A monovalent anion affected multi-functional cellulase EGX from the mollusca, Ampullaria crossean

Current perspective on production and applications of microbial cellulases: a review

The potential of cellulolytic enzymes has been widely studied and explored for bioconversion processes and plays a key role in various industrial applications. Cellulase, a key enzyme for cellulose-rich waste feedstock-based biorefinery, has increasing demand in various industries, e.g., paper and pulp, juice clarification, etc. Also, there has been constant progress in developing new strategies to enhance its production, such as the application of waste feedstock as the substrate for the production of individual or enzyme cocktails, process parameters control, and genetic manipulations for enzyme production with enhanced yield, efficiency, and specificity. Further, an insight into immobilization techniques has also been presented for improved reusability of cellulase, a critical factor that controls the cost of the enzyme at an industrial scale. In addition, the review also gives an insight into the status of the significant application of cellulase in the industrial sector, with its techno-economic analysis for future applications. The present review gives a complete overview of current perspectives on the production of microbial cellulases as a promising tool to develop a sustainable and greener concept for industrial applications.

Signatures of Divergence, Invasiveness, and Terrestrialization Revealed by Four Apple Snail Genomes

The family Ampullariidae includes both aquatic and amphibious apple snails. They are an emerging model for evolutionary studies due to the high diversity, ancient history, and wide geographical distribution. Insight into drivers of ampullariid evolution is hampered, however, by the lack of genomic resources. Here, we report the genomes of four ampullariids spanning the Old World (Lanistes nyassanus) and New World (Pomacea canaliculata, P. maculata, and Marisa cornuarietis) clades. The ampullariid genomes have conserved ancient bilaterial karyotype features and a novel Hox gene cluster rearrangement, making them valuable in comparative genomic studies. They have expanded gene families related to environmental sensing and cellulose digestion, which may have facilitated some ampullarids to become notorious invasive pests. In the amphibious Pomacea, novel acquisition of an egg neurotoxin and a protein for making the calcareous eggshell may have been key adaptations enabling their transition from underwater to terrestrial egg deposition.

Stipe wall extension of Flammulina velutipes could be induced by an expansin-like protein from Helix aspersa

Expansin proteins extend plant cell walls by a hydrolysis-free process that disrupts hydrogen bonding between cell wall polysaccharides. However, it is unknown if this mechanism is operative in mushrooms. Herein we report that the native wall extension activity was located exclusively in the 10 mm apical region of 30 mm Flammulina velutipes stipes. The elongation growth was restricted also to the 9 mm apical region of the stipes where the elongation growth of the 1st millimetre was 40-fold greater than that of the 5th millimetre. Therefore, the wall extension activity represents elongation growth of the stipe. The low concentration of expansin-like protein in F. velutipes stipes prevented its isolation. However, we purified an expansin-like protein from snail stomach juice which reconstituted heat-inactivated stipe wall extension without hydrolytic activity. So the previous hypotheses that stipe wall extension was resulted from hydrolysis of wall polymers by enzymes or disruption of hydrogen bonding of wall polymers exclusively by turgor pressure are challenged. We suggest that stipe wall extension may be mediated by endogenous expansin-like proteins that facilitate cell wall polymer slippage by disrupting noncovalent bonding between glucan chains or chitin chains.

Co-expression of two fibrolytic enzyme genes in CHO cells and transgenic mice

Cellulose is the main non-starch polysaccharides (NSP) in plant cell walls and acts as anti-nutritional factor in animal feed. However, monogastric animals do not synthesize enzymes that cleave such plant structural polysaccharides and thus waste of resources and pollute the environment. We described the vectors construction and co-expressions of a multi-functional cellulase EGX (with the activities of exo-β-1,4-glucanase, endo-β-1,4-glucanase, and endo-β-1,4-xylanase activities) from mollusca, Ampullaria crossean and a β-glucosidase BGL1 from Asperjillus niger in CHO cells and the transgenic mice. The recombinant enzymes were synthesised, secreted by the direction of pig PSP signal peptide and functionally active in the eukaryote systems including both of CHO cells and transgenic mice by RT-PCR analysis, western blot analysis and cellulolytic enzymes activities assays. Expressions were salivary glands-specific dependent under the control of pig PSP promoter in transgenic mice. 2A peptide was used as the self-cleaving sequence to mediate co-expression of the fusion genes and the cleavage efficiency was very high both in vitro and in vivo according to the western blot analysis. In summary, we have demonstrated that the single ORF containing EGX and BGL1 were co-expressed by 2A peptide in CHO cells and transgenic mice. It presents a viable technology for efficient disruption of plant cell wall and liberation of nutrients. To our knowledge, this is the first report using 2A sequence to produce multiple cellulases in mammalian cells and transgenic animals.

