Developing and evaluating lignocellulolytic hyper producing deregulated strains of Mycothermus thermophilus for hydrolysis of lignocellulosics

An indigenous thermophilic fungal strain of Mycothermus thermophilus (Syn. Scytalidium thermophilum ) designated as CM 4 T was subjected to a combination of cyclic mutagenesis and intra-specific protoplast fusion to induce heterokaryosis and diploidization for developing deregulated cellulase hyper-producer strain. The developed strain (23 U) produced 14.60, 45.50, 82.80, 3.28, and 264 U/ml of CBH, β-glucosidase, CMCase, Fpase, and xylanase at fermenter level, which were 8.6, 2.54, 6.58, 2.37, and 6.58 folds improved, respectively, in comparison to wild-type strain CM 4 T. Furthermore, the developed mutants produced cellulases constitutively during fed-batch (flask mode) using glucose feed at 0.375 g carbon/l/h. The creA gene and CreA protein structures of mutant 23 U showed truncated zinc finger motif linking it to the catabolite repression-resistant phenotype. The hydrolytic potential of cellulase produced of developed strain 23 U was evaluated using acid- and alkali-treated rice straw and bagasse at 10 % substrate loading rate. Furthermore, studies showed that hydrolytic efficiency of the cellulases produced by mutant 23 U can be further enhanced by custom designing of the cocktails that comprised of lignocellulolytic enzymes of mutant 23 U and different thermophilic/thermotolerant fungal strains.