A novel GH3-β-glucosidase from soda lake metagenomic libraries with desirable properties for biomass degradation

Beta-glucosidases catalyze the hydrolysis of the glycosidic bonds of cellobiose, producing glucose, which is a rate-limiting step in cellulose biomass degradation. In industrial processes, β-glucosidases that are tolerant to glucose and stable under harsh industrial reaction conditions are required for efficient cellulose hydrolysis. In this study, we report the molecular cloning, Escherichia coli expression, and functional characterization of a β-glucosidase from the gene, CelGH3_f17, identified from metagenomics libraries of an Ethiopian soda lake. The CelGH3_f17 gene sequence contains a glycoside hydrolase family 3 catalytic domain (GH3). The heterologous expressed and purified enzyme exhibited optimal activity at 50 °C and pH 8.5. In addition, supplementation of 1 M salt and 300 mM glucose enhanced the β-glucosidase activity. Most of the metal ions and organic solvents tested did not affect the β-glucosidase activity. However, Cu2+ and Mn2+ ions, Mercaptoethanol and Triton X-100 reduce the activity of the enzyme. The studied β-glucosidase enzyme has multiple industrially desirable properties including thermostability, and alkaline, salt, and glucose tolerance.

New alkali tolerant β-galactosidase from Paracoccus marcusii KGP - A promising biocatalyst for the synthesis of oligosaccharides derived from lactulose (OsLu), the new generation prebiotics

The enzyme β-galactosidase can synthesise novel prebiotics such as oligosaccharides derived from lactulose (OsLu) which can be added as a supplement in infant food formula. In this study, the intracellular β-galactosidase produced by the alkaliphilic bacterium Paracoccus marcusii was extracted and purified to homogeneity using hydrophobic and metal affinity chromatography. The purification resulted in 18 U/mg specific activity, with a yield of 8.86% and an 18-fold increase in purity. The purified enzyme was a monomer with an 86 kDa molecular weight as determined by SDS PAGE and Q-TOF-LC/MS. β-Galactosidase was highly active at 50 °C and pH 6-8. The enzyme displayed an alkali tolerant nature by maintaining more than 90% of its initial activity over a pH range of 5-9 after 3 h of incubation. Furthermore, the enzyme activity was enhanced by 37% in the presence of 5 M NaCl and 3 M KCl, indicating its halophilic nature. The effects of metal ions, solvents, and other chemicals on enzyme activity were also studied. The kinetic parameters K_M and V_max of β-galactosidase were 1 mM and 8.56 μmoles/ml/min and 72.72 mM and 11.81 μmoles/ml/min on using oNPG and lactose as substrates. P. marcusii β-galactosidase efficiently catalysed the transgalactosylation reaction and synthesised 57 g/L OsLu from 300 g/L lactulose at 40 °C. Thus, in this study we identified a new β-galactosidase from P. marcusii that can be used for the industrial production of prebiotic oligosaccharides.

Quality Control and Downstream Processing of Therapeutic Enzymes

Therapeutic enzymes are a commercially minor but clinically important area of biopharmaceuticals. An array of therapeutic enzymes has been developed for a variety of human diseases, including leukaemia and enzyme-deficiency diseases such as Gaucher's disease. Production and testing of therapeutic enzymes is strictly governed by regulatory bodies in each country around the world, and batch-to-batch consistency is crucially important. Manufacture of a batch starts with the fermentation or cell culture stage. After expression of the therapeutic enzyme in a cell culture bioreactor, robust and reproducible protein purification, or downstream processing (DSP) of the target product, is critical to ensuring safe delivery of these medicines. Modern processing technology, including the use of disposable processing equipment, has greatly improved the DSP development pathway in terms of robustness and speed to clinic. Once purified, the drug substance undergoes rigorous quality control (QC) testing according to current regulatory guidance, to enable release to the clinic and patient. QC testing is conducted to ensure the safety, purity, identity, potency and strength of the medicinal product, requiring multiple analytical methods that are rigorously validated and monitored for robust performance. Several case studies, including L-asparaginase and asfotase alfa, are discussed to illustrate the methods described herein.

