Abstract: β-Glucosidase is an important enzyme for production
of ethanol from lignocellulose. With hydrolytic activity on
cellooligosaccharides, especially cellobiose, β-glucosidase removes
product inhibitory effect on cellulases and forms fermentable sugars.
In this study, β-glucosidase encoding gene (BGL1) from traditional
starter yeast Saccharomycosis fibuligera BMQ908 was cloned and
expressed in Pichia pastoris. BGL1 of S. fibuligera BMQ 908 shared
98% nucleotide homology with the closest GenBank sequence
(M22475) but identity in amino-acid sequences of catalytic domains.
Recombinant plasmid pPICZαA/BGL1 containing the sequence
encoding BGL1 mature protein and α-factor secretion signal was
constructed and transformed into methylotrophic yeast P. pastoris by
electroporation. The recombinant strain produced single extracellular
protein with molecular weight of 120 kDa and cellobiase activity of
60 IU/ml. The optimum pH of the recombinant β-glucosidase was 5.0
and the optimum temperature was 50°C.
Abstract: A. niger XP isolated from Vietnam produces very low amount of acidic phytase with optimal pH at 2.5 and 5.5. The phytase production of this strain was successfully improved through gene cloning and expression. A 1.4 - kb DNA fragment containing the coding region of the phyA gene was amplified by PCR and inserted into the expression vector pPICZαA with a signal peptide α- factor, under the control of AOX1 promoter. The recombined plasmid was transformed into the host strain P. pastoris KM71H and X33 by electroporation. Both host strains could efficiently express and secret phytase. The multicopy strains were screened for over expression of phytase. All the selected multicopy strains of P. pastoris X33 were examined for phytase activity, the maximum phytase yield of 1329 IU/ml was obtained after 4 days of incubation in medium BMM. The recombinant protein with MW of 97.4 KW showed to be the only one protein secreted in the culture broth. Multicopy transformant P. pastoris X33 supposed to be potential candidate for producing the commercial preparation of phytase.