Cationic reverse micellar based purification of recombinant glutaminase free L-asparaginase II of Bacillus subtilis WB800N from fermentation media

Optimizing proinsulin production in E. coli BL21 (DE3) using taguchi method and efficient one-step insulin purification by on-column enzymatic cleavage

Diabetes is a critical worldwide health problem. Numerous studies have focused on producing recombinant human insulin to address this issue. In this research, the process factors of production of recombinant His-tagged proinsulin in E. coli BL21 (DE3) strain were studied. Bacterial culture factors with significant effects on the amount of produced recombinant proinsulin were screened using a Taguchi L8 orthogonal array. Proinsulin expression was conducted under predicted optimal conditions. The folded impure His-tagged proinsulin was purified using immobilized metal ion affinity chromatography (IMAC). A novel IMAC sequence order combined with the use of non-His-tagged C-peptide cleavage enzymes followed by His- tagged enterokinase enzyme enabled simultaneous protein purification and elimination of C-peptide and His-tag in just one step. Statistical analysis revealed that the amount of produced proinsulin was significantly affected by several factors including the post-induction incubation temperature, Isopropyl ß-D-1-thiogalactopyranoside (IPTG) concentration, pre-induction incubation temperature, the glucose concentration, bacterial cell population at induction step, and the time of harvesting. The optimized model resulted in an empirical maximum proinsulin concentration of 254.5 ± 11.7 µg/ml. The high purity of the purified insulin (> 96% by SDS-PAGE) indicated that applied IMAC sequence order could be considered an efficient technique for on-column cleavage and insulin purification.

Heterologous expression and molecular modelling of L-asparaginase from Bacillus subtilis ETMC-2

Bacterial L-asparaginase is the key therapeutic enzyme in cancer therapy and is also witnessing demand as a food processing aid. In this study, L-asparaginase of newly isolated Bacillus subtilis ETMC-2 was cloned and over-expressed in Escherichia coli as an active soluble protein using ligation independent cloning strategy. The molecular mass was estimated to be 40 kDa and was optimally active at 50 °C. Zymography revealed that the enzyme was active in homo-tetramer state (~160 KDa). The encoded protein after BLASTp analysis on NCBI showed 99.73% similarity with L-ASNase that of Bacillus sp. Physico-chemical properties were predicted using Protparam leading to categorization of the enzyme as a stable protein with an instability index (II) of 19.02. The calculated aliphatic index (85.44) indicated the high thermal stability of the protein with GRAVY value of -0.317. Protein-Ligand docking revealed that the residues Thr₈₉, Thr₁₂₁, and Asp₁₂₂ were fundamental in protein-ligand complexation. After homology modelling, model validation was performed using Ramachandran plot, VERIFY3D, and RMSD. The paper describes cloning, heterologous expression, catalytic characteristics and physico-chemical properties of the type II B. subtilis L-ASNase.

Application of experimental designs and response surface methods in screening and optimization of reverse micellar extraction

Reverse micellar extraction (RME) has emerged as a versatile and efficient tool for downstream processing (DSP) of various biomolecules, including structural proteins and enzymes, due to the substantial advantages over conventional DSP methods. However, the RME system is a complex dependency of several parameters that influences the overall selectivity and performance of the RME system, hence this justifies the need for optimization to obtain higher possible extraction results. For the last two decades, many experimental design strategies for screening and optimization of RME have been described in literature. The objective of this article is to review the use of different experimental designs and response surface methodologies that are currently used to screen and optimize the RME system for various types of biomolecules. Overall, this review provides the rationale for the selection of appropriate screening or optimization techniques for the parameters associated with both forward and backward extraction during the RME of biomolecules.

Spirulina maxima L-asparaginase: Immobilization, Antiviral and Antiproliferation Activities

BACKGROUND

L-asparaginase (L-AsnA) enzyme has gained significant attention in the food, biocatalysts and pharmaceutics industry. It (L-AsnA) has been widely used in food processing industries as a promising acrylamide mitigating agent and as a therapeutic agent in the treatment of certain human cancers.

OBJECTIVE

Based on US Patent (4,433,054; 1984), L-asparaginase (L-AsnA) enzyme is immobilized by admixing the active enzyme on the polysaccharide to be in a gel form. The storage stability of immobilized L-AsnA enzyme and its anti-proliferation and antiviral activity were determined.

METHODS

In the present study, S. maxima was cultured at large scales (300 liter) for the production of enough extracellular L-asparaginase (L-AsnA) using modified (high N concentration) Zarrouk medium as we reported in a previous study. L-AsnA was immobilized on natural polymers, as agar cake beads, agarose pieces and gelatin blocks, in order to evaluate the efficiency of physical entrapment techniques. Anti-proliferation properties of L-AsnA against lung carcinoma A549, hepatocellular carcinoma Hep-G2 and prostate carcinoma PC3 human cancer cell lines were assessed by the MTT cell viability method. In addition, the antiviral activity against Coxsackie B3 (CSB3) Virus was assessed.

RESULTS

The highest L-AsnA immobilized activity and immobilization yield were achieved with agar cakes bead. The purified S. maxima L-AsnA showed good antiviral activity against Coxsackie B3 (CSB3) Virus in a dose-dependent manner with an IC50 value 17.03 μg/ml. The antiviral mode of action is presumably due to their capability of inhibiting attachment, blocking the adsorption and penetration event of the viral replication cycle with 89.24%, 72.78% and 72.78%, respectively. Also, S. maxima L-AsnA showed anti-proliferation effect against lung carcinoma A549, hepatocellular carcinoma Hep-G2 and prostate carcinoma PC3 human cancer cell lines, with an IC50 of 22.54, 24.65 and 56.61 μg/ml, respectively.

CONCLUSION

It is interesting to favor L-asparaginase of S. maxima which showed antiviral activity and anti-proliferation effect against different types of human cell lines. Thus, S. maxima microalgae might be a good source for L-AsnA enzymes and can be immobilized on natural polymers.