In the meantime, a metabolic shift occurred resulting in high amounts of 3-hydroxy-γ-decalactone. At 0.493 vvm and 61 h of culture, the dissolved oxygen ratio was of 28.6% and cells grew to only 1.29 × 106 cells/mL in the liquid medium but 3-hydroxy-γ-decalactone accumulated to 1.7 g/L instead of less than 0.3 mg/L for lower aeration. Adhering cells had a particular elongated shape intermediate between the yeast and the pseudofilamentous forms. It is concluded that adhering Y. lipolytica cells are in a specific physiological state changing their structure but also their metabolic properties and these properties make them good candidate for simple immobilisation process.  相似文献   

4.
Bacillus macerans cyclodextrin glycosyltransferase (CGTase) (EC 2.4.1.19) was covalently immobilised on Eupergit C and used in a packed-bed reactor to investigate the continuous production of long-carbohydrate-chain alkyl glycosides from α-cyclodextrin (α-CD) and n-dodecyl-(1,4)-β-maltopyranoside (C12G2β). The effects of buffer ion strength and pH, and enzyme loading on the immobilisation yield and the enzyme activity were evaluated. Approximately 98% of the protein and 33% of the total activity were immobilised. At pH 5.15, the enzymatic half-life was 132 min at 60 °C and 18 min at 70 °C. The immobilised enzyme maintained 60% of its initial activity after 28 days storage at 4 °C. The degree of conversion was controlled by simple regulation of the flow rate through the reactor, making it possible to optimise the product distribution. It was possible to achieve a yield of the primary coupling product n-dodecyl-(1,4)-β-maltooctaoside (C12G8β) of about 50%, with a ratio between the primary and the secondary coupling product of about 10. Thermoanaerobacter sp. CGTase (Toruzyme 3.0 L) immobilised on Eupergit C had good operational stability at 60 and 70 °C thus showing the advantages of using more thermostable enzymes in biocatalysis. However, this enzyme was unsuitable for the production of C12G8β due to extensive disproportionation reactions, giving a broad product range.  相似文献   

5.
Poly-hydroxybutyrate particles (PHB) were used as support to immobilize porcine pancreatic lipase (PPL). The biocatalysts prepared were tested in the synthesis of pineapple flavor by esterification of butanol and butyric acid in heptane medium, and in the synthesis of ethyl esters by transesterification of macaw palm pulp (MPPO) and macaw palm kernel (MPKO) oils with ethanol in solvent-free systems. The effect of protein loading on the biocatalyst activity was assessed in olive oil hydrolysis. Maximum hydrolytic activity of 292.8 ± 8.60 IU/g was observed. Langmuir isotherm model was applicable to the adsorption of PPL on PHB particles. Maximum immobilized protein amount was 24.3 ± 1.70 mg/g. The optimal pH and temperature in hydrolysis reaction for the immobilized PPL were at pH 8.5 and 50 °C, while for the crude PPL extract were at pH 8.0 and 45 °C. Immobilized PPL exhibited full hydrolytic activity after 2 h of incubation in non-polar solvents. In esterification reaction, optimal conversion was around 93% after 2 h of reaction. After six esterification cycles, the biocatalyst retained 63% of its initial activity. The biocatalyst prepared attained transesterification yield of 50% after 48 h of reaction for MPKO and 35% after 96 h of reaction for MPPO.  相似文献   

6.
《Process Biochemistry》2004,39(11):1341-1345
Batch fermentation of glucose to gluconic acid was conducted using Aspergillus niger under growth and non-growth conditions using pure oxygen and air as a source of oxygen for the fermentation in 2 and 5 l stirred tank reactors (batch reactor). Production of gluconic acid under growth conditions was conducted in a 5 l batch reactor. Production and growth rates were higher during the period of supplying pure oxygen than that during supplying air, and the substrate consumption rate was almost constant. For the production of gluconic acid under non-growth conditions, conducted in the 2 l batch reactor, the effect of the pure oxygen flow rate and the biomass concentration on the gluconic acid production was investigated and an empirical equation suggested to show the dependence of the production rate rp on the biomass concentration Cx and oxygen flow rate Q, at constant operating conditions (30 °C, 300 rpm and pH 5.5). Biomass concentration had a positive effect on the production rate rp, and the effect of Q on rp was positive at high biomass concentrations.  相似文献   