The carbonic anhydrase of Clostridium autoethanogenum represents a new subclass of β-carbonic anhydrases

Carbonic anhydrase catalyses the interconversion of carbon dioxide and water to bicarbonate and protons. It was unknown if the industrial-relevant acetogen Clostridium autoethanogenum possesses these enzymes. We identified two putative carbonic anhydrase genes in its genome, one of the β class and one of the γ class. Carbonic anhydrase activity was found for the purified β class enzyme, but not the γ class candidate. Functional complementation of an Escherichia coli carbonic anhydrase knock-out mutant showed that the β class carbonic anhydrase could complement this activity, but not the γ class candidate gene. Phylogenetic analysis showed that the β class carbonic anhydrase of Clostridium autoethanogenum represents a novel sub-class of β class carbonic anhydrases that form the F-clade. The members of this clade have the shortest primary structure of any known carbonic anhydrase.

The hemicellulose-degrading enzyme system of the thermophilic bacterium Clostridium stercorarium: comparative characterisation and addition of new hemicellulolytic glycoside hydrolases

BACKGROUND

The bioconversion of lignocellulosic biomass in various industrial processes, such as the production of biofuels, requires the degradation of hemicellulose. Clostridium stercorarium is a thermophilic bacterium, well known for its outstanding hemicellulose-degrading capability. Its genome comprises about 50 genes for partially still uncharacterised thermostable hemicellulolytic enzymes. These are promising candidates for industrial applications.

RESULTS

To reveal the hemicellulose-degrading potential of 50 glycoside hydrolases, they were recombinantly produced and characterised. 46 of them were identified in the secretome of C. stercorarium cultivated on cellobiose. Xylanases Xyn11A, Xyn10B, Xyn10C, and cellulase Cel9Z were among the most abundant proteins. The secretome of C. stercorarium was active on xylan, β-glucan, xyloglucan, galactan, and glucomannan. In addition, the recombinant enzymes hydrolysed arabinan, mannan, and galactomannan. 20 enzymes are newly described, degrading xylan, galactan, arabinan, mannan, and aryl-glycosides of β-d-xylose, β-d-glucose, β-d-galactose, α-l-arabinofuranose, α-l-rhamnose, β-d-glucuronic acid, and N-acetyl-β-d-glucosamine. The activities of three enzymes with non-classified glycoside hydrolase (GH) family modules were determined. Xylanase Xyn105F and β-d-xylosidase Bxl31D showed activities not described so far for their GH families. 11 of the 13 polysaccharide-degrading enzymes were most active at pH 5.0 to pH 6.5 and at temperatures of 57-76 °C. Investigation of the substrate and product specificity of arabinoxylan-degrading enzymes revealed that only the GH10 xylanases were able to degrade arabinoxylooligosaccharides. While Xyn10C was inhibited by α-(1,2)-arabinosylations, Xyn10D showed a degradation pattern different to Xyn10B and Xyn10C. Xyn11A released longer degradation products than Xyn10B. Both tested arabinose-releasing enzymes, Arf51B and Axh43A, were able to hydrolyse single- as well as double-arabinosylated xylooligosaccharides.

CONCLUSIONS

The obtained results lead to a better understanding of the hemicellulose-degrading capacity of C. stercorarium and its involved enzyme systems. Despite similar average activities measured by depolymerisation tests, a closer look revealed distinctive differences in the activities and specificities within an enzyme class. This may lead to synergistic effects and influence the enzyme choice for biotechnological applications. The newly characterised glycoside hydrolases can now serve as components of an enzyme platform for industrial applications in order to reconstitute synthetic enzyme systems for complete and optimised degradation of defined polysaccharides and hemicellulose.