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1.
《Process Biochemistry》2010,45(6):887-891
For efficient production of (R)-(−)-mandelic acid, a nitrilase gene from Alcaligenes sp. ECU0401 was cloned and overexpressed in Escherichia coli. After simple optimization of the culture conditions, the biocatalyst production was greatly increased from 500 to 7000 U/l. The recombinant E. coli whole cells showed strong tolerance against a high substrate concentration of up to 200 mM, and the concentration of (R)-(−)-mandelic acid after only 4 h of transformation reached 197 mM with an enantiomeric excess (eep) of 99%. In a fed-batch reaction with 600 mM mandelonitrile as the substrate, the cumulative production of (R)-(−)-mandelic acid after 17.5 h of conversion reached 520 mM. The recombinant E. coli cells could also be repeatedly used in the biotransformation, retaining 40% of the initial activity after 10 batches of reaction. The highly substrate/product tolerable and enantioselective nature of this recombinant nitrilase suggests that it is of great potential for the practical production of optically pure (R)-(−)-mandelic acid.  相似文献   

2.
α-Arbutin is a glycosylated hydroquinone (HQ) which has inhibitory function against tyrosinase. The aim of present study is to develop an efficient and inexpensive method for the production of α-arbutin by using Xanthomonas maltophilia BT-112 as a biocatalyst. HQ, substrate for the bioconversion as glucosyl acceptor, was immobilized on different macroporous resins to reduce its toxic effect on the cells, and the optimal reaction conditions for α-arbutin synthesis were investigated. The research results indicated that H107 resin offered the best adsorption capacity for HQ than other resins. When immobilized hydroquinone (IMHQ) was applied, the maximal HQ tolerance of cells and yield of α-arbutin were 254 mM and 64.7 g L?1 respectively. The α-arbutin productivity (0.90 g L?1 h?1) was 526% higher than that of the control (free HQ) in 72 h reaction and the fermentation broth maintained its full activity for almost three consecutive batch reactions. Additionally, the product was one-step isolated and identified as α-arbutin by 13C NMR and 1H NMR analysis. In conclusion, the results in this work provide a cost-effective method for the production of α-arbutin.  相似文献   

3.
A nitrile hydratase (NHase) gene from Aurantimonas manganoxydans was cloned and expressed in Escherichia coli BL21 (DE3). A downstream gene adjacent to the β-subunit was necessary for the functional expression of the recombinant NHase. The structural gene order of the Co-type NHase was α-subunit beyond β-subunit, different from the order typically reported for Co-type NHase genes. The NHase exhibited adequate thermal stability, with a half-life of 1.5 h at 50 °C. The NHase efficiently hydrated 3-cyanopyridine to produce nicotinamide. In a 1-L reaction mixture, 3.6 mol of 3-cyanopyridine was completely converted to nicotinamide in four feedings, exhibiting a productivity of 187 g nicotinamide/g dry cell weight/h. An industrial auto-induction medium was applied to produce the recombinant NHase in 10-L fermenter. A glycerol-limited feeding method was performed, and a final activity of 2170 U/mL culture was achieved. These results suggested that the recombinant NHase was efficiently cloned and produced in E. coli.  相似文献   

4.
A highly active and stable derivate of immobilized Bacillus circulans β-galactosidase was prepared for the synthesis of galacto-oligosaccharides (GOS) under repeated-batch operation. B. circulans β-galactosidase was immobilized on monofunctional glyoxyl agarose and three heterofunctional supports: amino-, carboxy-, and chelate-glyoxyl agarose. Glyoxyl agarose was the support with highest immobilization yield and stability being selected for the optimization of immobilization conditions and application in GOS synthesis. A central composite rotatable design was conducted to optimize contacted protein and immobilization time, using maximum catalytic potential as the objective function. Optimal conditions of immobilization were 28.9 mg/g and 36.4 h of contact, resulting in a biocatalyst with 595 IU/g and a half-life 89-fold higher than soluble enzyme. Immobilization process did not alter the synthetic capacity of β-galactosidase, obtaining the same GOS yield and product profile than the free enzyme. GOS yield and productivity remained unchanged along 10 repeated batches, with values of 39% (w/w) and 5.7 g GOS/g of biocatalyst·batch. Total product obtained after 10 batches of reaction was 56.5 g GOS/g of biocatalyst (1956 g GOS/g protein). Cumulative productivity in terms of mass of contacted protein was higher for the immobilized enzyme than for its soluble counterpart from the second batch of synthesis onwards.  相似文献   

