Repetitive δ-integration of a cellulase-encoding gene into the chromosome of an industrial Angel Yeast-derived strain by URA3 recycling.
Biotechnol Appl Biochem
; 68(5): 953-963, 2021 Oct.
Article
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| MEDLINE
| ID: mdl-32658331
ABSTRACT
Genetic modification of industrial yeast strains often faces more difficulties than that of laboratory strains. Thus, new approaches are still required. In this research, the Angel Yeast-derived haploid strain Kα was genetically modified by multiple rounds of δ-integration, which was achieved via URA3 recycling. Three δ-integrative plasmids, pGδRU, pGδRU-BGL, and pGδRU-EG, were first constructed with two 167 bp δ sequences and a repeat-URA3-repeat fragment. Then, the δ-integrative strains containing the bgl1 or egl2 gene were successfully obtained by one-time transformation of the linearized pGδRU-BGL or pGδRU-EG fragment, respectively. Their counterparts in which the URA3 gene was looped out were also easily isolated by selection for growth on 5´-fluoroorotic acid plates, although the ratio of colonies lacking URA3 to the total number of colonies decreased with increasing copy number of the corresponding integrated cellulase-encoding gene. Similar results were observed during the second round of δ-integration, in which the δ-integration strain Kα(δbgl1-repeat) obtained from the first round was transformed with a linearized pGδRU-EG fragment. After 10 rounds of cell growth and transfer to fresh medium, the doubling times and enzyme activities of Kα(δbgl1-repeat), Kα(δegl2-repeat), and Kα(δbgl1-repeat)(δegl2-repeat) showed no significant change and were stable. Further, their maximum ethanol concentrations during simultaneous saccharification and fermentation of pretreated corncob over a 7-day period were 46.35, 33.13, and 51.77 g/L, respectively, which were all substantially higher than the parent Kα strain. Thus, repetitive δ-integration with URA3 recycling can be a feasible and valuable method for genetic engineering of Angel Yeast. These results also provide clues about some important issues related to δ-integration, such as the structural stability of δ-integrated genes and the effects of individual integration-site locations on gene expression. Further be elucidation of these issues should help to fully realize the potential of δ-integration-based methods in industrial yeast breeding.
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Bases de datos:
MEDLINE
Asunto principal:
Saccharomyces cerevisiae
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Celulasa
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Cromosomas
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Proteínas de Saccharomyces cerevisiae
Idioma:
En
Revista:
Biotechnol Appl Biochem
Asunto de la revista:
BIOQUIMICA
/
BIOTECNOLOGIA
Año:
2021
Tipo del documento:
Article