Purification and characterizations of a novel recombinant Bacillus velezensis endoglucanase by aqueous two-phase system

Enhancement of the catalytic activity of thermostable Endo-1,4-β-glucanase B (TnCelB) from Thermotoga neapolitana by error-prone PCR

Endo-1,4-β-glucanase plays a crucial role in converting cellulose from lignocellulosic biomass into fermentable sugars for biofuel production. However, its commercial utility is hindered by poor catalytic performance under extreme conditions. This study enhanced the catalytic activity of the endo-1,4-β-glucanase (TnCelB) from Thermotoga neapolitana through error-prone PCR directed evolution. After screening >4000 colonies, three mutants with enhanced activity were obtained. Mutants TnCelBY88F, TnCelBA233T, and TnCelBW219R displayed 52.14 U/mg, 44.90 U/mg, and 34.70 U/mg of specific activity on CMC, respectively, which is 1.9, 1.7, and 1.3 times higher than that of the wild-type (26.74 U/mg), correspondingly. Likewise, their enzyme activity on barley β-D-glucan increased by 3.5, 2.2, and 1.8 times, respectively. Notably, TnCelBY88F maintained over 90 % activity after 60 mins at high temperatures (80-100 °C), indicating an exceptional thermostability. Protein docking revealed that TnCelBY88F had higher binding affinity, aligned with kinetic studies. TnCelB was capble of released more non-oxidized sugars from the hydrolysis of regenerated amorphous cellulose (RAC) by synergy with auxiliary action family 10 (AA10), which is potential in development of efficient lignocellulosic saccharification. This study can provide useful insights for the future engineering of other endoglucanases in the glycoside hydrolases family 12.

Recombinant expression and characterization of the family 5 cellulase from Bacillus velezensis in Escherichia coli BL21-CodonPlus (DE3)-RIPL

B. velezensis RB. IBE29 is a chitinolytic bacterium originally isolated from agricultural soil of Vietnam. Previous studies demonstrated this bacterium was a promising chitinase producer, biocontrol agent, and biofertilizer for crop production. The complete genome sequence of the bacterium was reported and possesses the gene encoding family 5 cellulase; however, role of this enzyme has not been experimentally characterized. This work aimed to express and biologically characterize family 5 cellulase of strain RB. IBE29. The ORF (without signal peptide) of the celA of strain RB. IBE29 was expressed in E. coli BL21-CodonPlus (DE3)-RIPL using the vector pColdII, and the corresponding product (rBvCelA, 55.17 kDa) was successfully purified using the HisTrap FF column. The purified rBvCelA showed the highest cellulase activity against CMC, followed by sugarcane bagasse and rice straw, and had optimal temperature and pH at 60 °C and 6.0, respectively. Metal salts ZnCl2, FeCl2, MgCl2, CuSO4, and MnCl2 enhanced the cellulase activity by 103.85, 124.24, 109.38, 105.64, and 115.12 %, respectively. In addition, the supplementation of the purified rBvCelA in the feed enhanced the growth and improved the feed intake of broiler chickens by 5.88 and 5.19 %, respectively. These results indicated that family 5 cellulase of B. velezensis has a promising role in crop production and poultry breeding. As far as we know, this is the first report describing the contribution of family 5 cellulase from B. velezensis in broiler breeding.

A carboxymethyl cellulase from the yeast Cryptococcus gattii WM276: Expression, purification and characterisation

Cryptococcus gattii and its medical implications have been extensively studied. There is, however, a significant knowledge gap regarding cryptococcal survival in its environmental niche, namely woody material, which is glaring given that infection is linked to environmental populations. A gene from C. gattii (WM276), the predominant global molecular type (VGI), has been sequenced and annotated as a putative cellulase. It is therefore, of both medical and industrial intertest to delineate the structure and function of this enzyme. A homology model of the enzyme was constructed as a fusion protein to a maltose binding protein (MBP). The CGB_E4160W gene was overexpressed as an MBP fusion enzyme in Escherichia coli T7 cells and purified to homogeneity using amylose affinity chromatography. The structural and functional character of the enzyme was investigated using fluorescence spectroscopy and enzyme activity assays, respectively. The optimal enzyme pH and temperature were found to be 6.0 and 50 °C, respectively, with an optimal salt concentration of 500 mM. Secondary structure analysis using Far-UV CD reveals that the MBP fusion protein is primarily α-helical with some β-sheets. Intrinsic tryptophan fluorescence illustrates that the MBP-cellulase undergoes a conformational change in the presence of its substrate, CMC-Na+. The thermotolerant and halotolerant nature of this particular cellulase, makes it useful for industrial applications, and adds to our understanding of the pathogen's environmental physiology.

Overexpression and characterization of TnCel12B, a hyperthermophilic GH12 endo-1,4-β-glucanase cloned from Thermotoga naphthophila RKU-10T

A putative cellulolytic gene (825 bp) from Thermotoga naphthophila RKU-10^T was overexpressed as an active soluble endo-1,4-β-glucanase (TnCel12B), belongs to glycoside hydrolase family 12 (GH12), in a mesophilic expression host. Heterologous expression and engineered bacterial cell mass was improved through specific strategies (induction and cultivation). Hence, intracellular activity of TnCel12B was enhanced in ZYBM9 modified medium (pH 7.0) by 8.38 and 6.25 fold with lactose (200 mM) and IPTG (0.5 mM) induction, respectively; and 6.95 fold was increased in ZYP-5052 auto-inducing medium after 8 h incubation at 26 °C (200 rev min^-1). Purified TnCel12B with a molecular weight of ~32 kDa, was optimally active at 90 °C and pH 6.0; and exhibited prodigious stability over a wide range of temperature (50-85 °C) and pH (5.0-9.0) for 8 h TnCel12B displayed great resistance towards different chemical modulators, though activity was improved by Mg²⁺, Zn²⁺, Pb²⁺ and Ca²⁺. Purified TnCel12B had affinity with various substrates but peak activity was observed toward barley β-glucan (1664 U mg^-1) and carboxymethyl cellulose (736 U mg^-1). The values of K_m, V_max, k_cat, and k_catK_m^-1 were found to be 4.63 mg mL^-1, 916 μmol mg^-1min^-1, 1326.7 s^-1 and 286.54 mL mg^-1 s^-1, respectively using CMC substrate. All noteworthy features of TnCel12B make it an appropriate industrial candidate for bioethanol production and various other potential applications.