Genetically Modified Aspergillus Oryzae And A Plasmid To Use In Aspergillus For Production Of Alpha Amylase And Processes Thereof.
Abstract:
Genetically modified A.oryzae (MTCC 5177) for better production of amylase having
sequence as herein described from locally available GRAS fungus A.oryzae E212 from
the plasmid pAAC3 (9) obtained from cloning of 2.8213Kbpamylase fragment having a
blunt end BamH1 side and a staggered end EcoR1 at both the ends derived from
plasmid pSPK14 (1) and the 5Kbf"acetamidase gene of A. nidulans derived from p3SR2
(4) having a EcoR1 blunt end and Sal1 staggered end at both the ends with linearized
plasmid pGEM 3Z having Sal1 and EcoR1 sides at both the ends and process thereof.
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Specification
FIELD OF THE INVENTION :-
This invention relates to genetically modified Aspergillus oryzae (EIPW16, MTCC 5177) and a Plasmid to use in Aspergillus for production of alpha-amylase and processes for preparation of the same. More particularly Genetically modified filamentous fungus Aspergillus oryzae for hyper-production (4 to 5 times of original amylase producing Strain Aspergillus oryzae EIPW 212) and preparation of amylase from the said fungus by solid-state fermentation using agrowastes particularly wheat bran as the substrate, for use in degradation of starch.
The invention further discloses the process for protein expression in solid state fermentation by using a genetically modified GRAS fungus. It encompasses a process of transformation with the recombinant plasmid containing the DNA-sequence and a suitable marker for selection of transformants and the selection of a stable transformants of GRAS fungus Aspergillus oryzae having multiple integrations of the DNA-sequence encoding the desired protein product at various chromosomal sites facilitating higher amount of expression of the protein coded by the DNA-sequence in solid state fermentation. The process permits the industrial production of secretory proteins that are expressed in the host GRAS fungus which are economic and easy to implement in an industrial process for doing the same.
BACKGROUND OF THE INVENTION :-
Aspergillus oryzae is a filamentous fungus is being used from prehistoric dates in production of fermented food in Asian countries. A. oryzae has been designated as
generally regarded as safe (GRAS) organism by the US Food and Drug Administration.
It has earned considerable interest in the biotechnology and enzyme producing
industries due to its ability to produce and secrete hydrolyzing enzymes. A local isolate
of filamentous fungus of GRAS origin Aspergillus oryzae(EIPW 212), has been studied
for its capacity to secrete hydrolyzing enzymes.
Aspergillus oryzae is a significant filamentous fungus used in the fermentation industry It is being used for its capability to secrete the important enzyme Alpha-Amylases Taka-amylase A (TAA) [EC 3.2.1.1, a - 1, 4- giucan-4-glucanohydrolase] which constitute a group of enzymes catalyzing hydrolysis of starch and other linear and branched 1,4-glucosidic oligo- and polysaccharides to yield dextrin during the fermentation processes. TAA is a glycoprotein consisting of a single polypeptide chair of 478 amino acids residues of which the sequence except for the signal peptide has been determined.
Employing the synthetic oligonucleotides (26 oligomer each) as DNA probes corresponding to the N-terminal end and C-temninal end, the TAA gene was cloned frorr the genomic library of A.oryzae. The gene was located in a 3.7Kbp EcoR1 fragment anc A.oryzae transformants containing the EcoR1 fragment showed 2 to 5 fold enhancement in TAA activity. The complete nucleotide sequence of the gene was determined and it was found that the gene consisted of 2040 bp, with eight introns anc twenty-one amino acids comprising of a signal peptide. The deduced amino acid sequence contains one insertion, one deletion and ten substitutions of amino acids compared to that of the sequence reported earlier. a-Amylase enzyme and its coding multiple gene(s)/family members has been isolated and characterized from various sources of bacterial and eukaryotic systems.
EP 0 238 023 A2 teaches a process for expression of a protein product in Aspergillus oryzae and is disclosed. The process comprises transforming Aspergillus oryzae with a vector system comprising DNA-sequences encoding functions facilitating gene expression, a suitable marker for selection of transformants, and a DNA-sequence encoding the desired protein product. The process enables industrial production of many different polypeptides and proteins in A. oryzae. Examples of such products are chymosin or prochymosin and other rennets, proteases, lipases and amylases. Also disclosed is an effective promoter for expression of a protein in Aspergillus. A preferred promoter is the TAKA-amylase promoter or functional parts thereof.
EP 0 439 997 A1 states further a variant of a parent Fungamyl-like fungal alpha-amylase, which exhibits improved thermal stability at acidic pH suitable for, e.g., starch processes.