7.
The present work reports the gallic acid (GA) interference on polyphenolic amperometric biosensing using Trametes versicolor laccase (TvLac). GA′ inhibitory effect on TvLac activity was investigated on the oxidation of caffeic acid (CA) by free TvLac and its immobilised form on modified polyethersulfone membrane (PES/TvLac), using spectrophotometric and amperometric biosensor detection methods. The results have indicated that GA presents inhibitory behaviour on TvLac activity in a concentration-dependent manner. The GA concentration leading to 50% activity lost, IC50, was determined to be 19.15 ± 0.11 μM and 5.11 ± 0.19 μM for free and immobilised enzyme, respectively. The results have also shown that GA exhibited a competitive and a mixed inhibition types on the TvLac activity for spectrophotometric and amperometric biosensor methods, respectively. Further GA′ and CA′ cyclic voltammetry studies have demonstrated that GA′ oxidation products interfered with CA′ redox reaction products. In fact, a decrease of the reduction current was observed at cyclic voltammograms of CA, when mixed with GA. Therefore, the GA′ interference on polyphenolic amperometric biosensing is the result of the combination of two factors: on one hand, we have the inhibitory enzymatic effect, and on the other, the reaction of GA′ oxidation products with the o-quinones obtained by the enzymatic oxidation of CA. Both gave rise to the amperometric signal decreasing effect.  相似文献   

8.
Biolubricants derived from vegetable oils are environmentally compatible products due to their low toxicity and good biodegradability. Synthetic esters based on polyols and fatty acids possess suitable properties for lubricant applications, even at extreme temperatures. In this work, synthesis of esters from trimethylolpropane (TMP) and carboxylic acids from C5 to C18 has been studied and compared using different heterogeneous catalysts (silica–sulphuric acid, Amberlyst-15, and immobilised lipase B from Candida antarctica). Silica–sulphuric acid was found to be the most efficient catalyst followed by Amberlyst-15, especially when using short chain carboxylic acids. The reaction efficiency decreased with increasing alkyl chain length. On the other hand, the immobilised lipase (Novozym®435) did not exhibit any activity with C5 acid and the activity increased with increase in length of the fatty acid chain. For synthesis of C18-ester, the biocatalytic production turned out to be comparable to silica–sulphuric acid, and moreover led to a better quality of the final product. The products showed suitable cold-flow properties for application at low temperature. A general trend of increasing pour point (−75 °C to −42 °C) and viscosity index (80–208) with increase in alkyl chain of the carboxylic acid from C5 to C18 was observed. The synthesis of TMP-trioleate using the solid acid catalysts and the biocatalyst was compared using the freeware package EATOS (environmental assessment tool for organic synthesis) and showed the enzymatic route to have the least environmental impact.  相似文献   

9.
Nuclear diamination of p-hydrobenzoquinones with aromatic and aliphatic primary amines was catalysed by an immobilised commercial laccase, Denilite® II Base, from Novozymes. The amine and the p-hydrobenzoquinone was reacted under mild conditions (at room temperature and at 35 °C) in a reaction vessel open to air in the presence of laccase and a co-solvent to afford, exclusively, the diaminated p-benzoquinone. These compounds may have potential antiallergic, antibiotic, anticancer, antifungal, antiviral and/or 5-lipoxygenase inhibiting activity.  相似文献   

10.
Thermobifida fusca not only produces cellulases, hemicellulases and xylanases, but also excretes butyric acid. In order to achieve a high yield of butyric acid, the effect of different carbon sources: mannose, xylose, lactose, cellobiose, glucose, sucrose and acetates, on butyric acid production was studied. The highest yield of butyric acid was 0.67 g/g C (g-butyric acid/g-carbon input) on cellobiose. The best stir speed and aeration rate for butyric acid production were found to be 400 rpm and 2 vvm in a 5-L fermentor. The maximum titer of 2.1 g/L butyric acid was achieved on 9.66 g/L cellulose. In order to test the production of butyric acid on lignocellulosic biomass, corn stover was used as the substrate, on which there was 2.37 g/L butyric acid produced under the optimized conditions. In addition, butyric acid synthesis pathway was identified involving five genes that catalyzed reactions from acetyl-CoA to butanoyl-CoA in T. fusca.  相似文献   

11.
A new method for the synthesis of β-N-(γ-l(+)-glutamyl)-4-carboxyphenylhydrazine, a precursor of agaritine, is presented. This compound was prepared from l-glutamine and 4-hydrazinobenzoic acid through the transpeptidation reaction catalyzed by the Escherichia coli γ-glutamyltransferase. The optimum reaction conditions for the production of β-N-(γ-l(+)-glutamyl)-4-carboxyphenylhydrazine were 50 mM l-glutamine, 500 mM 4-hydrazinobenzoic acid and 40 U γ-glutamyltransferase/mL at pH 8 and 37 °C for 24 h. The product was obtained with a conversion rate of 90% (mol/mol). γ-Glutamyltransferase activity was not inhibited by 4-hydrazinobenzoic acid at concentrations up to 1000 mM. This simple and efficient method would facilitate the synthesis of glutamyl phenylhydrazine analogs, including agaritine.  相似文献   

