Enzymatic hydrolysis of cellulose by the cellobiohydrolase domain of CelB from the hyperthermophilic bacterium Caldicellulosiruptor saccharolyticus

The celB gene of Caldicellulosiruptor saccharolyticus was cloned and expressed in Escherichia coli to create a recombinant biocatalyst for hydrolyzing lignocellulosic biomass at high temperature. The GH5 domain of CelB hydrolyzed 4-nitrophenyl-β-d-cellobioside and carboxymethyl cellulose with optimum activity at pH 4.7-5.5 and 80 °C. The recombinant GH5 and CBM3-GH5 constructs were both stable at 80 °C with half-lives of 23 h and 39 h, respectively, and retained >94% activity after 48 h at 70 °C. Enzymatic hydrolysis of corn stover and cellulose pretreated with the ionic liquid 1-ethyl-3-methylimidazolium acetate showed that GH5 and CBM3-GH5 primarily produce cellobiose, with product yields for CBM3-GH5 being 1.2- to 2-fold higher than those for GH5. Confocal microscopy of bound protein on cellulose confirmed tighter binding of CBM3-GH5 to cellulose than GH5, indicating that the enhancement of enzymatic activity on solid substrates may be due to the substrate binding activity of CBM3 domain.     

An ethyl acetate sensor utilizing cataluminescence on Y2O3 nanoparticles

A cataluminescence (CTL) sensor using Y₂O₃ nanoparticles as the sensing materials was proposed for the determination of ethyl acetate. This ethyl acetate sensor showed high sensitivity and specificity at the optimal temperature of 264°C. Quantitative analysis was performed at a wavelength of 425 nm. The linear ranges of CTL intensity vs ethyl acetate concentrations were 2.0–250 ppm (r = 0.9965) and 250–6500 ppm (r = 0.9997) with a detection limit (3σ) of 0.5 ppm. There was no response or weak response when foreign substances such as formic acid, n‐hexane, toluene, acetic acid, benzene, and formaldehyde passing through the surface of Y₂O₃ nanoparticles. The sensor had a long lifetime more than 80 h with 3600 ppm ethyl acetate. It had been applied successfully to determine ethyl acetate in artificial air samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of adhesive on the morphology and mechanical properties of electrospun fibrous mat of cellulose acetate

Ultrafine fibers of cellulose acetate/poly(butyl acrylate) (CA/PBA) composite in which PBA acted as an adhesive and CA acted as a matrix, were successfully prepared as fibrous mat via electrospinning. The morphology observation from the electrospun CA/PBA composite fibers, after treatment with heat hardener, revealed that the fibers were cylindrical and had point-bonded structures. SEM, FT-IR spectra, Raman spectra, TGA analysis, and mechanical properties measurement were used to study the different properties of hybrid mats. The tensile strength of blend fibrous electrospun mats was found to be effectively increased. This resultant enhancement of the mechanical properties of polymer fibrous mats, caused by generating the point-bonded structures (due to adhesive), could increase the number of potential applications of mechanically weak electrospun CA fibers.     

Investigation of the binding of roxatidine acetate hydrochloride with cyclomaltoheptaose (β-cyclodextrin) using IR and NMR spectroscopy

NMR chemical shift changes of the cyclomaltoheptaose (β-cyclodextrin, β-CD) cavity protons as well as roxatidine acetate hydrochloride aromatic ring protons revealed the formation of a RAH–β-CD inclusion complex. Detailed FTIR and NMR spectroscopic (¹H NMR, COSY, NOESY, ROESY) studies have been done. The stoichiometry of the complex was determined to be 1:1, and the overall binding constant was also determined by Scott’s method. The NOESY spectrum confirmed the selective penetration of the aromatic ring of RAH into the β-CD cavity in comparison to that of the piperidine ring. The mode of penetration of the guest into the CD cavity and structure of the complex has been established.     

Characterization of cellulose acetate-reinforced aliphatic-aromatic copolyester composites

The biodegradability, morphology, mechanical, and thermal properties of composite materials composed of maleic anhydride-grafted poly(butylene adipate-co-terephthalate) (PBAT) and cellulose acetate (CA) were evaluated. Composites containing maleic anhydride-grafted PBAT (PBAT-g-MA/CA) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of CA in the PBAT-g-MA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules between the anhydride carboxyl groups of PBAT-g-MA and hydroxyl groups in CA. Each composite was buried in soil and monitored to assess biodegradability. Both the PBAT and the PBAT-g-MA/CA composite films were eventually completely degraded, and severe disruption of film structure was observed after 60-100 days of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable, even with high levels of CA, the higher water resistance of PBAT-g-MA/CA films indicated that they were more biodegradable than those made of PBAT.     

Selective recognition of acetate ion based on fluorescence enhancement chemosensor

Fluorescence study of the complexation between uranyl salophen (L) and some common anions in acetonitrile–water (90:10, v/v) solution showed a tendency of L toward acetate ion (AcO^?). The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and acetate ion which was utilized as the basis for the selective detection of AcO^?. The association constant of the 1:1 complex formation of L–AcO^? was calculated as 6.60 × 10⁶. The linear response range of the fluorescent chemosensor covers a AcO^? concentration range of 1.6 × 10^?7 to 2.5 × 10^?5 mol/L, with a detection limit of 2.5 × 10^?8 mol/L. L showed a selective and sensitive fluorescence enhancement response toward acetate ion over I₃^?, NO₃^?, CN^?, CO₃^2?, Br^?, Cl^?, F^?, H₂PO4^? and SO₄^2?, which was attributed to the higher stability of inorganic complex between acetate and L. Copyright © 2012 John Wiley & Sons, Ltd.     

酿酒酵母和异常毕赤酵母混菌发酵对白酒液态发酵效率和风味物质的影响

[目的]通过酿酒酵母(Saccharomyces cerevisiae)和异常毕赤酵母(Pichia anomala)在麸皮汁培养基中的混菌发酵,以增加发酵液的风味酯含量并保证发酵效率.[方法]采用两种酵母混合接种、顺序接种混菌发酵方式,以酵母单独接种发酵作对照,测定酵母的发酵性能和发酵液中乙酸乙酯含量,并对发酵结束时风味物质进行半定量;利用无细胞系统,分析两种酵母之间的相互作用.[结果]采用顺序接种混菌发酵方式,避免S.cerevisiae 对P.anomala的生长竞争性抑制,使两种酵母均能获得较高的生物量;发酵结束时,乙醇浓度为20.17 g/L,比酿酒酵母单菌种发酵时降低了9.14％;但乙酸乙酯含量达到0.74 g/L,比异常毕赤酵母单菌种发酵时提高了80％;发酵液风味物质的测定结果表明,酿酒酵母与异常毕赤酵母的混合发酵能够形成更多的酯类物质,总酸和高级醇含量却相对较低,有效改善了发酵液的风味特性;在混菌发酵时,碳源是影响酿酒酵母繁殖的重要因素,但酵母的代谢物对异常毕赤酵母产生明显的抑制作用.[结论]混菌发酵,为丰富发酵产物的风味复杂性和增强风格的独特性提供了一条有效的途径.