US Patent 7,163,816 further discloses a method of constructing a variant of a parent Termamyl-like alpha-amy/ase, which variant has alpha-amy/ase activity and at least one altered property as compared to the parent alpha-amy/ase, comprising (a) analyzing the structure of the parent Termamyl-like alpha-amy/ase to identify at least one amino acid residue or at least one structural part of the Termamyl-like alpha-amy/ase structure, which amino acid residue or structural part is believed to be of relevance for altering the property of the parent Termamyl-like alpha-amy/ase (as evaluated on the basis of structural or functional considerations), (b) constructing a Termamyl-like alpha-amy/ase variant, which as compared to the parent Termamyl-like alpha-amy/ase, has been modified in the amino acid residue or structural part identified in (a) so as to alter the property, and (c) testing the resulting Termamyl-like alpha-amy/ase variant for the property in question.
US Patent 6,664,095 describes an improved solid state fermentation device that combines all of the operations of microorganism cultivation (sterilization, inoculation, cultivation, extraction, and post extraction treatment). This solid state fermentation device is modular in nature and operates in a contained manner so that the live microorganisms from the reactor cannot come into contact with the environment and pollute the environment and also so that the environment inside the bioreactor is aseptic. Another aspect of this invention allows fermentation of microorganisms without inhibiting the growth of the microorganism. Specifically, the bioreactor is designed to remove heat that accumulates inside the bioreactor duing fermentation by conduction. Additionally, there is a mechanism to add fluid to the interior of the bioreactor that permits equal distribution and precise control of a variety of environmental parameters. For example, the bioreactor of the present invention provides a means to add nutritive media to the microorganisms at any time during the fermentation process without
disturbing the fermenting microorganisms. Furthermore, the bioreactor of the present invention provides a mechanism to mix the contents of the bioreactor at any time and for any duration during the fermentation process. Finally, the present bioreactor provides a means of extracting desired microbial products from the bioreactor without opening the bioreactor.
No prior art describes as such the requirements of production of alpha-amylase in high yield through genetically modified Aspergillus oryzae at a cheaper industrial process. Accordingly, there remains a need for a method of genetically modified Aspergillus oryzae and a Plasmid to use in Aspergillus for production of alpha-amylase and process for preparation of the same.
Cloning of TAA and hyper-expression TAA activity to the extent of 2 to 5 folds by transformants of A. oryzae with TAA gene was reported. In this report the enhanced TAA activity has been demonstrated by growing the TAA-transformant of A. oryzae in liquid Czapek-Dox medium supplemented with 1% starch with shaking for 5 days.
Accordingly, an attempt has been made to identify the local strain Aspergillus oryzae (EIPW212) and used here has been demonstrated to yield enhanced TAA activity to the extend of 4 to 5 fold upon solid state fermentation for more or less 48 hours using the agro waste wheat bran and like substances. The production of TAA employing the said strain is much cheaper and it produces TAA by employing the general method of solid state fermentation, which is considered to produce higher amount of TAA activity compared to liquid submerged fermentation culture.
OBJECT OF THE INVENTION :-
The object of the invention is to prepare genetically modified Aspergillus oryzae (EIPW16, MTCC 5177) for production of alpha-amylase using agrowastes e.g. wheat bran as substrate for degradation of starch.
The further object of the invention is to produce a Plasmid to use in Aspergillus for production of alpha-amylase.
The further object of the invention is to develop a solid-state fermentation process for preparation of alpha-amylase from hyper-producing (4 to 5 times of original amylase producing Strain Aspergillus oryzae EIPW 212), genetically modified Aspergillus oryzae (EIPW 16, MTCC 5177) for degradation of starch.
STATEMENT OF INVENTION
Genetically modified A.oryzae (MTCC) for better production of amylase having sequence as herein described from locally available GRAS fungus A.oryzae E212 from the plasmid pAAC3 (9) obtained from cloning of 2.826 Kbp amylase fragment having a blunt end BamH1 side and a staggered end EcoR1 at both the ends derived from plasmid pSPK14 (1) and the 5Kbp acetamidase gene of A. nidulans derived from p3SR2 (4) having a EcoR1 blunt end and Sail staggered end at both the ends with linearized plasmid pGEM 3Z having Sail and EcoR1 sides at both the ends and process thereof.
DESCRIPTION OF THE INVENTION WITH ACCOMPANYING DRAWINGS:
FIG. 1 Schematic Diagram of Preparation for the Construct having the amylase gene and the acetamidase gene biomarker in a recombinant plasmid pAAC3 (9)
FIG. 2 Pair of Primer Sequences of ASP1 and ASP4.
FIG. 3 DNA SEQUENCE of amylase gene (Sequence ID No. 1) derived from A. oryzae EIPW 212, cloned in pSPK14.
According to the invention, the genetically modified Aspergillus oryzae (EIPW16 having MTCC No. 5177) has been prepared comprising of the following steps.
i. Cloning (path lii, fig.1) of appropriate genomic DNA fragment from the host A. oryzae capable of expressing and secreting out of amylase enzyme in the medium supporting the growth of the fungus.
