Melanin pigment non-producing or low-producing β-glucan-producing bacterium, its artificial production method, and β-glucan produced using the same, and its production method

摘要

[Problem] To provide a β-glucan-producing fungus without a melanin pigment formation ability or with a low melanin pigment formation ability, which is mutated from a common β-glucan-producing fungus, does not have a melanin pigment formation ability or has a lower melanin pigment formation ability compared with an initial state before the mutation treatment of the microorganism, and has a β-glucan production ability. [Solution] The method comprises: a gene mutation treatment step of subjecting a fungus Aureobasidium pullulans (a black yeast fungus) to a mutation treatment by means of a physical or chemical treatment for causing a mutation in a gene of the fungus; and a mutant strain selection step of screening for a strain in which the occurrence of melanin formation is not observed, in both of the culturing of a mutant strain produced in the gene mutation treatment step in the presence of a tyrosinase pathway inhibitor and the culturing of the mutant strain in the presence of a polyketide pathway inhibitor. This double-screening enables the inhibition of the formation of a melanin pigment and, consequently, enables the production of a β-glucan-producing strain which has a β-glucan production ability and which does not have a melanin pigment formation ability or has a low melanin pigment formation ability. For example, a radioactive irradiation treatment with gamma ray is employed as the mutation treatment.