Hydrogenosomes in the rumen fungus Neocallimastix patriciarum.
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ABSTRACT:
SUBMITTER: Yarlett N
PROVIDER: S-EPMC1146905 | biostudies-other | 1986 Jun
REPOSITORIES: biostudies-other
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Project description:Cellulose, which is the most abundant renewable biomass on earth, is a potential bio-resource of alternative energy. The hydrolysis of plant polysaccharides is catalyzed by microbial cellulases, including endo-?-1,4-glucanases, cellobiohydrolases, cellodextrinases, and ?-glucosidases. Converting cellobiose by ?-glucosidases is the key factor for reducing cellobiose inhibition and enhancing the efficiency of cellulolytic enzymes for cellulosic ethanol production.In this study, a cDNA encoding ?-glucosidase was isolated from the buffalo rumen fungus Neocallimastix patriciarum W5 and is named NpaBGS. It has a length of 2,331 bp with an open reading frame coding for a protein of 776 amino acid residues, corresponding to a theoretical molecular mass of 85.1 kDa and isoelectric point of 4.4. Two GH3 catalytic domains were found at the N and C terminals of NpaBGS by sequence analysis. The cDNA was expressed in Pichia pastoris and after protein purification, the enzyme displayed a specific activity of 34.5 U/mg against cellobiose as the substrate. Enzymatic assays showed that NpaBGS was active on short cello-oligosaccharides from various substrates. A weak activity in carboxymethyl cellulose (CMC) digestion indicated that the enzyme might also have the function of an endoglucanase. The optimal activity was detected at 40°C and pH 5?~?6, showing that the enzyme prefers a weak acid condition. Moreover, its activity could be enhanced at 50°C by adding Mg2+ or Mn2+ ions. Interestingly, in simultaneous saccharification and fermentation (SSF) experiments using Saccharomyces cerevisiae BY4741 or Kluyveromyces marxianus KY3 as the fermentation yeast, NpaBGS showed advantages in cell growth, glucose production, and ethanol production over the commercial enzyme Novo 188. Moreover, we showed that the KY3 strain engineered with the NpaNGS gene can utilize 2 % dry napiergrass as the sole carbon source to produce 3.32 mg/ml ethanol when Celluclast 1.5 L was added to the SSF system.Our characterizations of the novel ?-glucosidase NpaBGS revealed that it has a preference of weak acidity for optimal yeast fermentation and an optimal temperature of ~40°C. Since NpaBGS performs better than Novo 188 under the living conditions of fermentation yeasts, it has the potential to be a suitable enzyme for SSF.
| S-EPMC3403894 | biostudies-other
Project description:BackgroundNeocallimastix patriciarum is one of the common anaerobic fungi in the digestive tracts of ruminants that can actively digest cellulosic materials, and its cellulases have great potential for hydrolyzing cellulosic feedstocks. Due to the difficulty in culture and lack of a genome database, it is not easy to gain a global understanding of the glycosyl hydrolases (GHs) produced by this anaerobic fungus.ResultsWe have developed an efficient platform that uses a combination of transcriptomic and proteomic approaches to N. patriciarum to accelerate gene identification, enzyme classification and application in rice straw degradation. By conducting complementary studies of transcriptome (Roche 454 GS and Illumina GA IIx) and secretome (ESI-Trap LC-MS/MS), we identified 219 putative GH contigs and classified them into 25 GH families. The secretome analysis identified four major enzymes involved in rice straw degradation: β-glucosidase, endo-1,4-β-xylanase, xylanase B and Cel48A exoglucanase. From the sequences of assembled contigs, we cloned 19 putative cellulase genes, including the GH1, GH3, GH5, GH6, GH9, GH18, GH43 and GH48 gene families, which were highly expressed in N. patriciarum cultures grown on different feedstocks.ConclusionsThese GH genes were expressed in Pichia pastoris and/or Saccharomyces cerevisiae for functional characterization. At least five novel cellulases displayed cellulytic activity for glucose production. One β-glucosidase (W5-16143) and one exocellulase (W5-CAT26) showed strong activities and could potentially be developed into commercial enzymes.
