Ethyl Oleate Synthesis Using Candida rugosa Lipase in a Solvent-Free System. Role of Hydrophobic Interactions

Enhanced Performance of Immobilized Rhizopus oryzae Lipase on Coated Porous Polypropylene Support with Additives

The immobilization of Rhizopus oryzae lipase (RoL) by hydrophobic adsorption on polypropylene supports with additives was investigated. Additives such as hen egg albumin, sodium caseinate and CAVAMAX® W6 were used to coat the support during immobilization where the immobilized RoL on coated support was compared to those of noncoated support. Following the immobilization, the catalytic activity of immobilized RoL was characterized based on different temperatures and pH. The immobilized RoL without additives showed optimal lipase activity at an optimum temperature of 50 °C and pH 6. However, RoL lipase that was immobilized on support treated with CAVAMAX® W6 had better performance in terms of hydrolytic activity and stability as compared to other additives. In addition, by having a support treated with hen egg albumin, the immobilized RoL was capable of yielding higher ester during esterification reactions.

Structural benefits of bisphenol S and its analogs resulting in their high sorption on carbon nanotubes and graphite

Bisphenol S (BPS), a new bisphenol analog, is considered to be a potential replacement for bisphenol A (BPA), which has gained concern because of its potentially adverse health impacts. Therefore, studies are needed to investigate the environmental fate and risks of this compound. In this study, the adsorption of BPS and four structural analogs on multi-walled carbon nanotubes (MWCNTs) and graphite (GP) were investigated. When solid-phase concentrations were normalized by the surface areas, oxygen-containing functional groups on the absorbents showed a positive impact on phenol sorption but inhibited the sorption of chemicals with two benzene rings. Among BPS analogs, diphenyl sulfone showed the lowest sorption when hydrophobic effects were ruled out. Chemicals with a butterfly structure, formed between the two benzene rings, showed consistently high sorption on MWCNTs, independent of the substituted electron-donating or accepting functional groups. This study emphasizes the importance of chemical conformation on organic, contaminant sorption on engineered, carbonaceous materials.

Adsorption and hysteresis of bisphenol A and 17alpha-ethinyl estradiol on carbon nanomaterials

Adsorption of 17alpha-ethinyl estradiol (EE2) and bisphenol A (BPA) on carbon nanomaterials (CNMs) was investigated. Single point adsorption coefficients (K) showed significant relationship with specific surface areas of CNMs for both chemicals, indicating surface area is a major factor for EDC adsorption on CNMs. BPA adsorption capacity is higher than EE2 on fullerene and single-walled carbon nanotubes (SWCNT). Our molecular conformation simulation indicated that BPA has a unique ability to adsorb on the curvature surface of CNMs because of its "butterfly" structure of two benzene rings. The higher adsorption capacity of BPA over EE2 is well explained by considering helical (diagonal) coverage of BPA on the CNMs surface and wedging of BPA into the groove and interstitial region of CNM bundles or aggregates. The comparison of K(HW) (hexadecane-water partition coefficient) normalized adsorption coefficients between EDCs and several polyaromatic hydrocarbons indicates that pi-pi electron donor--acceptor system is an important mechanism forthe adsorption of benzene-containing chemicals on CNMs. The high adsorption capacity and strong desorption hysteresis of both chemicals on SWCNT indicate that SWCNT is a potential adsorbent for water treatment.

Understanding Candida rugosa lipases: an overview

Candida rugosa lipase (CRL) is one of the enzymes most frequently used in biotransformations. However, there are some irreproducibility problems inherent to this biocatalyst, attributed either to differences in lipase loading and isoenzymatic profile or to other medium-engineering effects (temperature, a(w), choice of solvent, etc.). In addition, some other properties (influence of substrate and reaction conditions on the lid movement, differences in the glycosylation degree, post-translational modifications) should not be ruled out. In the present paper the recent developments published in the CRL field are overviewed, focusing on: (a) comparison of structural and biochemical data among isoenzymes (Lip1-Lip5), and their influence in the biocatalytical performance; (b) developments in fermentation technology to achieve new crude C. rugosa lipases; (c) biocatalytical reactivity of each isoenzyme, and methods for characterising them in crude CRL; (d) state-of-the-art of new applications performed with recombinant CRLs, both in CRL-second generation (wild-type recombinant enzymes), as well as in CRL-third generation, (mutants of the wt-CRL).

Frequent analytical/experimental problems in lipase-mediated synthesis in solvent-free systems and how to avoid them

Compared with chemical catalysis, enzymatic catalysis is a relatively new topic. Experimental work involving lipases deserves careful attention and accurate procedures still need to be implemented. A rapid but careful survey of published data immediately demonstrates that experiments performed under similar conditions with similar reagents have led to very different results. The aim of this work is to point out the importance of accurate and systematic procedures in order to ensure the reproducibility of experimental data. We strongly believe that different results found by different labs are due to problems detected in the procedures used. Quantification of the immobilisation efficiency of lipase on several supports through UV/visible methods and sampling methods used to obtain correct enzymatic activity values are specifically analysed. After a brief review which demonstrates the big discrepancies found in the literature, original data from Candida rugosa lipase adsorption on polypropylene powder and its use in the solvent-free synthesis of ethyl oleate are introduced in order to exemplify the difficulties found in these kinds of systems. Several procedures described in the literature are assayed and the accuracy of the results obtained is carefully analysed. The aim of the whole analysis performed is that it would be useful for any powdered solid to be used as a support for a lipase in a solvent-free system for any synthesis reaction, especially for those involving a volatile reagent. Throughout this contribution, special emphasis is placed on how catalytic reaction results using enzymes (free and immobilised) are reported so as to allow comparison between published data, something which is usually difficult since very different units are used and often complementary data are not included.