12.
This work studied the hydrolysis of lactose using β-galactosidase from Aspergillus oryzae immobilized with a combination of adsorption and glutaraldehyde cross-linking onto the ion exchange resin Duolite A568 as a carrier. A central composite design (CCD) was used to study the effects of lactose concentration and feed flow rate on the average hydrolysis reaction rate and lactose conversion in a fixed bed reactor operating continuously with an upflow at a temperature of 35 ± 1 °C. The optimal conditions for the average hydrolysis reaction rate and the lactose conversion included a lactose concentration of 50 g/L and a feed flow rate of 6 mL/min. The average reaction rate and conversion reached 2074 U and 65%, respectively. The immobilized enzyme activity was maintained during the 30 days of operation in a fixed bed reactor with a 0.3 mL/min feed flow rate of a 50 g/L lactose solution at room temperature. Feed flows ranging from 0.6 to 12 mL/min were used to determine the distribution of residence times and the kinetics of the fixed bed reactor. A non-ideal flow pattern with the formation of a bypass flow in the fixed bed reactor was identified. The conditions used for the kinetics study included a lactose solution concentration of 50 g/L at pH 4.5 and a temperature of 35 ± 1 °C. Kinetic models using a PFR and axial dispersion methods were used to describe the lactose hydrolysis in the fixed bed reactor, thus accounting for the competitive inhibition by galactose. To increase the lactose conversion, experiments were performed for two fixed bed reactors in series, operating in continuous duty with upflow, with the optimal conditions determined using the CCD for a fixed bed reactor. The total conversion for the two reactors in series was 82%.  相似文献   

13.
The synthesis of 1,2,5-trisubstituted benzimidazole derivatives was carried out using liquid phase combinatorial approach using soluble polymer assisted support (PEG5000). Synthesised compounds were characterised by FTIR, ESI-MS, 1H NMR and 13C NMR. The purity of compounds was confirmed with HPLC analysis. Compounds were also docked into the binding site of human dihydroorotate dehydrogenase (hDHODH). The synthesised compounds were screened for hDHODH enzyme inhibition assay using brequinar as standard compound. The synthesised compounds demonstrated comparative biological activity. Synthesised compounds 8d and 8e demonstrated IC50 value of 81 ± 2 nM and 97 ± 2 nM, respectively.  相似文献   

14.
《Process Biochemistry》2007,42(6):1010-1020
Acid hydrolysis of distilled grape marc, an useless agricultural residue from wineries, was carried out using dilute sulfuric acid (1–5%) at several reaction times and 130 °C, in order to obtain monomeric sugars which after supplementation with corn steep liquor (10 g/L) and yeast extract (10 g/L) were used to carry out the fermentation into lactic acid by Lactobacillus pentosus without detoxification stage. Xylose was the main sugar generated followed by glucose and arabinose. Possible inhibitor compounds such as acetic acid liberated from acetyl groups, and furfural and hydroxymethylfurfural generated by sugars dehydration, were produced as degradation byproducts. The hydrolysis stage was optimized by using an incomplete factorial design where the independent variables were the percentage of catalyzer, the reaction time and the temperature. The optima conditions in terms of xylose concentration were 3.3% H2SO4, 125 min and 130 °C, but due to the high furfural concentration, two other conditions using lower reaction times (30 and 77.5 min) were also selected to assay the fermentation. Although any condition was feasible to fully utilize the relatively broad spectra of sugars released by the acid hydrolysis, under the shorter reaction time the best results were achieved (QP = 0.476 g/L h; YP/S = 0.71 g/g) which represents a theoretical yield of 97%. Furthermore, L. pentosus produced 4.8 mg/L of intracellular biosurfactants, measured as biosurfactin, representing a yield of 0.60 mg of intracellular biosurfactant per g of sugars consumed.  相似文献   

