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Table 2 Molecular approaches towards enhanced enzymatic properties of cellulases

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

Microorganism Gene Characteristics of recombinant cellulase References
Batocera horsfieldi Bh-EGase I SA: 1030.87 IU/mg, 40 °C and pH 4.0 Mei et al. (2016); Zhong et al. (2012)
Corbicula japonica Glycoside hydrolase family (GHF) 9 β-1,4-glucanase gene, CjCel9A GHF45 (CjCel45A, CjCel45B). Both genes encode ORF of 627 bp corresponding to 208 amino acids
Key role as cellulose decomposer in estuarine environments
Sakamoto and Toyohara (2009)
Bacillus subtilis EG gene Introduced those benefits of commercial bioconversion of complex lignocellulosic materials to biofuels Ghadiri et al. (2020)
Streptomyces sp., Thermobispora bispora, Cellulomonas fimi, Streptomyces halstedii, Clostridium thermocellum   Comparative sequence alignment, molecular modeling, and docking analyses were performed taking 5 microbial (3 bacteria and 2 fungi) cellulase enzymes
Cellulose-binding site in endoglucanase E of Clostridium thermocellum Ser131, Met263, Gln298, and His310 which are reported to have differed with Ala119, Ala255, Ser298, and Cys304 in Streptococcus sp.
Molecular modeling and docking studies revealed that different microbial cellulase enzymes have the potential towards the use of cellulose as a substrate for the high yield of bioethanol
Paul et al. (2020)
Talaromyces emersonii Cellulase gene (cbh2) cbh2 has an open reading frame of 1377 bp, which encodes a putative polypeptide of 459 amino acids
Expression of the T. emersonii cbh2 gene induced by cellulose, xylan, xylose, gentiobiose, and repressed by glucose
Murray et al. (2003)
Fosmid library of Buffalo rumen metagenomic DNA Acid-cellulase gene (Cel-1) ORF encoding cellulase consisted of 1176-bp, corresponding to a protein of 391 amino acid and has catalytic domain belonging to glycosyl hydrolase family 5 Dadheech et al. (2018)
Trichoderma reesei Rut-C30 egl1 at the ace1 locus Cellulase production by T. reesei QS305 performed in the 5-L fermentor, cellulases activity of 10.7 FPU/mL achieved at 108 h, 75.4% higher than that produced by T. reesei Rut-C30 Meng et al. (2018)
Aspergillus niger   PCR product was 1311 bp, xylanase activity of the reconstructed A. niger was 3.28 U/mL. The activity of the exoglucanase from the constructed strain was increased to 1.95 U/mL from 0.21 U/mL of the original A. niger. Reconstructed A. niger cellulase could hydrolyze wheat straw to release 19.7 g/L of glucose, compared to 12.01 g/L of that released by the cellulase from the original A. niger Xue et al. (2019)
Acinetobacter sp.   These docking studies revealed that cellulase has the greater potential towards the cellotetraose as a substrate for the high yield of ethanol Selvam et al. (2017)
Cellulase produced by bacteria in gayal rumen Umcel-1 Putative gene Umcel-1 product belonged to the glycosyl hydrolase family 5 and showed the highest homology to the cellulase (GenBank accession no. YP_004310852.1) from Clostridium lentocellum DSM 5427, with 44% identity and 62% similarity. Open reading frame of 942 base pairs that encoded a product of 313 amino acids
The activity of purified recombinant Umcel-1 was assessed, and the results revealed that it hydrolyzed carboxymethyl cellulose with optimal activity at pH 5.5 and 45 °C
LI et al. (2016a)
Aspergillus niger   Exoglucanase increased from the original 0.21 U/mL to 0.89 U/mL of the transformant. Endoglucanase increased from the original 4.51 U/mL to 15.12 U/mL of the transformant. FPA increased nearly 7.1-fold from 0.63 to 4.47 U/mL
Cellulase from the transformant retained the halo-stable ability
Xue et al. (2017b)
Trichoderma reesei cellulase (TrCBH2) The final titer of more than 18 g/L of secreted protein was produced under controlled conditions in small-scale bioreactor cultivations after 60–70 h. High concentration of secreted enzyme in P. pastoris Mellitzer et al. (2014)
Trichoderma reesei Beta-glucosidase gene from Penicillium decumbens The beta-glucosidase activity of the enzyme complexes from two selected transformants increased six- to eightfold and their filter paper activity (FPAs) enhanced by 30% on average Ma et al. (2011)
Coprinus cinereus Cellulase gene mfc The highest activities of endo-β-1,4-glucanase (34.234 U/mL) and endo-β-1,4-xylanase (263.695 U/mL) were reached by the L. edodes gpd promoter Cheng et al. (2009)
C. shiraiana CscelA CsCelA expressed in P. pastoris high pH stability and affinity. The active protein of 55.3 kDa recombinant cellulase (CsCelA) was 17.44 U/mL and 135 U/g for freeze-dried powder
The Kmax and Vmax of CsCelA for sodium carboxymethylcellulose (CMC) were 4.6 mg/mL and 107.2 U/mg, respectively
A stable activity from pH 4.0 to 9.0, and at temperatures ranging from 30 to 55 °C
Lü et al. (2015)
Teleogryllus emma Novel endogenous β-1,4-endoglucanase (EG) gene belonging to the glycosyl hydrolase family 9 (GHF 9) TeEG-I Signature motifs and catalytic domains, of GHF 9 members, sharing high levels of identity with the termite, Mastotermes darwiniensis (64% protein sequence identity), and the cockroach, Panesthia cribrata (62%), GHF 9 cellulases
47-kDa, Optimal pH and temperature of pH 5.0 and 40 °C Km and Vmax values for digestion of carboxymethyl cellulose 5.4 mg/mL and 3118.4 U/mg results indicate that TeEG-I distributed throughout the entire digestive tract of T. emma, suggesting a functional role of endogenous TeEG-I in a sequential cellulose digestion process T. emma digestion tract
Kim et al. (2008)
Saccharomyces cerevisiae PSE1 and SOD1 cel6A of Neocallimastix patriciarum, β-glucosidase encoded cel3A of Saccharomycopsis fibuligera resulted in heterologous protein activity ranging between 10 and 373% high compared to the parental strains grown in complex media Kroukamp et al. (2013)
Coprinopsis cinerea Multi-functional cellulase gene mfc Growth substrate, highest activities of endo-β-1,4-glucanase (0.48 U/mL), total cellulase (0.26 U/mL), and endo-β-1,4-xylanase (38.10 U/mL) in culture liquid Cabm44, uses a 275 bp gpd fragment from A. bisporus Yang et al. (2011)
Cricket Teleogryllus emma Novel endogenous β-1,4-endoglucanase (EG) gene belonging to the glycosyl hydrolase family 9 (GHF 9) Optimal pH and temperature of pH 5.0 and 40 °C. Km and Vmax values for digestion of carboxymethyl cellulose 5.4 mg/mL and 3118.4 U/mg Kim et al. (2008)