Wen-Yong Lou

Efficient production of biodiesel from high free fatty acid-containing waste oils using various carbohydrate-derived solid acid catalysts.

In the present study, such carbohydrate-derived catalysts have been prepared from various carbohydrates such as d-glucose, sucrose, cellulose and starch. The catalytic and textural properties of the prepared catalysts have been investigated in detail and it was found that the starch-derived catalyst had the best catalytic performance. The carbohydrate-derived catalysts exhibited substantially higher catalytic activities for both esterification and transesterification compared to the two typical solid acid catalysts (sulphated zirconia and Niobic acid), and gave markedly enhanced yield of methyl esters in converting waste cooking oils containing 27.8wt% high free fatty acids (FFAs) to biodiesel. In addition, under the optimized reaction conditions, the starch-derived catalyst retained a remarkably high proportion (about 93%) of its original catalytic activity even after 50 cycles of successive re-use and thus displayed very excellent operational stability. Our results clearly indicate that the carbohydrate-derived catalysts, especially the starch-derived catalyst, are highly effective, recyclable, eco-friendly and promising solid acid catalysts that are highly suited to the production of biodiesel from waste oils containing high FFAs.

Preparation of a sugar catalyst and its use for highly efficient production of biodiesel.

Novel solid acid catalysts for esterification have recently been described that are made by incomplete carbonization of carbohydrates followed by sulfonation. Herein, such a ‘sugar catalyst’ is prepared from D-glucose and its catalytic properties and structure are investigated in detail. This type of sugar catalyst is, for the first time, applied for the effective production of biodiesel from waste oils. Our results indicate that sugar catalysts are highly effective, minimally polluting and re-usable catalysts that are highly suited to the production of biodiesel from waste oils with a high acid value.

Fabrication of electrospun polylactic acid nanofilm incorporating cinnamon essential oil/β-cyclodextrin inclusion complex for antimicrobial packaging

A novel antimicrobial packaging material was obtained by incorporating cinnamon essential oil/β-cyclodextrin inclusion complex (CEO/β-CD-IC) into polylacticacid (PLA) nanofibers via electrospinning technique. The CEO/β-CD-IC was prepared by the co-precipitation method and SEM and FT-IR spectroscopy analysis indicated the successful formation of CEO/β-CD-IC, which improved the thermal stability of CEO. The CEO/β-CD-IC was then incorporated into PLA nanofibers by electrospinning and the resulting PLA/CEO/β-CD nanofilm showed better antimicrobial activity compared to PLA/CEO nanofilm. The minimum inhibitory concentration (MIC) of PLA/CEO/β-CD nanofilm against Escherichia coli and Staphylococcus aureus was approximately 1 mg/ml (corresponding CEO concentration 11.35 μg/ml) and minimum bactericidal concentration (MBC) was approximately 7 mg/ml (corresponding CEO concentration 79.45 μg/ml). Furthermore, compared with the casting method, the mild electrospinning process was more favorable for maintaining greater CEO in the obtained film. The PLA/CEO/β-CD nanofilm can effectively prolong the shelf life of pork, suggesting it has potential application in active food packaging.

Effect of organic acids on the growth and lipid accumulation of oleaginous yeast Trichosporon fermentans

BackgroundMicrobial lipids have drawn increasing attention in recent years as promising raw materials for biodiesel production, and the use of lignocellulosic hydrolysates as carbon sources seems to be a feasible strategy for cost-effective lipid fermentation with oleaginous microorganisms on a large scale. During the hydrolysis of lignocellulosic materials with dilute acid, however, various kinds of inhibitors, especially large amounts of organic acids, will be produced, which substantially decrease the fermentability of lignocellulosic hydrolysates. To overcome the inhibitory effects of organic acids, it is critical to understand their impact on the growth and lipid accumulation of oleaginous microorganisms.ResultsIn our present work, we investigated for the first time the effect of ten representative organic acids in lignocellulosic hydrolysates on the growth and lipid accumulation of oleaginous yeast Trichosporon fermentans cells. In contrast to previous reports, we found that the toxicity of the organic acids to the cells was not directly related to their hydrophobicity. It is worth noting that most organic acids tested were less toxic than aldehydes to the cells, and some could even stimulate the growth and lipid accumulation at a low concentration. Unlike aldehydes, most binary combinations of organic acids exerted no synergistic inhibitory effects on lipid production. The presence of organic acids decelerated the consumption of glucose, whereas it influenced the utilization of xylose in a different and complicated way. In addition, all the organic acids tested, except furoic acid, inhibited the malic activity of T. fermentans. Furthermore, the inhibition of organic acids on cell growth was dependent more on inoculum size, temperature and initial pH than on lipid content.ConclusionsThis work provides some meaningful information about the effect of organic acid in lignocellulosic hydrolysates on the lipid production of oleaginous yeast, which is helpful for optimization of biomass hydrolysis processes, detoxified pretreatment of hydrolysates and lipid production using lignocellulosic materials.