5.
Physical (ionic exchange of ionic polymers) or chemical (aminoethylamidation, succinylation, hydroxyethylamidation) modifications of Novozym 435 have been performed and the resulting biocatalysts have been assayed in diverse reactions. The coating of the immobilized enzyme with dextran-sulphate via ionic exchange permitted to increase the asymmetric factor of the biocatalyst from A = 13 (ee = 83%) to 24 (ee > 90%) in the hydrolysis of 3-phenylglutaric acid dimethyl diester, producing the (R)-monomethyl ester. The chemical succinylation of Novozym 435 permitted to enhance the biocatalyst enantiospecificity from E = 1 to 13 in the hydrolysis of (±)-mandelic acid methyl ester. In the hydrolysis of (±)-2-O-butyryl-2-phenylacetic acid, the enantiospecificity of Novozym 435 was very high towards the S-enantiomer (E > 100) but it was inverted after the chemical hydroxyethylamidation of the immobilized enzyme (E = 6.6 towards R-enantiomer).Thus, these simple protocols seem to be a very powerful tool to generate a library of biocatalysts from Novozym 435 with very different catalytic properties.  相似文献   

6.
The aim of the present study is to develop an efficient and cost-effective method for α-arbutin production by using whole-cell of Xanthomonas maltophilia BT-112 as a biocatalyst. Hydroquinone (HQ), substrate for the bioconversion as glucosyl acceptor, was immobilized on H107 macroporous resin to reduce its toxic effect on the cells, and the optimal reaction conditions for α-arbutin synthesis were investigated. When 350 g/L H107 resin (254.5 mM HQ) and 20 g/L (4.2 U/g) of cells were shaken in 10 mL Na2HPO4–KH2PO4 buffer (50 mM, pH 6.5) containing 509 mM sucrose at 35 °C with 150 rpm for 48 h, the final yield of α-arbutin reached 65.9 g/L with a conversion yield of 95.2% based on the amount of HQ supplied. The α-arbutin production was 202% higher than that of the control (free HQ) and the cells maintained its full activity for almost six consecutive batch reactions, indicating a potential for reducing production costs. Additionally, the product was one-step isolated and identified as α-arbutin by 13C NMR and 1H NMR analysis. In conclusion, the combination of whole cells and immobilized hydroquinone (IMHQ) is a promising approach for economical and industrial-scale production of α-arbutin.  相似文献   

7.
This paper describes the kinetic characterization of a recombinant whole-cell biocatalyst for the stereoselective Baeyer–Villiger type oxidation of bicyclo[3.2.0]hept-2-en-6-one to its corresponding regio-isomeric lactones (−)-(1S,5R)-2-oxabicyclo[3.3.0]oct-6-en-3-one and (−)-(1R,5S)-3-oxabicyclo[3.3.0]oct-6-en-2-one. Escherichia coli TOP10 [pQR239], expressing cyclohexanone monooxygenase (CHMO) from Acinetobacter calcoaceticus (NCIMB 9871), was shown to be suitable for this biotransformation since it expressed CHMO at a high level, was simple to produce, contained no contaminating lactone hydrolase activity and allowed the intracellular recycle of NAD(P)H necessary for the biotransformation. A small-scale biotransformation reactor (20 ml) was developed to allow rapid collection of intrinsic kinetic data. In this system, the optimized whole-cell biocatalyst exhibited a significantly lower specific lactone production activity (55–60 μmol min−1 g−1 dry weight) than that of sonicated cells (500 μmol min−1 g−1 dry weight). It was shown that this shortfall was comprised of a difference in the pH optima of the two biocatalyst forms and mass transfer limitations of the reactant and/or product across the cell barrier. Both reactant and product inhibition were evident. The optimum ketone concentration was between 0.2 and 0.4 g l−1 and at product concentrations above 4.5–5 g l−1 the specific activity of the whole cells was zero. These results suggest that a reactant feeding strategy and in situ product removal should be considered in subsequent process design.  相似文献   