15.
Lipase from Mucor miehei immobilised by adsorption on microporous, asymmetric hollow fibre membrane reactors was used to hydrolyse two different oils, namely, palm and olive oils. The hydrolysis reaction was carried out at a temperature of 40 °C, an average transmembrane pressure (TMP) of 115 mmHg and oil and aqueous flow rates of 2.5 and 3.0 ml min−1, respectively. It was experimentally proven that adsorption of lipase increased with temperature and was higher on hydrophobic membranes than hydrophilic ones. The effluent concentrations of fatty acid products were measured using gas chromatograph with FID detector. Hydrolysis experimental results were fitted to a multisubstrate kinetic model derived from the Ping Pong Bi Bi mechanism. The final model expression is useful for predicting the free fatty acid profile of the enzymatic hydrolysis of palm and olive oils for different substrate flow rates and enzyme loading.  相似文献   

16.
《Process Biochemistry》2007,42(9):1362-1366
Hexyl laurate, a medium-chain ester carried about fruity flavor, is primarily used in personal care formulations as an important emollient for cosmetic applications. On the basis of the hexyl laurate could be successfully synthesized by lipase within a batch system in our previous report. This study aimed to develop an optimal continuous procedure of lipase-catalyzed hexyl laurate synthesis in a packed-bed bioreactor to investigate the possibility of large-scale production further. The ability of lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyze the direct-esterification of 1-hexanol and lauric acid in n-hexane was investigated. Response surface methodology (RSM) and 3-level-3-factor fractional factorial design were employed to evaluate the effects of synthesis parameters, such as reaction temperature (35–55 °C), mixture flow rate (1.5–4.5 mL/min) and substrate molar ratio 1-hexanol to lauric acid (1:1–1:3) on production rate (μmol/min) of hexyl laurate by direct-esterification. Based on the analysis of ridge max, the optimum synthesis conditions for hexyl laurate were as follows: 45 °C of reaction temperature, substrate molar ratio 1:2 and reaction flow rate 4.5 mL/min. The optimum predicted production rate was 435.6 ± 0.9 μmol/min and the actual value was 437.6 ± 0.4 μmol/min.  相似文献   

17.
The enzymatic reaction of benzoic acid and glycerol in the absence of organic solvents to obtain the 1- or 3-monobenzoate glycerol (α-MBG) is studied. Esterification runs were batch wise performed with a concentration of enzyme of 30 g/L, changing the initial concentration of the acid in glycerol from 20 to 60 g/L, and temperature from 50 to 70 °C. In these conditions, the most active lipase among those tested for this synthesis was lipase B isozyme from Candida antarctica (CALB), obtaining conversion values higher than 80% and a significant selectivity to α-MBG. Unlike the synthesis in organic media, water did not have an inhibitory behaviour; hence control of water activity was unnecessary. Temperature and benzoic acid act synergically as deactivating factors. Considering the aforementioned, a kinetic model according to a Michaelis–Menten mechanism is proposed. This model considers a partial enzymatic deactivation mechanism with two terms, one of them accounting for the deactivating action of the acid.  相似文献   

18.
《Cancer epidemiology》2014,38(5):556-562
BackgroundPopulation-based studies of breast cancer often aggregate all Asians into a single category termed Asian/Pacific Islander (API).Purpose(1) Describe the demographic and clinicopathologic features of early breast cancer utilizing all eight ER/PR/HER2 subtypes among white, black, Hispanic, American Indian, seven Asian ethnicities, and the aggregate API category; (2) ascertain the risk of the ER+/PR+/HER2+, ER−/PR−/HER2−, and ER−/PR−/HER2+ subtypes when compared with the ER+/PR+/HER2− subtype, among seven Asian ethnicities versus non-Hispanic white women and (3) contrast the results with the risk of these same subtypes when using the aggregate API category.MethodsUsing the California Cancer Registry, we identified 225,441 cases of stages 1–4 first primary female invasive breast cancer. Logistic regression was used to assess the association of race with the ER+/PR+/HER2+, ER−/PR−/HER2− (triple-negative), and the ER−/PR−/HER2+ subtypes versus the ER+/PR+/HER2− when adjusted for stage, age, tumor grade, and socioeconomic status. Models were fit separately for each subtype. Odds ratios for the seven Asian ethnicities and the aggregate API category using non-Hispanic white women as the reference category were computed.ResultsThere was an increased risk of the ER+/PR+/HER2+ subtype for the combined API category (OR = 1.16; 95% CI = 1.09–1.23). But only Southeast Asians (OR = 1.17; 95% CI = 1.04–1.31), Filipino (OR = 1.23; 95% CI = 1.12–1.36), and Korean (OR = 1.63; 95% CI = 1.38–1.99) women had an increased risk of this subtype. The reduced risk of the triple-negative subtype seen in APIs (OR = 0.84; 95% CI = 0.79–0.90) was only noted in Chinese (OR = 0.80; 95% CI = 0.70–0.91) and Filipino (OR = 0.65; 95% CI = 0.58–0.73) women whereas Indian Continent (OR = 1.25; 95% CI = 1.01–1.53) women had an increased risk of the triple-negative subtype.The race × stage interaction was statistically significant for the ER−/PR−/HER2+ subtype (p < 0.05). When stratified by stage, there was no statistically significant association of race with subtype in stages 3 and 4. APIs had an increased risk of the ER−/PR−/HER2+ subtype in stage 1 (OR = 1.59; 95% CI = 1.37–1.75) and stage 2 (OR = 1.42; 95% CI = 1.28–1.58) but this risk was not seen in Pacific Islander, Indian Continent, and Japanese women for either stage.ConclusionsAmong the Asian ethnicities, there is marked variability in the demographic and clinicopathologic features of breast cancer. Use of the ER/PR/HER2 subtypes reveals that the risk of the ER−/PR−/HER2−, ER+/PR+/HER2+, and ER−/PR−/HER2+ subtypes varies among the Asian population. The API category, is sometimes, but not always reflective of all Asian women.  相似文献   

