Table 3.

Comparative analysis of different genetic manipulation strategies in fungi and enhancement in cellulase production

Strategy/target component	Modified fungal strain	Manipulation method	Outcome	References
Transcriptional regulators	Trichoderma orientalis EU7-22	Overexpression of the transcription factors Xyr1 and Ace3	2.12- and 1.95- fold increment in FPase (2.55 IU/mL) and CMCase (90.38 IU/mL)	[98]
RNA interference strategy	Myceliophthora thermophile ATCC42464	RNA interference of the cre1 gene expression	3.76- and 1.31-fold increment in FPase and endoglucanase activity, respectively	[62]
Promoter engineering	Aspergillus niger	In T. reesei, the activation region of a strong inducible promoter PcbhI fused to a strongest promoter Pcdna 1–3 resulting in the production of a hybrid synthetic promoter Pcc, followed by its heterologous expression in A. niger	43.2- and 1.2- fold increment in β-glucosidase (27.2 IU/L) and endoglucanase (6.2 IU/L) activity	[118]
Heterologous strain production	Penicillium verruculosum B1-537	β-glucosidase gene from A. niger and LPMO gene from T. reesei, clone in Penicillium verruculosum B1-537 and expressed under the inducible promoter gene gla1	β-glucosidase (11.8 U/mg) and LPMO (8.2 U/mg)	[41]
Codon optimization	Trichoderma reesei TU-6	Codon-optimized endomannanase gene (Man5A) transformation from A. niger to T. reesei	FPase (1376 IU/L)	[119]
Directed evolution	Saccharomyces cerevisiae	Employing directed evolution strategy to bglI gene from A. niger to express a library of mutated S. cerevisiae bgl1 genes and utilized a two-round functional screen to recognize improved enzymes	(Variant7a, mutational amino acid position 65, from Thy to Ade) 2.03 U/L (relative activity)	[52]
Multiple gene expression	Aspergillus oryzae	Multiple expression of cbhI, egI, and bglI genes	Cellobiohydrolase (21.8 U/L), beta glucosidase (37.7 IU/L), and endoglucanase (400 IU/L)	[53]
Signal peptide	Pichia pastoris	Replace the native signal peptide with signal peptide of serum albumin from Homo sapiens	Endoglucanse (261.45 U/mL)	[120]
Site directed mutagenesis	Trichderma reesei	SDM mediated disulfide bonds removal from cel5A gene	Endoglucanase (3111.7 U/mg for C99V and 3178.3 U/mg for C323H)	[121]
Chaperone	Pichia pastoris	Overexpression of the key transcription factor HAC1 that controls the unfolded protein response	Endoglucanase (91 IU/L)	[54]
Vesicle trafficking	Saccharomyces cerevisiae	Overexpression of vesicle trafficking components involved in ER to Golgi transport (Snc2p, Sec4p, and Ypt32p) and Golgi to plasma membrane (Sso1p and Snc2p)	20, 22 and 23% increment in endoglucanase activity and 53 and 61% in β-glucosidase activity	[122]
Glycosylation	Trichoderma reesei	Glycosylation at the N224 of β-glucosidase of Aspergillus terreus expressed in T. reeesei	β-glucosidase (450 IU/L)	[154]
CRISPR-CAS9	Talaromyces pinophilus EMU	CRISPR-Cas9 facilitated degradation of seb1 gene	FPase (10.61 IU/mL)	[123]