A solvent tolerant isolate of Enterobacter aerogenes

A solvent tolerant strain of Enterobacter aerogenes was isolated from soil by cyclohexane enrichment. Presence of cyclohexane (20%) in culture media prolonged the lag phase and caused reduction in biomass. Transmission electron micrographs showed convoluted cell membrane and accumulation of solvent in case of the cells grown in cyclohexane. The Enterobacter isolate was able to grow in the range of organic solvents having log P above 3.2 and also in presence of mercury, thus showing potential for treatment of solvent rich wastes.

Purification and characterization of a solvent stable protease from Pseudomonas aeruginosa PseA

A solvent tolerant Pseudomonas aeruginosa PseA strain was isolated from soil. It secreted a novel alkaline protease, which was stable and active in the presence of range of organic solvents, thus potentially useful for catalysis in non-aqueous media. The protease was purified 11.6-fold with 60% recovery by combination of ion exchange and hydrophobic interaction chromatography using Q-Sepharose and Phenyl Sepharose 6 Fast Flow matrix, respectively. The apparent molecular mass based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was estimated to be 35,000 Da. The enzyme was stable in the pH range of 6.0-9.0, the optimum being 8.0. The Km and Vmax towards caseinolytic activity were found to be 2.7 mg/ml and 3 micromol/min, respectively. The protease was most active at 60 degrees C and characterized as a metalloprotease because of its sensitivity to EDTA and 1,10-phenanthroline. It was tested positive for elastase activity towards elastin-orcein, thus appears to be an elastase, which is known as pseudolysin in other strains of P. aeruginosa. The protease withstands range of detergents, surfactants and solvents. It is stable and active in all the solvents having log P above 3.2, at least up to 72 h. These two properties make it an ideal choice for applications in detergent formulations and enzymatic peptide synthesis.

One-step purification and characterization of an alkaline protease from haloalkaliphilic Bacillus sp

An alkaline protease producer haloalkaliphilic bacteria (isolate Vel) was isolated from west coast of India. It was related to Bacillus pseudofirmus on the basis of 16S r RNA gene sequencing, lipid profile and other biochemical properties. The protease secreted by this bacteria was purified 10-fold with 82% yield by a single step method on Phenyl Sepharose 6 Fast Flow column. The apparent molecular mass based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was estimated to be 29 000 Da. The Km and Vmax towards caseinolytic activity were found to be 2 mg ml(-1) and 289.8 microg min(-1), respectively. The enzyme was active over the pH range of 8.5-12.0, the optimum being 10-11.0. The purified enzyme when kept at 45 degrees C and 50 degrees C for 40 min retained 92% and 85% protease activity, respectively. Effect of NaCl concentration on protease activity showed that the enzyme was slightly inhibited with high concentration of salt. The proteolytic activity was inhibited by PMSF, suggesting that the enzyme may belong to serine type protease. Interestingly, the activity was slightly enhanced with SDS (0.1%) and Triton X-100 (0.1%) but remained unaffected by Tween 80 (0.1%). The activity was affected by metal ions to varying extent. While Mn2+, Zn2+ and Mg2+ had no significant effect on protease activity, the enzyme was activated with Ca2+ (1 mM) and Cu2+ (5 mM). The stability of the enzyme in the presence of detergent components and surfactants is particularly attractive for its application in detergent industries.

A microwave-assisted microassay for lipases

A quick and efficient two-step assay for monitoring and screening lipase activity that uses a microtitre plate is described.

Simultaneous refolding/purification of xylanase with a microwave treated smart polymer

Affinity precipitation with a smart polymer, Eudragit S-100 (a methyl methacrylate polymer), was exploited for simultaneous refolding and purification of xylanase. Affinity precipitation consisted of this reversibly soluble-insoluble polymer-binding xylanase selectively. The complex was precipitated by lowering the pH and xylanase was eluted off the polymer using 1 M NaCl. For refolding experiments, the commercial preparation of Aspergillus niger xylanase was denatured with 8 M urea. Addition of microwave irradiated Eudragit S-100 and affinity precipitation led to recovery of 96% enzyme activity by refolding. Simultaneously, the enzyme was purified 45 times. Thermally inactivated preparation, when subjected to similar steps, led to 95% recovery of enzyme activity with 42-fold purification. The strategy has the potential for recovering pure proteins in active forms from overexpressed proteins, which generally form inclusion bodies in E. coli.

An Integrated Process for Separation of Major and Minor Proteins From Goat Serum

Analysis of minor proteins in animal sera is of considerable clinical significance. To be able to detect these proteins, depletion of major proteins (albumin and immunoglobulin G [IgG]) is necessary. Many of these proteins are also required in pure form for a variety of biochemical applications. The present work uses goat serum as the system and describes the separation and purification of both major and several minor proteins. This was carried out by judicious adaptation and combination of separation technologies such as immobilized metal ion affinity chromatography (on a somewhat novel matrix), dye affinity chromatography, and lectin affinity chromatography. Albumin, IgG, alpha2-macroglobulin, alpha1-proteinase inhibitor, and transferrin were obtained from the serum. The purified preparations were found to be homogeneous on sodium dodecyl sulfate polyacrylamide gel electrophoresis.