19.
Enzymatic synthesis of aromatic esters of four different sugar alcohols (xylitol, arabitol, mannitol, and sorbitol) with 3-(4-hydroxyphenyl)propionic acid was performed in organic solvent medium, using immobilized Candida antarctica lipase (Novozyme 435), and molecular sieves for control of the water content. The influence of reaction parameters on the conversion has been investigated, including reaction time, temperature, alcohol/acid molar ratio, and enzyme amount. The highest conversions (94% for xylitol, 98% for arabitol, 80% for mannitol, and 93% for sorbitol) were obtained in pure tert-butanol at 60 °C and 72 h reaction time, 0.3 alcohol/acid molar ratio, and 0.5 g/mol enzyme/substrate ratio. The isolated new sugar alcohols esters were identified by different spectral analyses. MALDI-TOF MS analysis showed the formation of monoesters, diesters, and small quantities of triesters for all investigated sugar alcohols. The catalytic efficiency of the enzyme was higher for the pentitol substrates, decreasing in the following order: arabitol > xylitol > sorbitol > mannitol. These new compounds could have interesting applications in food, pharmaceutical and cosmetic formulations.  相似文献   

20.
《Process Biochemistry》2010,45(3):407-414
This paper studies the synthesis of triacylglycerols (TAGs) rich in palmitic acid (PA) at position 2, from palm oil stearin (POS), a vegetable oil highly rich in this acid (60%). The developed process consists of two steps: (1) obtaining PA enriched free fatty acids (FFAs), and (2) enrichment of POS in PA by acidolysis of this oil with PA enriched FFAs, catalyzed by lipase Novozym 435. In step (1) two PA enriched FFA mixtures were obtained: one by saponification of POS, and a PA concentrate (75.1% PA) obtained by crystallization at low temperature in solvents. The latter was obtained carrying out two crystallizations in acetone at −24 and −20 °C, from which PA was recovered in the solid phases with a total yield of 84%. These PA enriched FFA mixtures were used in step (2) of acidolysis of POS, along with commercial PA (98% PA). In this acidolysis step four factors were studied: temperature, hexane/reaction mixture ratio, FFA/POS molar ratio and the intensity of treatment (IOT = lipase amount × reaction time/POS amount). The best results (TAGs with 79% PA and 75% PA at position 2) were obtained with commercial PA, at 37 °C, 10 mL hexane/g reaction mixture, a FFA/POS molar ratio 3:1 (1:1, w/w) and an IOT = 9.6 g lipase × h/g POS (for example 48 h, 10 g lipase and 50 g POS). PA enriched TAGs were purified neutralizing the FFAs by KOH hydroethanolic solutions and extracting the TAGs with hexane. In this way 99% pure acylglycerols (TAG + DAG) were obtained; the recovery yield of this purification step was 95%. The experiments carried out with POS demonstrated that it is possible to use only this oil (60% PA, 23% PA at position 2) as a source of PA to obtain a TAG with 70.7% PA and 70.5% PA at position 2. This process consists of four steps: (1) saponification of POS, (2) crystallization of FFAs to obtain PA enriched FFAs (75.1% PA), (3) acidolysis of POS with these FFAs, catalyzed with Novozym 435, to produce PA enriched TAGs at position 2 (70.5% PA) and (4) purification of TAGs to obtain approximately 95% purity and yield. These PA enriched TAGs could be used to obtain structured TAGs rich in PA at position 2 and in oleic acid at positions 1 and 3 (OPO), which is the principal TAG of human milk fat.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号