Expression of multi-functional cellulase gene mfc in Coprinus cinereus under control of different basidiomycete promoters

Multi-functional cellulase gene mfc was expressed in Coprinus cinereus under naturally non-inductive conditions using three heterologous promoters. Endo-beta-1,4-glucanase expression was achieved in solid and liquid media with promoter sequences from the Lentinula edodesgpd gene, the Flammulina velutipes gpd gene and the Volvariella volvaceagpd gene. As measured by enzyme activity in liquid cultures, a 613-bp gpd promoter fragment from L. edodes was most efficient, followed by a 752-bp gpd fragment from F. velutipes. The V. volvacea gpd promoter sequence was less active, in comparison. Irrespective of the promoter used, enzymatic activities increase 34-fold for highly active transformants and 29-fold for less active one by using cellulase-inducing medium. The highest activities of endo-beta-1,4-glucanase (34.234 U/ml) and endo-beta-1,4-xylanase (263.695 U/ml) were reached by using the L. edodesgpd promoter.

Identification, expression, and characterization of the highly conserved D-xylose isomerase in animals

D-xylose is a necessary sugar for animals. The xylanase from a mollusk, Ampullaria crossean, was previously reported by our laboratory. This xylanase can degrade the xylan into D-xylose. But there is still a gap in our knowledge on its metabolic pathway. The question is how does the xylose enter the pentose pathway? With the help of genomic databases and bioinformatic tools, we found that some animals, such as bacteria, have a highly conserved D-xylose isomerase (EC 5.3.1.5). The xylose isomerase from a sea squirt, Ciona intestinali, was heterogeneously expressed in Escherichia coli and purified to confirm its function. The recombinant enzyme had good thermal stability in the presence of Mg(2+). At the optimum temperature and optimum pH environment, its specific activity on D-xylose was 0.331 micromol/mg/min. This enzyme exists broadly in many animals, but it disappeared in the genome of Amphibia-like Xenopus laevis. Its sequence was highly conserved. The xylose isomerases from animals are very interesting proteins for the study of evolution.

The N-terminal cellulose-binding domain of EGXA increases thermal stability of xylanase and changes its specific activities on different substrates

A full-length EGXA enzyme from a mollusk, Ampullaria crossean, was cloned into pFastBac vector and then heterogeneously expressed in insect Tn5 cells. Its natural N-terminal signal peptide worked well in the insect Tn5 cells. The recombinant EGXA was a 63 kDa protein and had active endo-beta-1,4-glucanase (EC 3.2.1.4) and endo-beta-1,4-xylanase (EC 3.2.1.8). The specific activity of endo-beta-1,4-xylanase was higher than in the EGX, which was purified from the stomach tissues of Ampullaria crossen. The N-terminal cellulose-binding domain of EGXA made it bind to cellulose and xylan more efficiently. This cellulose-binding domain also increased the thermal stability of this recombinant enzyme and decreased the recombinant EGXA's specific activities on p-nitrophenyl-beta-D-cellobioside and sodium carboxymethyl cellulose.

Expression and characterization of two secreted His6-tagged endo-beta-1,4-glucanases from the mollusc Ampullaria crossean in Pichia pastoris

Two endo-beta-1,4-glucanase cDNAs, eg27I and eg27II, from the mollusc Ampullaria crossean were expressed in Pichia pastoris cells. The secreted His6-tagged proteins were purified in a single chromatography step. The purified recombinant EG27I and EG27II showed enzymatic activity on carboxylmethyl cellulose sodium salt at 15.31 U/mg and 12.40 U/mg, respectively. The optimum pH levels of the recombinant EG27I and EG27II were 5.5 and 5.5-6.0, respectively, and the optimum temperatures were 50 degrees C and 50 degrees C-55 degrees C, respectively. The pH stability study revealed that both EG27I and EG27II showed their highest stability at pH 8.0. Analysis of their thermostability indicated that both EG27I and EG27II were relatively stable up to 40 degrees C. Site-directed mutagenesis of Asp43 and Asp153 of both EG27I and EG27II showed that the two Asp residues are critical for the enzymatic activity.