A highly active bagasse-derived solid acid catalyst with properties suitable for production of biodiesel.

A novel bagasse-based solid acid catalyst was successfully prepared through sulfonation of incompletely carbonized bagasse. A range of conditions for producing the catalyst were investigated, and the optimized catalyst, produced under carbonization at 648 K for 0.5 h and sulfonation at 423 K for 15 h, showed excellent catalytic activity and resulted in around 95 % yield of methyl oleate. Its activity was not only substantially greater than that of niobic acid and Amberlyst-15, but also comparable to or superior to that of catalysts made from pure starch or glucose, respectively. Additionally, the bagasse-derived catalyst could be repeatedly employed for at least eight cycles and still retained around 90 % of its original activity, exhibiting excellent operational stability. Furthermore, the catalyst efficiently converted waste cooking oils with 38.6 wt % free fatty acids into biodiesel and afforded a high yield of about 93.8 % within 12 h. These results clearly show that the bagasse-derived catalyst is economic, eco-friendly, and promising for biodiesel production from low-cost feedstocks and may find wide applications.

Use of ionic liquids to improve whole-cell biocatalytic asymmetric reduction of acetyltrimethylsilane for efficient synthesis of enantiopure (S)-1-trimethylsilylethanol

The two typical ionic liquids (ILs), one hydrophobic (BMIM·PF6) and one hydrophilic (BMIM·BF4), were tested as solvents for use in the asymmetric reduction of acetyltrimethylsilane (ATMS) to enantiopure (S)-1-trimethylsilylethanol {(S)-1-TMSE} catalyzed by immobilized Saccharomyces cerevisiae cells. The results demonstrate that BMIM·PF6 and BMIM·BF4 can markedly boost the activity and the stability of the immobilized cells. To better understand the reaction performed in these IL-containing systems, various variables that influenced the performance of the reaction were examined. The optimal buffer pH, reaction temperature and substrate concentration were 7.3, 30 °C and 84 mM, respectively, for the BMIM·PF6/buffer (1/6, v/v) biphasic system, and 7.5, 30 °C and 77 mM, respectively, for the 10% (v/v) BMIM·BF4–buffer co-solvent system. Under the optimal conditions, the initial reaction rate, maximum yield and product e.e. were 63.4 mM h−1, 99.9% and >99.9% with the former system, while those with the latter system were 74.5 mM h−1, 99.2% and >99.9%, respectively, which were much higher than those achieved with either n-hexane/buffer (2/1, v/v) biphasic system or aqueous buffer. It was also found that the optimal pH and substrate concentration changed when n-hexane was replaced by BMIM·PF6 or BMIM·BF4. Although the optimal reaction temperature remained the same in the four kinds of reaction systems, the temperature profile of the reaction varied from case to case. Additionally, BMIM·BF4 and especially BMIM·PF6 exhibited greater biocompatibility with Saccharomyces cerevisiae than n-hexane, and could be used repeatedly for economically interesting whole-cell biocatalytic processes with in situ coenzyme regeneration.

Efficient regioselective acylation of 1-β-D-arabinofuranosylcytosine catalyzed by lipase in ionic liquid containing systems

Seven ionic liquids (ILs) were tested for use in the regioselective acylation of 1-β-D-arabinofuranosylcytosine (ara-C) by vinyl propionate, catalyzed by immobilized Candida antarctica lipase B. The results demonstrated that the nature of both the cations and the anions of ILs had a significant effect on the initial rate and the substrate conversion, but little effect on the regioselectivity of the reaction. The lipase displayed enhanced activity toward ara-C when the alkyl chain of CnMIm·BF4 increased in length (n = 4–8) and no acylation reaction occurred in C4MIm·Cl or C4MIm·Br. To further enhance the initial rate and substrate conversion, co-solvent mixtures of ILs and organic solvents were investigated. Among various IL-containing systems examined, 10% (v/v) C4MIm·PF6–tetrahydrofuran gave the highest initial rate and substrate conversion. In this reaction medium, the optimal water activity, vinyl propionate/ara-C molar ratio, temperature and shaking rate were 0.07, 15 ∶ 1 (mol/mol), 60 °C and 250 rpm, respectively. Under these conditions, the initial rate, substrate conversion and the regioselectivity were 94.0 mM h−1, 98.5% and 99%, respectively. An additional comparative study demonstrated that the enzymatic acylation proceeded with very similar initial rate, substrate conversion, regioselectivity and activation energy whether the reaction medium was 10% (v/v) C4MIm·PF6–tetrahydrofuran or 28% (v/v) hexane–pyridine (the best organic solvent mixture for the reaction). However, the lipase exhibited a much higher stability in the IL-containing system, which may also have environmental advantages. The product of the lipase-catalysed reaction was characterized by NMR, FT-IR spectroscopy and was shown to be the 5′-O-monoester of ara-C.