Extraction of oil from Jatropha curcas L. seed kernels by combination of ultrasonication and aqueous enzymatic oil extraction

Use of ultrasonication as a pretreatment before aqueous oil extraction and aqueous enzymatic oil extraction was found to be useful in the case of extraction of oil from the seeds of Jatropha curcas L. The use of ultrasonication for 10 min at pH 9.0 followed by aqueous oil extraction gave a yield of 67%. However, the maximum yield of 74% was obtained by ultrasonication for 5 min followed by aqueous enzymatic oil extraction using an alkaline protease at pH 9.0. Use of ultrasonication also resulted in reducing the process time from 18 to 6 h.

Preparation of highly active alpha-chymotrypsin for catalysis in organic media

A simple one step process for the preparation of free alpha-chymotrypsin, using an organic solvent to precipitate the enzyme from a buffered solution, followed by washing with organic solvents, is described. This preparation gave 132 times greater esterification activity than lyophilized powder.

Detection of native peptides as potent inhibitors of enzymes

Chymotrypsin is a prominent member of the family of serine proteases. The present studies demonstrate the presence of a native fragment containing 14 residues from Ile16 to Trp29 in alpha-chymotrypsin that binds to chymotrypsin at the active site with an exceptionally high affinity of 2.7 +/- 0.3 x 10(-11) M and thus works as a highly potent competitive inhibitor. The commercially available alpha-chymotrypsin was processed through a three phase partitioning system (TPP). The treated enzyme showed considerably enhanced activity. The 14 residue fragment was produced by autodigestion of a TPP-treated alpha-chymotrypsin during a long crystallization process that lasted more than four months. The treated enzyme was purified and kept for crystallization using vapour the diffusion method at 295 K. Twenty milligrams of lyophilized protein were dissolved in 1 mL of 25 mM sodium acetate buffer, pH 4.8. It was equilibrated against the same buffer containing 1.2 M ammonium sulfate. The rectangular crystals of small dimensions of 0.24 x 0.15 x 0.10 mm(3) were obtained. The X-ray intensity data were collected at 2.2 angstroms resolution and the structure was refined to an R-factor of 0.192. An extra electron density was observed at the binding site of alpha-chymotrypsin, which was readily interpreted as a 14 residue fragment of alpha-chymotrypsin corresponding to Ile-Val-Asn-Gly-Glu-Glu-Ala-Val-Pro-Gly-Ser-Trp-Pro-Trp(16-29). The electron density for the eight residues of the C-terminus, i.e. Ala22-Trp29, which were completely buried in the binding cleft of the enzyme, was of excellent quality and all the side chains of these eight residues were clearly modeled into it. However, the remaining six residues from the N-terminus, Ile16-Glu21 were poorly defined although the backbone density was good. There was a continuous electron density at 3.0 sigma between the active site Ser195 Ogamma and the carbonyl carbon atom of Trp29 of the fragment. The final refined coordinates showed a distance of 1.35 angstroms between Ser195 Ogamma and Trp29 C indicating the presence of a covalent linkage between the enzyme and the native fragment. This meant that the enzyme formed an acyl intermediate with the autodigested fragment Ile16-Trp29. In addition to the O-C covalent bond, there were several hydrogen bonds and hydrophobic interactions between the enzyme and the native fragment. The fragment showed a high complementarity with the binding site of alpha-chymotrypsin and the buried part of the fragment matched excellently with the corresponding buried part of Turkey ovomucoid inhibitor of alpha-chymotrypsin.

Chitosan as a macroaffinity ligand

(1) Chitosan was found to be a suitable macroaffinity ligand for affinity precipitation of chitinase from Neurospora crassa, cabbage and puffballs. (2) The activity recoveries of 85, 82 and 90% with concomitant fold purifications in terms of specific activities were 27, 15 and 30 with N. crassa, cabbage and puffballs and were obtained with affinity precipitation. These results were obtained with clarified extracts/homogenates as the starting materials. (3) The incorporation of chitosan in poly(ethylene glycol) (PEG)-salt aqueous two-phase system allowed purification of chitinases from these sources directly from unclarified extracts/homogenates. (4) The 96% (w/v) chitosan (of initially introduced into the aqueous two-phase system) partitioned into PEG-phase and this enhanced the partitioning of chitinases into PEG-phase. The chitosan, free as well as bound to chitinases, could be separated from PEG-phase by increasing the pH to 7. (5) By the process of desorption with 2.0 M MgCl2, 86, 80 and 88% activity recoveries (% expressed in terms of total units of enzyme activities in the crude extract) were obtained in the case of N. crassa, cabbage and puffballs, respectively. The corresponding fold purifications in terms of specific activities were 34, 20 and 38. (6) The purified preparations gave single bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the estimated molecular masses agreed with the reported values in the literature.