The DNA fragment should code for the functional regions (including the preregion upstream activating sequences and promoter) to code and express for the enzyme amylase capable to perform the amylolytic activity.
The DNA fragment should also code for the essential region to confer the functions of Promoter activity or the functional parts thereof optionally preceded by upstream activating sequences.
It can also have additional DNA sequences related to the expressions.
The coding region of the DNA should also have the essential leader sequences leading to expression of the pre-protein to facilitate the transport of expressed protein for producing the active and mature-amylase enzyme. It is preferred that the expressed protein should be secreted out of the cell without accumulating inside. Proteins that are secreted out of the cells are preferred for isolation as the cells are not required to be disrupted resulting less deterioration of the proteins due to the processes. Thus the presence of a preregion which is a leader peptide or a synthetic sequence or a naturally occurring signal or functional parts thereof ensures the effective direction of the expressed product into the secretory pathway of the cell. The preregion results the secretion and is generally cleaved from the desired product during secretion leaving the mature product ready for isolation from the culture medium.
The DNA sequence should also have the transcription termination and polyadenylation signal essential to terminate the expression of the protein.
ii. Genomic DNA was isolated from the GRAS Aspergillus oryzae E1PW 212 a local isolate of filamentous fungus. Restriction endonucleases mediated digestions of the isolated chromosomal DNA and fractionation of the digested chromosomal DNA fragments is performed followed by the southern hybridization employing a probe DNA fragment capable of specific hybridization to the genomic DNA fragment that codes for the amylolytic activity or a part thereof of the host A. oryzae EIPW 212.
The DNA fragment that codes for the amylase activity or a part thereof was fished out from the chromosomal DNA isolated from A. oryzae EIPW 212 using a specific probe that was designed from the genomic gene sequence of Aspergillus oryzae (Norihiro, T. et al, Gene, vol. 84, 1989, pages 319 - 327).
Genomic clones of amylase enzyme have been studied to find the most conserved region. A conserved region in all these clones was identified.
The probe has been designed to the corresponding location of the amylase enzyme having the conserved region of the enzymatic activity encompassing the active sites of the amylase enzyme. A pair of primers ASP1 and ASP4 (fig.2) was synthesized corresponding to the two_ sites in or adjacent to the conservative region of amylase enzyme.
Therefore it was suggested that the unknown genomic clone of A. oryzae EIPW 212 might also have partial or a full homology to the conserved region.
iii. Chromosomal DNA isolated from A. oryzae EIPW 212 was amplified by PCR employing the pair of primers ASP1 and ASP4 corresponding to the two specific sites in the conservative region of amylase enzyme. A PCR product of 1.589 Kbp DNA was obtained using very stringent parameters of PCR amplification.
iv. The PCR amplified 1.589 KbPDNA fragment was radiolabeled to be used as a probe in the DNA hybridization to identify the homologous chromosomal DNA fragments from BamH1 and EcoR1 restriction enzymes digested A. oryzae EIPW 212 in a southern blotting experiment. This specific homologous DNA fragments complementary to the probe has been purified and cloned in. appropriate site of a suitable plasmid pGEM4 to construct the recombinant plasmid pSPK14 (1, fig.1) and transformed in the E. coli using the standard technique of gene cloning.
v. The transformed E. coli cells were detected by colony hybridization employing the PCR amplified 1.589 Kbp radiolabeled DNA fragment probe. Bacterial colonies harboring the A. oryzae EIPW 212 DNA fragments coding for amylase gene or a part thereof was detected by the specific colony hybridization experiment. The bacterial colony was further purified and the plasmid DNA pSPK14 containing the DNA fragment of fungal origin was isolated. DNA sequencing of the plasmid pSPK14 containing the 2.826 KbpDNA fragment derived from the fungal origin was done and the amylase gene of A. oryzae EIPW 212 has been detected in the sequence.
vi. Recombinant plasmid pAAC3 (9, fig. 1) was constructed harboring the amylase gene of fungus A.oryzae EIPW 212 and a suitable marker from plasmid p3SR2 (4, fig. 1) to permit selection of transformants of the host A oryzae (ATCC 66222) funqal strain. The successful transformants was screened out by its ability to utilize the biomarker. In this case the nitrogen utilization gene of amdS from A. nidulans was employed for the selection of transformants by its ability to grow in acetamide containing growth plates (Kelly, J.M. and Hynes, M.J., EMBO Journal vol. 4, 1985, pages 475 - 479).
vii. From all the transformants the fungal transformants having efficient and homologous hyper expression of the amylase enzyme in appropriate media of solid state fermentation using wheat bran as the substrate was screened out.