8.
The production of a two-layer composite biocatalyst for immobilization of two different microorganisms for simultaneous alcoholic and malolactic fermentation (MLF) of wine in the same bioreactor is reported. The biocatalyst consisted of a tubular delignified cellulosic material (DCM) with entrapped Oenococcus oeni cells, covered with starch gel containing the alcohol resistant and cryotolerant strain Saccharomyces cerevisiae AXAZ-1. The biocatalyst was found effective for simultaneous low temperature alcoholic fermentation resulting to conversion of malic acid to lactic acid in 5 days at 10 °C. Improvement of wine quality compared with wine fermented with S. cerevisiae AXAZ-1 immobilized on DCM was attributed to MLF as well as to increased ester formation and lower higher alcohols produced at low fermentation temperatures (10 °C) as shown by GC and headspace SPME GC/MS analysis. Scanning electron microscopy showed that the preparation of a three-layer composite biocatalyst is also possible. The significance of such composite biocatalysts is the feasibility of two or three bioprocesses in the same bioreactor, thus reducing production cost in the food industry  相似文献   

9.
《Process Biochemistry》2010,45(2):147-152
A highly active recombinant whole-cell biocatalyst, Escherichia coli pETAB2/pG-KJE1, was developed for the efficient production of (S)-styrene oxide from styrene. The recombinant E. coli overexpressed styAB the genes of styrene monooxygenase of Pseudomonas putida SN1 and coexpressed the genes encoding chaperones (i.e., GroEL–GroES and DnaK–DnaJ–GrpE). The styrene monooxygenases were produced to ca. 40% of the total soluble proteins, enabling the whole-cell activity of the recombinant of 180 U/g CDW. The high StyAB activity in turn appeared to direct cofactors and molecular oxygen to styrene epoxidation. The product yield on energy source (i.e., glucose) reached ca. 40%. In addition, biotransformation in an organic/aqueous two-liquid phase system allowed the product to accumulate to 400 mM in the organic phase within 6 h, resulting in an average specific and volumetric productivity of 6.4 mmol/g dry cells/h (106 U/g dry cells) and 67 mM/h (1110 U/Laq), respectively, under mild reaction conditions. These results indicated that the high productivity and the high product yield on energy source were driven by the high enzyme activity. Therefore, it was concluded that oxygenase activity of whole-cell biocatalysts is one of the critical factors to determine their catalytic performance.  相似文献   

10.
The novel whole-cell biocatalyst Candida antarctica lipase B displaying-Pichia pastoris (Pp-CALB) is characterized by its low preparation cost and could be an alternative to the commercial immobilized Candida antarctica lipase B (CALB). This study addresses the feasibility of using Pp-CALB in large scale glucose fatty acid esters production. 1,2-O-Isopropylidene-α-d-glucofuranose (IpGlc) was used as the acyl acceptor to overcome the low solubility of glucose in an organic solvent and to avoid the addition of toxic co-solvents. IpGlc significantly improved the Pp-CALB catalyzing esterification efficiency when using long chain fatty acids as the acyl donor. Under the preferred operating conditions (50 °C, 40 g/L molecular sieve dosage and 200 rpm mixing intensity), 60.5% of IpGlc converted to 6-O-myristate-1, 2-O-isopropylidene-α-d-glucofuranose (C14-IpGlc) after a 96-h reaction in a 2-L stirred reactor. In a 5-L pilot scale test, Pp-CALB also showed a similar substrate conversion rate of 55.4% and excellent operational stability. After C14-IpGlc was collected, 70% trifluoroacetic acid was adopted to hydrolyze C14-IpGlc to myristate glucose ester (C14-Glc) with a high yield of 95.3%. In conclusion, Pp-CALB is a powerful biocatalyst available for industrial synthesis, and this study describes an applicable and economical process for the large scale production of myristate glucose ester.  相似文献   