| S-EPMC3177772 | biostudies-literature
Project description:Four types of ?-1,3-1,4 glucanase (?-glucanase, EC 3.2.1.73) genes, designated bglA13, bglA16, bglA51, and bglM2, were found in the cDNA library of Neocallimastix patriciarum J11. All were highly homologous with each other and demonstrated a close phylogenetic relationship with and a similar codon bias to Streptococcus equinus. The presence of expansion and several predicted secondary structures in the 3' untranslated regions (3'UTRs) of bglA16 and bglM2 suggest that these two genes were duplicated recently, whereas bglA13 and bglA16, which contain very short 3'UTRs, were replicated earlier. These findings indicate that the ?-glucanase genes from N. patriciarum J11 may have arisen by horizontal transfer from the bacterium and subsequent duplication in the rumen fungus. ?-Glucanase genes of Streptococcus equinus, Ruminococcus albus 7, and N. patriciarum J11 were cloned and expressed by Escherichia coli. The recombinant ?-glucanases cloned from S. equinus, R. albus 7, and N. patriciarum J11 were endo-acting and had similar substrate specificity, but they demonstrated different properties in other tests. The specific activities and catalytic efficiency of the bacterial ?-glucanases were also significantly lower than those of the fungal ?-glucanases. Our results also revealed that the activities and some characteristics of enzymes were changed during the horizontal gene transfer event. The specific activities of the fungal ?-glucanases ranged from 26,529 to 41,209 U/mg of protein when barley-derived ?-glucan was used as the substrate. They also demonstrated similar pH and temperature optima, substrate specificity, substrate affinity, and hydrolysis patterns. Nevertheless, BglA16 and BglM2, two recently duplicated ?-glucanases, showed much higher k(cat) values than others. These results support the notion that duplicated ?-glucanase genes, namely, bglA16 and bglM2, increase the reaction efficiency of ?-glucanases and suggest that the catalytic efficiency of ?-glucanase is likely to be a criterion determining the evolutionary fate of duplicate forms in N. patriciarum J11.
| S-EPMC3370538 | biostudies-literature
Project description:Primary pathways for glucose metabolism were established in the anaerobic rumen fungus Neocallimastix frontalis EB188. This highly capable cellulolytic organism demonstrated a strict anaerobic integration of metabolic pathways. Glycolysis in N. frontalis EB188 was coupled to malate dehydrogenase, 'malic' enzyme and specified hydrogenosome reactions. Pyruvate, as in most life forms, was a pivotal compound. The major fermentation products of N. frontalis EB188 were acetate, ethanol and lactate, with the concomitant generation of H2. On the basis of its unique characteristics and streamlined fermentation pathways, it was concluded that N. frontalis EB188 should be an important contributor to programs generating energy and selected chemicals from currently intractable biomass.
| S-EPMC1150180 | biostudies-other
Project description:The cDNA designated celB from the anaerobic rumen fungus Neocallimastix patriciarum contained a single open reading frame of 1422 bp coding for a protein (CelB) of M(r) 53,070. CelB expressed by Escherichia coli harbouring the full-length gene hydrolysed carboxymethylcellulose in the manner of an endoglucanase, but was most active against barley beta-glucan. It also released reducing sugar from xylan and lichenan, but was inactive against crystalline cellulose, laminarin, mannan, galactan and arabinan. The rate of hydrolysis of cellulo-oligosaccharides by CelB increased with increasing chain length from cellotriose to cellopentaose. The predicted structure of CelB contained features indicative of modular structure. The first 360 residues of CelB constituted a fully functional catalytic domain that was homologous with bacterial endoglucanases belonging to cellulase family A, including five which originate from three different species of anaerobic rumen bacteria. Downstream from this domain, and linked to it by a serine/threonine-rich hinge, was a non-catalytic domain containing short tandem repeats, homologous to the C-terminal repeats contained in xylanase A from the same anaerobic fungus. Unlike previous fungal cellulases, genomic celB was devoid of introns. This lack of introns and the homology of its encoded product with rumen bacterial endoglucanases suggest that acquisition of celB by the fungus may at some stage have involved horizontal gene transfer from a prokaryote to N. particiarum.
