Transformant and process for production thereof, and process for production of lactic acid
View Patent ↗The present invention relates to a transformant, containing a lactate dehydrogenase gene which is introduced into Schizosaccharomyces pombe as a host, in which a part of a gene cluster encoding a pyruvate decarboxylase in the Schizosaccharomyces pombe host is deleted or inactivated.
1. A Schizosaccharomyces pombe transformant, wherein the transformant is transformed with a lactate dehydrogenase gene, wherein the chromosomal pyruvate decarboxylase (PDC) 2 gene in the transformant is deleted or inactivated, wherein the chromosomal PDC 4 gene in the transformant is not deleted or inactivated, and wherein the transformant produces lactic acid at a pH of 3.5 or less, while maintaining ethanol production suitable for growth of the transformant.
2. The transformant according to claim 1 , wherein the lactate dehydrogenase gene is a mammalian lactate dehydrogenase gene.
3. The transformant according to claim 1 , wherein the lactate dehydrogenase gene is inserted into the chromosome of the transformant.
4. A method for producing the transformant of claim 1 , comprising:
transforming a Schizosaccharomyces pombe host cell with a vector comprising an expression cassette that comprises a promoter, a terminator and a lactate dehydrogenase gene functioning in the Schizosaccharomyces pombe host to obtain a transformant,
wherein a PDC 2 gene in the Schizosaccharomyces pombe host cell or transformant is deleted or inactivated, wherein the chromosomal PDC 4 gene in the transformant is not deleted or inactivated, and wherein the transformant produces lactic acid at a pH of 3.5 or less, while maintaining ethanol production suitable for growth of the transformant.
5. The method according to claim 4 , wherein the vector further comprises a recombination region for carrying out a homologous recombination for the chromosome of the Schizosaccharomyces pombe host cell, and the expression cassette is inserted into a target region of the chromosome of the Schizosaccharomyces pombe host cell.
6. The method according to claim 5 , wherein the target region where the homologous recombination is carried out in the chromosome of the host cell is a transposon gene Tf2.
7. The method according to claim 4 , wherein the lactate dehydrogenase gene is a mammalian lactate dehydrogenase gene.
8. A method for producing lactic acid, which comprises culturing the transformant according to claim 1 in a culture medium and obtaining lactic acid from the culture medium.
9. The method according to claim 8 , wherein the culture medium comprises from 1% by mass to 50% by mass in concentration of glucose.
10. The method according to claim 8 , wherein the culturing is continued after the pH of the culture becomes 3.5 or less due to the lactic acid produced by the transformant.
11. The method according to claim 8 , wherein the initial cell density of the transformant in the culture medium is from 0.1 g to 50 g/L on a dry cell basis.
12. The method according to claim 8 , wherein the culturing is continued without neutralizing the lactic acid in the culture medium produced by the transformant.
13. The method according to claim 8 , wherein the lactic acid is separated from the culture medium without neutralizing lactic acid in the culture produced by the transformant.
14. The transformant according to claim 1 , wherein
the lactate dehydrogenase gene is a mammalian lactate dehydrogenase gene, and
the lactate dehydrogenase gene is inserted into the chromosome of the transformant.