A symbiont-independent endo-1,4-beta-xylanase from the plant-parasitic nematode Meloidogyne incognita

Substituted xylan polymers constitute a major part of the hemicellulose fraction of plant cell walls, especially in monocotyledons. Endo-1,4-beta-xylanases (EC 3.2.1.8) are capable of hydrolyzing substituted xylan polymers into fragments of random size. Many herbivorous animals have evolved intimate relationships with endosymbionts to exploit their enzyme complexes for the degradation of xylan. Here, we report the first finding of a functional endo-1,4-beta-xylanase gene from an animal. The gene (Mi-xyl1) was found in the obligate plant-parasitic root-knot nematode Meloidogyne incognita, and encodes a protein that is classified as a member of glycosyl hydrolase family 5. The expression of Mi-xyl1 is localized in the subventral esophageal gland cells of the nematode. Previous studies have shown that M. incognita has the ability to degrade cellulose and pectic polysaccharides in plant cell walls independent of endosymbionts. Including our current data on Mi-xyl1, we show that the endogenous enzyme complex in root-knot nematode secretions targets essentially all major cell wall carbohydrates to facilitate a stealthy intercellular migration in the host plant.

Purification and characterization of two endo-beta-1,4-glucanases from mollusca, Ampullaria crossean

Two novel endo-beta-1,4-glucanases, EG45 and EG27, were isolated from the gastric juice of mollusca, Ampullaria crossean, by anion exchange, hydrophobic interaction, gel filtration and a second round of anion exchange chromatography. The purified proteins EG45 and EG27 appeared as a single band on sodium dodecylsulfate polyacrylamide gel electrophoresis with a molecular mass of 45 kDa and 27 kDa, respectively. The optimum pH for CMC activity was 5.5 for EG45 and 4.4-4.8 for EG27. The optimum temperature range for EG27 was broad, between 50 degrees and 60 degrees; for EG45 it was 50 degrees. The analysis on the stability of these two endo-beta-1,4-glucanases showed that EG27 was acceptably stable at pH 3.0-11.0 even when the incubation time was prolonged to 24 h at 30 degrees, whereas EG45 remained relatively stable at pH 5.0-8.0. About 85% of the activity of EG27 could be retained upon incubation at 60 degrees for 24 h. However, less than 10% residual activity of EG45 was detected at 50 degrees. Among different kinds of substrates, both enzymes showed a high preference for carboxymethyl cellulose. EG45, in particular, showed a carboxymethyl cellulose hydrolytic activity of 146.5 IU/mg protein. Both enzymes showed low activities to xylan (from oat spelt) and Sigmacell 101, and they were inactive to p-nitrophenyl-beta-D-cellobioside, salicin and starch.

Purification and properties of a low molecular weight 1,4-β-d-glucan glucohydrolase having one active site for carboxymethyl cellulose and xylan from an alkalothermophilic Thermomonospora sp

A low molecular weight 1,4-beta-D-glucan glucohydrolase from an extracellular culture filtrate of Thermomonospora sp. was purified to homogeneity. The molecular weight of the purified enzyme was 14.2 kDa by MALDI-TOF analysis and is in agreement with SDS-PAGE and gel filtration chromatography. The purified enzyme exhibited both endocarboxymethyl cellulase and endoxylanase activities. A kinetic method was employed to study the active site of the enzyme that hydrolyzes both carboxymethyl cellulose and xylan. The experimental data coincide well with the theoretical values calculated for the case of a single active site. Conformation and microenvironment at the active site was probed with fluorescent chemo-affinity labeling using o-phthalaldehyde as the chemical initiator. Formation of isoindole derivative resulted in complete inactivation of the enzyme to hydrolyze both xylan and CMC as judged by fluorescence studies corroborating a single active site for the hydrolysis of xylan and CMC.