Obtaining higher transesterification rates with subtilisin Carlsberg in nonaqueous media

Three phase partitioning (protein precipitate obtained as an interfacial layer between lower aqueous and upper t-butanol phases, formed by the addition of ammonium sulphate and t-butanol to the aqueous solution of protein) followed by lyophilization in the presence of two-component excipient resulted in 400-480x increases in transesterification activity of lyophilized powders of subtilisin Carlsberg, depending on the solvent. The three phase partitioned enzyme, 'dried' by washing with butanol, gave 3-4x higher rates (depending on the solvent used) than the enzyme preparation dried by lyophilization in the presence of two-component excipient system.

Accelerating enzymatic hydrolysis of chitin by microwave pretreatment

Response surface analysis was used to determine optimum conditions [2% (w/v) chitin, 57.5 degrees C, 38 min] for microwave irradiation of chitin to improve its enzymatic hydrolysis. V(max)/K(m) of cabbage chitinase toward untreated and microwave-irradiated chitin was found to be 21.1 and 31.7 nmol h(-1) mg(-2) mL, respectively. Similar improvement was observed in the case of pectinase in its unusual catalytic activity of chitin degradation. It was found that a greater extent of chitin hydrolysis by chitinase was possible after the substrate chitin was irradiated with microwaves.

Purification of green fluorescent protein overexpressed by a mutant recombinant Escherichia coli

Green fluorescent protein was purified from sonicated recombinant Escherichia coli and its mutant obtained after exposure to UV light. The latter overexpresses green fluorescent protein. The two-step procedure consisted of a two-phase aqueous extraction with PEG/salt and precipitation of the proteins from PEG phase by free Zn2+. The recoveries of green fluorescent protein were 73 and 83% in the cases of recombinant E. coli and its mutant, respectively. The corresponding fold purifications were 24 and 9, respectively. In both cases, the purified protein showed a single band on SDS-PAGE corresponding to 28 kDa.

Enzymes in organic media

Enzyme catalysis in low water containing organic solvents is finding an increasing number of applications in diverse areas. This review focuses on some aspects which have not been reviewed elsewhere. Different strategies for obtaining higher activity and stability in such media are described. In this context, the damaging role of lyophilization and the means of overcoming such effects are discussed. Ultrasonication and microwave assistance are two emerging approaches for enhancing reaction rates in low water media. Control of water activity and medium engineering are two crucial approaches in optimization of catalytic behaviour in nonaqueous enzymology. Organometallics and synthesis/modification of polymers are two areas where nonaqueous enzymology can play a greater role in the coming years. The greater understanding of enzyme behaviour in nonaqueous media is expected to lead to larger and even more diverse kinds of applications.

Purification of goat immunoglobulin G by immobilized metal-ion affinity using cross-linked alginate beads

The alginate beads obtained by cross-linking of the polymer by epichlorohydrin were charged with Cu(II). The copper-charged beads could be directly used as a immobilized-metal-affinity-chromatographic medium for purification of goat IgG. The best results in the packed-bed mode were obtained by using beads charged with 95.4 micromol/ml Cu(II). We found that we could recover 97.4% IgG with an 8-fold purification.

Microwave-assisted method for microassay of proteins using bicinchoninic acid

A microwave-assisted microassay has been developed for estimation of proteins, using bicinchoninic acid (BCA). The protocol described here is rapid with a reaction time of merely 95 sec, requires lesser amounts of BCA and other reagents, and tolerates larger or comparable concentration of various interfering substances.

Purification of recombinant green fluorescent protein by three-phase partitioning

The technique of three-phase partitioning (TPP) was used to purify the green fluorescent protein (GFP) in a single step. TPP uses a combination of ammonium sulphate and tert-butanol to precipitate proteins from their crude extracts. In the first round of TPP with 20% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:1 (v/v), most of the GFP remains in the lower aqueous phase. When subjected to a second round of TPP with 60% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:2 (v/v) gives 78% recovery of GFP with a 20-fold purification. The sodium dodecyl sulphate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis of purified preparation shows single band. The fluorescence excitation and emission spectra agreed with values reported in literature.

