TECHNICAL FIELD

This disclosure relates to aTrichoderma reeseimutant strain having an enhanced protein-producing ability, and a protein production method using the mutant strain.

BACKGROUND

Trichoderma reeseiis known to have a high protein-producing ability, and studies have heretofore been made on protein production using this filamentous fungus.Trichoderma reeseihas an excellent ability of producing, among proteins, particularly a cellulase classified as a saccharifying enzyme, and to further enhance, for example, the cellulase production amount, overexpression or deletion of the factor controlling the cellulase production is performed. In Juliano de Oliveira Porciuncula et al., “Single Nucleotide Polymorphism Analysis of aTrichoderma reeseiHyper-Cellulolytic Mutant Developed in Japan,” Bioscience, Biotechnology, and Biochemistry, Volume 77, 2013, Issue 3, pp 534-543, aTrichoderma reeseimutant strain having a high cellulase-producing ability is acquired by reducing, among factors controlling the cellulase production inTrichoderma reesei, the function of Cre1 which is a transcription factor repressing the cellulase production.

As described above, a transcription factor that is one of factors controlling protein production inTrichoderma reeseiis identified, but this is considered to be merely a part of the control mechanism. There is thus a need to acquire aTrichoderma reeseimutant strain having enhanced protein-producing ability by searching for a novel factor controlling the protein production inTrichoderma reeseiand provide a protein production method using theTrichoderma reeseimutant strain.

SUMMARY

We found that when a previously unknown control factor for the protein production inTrichoderma reeseiis identified, the protein production amount inTrichoderma reeseican be increased, and we found that the protein production property can be improved by cultivating aTrichoderma reeseimutant strain reduced in the function of a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 2.

We thus provide (1) to (5):

(1) ATrichoderma reeseimutant strain in which a function of a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 2 is reduced.

(2) TheTrichoderma reeseimutant strain according to (1), in which two amino acid residues of 347th and 348th in the amino acid sequence represented by SEQ ID NO: 2 are deleted.

(3) A method of producing a protein, the method including a step of cultivating theTrichoderma reeseimutant strain according to (1) or (2).

(4) A method of producing a cellulase, the method including a step of cultivating theTrichoderma reeseimutant strain according to (1) or (2).

(5) A method of producing a sugar from a cellulose-containing biomass, the method including:

step a of producing a cellulase by cultivating aTrichoderma reeseimutant strain in which a function of a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 2 is reduced; and

step b of saccharifying the biomass by using the cellulase obtained in the step a.

TheTrichoderma reeseireduced in the function of a polypeptide consisting of the amino acid sequence represented by SEQ ID NO: 2 has an improved protein-producing ability, compared toTrichoderma reeseiin which the function of the polypeptide is not reduced. In addition, use of theTrichoderma reeseienables enhanced production of a protein. Furthermore, when the produced protein is a cellulase, there is also obtained an unexpected effect that various specific activities of the cellulase are improved.

