Enzyme-ion exchanger interactions in serine alkaline protease separation: theory, equilibria and kinetics

Application of mixed modal resin for purification of a fibrinolytic enzyme

Recent advances in purification technologies for therapeutic molecules have stirred the research consortium. Mixed mode chromatography, having multiple interactions with the solute molecule, has drawn significant attention due to its overall advantage over traditional ion-exchange and reverse-phase chromatography. Capto adhere, a mixed mode chromatography resin with strong anion-exchange and reverse-phase interaction with solutes, was explored for purification of fibrinolytic enzyme from Bacillus sphaericus MTCC 3672. Static and dynamic resin binding study revealed that 30°C temperature, pH 8, and 0.5 mL/min flow rate were optimum for maximum binding of fibrinolytic enzyme. Maximum static dynamic binding and breakthrough capacities for Capto adhere were 249 and 196 U/mL of resin, respectively. Final purification with Sephadex G 100 gel chromatography resulted in 38-fold purity of fibrinolytic enzyme with 39% enzyme recovery. Purified enzyme was further characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis to homogeneity, and molecular mass was found to be around 55-70 kD. Like most of the serine alkaline proteases, purified fibrinolytic enzyme was stable in a temperature range of 25-40°C and pH range of 7-9. Offshoots of our research findings have revealed a broad application area of mixed mode chromatography.

Angiotensin I-converting enzyme inhibitory activity and bioconversion of isoflavones by probiotics in soymilk supplemented with prebiotics

Lactobacillus sp. FTDC 2113, L. acidophilus FTDC 8033, L. acidophilus ATCC 4356, L. casei ATCC 393, Bifidobacterium FTDC 8943 and B. longum FTDC 8643 were incorporated into soymilk supplemented with fructooligosaccharides (FOS), inulin, mannitol, maltodextrin and pectin. The objective of the present study was to evaluate the effects of prebiotics on the bioactivity of probiotic-fermented soymilk. Proteolytic activity was increased in the presence of FOS, while the supplementation of inulin and pectin increased the angiotensin I-converting enzyme inhibitory activity accompanied by lower IC(50) values. The beta-glucosidase activity was also enhanced in the presence of pectin. This led to higher bioconversion of glucosides to aglycones by probiotics, especially genistin and malonyl genistin to genistein. Results from this study indicated that the supplementation of prebiotics enhanced the in-vitro antihypertensive effect and production of bioactive aglycones in probiotic-fermented soymilk. Therefore, this soymilk could potentially be used as a dietary therapy to reduce the risks of hypertension and hormone-dependent diseases such as breast cancer, prostate cancer and osteoporosis.

Human growth hormone-specific aptamer identification using improved oligonucleotide ligand evolution method

LETEG is a method developed and used for the separation and purification of proteins employing a single-step ligand (aptamers) evolution in which aptamers are eluted with an increasing temperature gradient. Using recombinant human growth hormone (rhGH) as the test purification target, and after avoiding cross reactions of aptamers with Bacillus subtilis extracellular proteins by negative SELEX, the effects of time and pH on aptamer binding to rhGH were investigated. The highest binding efficiency of aptamers on rhGH-immobilized microparticles was obtained at pH 7.0. The aptamers that interacted with rhGH were eluted by a multi-stage step-up temperature gradient in DeltaT=10 degrees C increments within the range T=55-95 degrees C; and the strongest affinity binding was disrupted at T=85 degrees C where C(Apt)=0.16muM was eluted. The equilibrium binding data obtained was described by a Langmuir-type isotherm; where the affinity constant was K(D)=218nM rhGH. RhGH was separated from the fermentation broth with 99.8% purity, indicating that the method developed is properly applicable even for an anionic protein.