Purification of phospholipase D by two-phase affinity extraction

An aqueous two-phase system of polyethylene glycol (PEG)-salt was used for purification of phospholipase D (PLD) from peanuts and carrots. Alginate, a known macroaffinity ligand for PLD, was incorporated in the PEG phase and resulted in 91 and 93% of the enzyme activity (from peanuts and carrots, respectively) getting partitioned in the PEG phase. The elution of the enzyme from alginate was facilitated by exploiting the fact that the latter can be reversibly precipitated in the presence of Ca2+. The enzyme was eluted from the polymer by using 0.5 M NaCl. Peanuts and carrots PLD could be purified 78- and 17-fold with 82 and 85% activity recovery, respectively. The purified enzyme from both sources gave a single band on sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) electrophoresis.

Affinity precipitation of Aspergillus niger pectinase by microwave-treated alginate

Affinity precipitation is a simple, single plate separation process in which the complex of a smart macroaffinity ligand with the target protein (from a crude broth) can be selectively precipitated by application of a suitable stimulus. Alginate is a copolymer of guluronic acid and mannuronic acid residues and precipitates with Ca(2+) ions. It was found to bind to pectinase present in a commercial preparation of Aspergillus niger, Pectinex Ultra-SPL. Microwave pretreatment of alginate at 75 degrees C was found to enhance the selectivity of the affinity precipitation. Using microwave-treated alginate, 83% of the enzyme activity with 20-fold purification could be recovered. SDS-PAGE upon silver staining confirmed the enhanced selectivity of affinity precipitation when microwave-treated alginate was used.

Smart Biocatalysts: Design and Applications

Smart materials respond to chemical or physical changes in their environment in a predictable fashion. One class of such materials are smart polymers which can be used to design reversibly soluble-insoluble biocatalysts. One important advantage of such soluble polymer enzyme conjugates is in bioconversion of macromolecular or insoluble substrates. In addition, they share the advantage of reusability with conventional immobilized enzymes. Stimuli that are used to "recover" smart polymer - enzyme conjugates for reuse include changes in pH, temperature, ionic strength and addition of chemical species like calcium. In addition to these, enzymes linked to photoresponsive polymers have also been described in the literature. Both adsorption and covalent coupling have been used to create such polymer conjugates. End-group conjugation and site-specific conjugation are recently described strategies to obtain biocatalysts with better designs for solving mass transfer constraints. Some important applications of such smart biocatalysts are hydrolysis of starch, cellulose and proteins. Work has also been carried out on hydrolysis of pectins and xylans. All the above applications involve hydrolysis and are hence carried out in aqueous media. For synthetic applications such as synthesis of peptides, some photoresponsive polymers linked to proteases have recently been described.

A Smart Bioconjugate of Alginate and Pectinase with Unusual Biological Activity toward Chitosan

The commercial preparation of pectinase (Pectinex Ultra SP-L) was conjugated to alginate by noncovalent interactions by employing 1% alginate during the conjugation protocol. The optimum "immobilization efficiency" was 0.76. The pH optimum and the thermal stability of the enzyme remained unchanged upon conjugation with alginate. The soluble bioconjugate showed a 3-fold increase in V(max)/K(m) as compared to the free enzyme when the smart biocatalyst was used for chitosan hydrolysis. Time course hydrolysis of chitosan thus showed higher conversion of chitosan into reducing oligosaccharides/sugars. The smart bioconjugate could be reused five times without any detectable loss of chitosanase activity.

pH-responsive polymer-assisted refolding of urea- and organic solvent-denatured -chymotrypsin

A pH-responsive polymer Eudragit S-100 has been found to assist in correct folding of alpha-chymotrypsin denatured with 8 M urea and 100 mM dithiothreitol at pH 8.2. The complete activity could be regained within 10 min during refolding. Both native and refolded enzymes showed emission of intrinsic fluorescence with lambda(max) of 342 nm. Gel electrophoresis showed that the presence of Eudragit S-100 led to dissociation of multimers followed by the appearance of a band at the monomer position. The unfolding (by 8 M urea) and folding (assisted by the polymer) also led to complete renaturation of alpha-chymotrypsin initially denatured by 90% dioxane. The implications of the data in recovery of enzyme activity from inclusion bodies and the interesting possibility in the in vivo context of reversing protein aggregation in amyloid-based diseases have been discussed.

Enzymatic transesterification for biodiesel production

Biodiesel consists monoalkyl esters of long chain fatty acids. It is produced from vegetable oils or fats either by chemical transesterification or by lipase-catalyzed transesterification with methanol or ethanol. Biodiesel is a green fuel and can be used as a blend with diesel or alone. Either way, it does not require any modification in engine design or storage facilities. The enzymatic process offers several advantages over the chemical routes. The handicap of increase in process cost because of the cost of the enzyme can be overcome by using efficient production process for enzyme and using reusable derivatives of enzymes, such as immobilized enzyme. Numerous strategies available in the area of non-aqueous enzymology can be exploited during the enzymatic alcoholysis for biodiesel production. Some of the technical challenges and their possible solutions are also discussed.