Aspergillus oryzae ATCC 66222 strain was chosen as the host for homologous expression of the amylase gene due to its ability to produce amylase enzyme and its inability to grow stongly on acetamide as the sole nitrogen source. When A. nidulans amdS gene (Tilburn, J. G. et al Gene 26 1983, pages 1470-1474) is used for the genetic transformation of the host A. oryzae ATCC 662225the transformed cell can be screened on the acetamide as the transformed fungus are able to utilize nitrogen utilizing amdS (biomarker) gene.
Chromosomal DNA isolated from A. oryzae EIPW 212 were digested with restriction enzymes BamH1 and subjected to southern hybridization using the radiolabeled 1.589Kb DNA probe corresponding to the conserved region of amylase enzyme. Autoradiography revealed the hybridized bands at positions of 7.3KbP6.4Kbpand 3.8Kbp When BamH1 and EcoR1 double digested chromosomal DNA of A. oryzae EIPW 212 was utilized for the southern hybridization employing the same DNA probe it revealed the hybridized bands at the positions of 5.3 Kbpand 2.9 Kbp The intensity of the band located at the region of 2.9 Kbpwas found to be higher than the intensity of the hybridized band located at 5.3 Kbpband.
BamH1 and EcoR1 double digested chromosomal DNA of A. oryzae ATCC 66222 strain was utilized for southern hybridization employing the radiolabeled 1.589KbpPCR fragment and hybridized bands at the positions of 5.8Kbp4.7Kbjand 3.7Kbpwere located to indicate the presence of the amylase gene or a part thereof in these fragments of hybridized bands.
The DNA fragments corresponding to the 2.9 Kbphybridized DNA fragment derived from BamH1 and EcoR1 digested A. oryzae EIPW 212 chromosomal DNA and the acetamide utilizing amdS from A nidulans were cloned in a plasmid pGEM3Z (7, fig. 1) to construct a recombinant plasmid pAAC3 (9, fig. 1) harboring the fungal amylase gene located in a BamH1 and EcoR1 2.9KbpDNA fragment of A. oryzae EIPW 212 origin.
The protoplasts of Aspergillus oryzae have been transformed to the amdS+ phenotype with the recombinant plasmid pAAC3 (9). The particular transformants for the hyper producing phenomenon of amylase production was picked up after a thorough screening.
Amylase hyper producing recombinant strain was further tested by isolation of the chromosomal DNA from the recombinant amylase hyper producing A. oryzae (EIPW16, MTCC 5177). The chromosomal DNA was digested with BamH1 and EcoR1 restriction enzymes and southern blotting was performed using the radiolabeled 1.589KbpDNA fragment and also with the amdS gene.
Autoradiography revealed that both the radiolabeled 1.589 KbpDNA fragment and the acetamide utilizing amdS gene has been inserted in the chromosome of A. oryzae 66222 in sites as revealed by the multiple hybridization bands with a very predominant higher intensity in a one band using both the above mentioned probes in separate experiments.
The chromosomal DNA of local Aspergillus oryzae (EIPW 212), a filamentous fungus capable of producing the enzyme amylase was isolated (exemplified in example 1) after harvesting the fungal mass grown in M-15 starch media for 72 hours at 32°C. The purified chromosomal DNA was doubly digested with BamH1 and EcoR1 restriction enzymes and resolved in 0.8% agarose gel, followed by Southern blotting to Nytran membrane following the standard procedures.
From the genomic amylase gene sequence of Aspergillus oryzae (Sequence Ref: Norihiro, T. et al, Gene, vol. 84, 1989 pages 319-327, 1989) oligo nucleotide primers within the conserved active sites of the enzyme amylase were chosen. The locations of primer ASP1 (24 mer) is within 967 5' 3: 990 bp and ASP4 (24 mer) is within 2556 5-3 2533 bp in the 2935 bp sequence of amylase gene. ASP1 and ASP4 (FIG. 2) primers are employed to PCR amplify the corresponding segment (967-2556 bp) of amylase
gene of A. oryzae, using the isolated local A. oryzae EIPW 212 chromosomal DNA as the template. A PCR amplified product of 1.589 kbpwas obtained (exemplified in example 2) and purified. 1.589 kbcsegment of the amylase gene was radiolabelled by random primer labeling system using the radionucleotide dATP- =c P32 and was used as the probe for hybridization experiment with the above Nytran membrane already southern blotted with BamH1 and EcoR1 double digested chromosomal DNA from A. oryzae EIPW 212. Autoradiography revealed the hybridized bands at the positions of 5.3 Kbpand 2.9 Kbp However, the intensity of 5.3 Kbfband was found to be less than 2.9 Kbfband. The DNA fragments corresponding to the 2.9 Kbpsize, was purified and cloned in EcoR1- BamH1 sites of pGEM4 plasmid employing E. coli DH 5