11.
Microbial hydroxylation of long chain fatty acids has been extensively investigated. However, biotransformation productivity remains below ca. 1.0 g/g cell dry weight (CDW)/h under process conditions. In the present study, a highly efficient microbial hydroxylation process to convert oleic acid into 10-hydroxystearic acid was developed. A recombinant Escherichia coli expressing ohyA, the gene encoding oleate hydratase of Stenotrophomonas maltophilia, was used as the biocatalyst. Investigation of the ohyA expression and biotransformation conditions (e.g., inducer concentration, gene expression period before initiating biotransformation, mixing condition of reaction medium) enabled 10-hydroxystearic acid to accumulate to a final concentration of approximately 46 g/L in the culture medium. The specific product formation rate and product yield reached approximately 2.0 g/g CDW/h (i.e., 110 U/g CDW) and 91%, respectively. The specific product formation rate was more than 3-fold higher than those of a bioprocess using wild type Stenotrophomonas sp. cells. Additionally, the product of the whole-cell biotransformation was recovered at a yield of 70.9% and a purity of 99.7% via solvent fraction crystallization at low temperature. These results will contribute to developing a biological process for hydroxylation of oleic acid.  相似文献   

12.
《Process Biochemistry》2007,42(2):141-147
Haploid Saccharomyces cerevisiae W303-1A cells grown on different carbon sources were employed as the biocatalyst for ethyl acetoacetate reduction in n-hexane. The effects of cell immobilization on montmorillonite, as well as the addition of trehalose or sucrose solutions, were also tested. Best conversions (∼50%) to the chiral alcohol ethyl (S)-(+)-3-hydroxybutanoate (ee > 99%) were obtained with cells grown under respiratory metabolism with glycerol–ethanol, and higher yields were observed when trehalose was added to the reaction media. Although cells with fermentative metabolism grown on glucose were able to reduce the substrate when sucrose was added, the disaccharide was consumed by the cells during the course of the reaction, and no enantioselective product was obtained. Immobilized cells also required the addition of trehalose in order to reduce the substrate with high yield. Thus, our results indicate that trehalose may be an efficient protector of immobilized or free yeast cells during enantioselective reductions in organic solvent.  相似文献   

13.
《Process Biochemistry》2004,39(11):1331-1339
Bacillus subtilis PE-11 cells were immobilized in calcium alginate and used for the production of alkaline protease. The influence of alginate concentration, different cations, concentration of cation, curing time, bead diameter and nutrient strength on alkaline protease production and stability of biocatalyst were investigated. Repeated batch fermentations of immobilized cells in shake flasks were carried out with the optimized parameters such as; 3% alginate, 0.25 M calcium chloride with 1 h curing time, 3.24 mm bead diameter and 0.75% glucose and 0.75% peptone as nutrients. The results indicated that, a good level of enzyme was maintained for a period of about 9 days. The immobilized cells of B. subtilis PE-11 in calcium alginate are more efficient for the production of alkaline protease with repeated batch fermentation.  相似文献   

14.
Palatinose is a non-cariogenic disaccharide obtained from the enzymatic conversion of sucrose, used in food industries as a sugar substitute. Free and Ca-alginate immobilized cells of Erwinia sp. D12 were used to produce palatinose from sucrose. Palatinose production was studied in a repeated-batch process using different immobilized biocatalysts: whole cells, disrupted cells and glucosyltransferase. Successive batches were treated with the immobilized biocatalyst, but a decrease in palatinose production was observed. A continuous process using a packed-bed reactor was investigated, and found to produce 55–66% of palatinose during 17 days using immobilized cells treated with glutaraldehyde and a substrate flow speed of 0.56 ml min−1. However, immobilized cells in a packed-bed reactor failed to maintain the palatinose production for a prolonged period. The free cells showed a high conversion rate using batch fermentation, obtaining a palatinose yield of 77%. The cells remained viable for 16 cycles with high palatinose yields (65–77%). Free Erwinia sp. D12 cells supported high production levels in repeated-batch operations, and the results showed the potential for repeated reuse.  相似文献   