| S-EPMC1137837 | biostudies-other
Project description:Acetyl xylan esterase (AXE), which hydrolyzes the ester linkages of the naturally acetylated xylan and thus known to have an important role for hemicellulose degradation, was isolated from the anaerobic rumen fungus Neocallimastix frontatlis PMA02, heterologously expressed in Escherichi coli (E.coli) and characterized. The full-length cDNA encoding NfAXE1 was 1,494 bp, of which 978 bp constituted an open reading frame. The estimated molecular weight of NfAXE1 was 36.5 kDa with 326 amino acid residues, and the calculated isoelectric point was 4.54. The secondary protein structure was predicted to consist of nine α-helixes and 12 β-strands. The enzyme expressed in E.coli had the highest activity at 40°C and pH 8. The purified recombinant NfAXE1 had a specific activity of 100.1 U/mg when p-nitrophenyl acetate (p-NA) was used as a substrate at 40°C, optimum temperature. The amount of liberated acetic acids were the highest and the lowest when p-NA and acetylated birchwood xylan were used as substrates, respectively. The amount of xylose released from acetylated birchwod xylan was increased by 1.4 fold when NfAXE1 was mixed with xylanase in a reaction cocktail, implying a synergistic effect of NfAXE1 with xylanase on hemicellulose degradation.
| S-EPMC5088377 | biostudies-literature
Project description:The catalytic domain of XynCDBFV, a glycoside hydrolase family 11 (GH11) xylanase from ruminal fungus Neocallimastix patriciarum previously engineered to exhibit higher specific activity and broader pH adaptability, holds great potential in commercial applications. Here, the crystal structures of XynCDBFV and its complex with substrate were determined to 1.27-1.43 Å resolution. These structures revealed a typical GH11 β-jelly-roll fold and detailed interaction networks between the enzyme and ligands. Notably, an extended N-terminal region (NTR) consisting of 11 amino acids was identified in the XynCDBFV structure, which is found unique among GH11 xylanases. The NTR is attached to the catalytic core by hydrogen bonds and stacking forces along with a disulfide bond between Cys-4 and Cys-172. Interestingly, the NTR deletion mutant retained 61.5% and 19.5% enzymatic activity at 55 °C and 75 °C, respectively, compared with the wild-type enzyme, whereas the C4A/C172A mutant showed 86.8% and 23.3% activity. These results suggest that NTR plays a role in XynCDBFV thermostability, and the Cys-4/Cys-172 disulfide bond is critical to the NTR-mediated interactions. Furthermore, we also demonstrated that Pichia pastoris produces XynCDBFV with higher catalytic activity at higher temperature than Escherichia coli, in which incorrect NTR folding and inefficient disulfide bond formation might have occurred. In conclusion, these structural and functional analyses of the industrially favored XynCDBFV provide a molecular basis of NTR contribution to its thermostability.
