One-step purification of glucoamylase by affinity precipitation with alginate

Identification of the Major Effector StSROs in Potato: A Potential StWRKY-SRO6 Regulatory Pathway Enhances Plant Tolerance to Cadmium Stress

SIMILAR TO RCD-ONE (SRO) family members and transcription factors (TFs) often improve plant antioxidant capacity through interaction and co-regulation and participate in plant resistance to drought and high-salt stress. However, whether SROs are involved in the response to heavy metal stress, especially SRO genes with a specific response and tolerance characteristics to cadmium (Cd) stress, remains unclear. We first identified six SRO genes in the potato genome by PARP and RST domains. Special and conserved StSROs were found, and the spatio temporal tissue-specific expression patterns and co-expression network diagrams of StSROs under the stress of 5 heavy metals were constructed. Second, we identified StSRO6 as a major effector gene (StSRO6-MEG) and StSRO5 as a secondary effector gene (StSRO5-SEG) through a comprehensive analysis. Interestingly, they may hold true for various physiological or stress responses in plants. In addition, using systematic genomics and comparative omics techniques, the key gene StSRO6 that affects the difference in Cd accumulation was discovered, cloned in the low-Cd accumulation "Yunshu 505", and transformed into the yeast mutant ycf1 for overexpression. The results proved that StSRO6 could confer Cd tolerance. Finally, through transient expression and in vitro culture tests, we hypothesized that StSROs 5/6 are regulated by the transcription factor StWRKY6 and mediates the reactive oxygen species (ROS) system to confer Cd tolerance. These findings offer a new perspective for understanding the mechanisms underlying Cd tolerance in plants, and simultaneously provide clues for the development of biological agents for preventing and controlling Cd migration and transformation.

Purification of anti-bromelain antibodies by affinity precipitation using pNIPAm-linked bromelain

Affinity precipitation has emerged as a very useful technique for the purification of proteins. Here it has been employed for the purification of anti-bromelain antibodies from rabbit serum. A system has been developed for reversibly binding and thermoprecipitating antibodies. Anti-bromelain antibodies were raised in rabbit by immunizing it with bromelain. Poly-N-isopropylacrylamide (pNIPAm)-bromelain conjugate was prepared and incubated with rabbit serum. After that the temperature was raised for thermal precipitation of the polymer. Antibodies were then eluted from the complex by incubating it with a small volume of buffer, pH 3.0. This method is very effective in concentrating the antibodies. Purity and specificity of the antibodies were checked by gel electrophoresis and enzyme-linked immunosorbent assay (ELISA), respectively. The study of the effect of pH and temperature on the binding of the antibodies to the conjugate showed that the optimum binding occurred at pH 8.0 and 25°C.The polymer enzyme conjugate was further used for another cycle.

Simultaneous purification and refolding of proteins by affinity precipitation and macro (affinity ligand)-facilitated three phase partitioning (MLFTPP)

This chapter describes two simple interrelated non-chromatographic methods of protein purification. In the first method, called affinity precipitation, inherent affinity of reversibly soluble-insoluble polymers (also called stimuli-sensitive or smart polymers) is exploited to form an affinity complex in free solution with target protein. The affinity complex is precipitated by a suitable change in the medium. The desired protein is dissociated from the smart polymer. In the second method called macro (affinity ligand)-facilitated three phase partitioning (MLFTPP), the affinity complex is precipitated at an interface between upper t-butanol-rich phase and lower aqueous phase. These three phases are achieved by adding appropriate amounts of ammonium sulfate and t-butanol to the initial crude extract. In the first protocol, sequential MLFTPP is used with two different smart polymers to purify pectinase and cellulase from a single crude preparation. The second protocol illustrates the application of the affinity precipitation in simultaneous purification and refolding of a urea-denatured xylanase.

A highly efficient and thermostable α-amylase from soya bean seeds

The α-amylase from soya bean seeds was purified by affinity precipitation, resulting in approx. 20-fold purification with approx. 84% recovery. The purified α-amylase had an optimum pH of 5.5, optimum temperature of 75 °C, Arrhenius energy of activation of 6.03 kcal/mol (1 kcal≈4.184 kJ) and a Km of 2.427 mg/ml (starch substrate). The enzyme had maximum substrate specificity for starch. Among the various metal ions tested, Co2+ and Mn2+ were found to be strong activators. The effect of thiol group modifying agents showed that the thiols of soya bean α-amylase are not directly involved in catalysis. The thermostability of the enzyme makes it suitable for starch liquefaction and the detergent industry respectively.

Affinity covalent immobilization of glucoamylase onto ρ-benzoquinone activated alginate beads: I. Beads preparation and characterization

ρ-Benzoquinone-activated alginate beads were presented as a new carrier for affinity covalent immobilization of glucoamylase enzyme. Evidences of alginate modification were extracted from FT-IR and thermal gravimetric analysis and supported by morphological changes recognized through SEM examination. Factors affecting the modification process such as ρ-benzoquinone (PBQ) concentration, reaction time, reaction temperature, reaction pH and finally alginate concentration, have been studied. Its influence on the amount of coupled PBQ was consequently correlated to the changes of the catalytic activity and the retained activity of immobilized enzyme, the main parameters judging the success of the immobilization process. The immobilized glucoamylase was found kept almost 80% of its native activity giving proof of non-significant substrate, starch, diffusion limitation. The proposed affinity covalent immobilizing technique would rank among the potential strategies for efficient immobilization of glucoamylase enzyme.

Applications of Alginate in Bioseparation of Proteins

Alginate is a polysaccharide that is a block polymer consisting of block units of guluronic acid and mannuronic acid. It shows inherent biological affinity for a variety of enzymes such as pectinase, lipase, phospholipase D, a and ss amylases and glucoamylase. Taking advantage of its precipitation with Ca2+ and the above-mentioned property, alginate has been used for purification of these enzymes by affinity precipitation, aqueous two phase separation, macroaffinity ligand facilitated three phase partitioning, immobilized metal affinity chromatography and expanded bed affinity chromatography. Thus, this versatile marine resource has tremendous potential in bioseparation of proteins.

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.

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.

Protein purification by affinity precipitation

Developing the most efficient strategy for the purification of a (recombinant) protein especially at large scale remains a challenge. A typical problem of the downstream process of mammalian cell products is, for instance, the early capture of the highly diluted product from the complex process stream. Affinity precipitation has been suggested in this context. The technique is known for over 20 years, but has recently received more attention due to the development of new materials for its implementation, but also because it seems ideally suited to specific product capture at large scale. The present review gives a comprehensive overview over this technique. Besides an introduction to the basic principle and a brief summary of the historical development, the main focus is on the current state-of-art of the technique, the available materials, important recent applications, as well as process design strategies and operating procedures. Special consideration is given to affinity precipitation for product recovery at large scale.