15.
The use of free, immobilized and reused immobilized cells of the microalga Nostoc muscorum was studied for bioconversion of androst-4-en-3,17-dione (AD) to testosterone in hexadecane. Among polymers such as agar, agarose, κ-carrageenan, polyacrylamide, polyvinyl alcohol, and sodium alginate that were examined for cell entrapment, sodium alginate with a concentration of 2% (w/v) proved to be the proper matrix for N. muscorum cells immobilization. The bioconversion characteristics of immobilized whole algal cells at ranges of temperatures, substrate concentrations, and shaking speeds were studied followed by a comparison with those of free cells. The conditions were 30 °C, 0.5 g/L, and 100 rpm, respectively. The immobilized N. muscorum showed higher yield (72 ± 2.3%) than the free form (24 ± 1.3%) at the mentioned conditions. The bioconversion yield did not decrease during reuse of immobilized cells and remained high even after 5 batches of bioreactions while Na-alginate 3% was used; however, reuse of alginate 2% beads did not give a satisfactory result.  相似文献   

16.
An investigation was conducted on the production of β-galactosidase (β-gal) by different strains of Kluyveromyces, using lactose as a carbon source. The maximum enzymatic activity of 3.8 ± 0.2 U/mL was achieved by using Kluyveromyces lactis strain NRRL Y1564 after 28 h of fermentation at 180 rpm and 30 °C. β-gal was then immobilized onto chitosan and characterized based on its optimal operation pH and temperature, its thermal stability and its kinetic parameters (Km and Vmax) using o-nitrophenyl β-d-galactopyranoside as substrate. The optimal pH for soluble β-gal activity was found to be 6.5 while the optimal pH for immobilized β-gal activity was found to be 7.0, while the optimal operating temperatures were 50 °C and 37 °C, respectively. At 50 °C, the immobilized enzyme showed an increased thermal stability, being 8 times more stable than the soluble enzyme. The immobilized enzyme was reused for 10 cycles, showing stability since it retained more than 70% of its initial activity. The immobilized enzyme retained 100% of its initial activity when it was stored at 4 °C and pH 7.0 for 93 days. The soluble β-gal lost 9.4% of its initial activity when it was stored at the same conditions.  相似文献   

17.
《Process Biochemistry》2010,45(6):829-834
Biocatalytic synthesis is a promising environmentally friendly process for the production of biodiesel, a sustainable alternative fuel from renewable plant resources. In order to develop an economical heterogeneous biocatalyst, protein-coated microcrystals (PCMCs) were prepared from a commercial enzyme preparation from a recombinant Aspergillus strain expressing Thermomyces lanuginosus lipase and used for synthesis of biodiesel from palm olein by ethanolysis. Reaction parameters, including catalyst loading, temperature, and oil/alcohol molar ratio have been systematically optimized. Addition of tert-butanol was found to markedly increase the biocatalyst activity and stability resulting in improved product yield. Optimized reactions (20%, w/w PCMC-lipase to triacylglycerol and 1:4 fatty acid equivalence/ethanol molar ratio) led to the production of alkyl esters from palm olein at 89.9% yield on molar basis after incubation at 45 °C for 24 h in the presence of tert-butanol at a 1:1 molar ratio to triacylglycerol. Crude palm oil and palm fatty acid distillate were also efficiently converted to biodiesel with 82.1 and 75.5% yield, respectively, with continual dehydration by molecular sieving. Operational stability of PCMC-lipase could be improved by treatment with tert-butanol allowing recycling of the biocatalyst for at least 8 consecutive batches with only slight reduction in activity. This work thus shows a promising approach for biodiesel synthesis with microcrystalline lipase which could be further developed for cost-efficient industrial production of biodiesel.  相似文献   