| S-EPMC4036243 | biostudies-literature
Project description:Wheat bran is an effective raw material for preparation xylooligosaccharides; however, current research mainly focuses on alkali extraction and enzymatic hydrolysis methods. Since ester bonds are destroyed during the alkali extraction process, xylanase and arabinofuranosidase are mainly used to hydrolyze xylooligosaccharides. However, alkali extraction costs are very high, and the method also causes pollution. Therefore, this study focuses on elucidating a method to efficiently and directly degrade destarched wheat bran. First, an acidic acetyl xylan esterase (AXE) containing a carbohydrate-binding module-1 (CBM1) domain was cloned from Talaromyces leycettanus JCM12802 and successfully expressed in Pichia pastoris. Characterization showed that the full-length acetyl xylan esterase AXE?+?CBM1 was similar toe uncovered AXE with an optimum temperature and pH of 55 °C and 6.5, respectively. Testing the acetyl xylan esterase and xylanase derived from Neocallimastix patriciarum in a starch-free wheat bran cooperative experiment revealed that AXE?+?CBM1 and AXE produced 29% and 16% reducing sugars respectively, compared to when only NPXYN11 was used. In addition, introduced the CBM1 domain into NPXYN11, and the results indicated that the CBM1 domain showed little effect on NPXYN11 properties. Finally, the systematically synergistic effects between acetyl xylan esterase and xylanase with/without the CBM1 domain demonstrated that the combined ratio of AXE?+?CBM1 coming in first and NPXYN11?+?CBM1 s increased reducing sugars by almost 35% with AXE and NPXYN11. Furthermore, each component's proportion remained the same with respect to xylooligosaccharides, with the largest proportion (86%) containing of 49% xylobiose and 37% xylotriose.
| S-EPMC6351639 | biostudies-literature
Project description:The nucleotide sequence of a cellulase cDNA (celA) from the rumen fungus Neocallimastix patriciarum and the primary structure of the protein which it encodes were characterized. The celA cDNA was 1.95 kb long and had an open reading frame of 1,284 bp, which encoded a polypeptide having 428 amino acid residues. A sequence alignment showed that cellulase A (CELA) exhibited substantial homology with family B cellulases (family 6 glycosyl hydrolases), particularly cellobiohydrolase II from the aerobic fungus Trichoderma reesei. In contrast to previously characterized N. patriciarum glycosyl hydrolases, CELA did not exhibit homology with any other rumen microbial cellulases described previously. Primary structure and function studies in which deletion analysis and a sequence comparison with other well-characterized cellulases were used revealed that CELA consisted of a cellulose-binding domain at the N terminus and a catalytic domain at the C terminus. These two domains were separated by an extremely Asn-rich linker. Deletion of the cellulose-binding domain resulted in a marked decrease in the cellulose-binding ability and activity toward crystalline cellulose. When CELA was expressed in Escherichia coli, it was located predominantly in the periplasmic space, indicating that the signal sequence of CELA was functional in E.coli. Enzymatic studies showed that CELA had an optimal pH of 5.0 and an optimal temperature of 40 degrees C. The specific activity of immunoaffinity-purified CELA against Avicel was 9.7 U/mg of protein, and CELA appeared to be a relatively active cellobiohydrolase compared with the specific activities reported for other cellobiohydrolases, such as T. reesei cellobiohydrolases I and II.
| S-EPMC167968 | biostudies-other
Project description:BackgroundAnaerobic fungi of the phylum Neocallimastigomycota have a high biotechnological potential due to their robust lignocellulose degrading capabilities and the production of several valuable metabolites like hydrogen, acetate, formate, lactate, and ethanol. The metabolism of these fungi, however, remains poorly understood due to limitations of the current cultivation strategies in still-standing bottles, thereby restricting the comprehensive evaluation of cultivation conditions.ResultsWe describe the analysis of growth conditions and their influence on the metabolism of the previously isolated fungus Neocallimastix cameroonii G341. We established a bioreactor process in a stirred tank, enabling cultivation under defined conditions. The optimal growth temperature for the fungus was between 38.5 °C and 41.5 °C, while the optimal pH was 6.6-6.8. Like other dark fermentation systems, hydrogen production is dependent on the hydrogen partial pressure and pH. Shaking the bottles or stirring the fermenters led to an increase in hydrogen and a decrease in lactate and ethanol production. Regulation of the pH to 6.8 in the fermenter nearly doubled the amount of produced hydrogen.ConclusionsNovel insights into the metabolism of Neocallimastix cameroonii were gained, with hydrogen being the preferred way of electron disposal over lactate and ethanol. In addition, our study highlights the potential application of the fungus for hydrogen production from un-pretreated biomass. Finally, we established the first cultivation of an anaerobic fungus in a stirred tank reactor system.
| S-EPMC9484062 | biostudies-literature