Controlled enzymatic hydrolysis on characteristic and antioxidant properties of soybean protein isolate-maltodextrin conjugates

This study aimed to investigate the effect of limited hydrolysis on conformational and antioxidant properties of soy protein isolate-maltodextrin (SPI-Md) conjugates. Extrinsic fluorescence analysis showed unfolding of the protein molecule and exposure of hydrophobic groups in SPI-Md conjugate hydrolysates. Free amino acid analysis showed that, the contents of hydrophobic amino acids in SPI-Md conjugates increased after hydrolysis. The contents of leucine, isoleucine, phenylalanine increased from 0.32, 0.30 and 0.54 to 1.36, 1.86 and 2.60, respectively, when the hydrolysis degree (DH) gradually increased from 0% to 5.7%. The FT-IR spectrum showed that C = O absorption of the amide group formed by glycosylation continued unabated after limited hydrolysis (DH 2.9%). The glycated SPI products showed good reducing power and superior resistance to lipid oxidation (34%, 12 mg mL^?1), whereas the limit hydrolysates (DH 2.9%) of SPI-Md conjugates showed more ef?cient radical-scavenging capacity (89.5%, at 12 mg mL^?1) and iron-chelation activity (91.3%, at 12 mg mL^?1). Results of this study indicated that, slight enzymatic hydrolysis (DH 0–2.9%) could help partially unfolding the globular structure of SPI-Md conjugates without deteriorating amide bonds and had a positive effect on their antioxidant properties.     

Soluble Dietary Fiber from Canna edulis Ker By-Product and its Enzymatic and Antioxidant Activities

Soluble dietary fiber (SDF) was prepared from Canna edulis Ker by-product by physical-enzymatic method and its structure was characterized using GC, FT-IR, ¹H-NMR, and solid ¹³C-NMR spectroscopy. The results exhibit that SDF is mainly composed of polysaccharides with minor phenolic compounds. Moreover, influences of SDF on protease hydrolysis of β-lactoglobulin (β-lg) and lipase hydrolysis of tributyrin (TBG) were determined. The results indicate that SDF promotes N release of β-lg by pepsin, despite it inhibiting the enzymatic activity of pepsin. Inversely, tryptic hydrolysis of β-lg is inhibited by the addition of SDF, which has no obvious effect on tryptic activity. SDF also inhibits lipase hydrolysis of TBG and the inhibition rate increases with increasing SDF concentration. Furthermore, antioxidant activities of SDF were evaluated by six different modes, and the relationship between concentration and activity was discussed. The results indicated different activities determined by different methods, suggesting that antioxidant mechanisms of SDF are complicated.     

Enzymatic sensing with laccase-functionalized textile organic biosensors

Herein we present a textile wearable electrochemical transistor by functionalizing a single cotton yarn with semiconducting polymer. The organic electrochemical transistor (OECT), which is low cost and completely integrated e-textile, is decorated by adsorption of the fungal laccase POXA1b, and is used as biosensor for the direct detection of Tyrosine (L-Tyr) without the use of electron mediators. The detection of Tyr in real-case scenario such as human physiological fluids would own a paramount importance in noninvasive analysis of the patient's condition, monitoring and preventing several pathologies. To assess the reaction progression, the redox process is studied by UV–visible absorption with test reference molecule of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS): the results confirmed that the oxidation reaction is driven by the presence of laccase enzyme and direct electron transfer occurred. The modulation of the signal response and the kinetic of the signal is used to detect Tyr molecule in aqueous solution and the role of the enzyme adsorption on the textile is analyzed. A kinetic analysis of the characteristic modulation times of the sensing curves, confirm the sensing properties of the textile device. The textile-based biosensor is demonstrated to monitor human health biomarkers through wearable applications in a non-invasive way, finding potential application in sport, healthcare and working safety.     

Comparison of ionic liquid,acid and alkali pretreatments for sugarcane bagasse enzymatic saccharification

BACKGROUND: Much attention has been given to applying ionic liquids (ILs) as an alternative pretreatment method for lignocellulosic biomass. This study aims to select the most suitable type of IL for pretreating sugarcane bagasse (SCB). The potential of ILs for pretreatment was evaluated and compared with conventional pretreatment media, acids and alkalis. The performance of the pretreatment media was evaluated based on the amount of reducing sugar produced from enzymatic saccharification, the energy requirement, and changes in the chemical structure and crystallinity index of the pretreated bagasse. RESULTS: 1‐ethyl‐3‐methylimidazolium acetate [EMIM]oAc was selected as the most suitable IL for SCB pretreatment. The optimum yields of reducing sugar obtained from [EMIM]oAc‐, alkali‐, and acid‐pretreated SCB were 69.5%, 92.8% and 41.3%, respectively. Although a lower yield of reducing sugar was obtained, [EMIM]oAc pretreatment required the least energy to pretreat 1 kg of SCB. Moreover, the percentage of SCB loss during [EMIM]oAc pretreatment was the lowest. [EMIM]oAc‐pretreated SCB also had the lowest crystallinity index (CI) with the most amorphous structure. CONCLUSION: [EMIM]oAc appears to be another option for pretreating SCB, and other issues such as the recyclability of [EMIM]oAc is worth investigating. Copyright © 2011 Society of Chemical Industry     

酶法合成头孢菌素类抗生素的研究进展

半合成抗生素的生产在医药工业中占有十分重要的地位，青霉素酰化酶是半合成β-内酰胺类抗生素的重要用酶，由于酶法合成与化学合成相比具有一定的优越性，随着酶工程技术的发展，酶法合成头包菌素类抗生素已日益受到重视。提高合成产率，降低侧链消耗，从而降低生产成本是酶法合成头隐菌素类抗生素研究的关键问题，平衡控制和动力学控制是酶法合成过程的两大研究策略，通过改变底物，降低水活度，添加高聚物，采用固定化技术及新型应体系等措施可改善酶促反应的微环境，改变酶的动力学特性，从而起到强化合成途径的作用，本文综述了该领域的一些研究进展并进行了展望。