Cross-linked enzyme aggregates of Mung bean epoxide hydrolases: a highly active, stable and recyclable biocatalyst for asymmetric hydrolysis of epoxides

A highly active and stable cross-linked enzyme aggregates (CLEAs) of epoxide hydrolases (EHs) from Mung bean, which plays a crucial role in synthesis of valuable enantiopure diols, were successfully prepared and characterized. Under the optimum preparation conditions, the activity recovery of CLEAs recorded 92%. The CLEAs were more efficient than the free enzyme in catalyzing asymmetric hydrolysis of styrene oxide to (R)-1-phenyl-1,2-ethanediol in organic solvent-containing biphasic system. The biocatalytic reaction performed in n-hexane/buffer biphasic system had a clearly faster initial reaction rate, much higher product yield and product e.e. value than that in aqueous medium. Moreover, the optimal volume ratio of n-hexane to buffer, reaction temperature, buffer pH value and substrate concentration for the enzymatic hydrolysis were found to be 1:1, 40 °C, 7.5 and 30 mM, respectively, under which the initial reaction rate, product yield and product e.e. value were 13.26 mM/h, 46% and 93.5%, respectively. The CLEAs retained more than 50% of their initial activity after 8 batches of re-use in phosphate buffer and maintained 53% of their original activity after 8 reaction cycle in biphasic system. The efficient biocatalytic process with CLEAs proved to be feasible on a 250-mL preparative scale, exhibiting great potential for asymmetric synthesis of chiral diols.

Preparation and Characterization of Immobilized Lipase from Pseudomonas Cepacia onto Magnetic Cellulose Nanocrystals

Magnetic cellulose nanocrystals (MCNCs) were prepared and used as an enzyme support for immobilization of Pseudomonas cepacialipase (PCL). PCL was successfully immobilized onto MCNCs (PCL@MCNC) by a precipitation-cross-linking method. The resulting PCL@MCNC with a nanoscale size had high enzyme loading (82.2 mg enzyme/g) and activity recovery (95.9%). Compared with free PCL, PCL@MCNC exhibited significantly enhanced stability and solvent tolerance, due to the increase of enzyme structure rigidity. The observable optimum pH and temperature for PCL@MCNC were higher than those of free PCL. PCL@MCNC manifested relatively higher enzyme-substrate affinity and catalytic efficiency. Moreover, PCL@MCNC was capable of effectively catalyzing asymmetric hydrolysis of ketoprofenethyl ester with high yield of 43.4% and product e.e. of 83.5%. Besides, immobilization allowed PCL@MCNC reuse for at least 6 consecutive cycles retaining over 66% of its initial activity. PCL@MCNC was readily recycled by magnetic forces. Remarkably, the as-prepared nanobiocatalyst PCL@MCNC is promising for biocatalysis.

Using a water-immiscible ionic liquid to improve asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one catalyzed by immobilized Candida parapsilosis CCTCC M203011 cells.

BackgroundWhole cells are usually employed for biocatalytic reduction reactions to ensure efficient coenzyme regeneration and to avoid problems with enzyme purification and stability. The efficiency of whole cell-catalyzed bioreduction is frequently restricted by pronounced toxicity of substrate and/or product to the microbial cells and in many instances the use of two-phase reaction systems can solve such problems. Therefore, we developed new, biphasic reaction systems with biocompatible water-immiscible ionic liquids (ILs) as alternatives to conventional organic solvents, in order to improve the asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one (TMSB) to (S)-4-(trimethylsilyl)-3-butyn-2-ol {(S)-TMSBOL}, a key intermediate for synthesis of 5-lipoxygenase inhibitors, using immobilized Candida parapsilosis CCTCC M203011 cells as the biocatalyst.ResultsVarious ILs exerted significant but different effects on the bioreduction. Of all the tested water-immiscible ILs, the best results were observed with 1-butyl-3-methylimidazolium hexafluorophosphate (C4MIM·PF6), which exhibited not only good biocompatibility with the cells but also excellent solvent properties for the toxic substrate and product, thus markedly improving the efficiency of the bioreduction and the operational stability of the cells as compared to the IL-free aqueous system. 2-Propanol was shown to be the most suitable co-substrate for coenzyme regeneration, and it was found that the optimum volume ratio of buffer to C4MIM·PF6, substrate concentration, buffer pH, 2-propanol concentration and reaction temperature were 4/1 (v/v), 24 mM, 5.5, 130 mM and 30°C, respectively. Under these optimized conditions, the maximum yield and the product e.e. wer 97.7% and >99%, respectively, which are much higher than the corresponding values previously reported. The efficient whole-cell biocatalytic process was shown to be feasible on a 250-mL scale.ConclusionThe whole cell-catalyzed asymmetric reduction of TMSB to (S)-TMSBOL can be substantially improved by using a C4MIM·PF6/buffer biphasic system instead of a single-phase aqueous system and the resulting biocatalytic process appears to be effective and competitive on a preparative scale.