18.
Nitrilases have long been considered as an attractive alternative to chemical catalyst in carboxylic acids biosynthesis due to their green characteristics and the catalytic potential in nitrile hydrolysis. A novel nitrilase from Pseudomonas putida CGMCC3830 was purified to homogeneity. pI value was estimated to be 5.2 through two-dimensional electrophoresis. The amino acid sequence of NH2 terminus was determined. Nitrilase gene was cloned through CODEHOP PCR, Degenerate PCR and TAIL-PCR. The open reading frame consisted of 1113 bp encoding a protein of 370 amino acids. The predicted amino acid sequence showed the highest identity (61.6%) to nitrilase from Rhodococcus rhodochrous J1. The enzyme was highly specific toward aromatic nitriles such as 3-cyanopyridine, 4-cyanopyridine, and 2-chloro-4-cyanopyridine. It was classified as aromatic nitrilase. The nitrilase activity could reach up to 71.8 U/mg with 3-cyanopyridine as substrate, which was a prominent level among identified cyanopyridine converting enzymes. The kinetic parameters Km and Vmax for 3-cyanopyridine were 27.9 mM and 84.0 U/mg, respectively. These data would warrant it as a novel and potential candidate for creating effective nitrilases in catalytic applications of carboxylic acids synthesis through further protein engineering.  相似文献   

19.
Industrial application of α-galactosidase requires efficient methods to immobilize the enzyme, yielding a biocatalyst with high activity and stability compared to free enzyme. An α-galactosidase from tomato fruit was immobilized on galactose-containing polymeric beads. The immobilized enzyme exhibited an activity of 0.62 U/g of support and activity yield of 46%. The optimum pH and temperature for the activity of both free and immobilized enzymes were found as pH 4.0 and 37 °C, respectively. Immobilized α-galactosidase was more stable than free enzyme in the range of pH 4.0–6.0 and more than 85% of the initial activity was recovered. The decrease in reaction rate of the immobilized enzyme at temperatures above 37 °C was much slower than that of the free counterpart. The immobilized enzyme shows 53% activity at 60 °C while free enzyme decreases 33% at the same temperature. The immobilized enzyme retained 50% of its initial activity after 17 cycles of reuse at 37 °C. Under same storage conditions, the free enzyme lost about 71% of its initial activity over a period of 7 months, whereas the immobilized enzyme lost about only 47% of its initial activity over the same period. Operational stability of the immobilized enzyme was also studied and the operational half-life (t1/2 was determined as 6.72 h for p-nitrophenyl α-d-galactopyranoside (PNPG) as substrate. The kinetic parameters were determined by using PNPG as substrate. The Km and Vmax values were measured as 1.07 mM and 0.01 U/mg for free enzyme and 0.89 mM and 0.1 U/mg for immobilized enzyme, respectively. The synthesis of the galactose-containing polymeric beads and the enzyme immobilization procedure are very simple and also easy to carry out.  相似文献   

20.
To develop a robust whole-cell biocatalyst that works well at moderately high temperature (40–50 °C) with organic solvents, a thermostable lipase from Geobacillus thermocatenulatus (BTL2) was introduced into an Aspergillus oryzae whole-cell biocatalyst. The lipase-hydrolytic activity of the immobilized A. oryzae (r-BTL) was highest at 50 °C and was maintained even after an incubation of 24-h at 60 °C. In addition, r-BTL was highly tolerant to 30% (v/v) organic solvents (dimethyl carbonate, ethanol, methanol, 2-propanol or acetone). The attractive characteristics of r-BTL also worked efficiently on palm oil methanolysis, resulting in a nearly 100% conversion at elevated temperature from 40 to 50 °C. Moreover, r-BTL catalyzed methanolysis at a high methanol concentration without a significant loss of lipase activity. In particular, when 2 molar equivalents of methanol were added 2 times, a methyl ester content of more than 90% was achieved; the yield was higher than those of conventional whole-cell biocatalyst and commercial Candida antarctica lipase (Novozym 435). On the basis of the results regarding the excellent lipase characteristics and efficient biodiesel production, the developed whole-cell biocatalyst would be a promising biocatalyst in a broad range of applications including biodiesel production.  相似文献   

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